[X] My Assistant

[deglr6328]

What is going on with SETI@home? I have in the past, (like many of the other users of this board I suspect!) run the SETI@home screensaver on my computer. I ran it for about 4 years and then uninstalled it. Not because I was fed up with not having an ET directly send to me personally a big "HELLO THERE" message, but rather because I saw little in the way of actual science being done with the SETI results we volunteers were all producing and because there seemed to be no plan for any kind of endpoint of the project in the future.

I recall seeing in a 2000 edition of Scientific American a plot of the already searched parameter space by SETI@home and it looked like most of our galaxy was searched and found empty obviously, of "type I civilizations" and higher. (ah. found it) Now, its been 6 years since then and we've since viewed ~97% of the observable sky from Arecibo at least once since the start of the project (~86% at least twice). Why are there no papers published on this result? It IS a significant result even if its negative one. Were there SETI papers published that I've just not seen? The SETI and SETI@home web sites are of very little help when looking for actual peer reviewed published papers that the projects have produced.

[Guest_Richard Trigaux_*]

I think this is an interesting topic, and that it fully deserves its place here as a science/technology concern, if we left besides any childish a priori in the style "life on other planets must/cannot exist" and any mockery about "little green men" or fear about "aliens".

Like many others I ran the SETI@home screensaver, but I abandonned because I have only an old slow computer which took too long to analyse one block.

The diagram deglr6328 found here summarizes the actual result of SETI searches:

-SETI cannot detect the equivalent of Earth at any distance, even very close (Barnard, Sirius)
-there is nobody at least than 100 light-years aiming at us powerfull radio beams. We know for long that the Arecibo radio telescope can communicate with its equivalent at about 5000 light-years. But nothing such was found.
-there are no type I civilization in our part of the galaxy.
-there is no type II civilization in our galaxy and local cluster.


But these results are still very incomplete, and just reflect a lesser blindness that previous studies. There are still plenty of place for many discreete civilizations and some larger ones. We can only rule out a powerful starwars-like galactic civilization sending a tremendous amount of energy in space. But we have still many possible scenarios:

-many civilization using "environmental friendy" radio communication
-they use laser communication instead, which are believed to be more efficient (thanks to a better focusing, or larger transmission rate).
-they use some quatum non-local technology, which cannot be detected. (I evoke this possibility in my fiction novels "The missing planets" and "Dumria")
-the civilizations evolve in a different way that just increasing technology power (I also evoke this possibility in a third novel to come, and many other possibilities can be imagined)


So, I think, we cannot yet say "there is nobody". We just tested a possibility. We are not with SETI as we are now with Mars, grasping to the last hope of finding life in very special places.


The fact that astrophysics predicts that there can be perhaps millions (or billions) of planets suitable for life in our galaxy, and the fact that we did not received any past visit or did not detected any radio communication, this is a riddle that nobody yet can answer.
It is the equivalent of the astronomy paradox of the black sky. The black sky paradox was solved with an element we could not predict (the universe has a finite past time) so I think some elements are missing to fully understand what we know today about SETI. Some possible hints:

-something we do not know makes civilisation much more rare than expected from astrophysics results
-we were very fast compared to others, and thus appeared among the firsts
-the assumptions describing type I or II civilisations are false
-they use other communication means
-they developed other type of behaviours than just colonialism/predation, and left planets evolve in their own way, so far as avoiding any interference, just like we are doing now with the last unspoiled tribes in Amazonia/Papua.
-they evolve in a different way than just increasing technology achievements in an exponential way.

Examining how life can emerge on a given star system is a matter of astrophysics and biology, but examining how civilisations (like ours) can last and evolve in the future is much more speculative and rather a matter of philosophy.

[helvick]

I'm also a lapsed SETI@home participant. I had a bunch of systems running under the name Dennis D. Gnome for the Ars Technica Team Lamb Chop group. I think I pulled the plug on the last one in 2002 after I'd clocked in 4331 work units (about 5 years of total CPU time). I had a chunk of systems in a test environment that weren't doing anything most of the time so SETI seemed like a good use for them.

Richard,

You left out out overt aggression as a possible reason for the silence. Even if intelligent life and space faring civilisations are common then even a tiny percentage that tended towards aggression\predation would create very strong evolutionary pressure that encourages "silent" civilisations that tend not to broadcast their presence. Greg Bear's "The Forge of God" and "Anvil of the Stars" set explores some of the possibilities that might result. This is a very pessimistic idea but one that I think is plausible.

There is also the "Intelligence Singularity" concept that Vernor Vinge explores in "Across Realtime". As the overall intelligence\information density of a civilisation rises the rate at which it increases also expands leading to a singularity effect. Since all bets are off at that point it is quite plausible that the resulting civilisation\intelligence might be unrecognizable and undetectable to us. Charlie Stross deals with similar ideas in Singularity Sky, one of the better Sci Fi books of the last year IMO. I'm not 100% sold on the singularity idea but I certainly think that it has merit as an idea beyond being a useful literary conceit.

[Guest_Richard Trigaux_*]

Richard,

You left out out overt aggression as a possible reason for the silence. Even if intelligent life and space faring civilisations are common then even a tiny percentage that tended towards aggression\predation would create very strong evolutionary pressure that encourages "silent" civilisations that tend not to broadcast their presence. Greg Bear's "The Forge of God" and "Anvil of the Stars" set explores some of the possibilities that might result. This is a very pessimistic idea but one that I think is plausible.

Of course yes, it is enough of only one civilization practicizing predation/agression to create a strong evolutionary pressure... too strong perhaps, it would likely eliminate every other lifestyle (how could a low tech civilization withstand an attack with spacefaring technology?) or the existence of one agressive civ would make that the other civs need to have allies, and in this case they would actively contact us. This hypothesis leads to a starwars-like situation where war falls on innocent unsuspecting worlds, and both camps contact/exploit all the planets they find. But we were never attacked or contacted by a coalition, and this makes the possibility of an agressive civilisation weaker (Thanks God) without however completelly ruling it out. We are still in the black sky paradox.

Richard,
There is also the "Intelligence Singularity" concept that Vernor Vinge explores in "Across Realtime". As the overall intelligence\information density of a civilisation rises the rate at which it increases also expands leading to a singularity effect. Since all bets are off at that point it is quite plausible that the resulting civilisation\intelligence might be unrecognizable and undetectable to us. Charlie Stross deals with similar ideas in Singularity Sky, one of the better Sci Fi books of the last year IMO. I'm not 100% sold on the singularity idea but I certainly think that it has merit as an idea beyond being a useful literary conceit.

I also explore this possibility in my novels "The missing planets" (where empty planetary orbits are found where accurate models of planet formation predict Earth-like planets) and "Dumria" and another one to come. But my stance is a bit different: at a certain moment of their evolution (we are close to it) the worlds master paraphychology, and thus need no more technology, and they become "invisible" in nanother state. More mainstream-science explanations of this style are possible, such as a change of quantum state, leading to the same result: civilisations disappear from the physical world, or emit no signals.


Another interesting point is that we do not need sci-fi technologies to colonize the whole galaxy. We are near to discover techs such as fusion, or biotechs, will would allow to send seed ships to close stars. Once this process started, only some tens of million years are required to colonize the whole galaxy, a blinkeye in he history of Earth and of the galaxy. Did this happened in the past? It is likely, say physics and astrophysics. But if this happened, we would have received past visits, or found some control system near Earth. (such speculations are usually made by hoaglandites, but we would gain to make them seriously). Until now we found nothing. Still the dark sky.

Are we searching in the right way?

[David]

I'm going to add and consolidate some comments on this topic that I made in another section of unmannedspaceflight, where they were out of place (so I can remove them from there).

Nov 14 2005, 05:02 PM
Space is very, very big, and there is a lot of small stuff floating in it. Unless that stuff calls attention to itself in some way, there is no particular reason to investigate it. Even if there were "Vulcans", or some other alien intelligences quite close by, they would have no reason to investigate every tiny asteroid exiting the solar system. Nor would we, in the distant future have any reason to investigate every odd scrap of space debris coming from other systems. I think that any probe leaving our system -- Pioneers, Voyagers, New Horizons -- is permanently lost, to anybody, except in the unlikely event that some future humans decide to track it down and retrieve it.

Any records that we place on these probes therefore have a merely symbolic value. They are the human race's way of saying hello to itself, of patting itself on the shoulder and wishing that it were not so alone. As messages, they are the equivalent of a letter in a bottle, except that bottles set adrift in the sea do occasionally wash ashore. The sea of space is much bigger, and the shorelines are far rarer.

If we intend to communicate to any beings beyond Earth, we need not a message in a bottle but a lighthouse, some sort of beacon that can continuously broadcast the presence of Earth as something extraordinary in the night sky.

Not that, in my opinion, that would do much good. I think the complete failure of SETI to turn up anything thus far tells us one of two things, and probably both: one, that intelligent species, assuming there to be others than humans, are scattered thinly across the universe; there might be no more than one per galaxy. Two, that carrying living beings across interstellar space is very, very difficult, and that optimistic scenarios about colonizing the entire galaxy in a matter of a millennia are untenable.

One thing we can be pretty sure about is that when humans emerge from the solar system, they are not going to find great Star Empires and Space Trading Federations full of busy aliens waiting for them -- or we would have learned of them already. Instead there will be a vast, desolate, and wild sky.

Nov 14 2005, 08:23 PM
I have no problem with putting anything on a probe that doesn't hinder its primary mission, but my understanding is that the odds are not merely slim, they are infinitesimal. That is, we could send out a million such bottle-messages, and the probability that all of them would simply disappear would not be significantly reduced. I think it is truer to say that these messages are poetic expression of human hopes and aspirations, than that they are really meant as messages to alien adventurers. No offense is intended to anyone who has worked on these things and truly believes in them.

I think that any effort to put ourselves in the shoes of a putative extra-terrestrial intelligence, and imagining what they might or might not do to communicate (or willfully fail to communicate with us), before we know that such creatures exist, is absolutely futile. We barely know what intelligence is with respect to Earth animals other than humans. We have no idea what intelligence would look like in non-terrestrial beings. There are no grounds for extrapolating from humans to other intelligent beings that might exist.

The negative results of SETI searches, and our other exploration of nearer space thus far, do not merely provide an "absence of evidence"; they do put definite constraints on what may be out there. One thing we now know is that near space is not packed with beings tending high-powered radio beacons. There could be lots of explanations for that, but the simplest hypothesis is that no intelligent and technologically advanced civiilization exists to do it in this region of space. That may be a disappointing thought; on the other hand, if one simply operates on an unfalsifiable assumption that such beings do exist, and have a bottomless bag of excuses for why they might not be detectable by any any increase in our technological powers, then the hypothesis is no longer strictly scientific.

[Rakhir]

What is going on with SETI@home?

You may find some articles on The Planetary Society website (http://www.planetary.org/home/).
Just browse in the project list :
- SETI Optical Searches
- SETI Radio Searches
- SETI@Home

There was also a recent update at spacedaily.com :
http://www.spacedaily.com/news/seti-05f.html

I have in the past, (...) run the SETI@home screensaver on my computer. I ran it for about 4 years and then uninstalled it. (...) because I saw little in the way of actual science being done with the SETI results we volunteers were all producing and because there seemed to be no plan for any kind of endpoint of the project in the future.

If you are not interested in processing SETI data anymore, you could switch to another project (the new processing engine allows also to share the processing capacity among several projects), like climate study or developing cures for human diseases...
- Climateprediction.net: study climate change
- Einstein@home: search for gravitational signals emitted by pulsars
- LHC@home: improve the design of the CERN LHC particle accelerator
- Predictor@home: investigate protein-related diseases
- Rosetta@home: help researchers develop cures for human diseases
- SETI@home: Look for radio evidence of extraterrestrial life
- Cell Computing biomedical research (Japanese; requires nonstandard client software)
- World Community Grid: advance our knowledge of human disease.

More info at : http://boinc.berkeley.edu/

Rakhir

[helvick]

Good comments David.

There are a couple of additional thoughts that I have in relation to the black sky problem.

We assume that Intelligent civilisations will be detectable remotely because they should leak quite a lot of RF signals. Our current communications technology is still relatively crude, we have only been refining it for a little over a century after all. I think it's reasonable to assume that ever increasing communications efficiency will lead to systems that are substantially less wasteful, much more precisely targeted and in general far more power efficient. Improvements in coding\modulation\signalling techniques are very likely to result in RF signals that are indistinguishable from noise for any but the intended recipient.

It seems very likely to me that the current "lighthouse" mode that we operate in will be a relatively short term thing. It wouldn't surprise me at all if changes in telecomm's over the next century led to a "dark earth" from an RF point of view.

If the above is true as a general rule then there could be hundreds of thousands of advanced civilisations in the galaxy. Some could be very close to us and we still wouldn't be able to detect them from their accidental leakage of RF energy.

The question remains as to why they would also choose not to attempt to communicate deliberately. Cosmic Zoos and Galactic Wildlife Parks that are intended to nurture primitive intelligense seem like a whole load of hokum to me. For starters such things would need galactic scale civilisations and unless our current laws of physics are totally rewritten such concepts just cannot happen, at least not over timescales that have any meaning for civilisation as we know it.

[deglr6328]

.....The negative results of SETI searches, and our other exploration of nearer space thus far, do not merely provide an "absence of evidence"; they do put definite constraints on what may be out there. One thing we now know is that near space is not packed with beings tending high-powered radio beacons. There could be lots of explanations for that......

YES. That was the main gist of my post. We are now getting the first really scientifically interesting significant constraints on these things and I want to see more coming from the various SETIs than simply "nope not yet"....."nope not yet"....."nope not yet". I want to see these negative results presented rigorously in peer reviewed journals.

[Guest_Richard Trigaux_*]

It is false to say that the SETI results are negative!! They simply found that scifi-like or starwar-like scenarios are not true: there are no giant technologies and galactic dictature, no Independance Day to fear. That is reassuring in a way.

SETI operating from Proxima centauri (the closest star) would not have detected Earth!!!!! Even if Earth-like civilizations are common, SETI still needs an increase in 1000 in sensitivity to have some chance to find a close one.


This result weakens only very little the odds to find intelligent life. But not very much yet, it is not like finding 460°C at the surface of Venus, a simple figure which definitively and dramatically ousted all the dreams of finding luxurient jungles on Venus.


The SETI result still lefts many possibilities open. It just tells us that what we imagined was wrong. If there is life out there, it is just not like we imagined. And it is very interesting to guess what could be their motives, their purposes, their values, even if, of course, this is still untestable in a scientific meaning. This is the process of thinking, and perhaps one day one of these speculations will prove useful or even true.

I do not understand the pessimism of many science-minded people about finding life out there. In the beginning of the 19th century, it was understandable, as the mainstream hypothesis was that the planets formed at time of a close encounter of the Sun with another star, a much rare event which condemned the planet sytems to be only some in a galaxy. But today astrophysics and biology all show that the odds are hight to find life on many planets. So there is many reasons to be optimistic and few to be pessimistic.


I think this pessimism has philosophical reasons more than science reasons. Life elsewhere is felt as threatening, its attitude and even its very existence are felt like a threat to our values, our ego or something of this kind. Or are we so afraid of being considered hoaglandites that we do not consider the possibility of another life form? Be reassured, the SETI institute does not deal with UFOs and abduction...

[ElkGroveDan]

It's an interesting topic, but it doesn't belong here.

[ElkGroveDan]

Do you guys realize the search terms that have been added in just the first 8 posts here?

little green men
UFO's
aliens
galactic civilizations
star wars
Vulcans
missing planets
attack with spacefaring technology
Independence Day
unsuspecting worlds
colonize the whole galaxy
Cosmic Zoos
Galactic Wildlife Parks
galactic scale civilisations
Earth-like civilizations

[David]

I do not understand the pessimism of many science-minded people about finding life out there. [...] But today astrophysics and biology all show that the odds are high to find life on many planets. So there is many reasons to be optimistic and few to be pessimistic.
I think this pessimism has philosophical reasons more than science reasons. Life elsewhere is felt as threatening, its attitude and even its very existence are felt like a threat to our values, our ego or something of this kind.

I'm not (relatively) pessimistic because I want to be; I'd be thrilled if we made contact with other intelligent life forms. My dream job would be working on deciphering extraterrestrial languages. I just have no confidence that I'll ever have that data to work on.

The root of the problem, is, of course, having a data set of one for life, intelligence, and high technology. We therefore have no basis for evaluating probabilities.

We are lucky now to know that a very large number of stars develop planetary systems. That means that there are going to be a lot of platforms on which life could develop. Which is great. Unfortunately, we don't know what the chances of life spontaneously developing on any one of those platforms is. We can't conduct experiments over the requisite timescales in the lab; hence, the search to see if non-terrestrial life has developed on other worlds of the Solar System, Mars or Europa or Titan or maybe Enceladus. If we find them, we have some basis for suggesting that when the conditions are right, life will develop; if we don't, we might suppose that the development of life occurs only under very favorable circumstances, and we still wouldn't know how favorable they need to be.

And then there's a long, long gap between "life" and "multicellular life" and "intelligent life". We can make some guesses at this based on how long it took to develop multicellular life on this planet (over 3 billion years), but that's still a data set of one. And the development of intelligent life a billion years after that seems to have been a completely freak occurrence; there's no special reason for it to have happened when it did, rather than earlier or later or in a different branch of animal life. Indeed, small differences in the history of the planet could have led to a present-day Earth entirely devoid of intelligent animal life. So we have a good idea that intelligence is freakish and improbable. We just have no idea how improbable it is -- because, once again, we have a data set of one.

So if we were able to start testing planets with some unobtainable "tricorder" technology, the odds seem to be that most of them would be heaps of rock, ice, or gas. And those that have life are most likely going to have seas fermenting with invisible monocellular organisms, but nothing else. And the others -- interesting ones, that humans might actually be able to live on -- will be dominated by various kinds of macroscopic, mobile and sessile life -- but nothing intelligent. When you consider these layers of improbabilities, and the possibility that some of them might be very improbable, then the possibility that humans might be the only intelligent species in the Milky Way does not seem so far-fetched, even if life is relatively common. And even if there is intelligent life, we don't know how long it takes to develop a technological civilization. Humans were around for over 90,000 years before they even learned to write. Maybe other intelligent life forms could go for a million years without feeling the need to attain more than very rudimentary technology. But here we have a paradox; the data we need to answer these questions is the very data we're trying to guess at. Our ignorance is that profound.

[deglr6328]

EG-Dan, while I share your apprehension about using terms which are sometimes associated with kooks and "ufologists" as they may attract those unsavoury characters to the boards here through google searches, I must differ with you on the notion that we should not discuss these things (SETI) here because of that fact. I think we should never have to censor ourselves here merely because of the existence of hoaxers and paranormalists "out there". I think that there is definitely very interesting and worthwhile discussion on the topic of the search for extraterrestrial intelligence, which can be had here in a rational and skeptically scientific manner. This place is exceptional in that respect. We should never feel forced to shy away from legitimate levelheaded inquiry on these boards and it looks to me like Doug keeps it safe for that here.


Richard, with respect to suspicions of pessimism on ETI among the scientific community, I personally don't see it that way. I fully endorse the view outlined by David above. I'm not a pessimist, just a realist. I would love it so very much if we were to discover ETI in my lifetime and I am hopeful that it is within the realm of (albeit extreme) possibility. But at the same time, I'm not holding my breath. See, the question is of such extremely grave importance and consequence that I want to be 1000% certain that its real when or if we do actually discover it and I think that this kind of stern reservation and insistence on evidence would make such a discovery just that much more wonderful.

[Guest_Richard Trigaux_*]

EG-Dan, while I share your apprehension about using terms which are sometimes associated with kooks and "ufologists" as they may attract those unsavoury characters to the boards here through google searches, I must differ with you on the notion that we should not discuss these things (SETI) here because of that fact. I think we should never have to censor ourselves here merely because of the existence of hoaxers and paranormalists "out there". I think that there is definitely very interesting and worthwhile discussion on the topic of the search for extraterrestrial intelligence, which can be had here in a rational and skeptically scientific manner. This place is exceptional in that respect. We should never feel forced to shy away from legitimate levelheaded inquiry on these boards and it looks to me like Doug keeps it safe for that here. 

I can only agree with this. My only remark is that, I think, we can study UFOs and parapsychology in a rational non-belief way (interested people see my site for link pages). But I shall not try to start any discutions on these topics here, unless of course Doug asks me to do so.

[Guest_Richard Trigaux_*]

deglr6328 and David, thank you for your replies. I must confess I was a bit angry, but I better understand your arguments.

But I still maintain that there are very large uncertainties about the number of intelligent civilizations, between one per galaxy to millions per galaxy. So we have no reason to choose one of these numbers rather than another. Simply we do not know, and no more than you deglr6328 I expect to meet other beings in my lifetime, and I would be as much cautious than you (especially it happens that I have been deceived by so-called "contactees")


What I should say, in summary, is that the Drake equation is too simplistic, as we must keep with time. The appearance of a civilization is an evolution process, with advances by sudden breakthroughs, and which can be stopped by astrophysical conditions (the star dies, a super-nova close by, etc).


To explain my idea, I would make a simple comparizon with something we have at hand, and even, alas, we have too much of it: the growth of a tumour, a cancer. These mechanisms were unveiled recently, and it is a pity we do not speak much of them. A tumour starts at random, when a cell mutates somewhere and begins to escape its growth control mechanisms. But, as such, this baby tumour is harmless, just mechanical. To become a real deadly cancer, it has to undergo several other mutations. But mutations happen at random, anywhere in the cell mass. So how things take place? simply, if we have, for instance, a probability of one billionth to have a mutation, we think it is very unlikely. But when the cell mass reaches ten or hundred billions, thus the mutation becames MANDATORY. So the tumour gets all the "necessary" mutation, in a deterministic-like way, by steps according to is growth. 1 million cell, step one. 1 billion cells, step two. Ten billion cells, step three, etc. So the tumour evolves in a deteministic-like way, with only probabilistic causes. And this process is so constraining, that only a little number of recognizable types of tumours can form (less than 50), and the same precise types of tumours appear on million of different individuals, without any causal relation between them!!


This simplistic model would be useful, I think, to model the evolution of life on a planet. Like tumours, life evolves by breakthroughs: -drops with a membrane -autocatalytic reactions -DNA like mechanism -multicellular -neurones -brain -emotions, intelligence -civilization -after we cannot foresee, perhaps wisdom. So the model applies, except that the life mass on a planet does not grow exponentially like a tumour, so breakthroughs do not happen at a given moment, there are rather steps, with a probability, linear function of time, to pass to the next step at a given moment. (but if this probability if one half every ten million years, we can expect this step will not last one billion years). On Earth, the longest step was multicellular organisms, three billion years. So we can expect similar times on other planets.

Of course, there are environment factors which constrain the evolution of life. First, the life can modify the chemistry of the planet. (if Earth was sterilized today, life could not reappear). This is even a mandadory step, for instance only an oxygen-rich atmosphere could allow the appearance of movement (muscles) and brain. This kind of considerations could be very constraining: intelligence could appear only in animals on a planet with plants and photosynthesis. Like with tumours, only a small number of types of life would be possible. On the other hand a place like Jupiter's moon Europa could be full of worms and bugs, intelligence will never appear here, by lack of a powerfull energy source like oxygen to feed a large brain.

So the modeling of the evolution of a planet is more complex, with interactions between geologic/chemical/climatic conditions and biology.

The second set of environment factors are rather astrophysical, linked to the evolution of stars and planets. Some hints: Venus could have experienced Earth-like conditions in the beginning. So life could have appeared. But the catastrophic climate change which occured here (greenhouse divergence) stopped it. When? two billion years after formation? So we can guess that only monocellular life could exist at this time, and look for microscopic fossils in venusian mountains, but not for large animal fossils. The same is true with stars a bit larger than the Sun: their life time is too short, an Earth around them would have been destroyed at the stage of bacteria or worms. So it is useless, I think, to search radio signals around large stars. Too small stars like the Barnard star are also too red to give an efficient photosynthesis (although we do not know where is the limit)

At last we must account with catastrophic events: orbit changes, impacts, other star encounters, close supernovas, etc. What is the probability of having a supernova destroying life on a planet? At rough guess it varies widely. The diffuse halo of a galaxy and the bulb are good places. The arms are not very good. Center of globular clusters may be uninhabitable infernos. If we have a probability of a half every 100 million years to be destroyed by a supernova close by, so, with our 4500 million years, we are very unlikely survivors, and in this case civilizations would be indeed very rare, less than one per galaxy, even if life starts at once on every new planet system. But I think that probabilities are much better than half every 100 million years: in the halo there are never supernovas.

So I think the best estimate we can do today about the probability to have civs around there should account with all these probabiliies in a time-dependent scenario more complex that the time-independent Drake model. But, despites this, I think this calculus would still left very wide uncertainties, of many orders of magnittude, about the number of civilization in the Galaxy. That still justifies the SETI program. And anyway SETI is supported by who wants, these people have the right to spent their money in this. And the results already acquired are beginning to bite into the error box about the number and size of civilizations: we now know that there are no galactic dictature and starwars-like galactic network. Great.

[edstrick]

Richard Trigaux: ".... Too small stars like the Barnard star are also too red to give an efficient photosynthesis...."

Note that there is no problem in general with growing plants under incandescent lamps. The temperature of tungsten filaments is well under the temperature of red dwarf photospheres. The 99.9% bad astronomical art showing crimson red giants and red dwarfs is just that: Bad art.

Evolution on red-dwarf planets may well be pushed to "try" to evolve photosynthetic light absorbing systems that capture light beyond the "red-edge" of chlorophyll, where it's reflectance rises over 10 times from some 5% to some 50%, but that would not be necessary, just helpful.

[ljk4-1]

Do you guys realize the search terms that have been added in just the first 8 posts here?

little green men
UFO's
aliens
galactic civilizations
star wars
Vulcans
missing planets
attack with spacefaring technology
Independence Day
unsuspecting worlds
colonize the whole galaxy
Cosmic Zoos
Galactic Wildlife Parks
galactic scale civilisations
Earth-like civilizations

With that thinking, we better remove the word Mars from this forum, because we all know that will lead to the Mars Face!

On another SETI issue, are elements of art as universal as math?

http://www.jonlomberg.com/articles-Capri_paper.html

[Guest_Richard Trigaux_*]

Richard Trigaux:  ".... Too small stars like the Barnard star are also too red to give an efficient photosynthesis...."

Note that there is no problem in general with growing plants under incandescent lamps.  The temperature of tungsten filaments is well under the temperature of red dwarf photospheres.  The 99.9% bad astronomical art showing crimson red giants and red dwarfs is just that: Bad art. 

Evolution on red-dwarf planets may well be pushed to "try" to evolve photosynthetic light absorbing systems that capture light beyond the "red-edge" of chlorophyll, where it's reflectance rises over 10 times from some 5% to some 50%, but that would not be necessary, just helpful.

Thanks for the info, edstrick. If I understand well, stars are not really "red" or "yellow", but astrophysicists name them this way because the maximum radiation is in the red, or yellow, but this does not make the stars red or yellow.

And if the 3000°C tungsten lamps allow for photosynthesis, any star can do it, except some brown dwarves, the only stars below the 3000°C.

Back to my statistical analysis, there are perhaps 10 of 50 more time red dwarves than sun-like stars. This multiplies by the same figure the odds to develop photosynthesis (and further civilization).

The setback is that we are not sure that red dwarves have suitable planets. The most commonly accepted hypothesis is that they have, but we have no evidence, and the planets could be too small, from lesser mass and metallicity of the star. In the most extreme case, only recent high-metal yellow stars would have planets large enough to retain air and water. This mades in fact an uncertainty of 20 to 100 about the number of planets able to develop photosynthesis. With other sources of uncertainties, we easily obtain overal uncertainties of 1 over 1 billion about the total number of civilizations. And IN NO CASE we can state that we are closer from one extreme rather than from the other.


Red dwarves have other interesting features. Many are very old, as much as 12 billion years. And their overal evolution is much slower, so that the life-supporting period could last for 10 billion years, much more than for Earth (due to the slow evolution of the sun). So, if ancient red dwarves have suitable planets, we have the best chances to find something there. From where the interest of an effort to detect eventual Earth-like planets specially around close red dwarves, if possible with low metallicity.

[ElkGroveDan]

With that thinking, we better remove the word Mars from this forum, because we all know that will lead to the Mars Face! 
[/url]

The way google and other search engines work when you enter multiple search terms is that they look for frequency of terms on a page, as well as proximity of the terms to each other.

So a search for "Mars Pathfinder" or "Mars Opportunity" will likely turn up this site.

Prior to this thread, a search on "Mars alien civilization attacks by UFO's" would not have resulted in a hit here, it would have taken the kook to OTHER places.

[ljk4-1]

Thanks for the info, edstrick. If I understand well, stars are not really "red" or "yellow", but astrophysicists name them this way because the maximum radiation is in the red, or yellow, but this does not make the stars red or yellow.

And if the 3000°C tungsten lamps allow for photosynthesis, any star can do it, except some brown dwarves, the only stars below the 3000°C.

Back to my statistical analysis, there are perhaps 10 of 50 more time red dwarves than sun-like stars. This multiplies by the same figure the odds to develop photosynthesis (and further civilization).

The setback is that we are not sure that red dwarves have suitable planets. The most commonly accepted hypothesis is that they have, but we have no evidence, and the planets could be too small, from lesser mass and metallicity of the star. In the most extreme case, only recent high-metal yellow stars would have planets large enough to retain air and water. This mades in fact an uncertainty of 20 to 100 about the number of planets able to develop photosynthesis. With other sources of uncertainties, we easily obtain overal uncertainties of 1 over 1 billion about the total number of civilizations. And IN NO CASE we can state that we are closer to one extreme rather from the other.
Red dwarves have another interesting features. Many are very old, as much as 12 billion years. And their overal evolution is much slower, so that the life-supporting period could last for 10 billion years, much more than for Earth (due to the slow evolution of the sun). So, if ancient red dwarves have suitable planets, we have the best chances to find something there. From where the interest of an effort to detect eventual Earth-like planets specially around close red dwarves, if possible with low metallicity.

Have you seen the recent National Geographic Channel special titled Extraterrestrial? Its first hour depicts speculations about life on a planet
circling a red dwarf sun, complete with dealing with the issues of such stars
creating massive flares.

http://channel.nationalgeographic.com/chan...traterrestrial/

The Discovery Channel also came out with its own special on an alien world
and its life forms, based on the 1990 book Expedition by Wayne Barlowe, which you can learn more about here:

http://www.discoverychannelasia.com/alienplanet/index.shtml

[Guest_Richard Trigaux_*]

With that thinking, we better remove the word Mars from this forum, because we all know that will lead to the Mars Face! 

What I would like is that we could speak freely of this poetical trick of nature, and take it as our icon, without being mandatorily associated with kooks.

There are other such tricks on Mars, sometimes really puzzling: the Inca city, the pyramid, the smile, etc. And astronomers refer to them under these names, because it is much more convenient. That kooks would be able to forbid such a language is perhaps the most pervert effect of kookery.

[Guest_Richard Trigaux_*]

Have you seen the recent National Geographic Channel special titled Extraterrestrial?  Its first hour depicts speculations about life on a planet
circling a red dwarf sun, complete with dealing with the issues of such stars
creating massive flares.

http://channel.nationalgeographic.com/chan...traterrestrial/

The Discovery Channel also came out with its own special on an alien world
and its life forms, based on the 1990 book Expedition by Wayne Barlowe, which you can learn more about here:

http://www.discoverychannelasia.com/alienplanet/index.shtml

Interesting, and well done, I recommend the visit.

about flares, there are some stars which create huge flares, but we don't know why and why only these stars. Maybe the proportion of flare-prone red stars is higher, but really I have no information on this. The only thing sure is that our sun never did, otherwise we should not be here.

[Guest_Richard Trigaux_*]

The way google and other search engines work when you enter multiple search terms is that they look for frequency of terms on a page, as well as proximity of the terms to each other.

So a search for "Mars Pathfinder" or "Mars Opportunity" will likely turn up this site.

Prior to this thread, a search on "Mars alien civilization attacks by UFO's" would not have resulted in a hit here, it would have taken the kook to OTHER places.

perhaps that if the people who do searches like "Mars alien civilization attacks by UFO's" find this forum, they will get instruction, and realise that those who spread false theories are kooks.

Each time I was speaking of kooks on this site, it was alway about the spreaders of false theories. That 20% of the population believe them is not because 20% of the population are mad, it is because they are not enough instructed, or they are not confident with a society wich deceived them in a way or another. In such a situation, kooks have an easy play. If, with this forum, we can contribute to revert this situation, it would be of some use, not just a pass time for us.

A wise caution would be to use a language more accessible to common people, avoid "scientific style" and obscure abbreviations, and when we use an uncommon word, give the explanation. I began to do so recently , realizing that more and more people are reading us, not just specialist or enlightened amateurs.


Thas does not forbid to expell real kooks when there are some. Or to answer briefly but accurately to suspicious questions, as Doug used to do in many occasions. He did in this way, I think, to avoid to straightforwardly rebuff people who are just mislead by kooks, but who are not kooks themselves.

[deglr6328]

We probably should not be so quick to dismiss the possibility of photosynthesis on planets orbiting stars which dominantly radiate in the IR.....


article and the PNAS paper.

[jamescanvin]

perhaps that if the people who do searches like "Mars alien civilization attacks by UFO's" find this forum, they will get instruction, and realise that those who spread false theories are kooks.

Each time I was speaking of kooks on this site, it was alway about the spreaders of false theories. That 20% of the population believe them is not because 20% of the population are mad, it is because they are not enough instructed, or they are not confident with a society wich deceived them in a way or another. In such a situation, kooks have an easy play. If, with this forum, we can contribute to revert this situation, it would be of some use, not just a pass time for us.

A wise caution would be to use a language more accessible to common people, avoid "scientific style" and obscure abbreviations, and when we use an uncommon word, give the explanation. I began to do so recently , realizing that more and more people are reading us, not just specialist or enlightened amateurs.
Thas does not forbid to expell real kooks when there are some. Or to answer briefly but accurately to suspicious questions, as Doug used to do in many occasions. He did in this way, I think, to avoid to straightforwardly rebuff people who are just mislead by kooks, but who are not kooks themselves.

Well said Richard.

The kooks probably already have there sites and beliefs. It seems more likely to me that most people typing such terms into google are doing so to find out about the subject and are only potential kooks. If they head off to the kook site which tops the search then a new kook may be born; much better that they get directed here where we can persuade them otherwise.

[Guest_Richard Trigaux_*]

We probably should not be so quick to dismiss the possibility of photosynthesis on planets orbiting stars which dominantly radiate in the IR.....
article and the PNAS paper.

Wow! this is incredible.


Photosynthesis working with the radiation of nearby red-hot hydrothermal water... No sci-fi writer imagined such a thing!


That makes photosynthesis something much likely to appear. And in a statistic view of the Drake equation*, it increases the odds for civilizations. Not so fast, photosynthesis is just one of the numerous mandatory steps toward the appearance of a civilization. It is not enough for this, especially if it is available only around some very located hydrothermal vents, like in Earth deep oceans, or like in Europa moon. To evolve fast, life requires a lot of opportunities to mutate, and lot of different ecological niches to be able to select these mutations. So a complex environment, that a place like Europa is not likely to provide. On the other hand, Europa provides a stable environment since 4.5 billion years, and the bottom of its ocean may offer varied temperatures, shapes and chemical composition, if it has hydrothermal vents (very likely) or volcanoes (likely). So, if a microbial life appeared on Europa, it had enough time to evolve into complex multicellular beings. But no more brains than with worms or bugs, for the lack of a powerful source of oxygen.

* the Drake equation tries to calculate the number of civilizations in a galaxy, by multiplying various numbers such as the probablility for a star to have planets, the probability for this planet to have water, etc. Most of these numbers are still widely uncertain today.

[ljk4-1]

Paper: astro-ph/0511583

Date: Fri, 18 Nov 2005 21:35:43 GMT (30kb)

Title: Hot Jupiters: Lands of Plenty

Authors: David Charbonneau

Comments: 8 pages, 2 figures, summary of conference "The Tenth Anniversary of
51 Peg b: Status and Prospects for Hot Jupiter Studies", held August 22 - 25,
2005
\\
In late August 2005, 80 researchers from more than 15 countries convened for
a 4-day conference entitled ``The Tenth Anniversary of 51 Peg b: Status and
Prospects for Hot Jupiter Studies''. The meeting was held at l'Observatoire de
Haute-Provence, the location of the 1.93-m telescope and ELODIE spectrograph
used to discover the planetary companion to 51 Peg roughly 10 years ago. I
summarize several dominant themes that emerged from the meeting, including (i)
recent improvements in the precision of radial velocity measurements of nearby,
Sun-like stars, (ii) the continued value of individual, newly-discovered
planets of novel character to expand the parameter space with which the theory
must contend, and (iii) the crucial role of space-based observatories in
efforts to characterize hot Jupiter planets. I also present the returns of an
informal poll of the conference attendees conducted on the last day of the
meeting, which may be amusing to revisit a decade hence.

\\ ( http://arXiv.org/abs/astro-ph/0511583 , 30kb)

[ljk4-1]

I have been wondering whatever became of The Planetary Society's Project BETA Radio SETI program, begun ten years ago, ever since the 84-foot Harvard radio dish broke and fell during a windstorm in March of 1999.

The TPS Web site has an article from 2000 describing and showing a repair job undeway:

http://seti.planetary.org/BETA/default.html

But when I went to Harvard University's Oak Ridge Observatory site, I found out that the BETA dish has since been "retired":

http://cfa-www.harvard.edu/oir/OakRidge/oak.ridge.html

I also learned from there, to my surprise, that the 61-inch telescope that had conducted their Optical SETI program since 1998 has also been retired - retired in this case meaning dismantled!

Why didn't the TPS or Harvard or someone inform us about this?

A few years back, TPS began a new Optical SETI project with much fanfare. I looked on their Web site but could find no new updates on it since 2002 (with lots of broken links here), when it was supposed to have its "first light":

http://seti.planetary.org/OsetiConstruction2.htm

The latest version of their Optical SETI page also reveals no recent news on this project:

http://planetary.org/programs/projects/set...tical_searches/

So what is happening with what is supposed to be the "largest Optical SETI project east of the Mississippi"? Is it still being built? Is it up and running? Has it too been abandonded? Has the TPS been slipping away from SETI ever since Carl Sagan's passing, as I suspect?

I and many other have supported this project financially as well as verbally, so I would hope to at least know what progress is being made - and why BETA was abandonded. Why didn't TPS at least transfer it to another radio telescope?

[elakdawalla]

I have been wondering whatever became of The Planetary Society's Project BETA Radio SETI program, begun ten years ago, ever since the 84-foot Harvard radio dish broke and fell during a windstorm in March of 1999. 

Hi ljk4-1, all of these older projects that you mention unfortunately predate my joining the staff at The Planetary Society, and they're out of my usual purview, so I'm afraid I don't know any information to give you. I have forwarded your comments to the people here who particpate in the SETI projects.

I do know, however, that we continue to support SETI projects financially thanks to member dues and donations, and that we currently have active projects in optical and radio SETI, along with our other projects in technology development, Mars exploration, Near Earth Objecs searches, extralsolar planets, and others. The stuff on our website is a little thin right now because we just completed our redesign and have only filled out the barest skeleton of necessary content. I know that filling in more depth in the SETI section (as well as all the rest of the projects) is one of the priorities. Here's the most recent update from our Director of Projects, Bruce Betts, about our SETI work, which was published in the September/October 2004 issue of The Planetary Report:

We Make It Happen!
by Bruce Betts

The Search for Extraterrestrial Intelligence (SETI) has been actively pursued by the human species for more than 40 years . . . so why have we not found ET? In early August, The Planetary Society gathered major players in SETI, such as Frank Drake, Paul Horowitz, and Dan Werthimer, to address this question. In a scientific workshop titled “The Significance of Negative SETI Results,” SETI experts, astrobiologists, and planet hunters discussed what’s currently happening in SETI and what the future might hold. Here I review some of the broad conclusions, assumptions, and implications of the meeting.

Where Are We With the Search?
Rarely does the small SETI community get an opportunity to come together as a focused group. The first step of the workshop was to review what everyone there had done, was doing, and planned to do—and the accomplishments were impressive. When SETI started looking at radio wavelengths, people looked in only a few “channels” (think of different radio station channels). Now groups analyze billions of radio channels. Surveys of the whole sky have been completed around a few key wavelengths, and other searches have focused on a smaller number of stars with greater observing frequency or radio channel resolution. In addition, a whole new field of SETI has arisen in recent years: optical SETI. Whereas original searches focused only on radio frequencies, the invention of extremely high power lasers made several of the groups realize that laser communication across the cosmos could be very efficient.

I could spend an entire issue of The Planetary Report reviewing even just the Planetary Society–funded searches. Lacking that space right now, we will be putting both summaries of the talks, written by the speakers themselves, and their PowerPoint presentations on our website. I encourage you to keep checking seti.planetary.org for updates.

The Cosmic Haystack
The workshop discussed how far we’ve come in SETI and how much computing power is now being brought to bear on all the SETI searches. But what are we to make of the fact that 40 years have yielded exactly nothing in terms of finding ET?

What became clear was that despite all the advances in SETI, we’ve only just begun to search. As it turns out, the cosmic haystack in which we are searching for the ET needle is enormous. First, you need to choose a wavelength—even if you concentrate only on looking in the electromagnetic spectrum (all forms of “light” including gamma rays, visible light, and radio waves), you still have to make a choice what you’re looking for. Then there’s space—you can process and search only so many places in a certain amount of time, and there is a lot of sky up there. Then, there is time—even if you are searching the whole sky, you are searching only a piece at a time, so what if you’re not looking when ET is broadcasting? Finally, there have been hypothetical discussions of communication that, instead of using electromagnetic waves, uses something else such as gravity waves or particles or objects.

To be frank, we would have to have been really lucky to have found ET by now, even if there are lots of ETs out there broadcasting. And what if we’re missing the boat entirely in the approaches we’ve taken? If ET is broadcasting at infrared or millimeter wavelengths, we haven’t even been looking there, or not much. Why? Because a lot of this part of the electromagnetic spectrum is absorbed by our atmosphere. These wavelengths turn out to be efficient means to communicate across the cosmos, however, so perhaps using these wavelengths is very common for other civilizations. Space-based SETI, looking for signals from above the atmosphere, is an intriguing idea—one The Planetary Society plans to investigate further.

Humanity Is Quieting Down
There are interesting implications of the fact that our species has been quieting down in the electromagnetic spectrum. When SETI was starting out, there was quite a lot of “leakage” from Earth. Our TV and radio transmitters, and even defense radars, were putting out tens of kilowatts each, a good portion of which was spewed into space. But things are quieting down. Cable TV and satellite TV (which uses much less power) are starting to replace on-air broadcasting; defense radars have gone to “digital spread spectrum” technologies that, even if they do leak, are hard to discern from the noise of the universe. Even cell phone and other wireless technologies are focusing more on low power and on digital technology that uses lower power and requires clever work to decode.

If other civilizations follow a similar pattern—quieting down within decades after their invention of electromagnetic communication technologies—then leakage may be utterly impossible to detect as we search for ET. There was more optimism of leakage detection in the past. Now, most researchers think that detectable signals would be intentional beacons: ET sending out signals intentionally to let others know they are there.

Where Are We Going?
Although we’ve barely picked the surface of the haystack, we’ve come a long way in our capabilities in the last 40 years, and our capabilities are expected to expand massively in the coming decades, allowing us to churn through the hay faster and faster. Computing power is improving rapidly, telescopes are being built, and strategies are improving: life is good.

There’s even more good news—extrasolar planets. The meeting included discussions of planet finding around other stars, led by Geoff Marcy, whose planet-hunting team has discovered the majority of extrasolar planets found so far. Their searches have many interesting implications and have taught us much about how normal or anomalous our solar system may be (see planetary.org/extrasolar/ for more information). Estimates of the number of planets within our galaxy alone are at least in the tens of billions. That’s a lot of places where one might tuck away some advanced ET who wants to broadcast its version of Planetary Radio to the universe.

The searches continue, and they continue to improve. We’ll have lots more in The Planetary Report and on planetary.org about SETI searches and extrasolar planets. In addition to sponsoring SETI research, something that NASA still cannot legally do, The Planetary Society can put together special workshops like this one to facilitate advances in SETI. Searching for ET truly is looking for a needle in a haystack, but if we succeed, it arguably will be the most significant discovery in the history of our species. That’s a very big prize. With your help, we’ll continue the search. Will we find a signal from ET? I remain patiently but firmly optimistic.

[Bob Shaw]

The way google and other search engines work when you enter multiple search terms is that they look for frequency of terms on a page, as well as proximity of the terms to each other.

So a search for "Mars Pathfinder" or "Mars Opportunity" will likely turn up this site.

Prior to this thread, a search on "Mar5 a1ien c1vilization a77acks by U70's" would not have resulted in a hit here, it would have taken the kook to OTHER places.

All very true, and (hint!) perhaps a good reason *not* to quote the phrase directly!

Perhaps Doug can install the new Invision CensorBot ™ (if it exists) so that it can reject certain, er, words. Not thoughts, not deeds, just words - the very ones which feed the k00ks! There *are* such nanny-programs out there, and (famously) they have denied access to sensible sites about breast cancer, and (it has been alleged) the official website of Scunthorpe Town Council!

(Tongue slightly in cheek)

Bob Shaw

[David]

The way google and other search engines work when you enter multiple search terms is that they look for frequency of terms on a page, as well as proximity of the terms to each other.

If you wished to avoid this, grouping all the suspect phrases together in a single post, as you did, was certainly not the best way to do so.

However, I tried searching for your questionable long phrase on Google, just to see whether unmannedspaceflight would turn up; if it does, it is buried very deeply. I tried using several terms from your list in combination, to narrow the list, and turned up nothing. So at the moment, there is nothing immediate to fear.

And on reconsidering your list, you seem to want to ban any word with a "science fiction" connotation. However, I have noticed that on this forum, simply due to the subject matter and the personalities involved, every tenth or twentieth message has some sort of science fiction allusion; I've seen discussions of science fiction novels, and of course repeated jokes about "Marvin the Martian", possible fossils and so on. I don't think you can practically hope to wipe those sorts of allusions out.

Moreover, banning such phrases as "unsuspecting worlds" or "missing planets" seems like overkill, as there are legitimate uses for such phrases even quite outside any discussion of ETIs, and they are hardly likely to be high upon any anomalist's list of search terms. Perhaps what bothers you is not so much the phrases, or the possibility of them being detected by a web-searching anomalist, as their context? --that is, the sense that a scientific forum such as this is degraded by the discussion of anything so "science fictional" as SETI?

[ljk4-1]

Hi ljk4-1, all of these older projects that you mention unfortunately predate my joining the staff at The Planetary Society, and they're out of my usual purview, so I'm afraid I don't know any information to give you.  I have forwarded your comments to the people here who particpate in the SETI projects.

I do know, however, that we continue to support SETI projects financially thanks to member dues and donations, and that we currently have active projects in optical and radio SETI, along with our other projects in technology development, Mars exploration, Near Earth Objecs searches, extralsolar planets, and others.  The stuff on our website is a little thin right now because we just completed our redesign and have only filled out the barest skeleton of necessary content.  I know that filling in more depth in the SETI section (as well as all the rest of the projects) is one of the priorities.  Here's the most recent update from our Director of Projects, Bruce Betts, about our SETI work, which was published in the September/October 2004 issue of The Planetary Report:

Thank you, Emily. I hope to receive a detailed reply soon from the SETI portion of TPS, especially on the Optical SETI project at Harvard. Three years with no substantial news, positive or negative, on the project is a bit surprising. The telescope being used is no department-store model, thus my wondering.

[elakdawalla]

Three years with no substantial news, positive or negative, on the project is a bit surprising.

Chalk it up to having only one full-time and two part-time people here who develop the entire Society website...so much to do, so little time. Seriously, we've heard you and will try to get more information up there... --Emily

[elakdawalla]

Perhaps what bothers you is not so much the phrases, or the possibility of them being detected by a web-searching anomalist, as their context?  --that is, the sense that a scientific forum such as this is degraded by the discussion of anything so "science fictional" as SETI?

I'm finding this conversation interesting because SETI is probably the one thing we do that gets our members most fired up -- both for and against. I'd say (based upon a completely unscientific survey of letters to the editor published in our magazine) that probably 10% of our members think that SETI is the most important activity we should be supporting, bar none, and 10% just as strongly feel that it is a monstrous waste of resources. I think the only other thing that gets people fired up in the same way is the question of human vs. robotic spaceflight -- again, some feel that there's no point to the space program at all unless its goal is to send humans out into the universe, while some feel that the point is science and that human spaceflight is a monstrous waste of resources. We -- not to mention the world's space agencies -- represent all these people with all these different opinions, and it's not always easy to walk a course among all the competing interests.

--Emily

[ElkGroveDan]

Chalk it up to having only one full-time and two part-time people here who develop the entire Society website...so much to do, so little time.   Seriously, we've heard you and will try to get more information up there... --Emily

Emily have you thought about an overt effort to recruit qualified staff volunteers? I know that Southern California is full of brilliant retired and semi-retired people with vast engineering and science backgrounds.

I recall that when the Rutans were building the Voyager aircraft I used to drive up to Mojave from the Valley to chat with them about it. There were several old retired engineers who were there as volunteers for the intellectual challenge alone. It was a thrill for me as an ME student at the time to meet these guys. I remember thinking what a vast pool of talent must be in So. Cal. alone just waiting to be tapped into.

[elakdawalla]

Emily have you thought about an overt effort to recruit qualified staff volunteers?  I know that Southern California is full of brilliant retired and semi-retired people with vast engineering and science backgrounds.

We have certainly done this in the past -- in fact you can look at all the articles written for The Planetary Report as experts volunteering their time and expertise to us (we don't pay for articles in TPR). And in fact I'm working right now with a guy who spent a bajillion years working in the various incarnations of JPL's image processing laboratory to develop some new stuff for the site. But expertise doesn't translate directly into good Web content. In fact, the more expert somebody is, the more work it usually takes to turn what they write into something that's suitable for our audience. I'm not talking about "dumbing down" content, which is what many scientists contemptuously (and contemptibly) call the process of writing for the public. But you do have to do some work to explain certain terms, and also to explain the significance and context of achievements, which may be obvious or go without saying to the expert but which are not so obvious to the layperson.

In addition to that, it takes a lot of work to punch up the writing, and allow it to reflect the human emotions that all of us on this forum feel in response to space exploration. It's funny because these people are really interesting to talk to, but when they sit down and write they often produce stuff that is both extremely informative and extremely dull. There are a few notable exceptions, like Steve Squyres, people who are capable of writing great stories that also contain great quantities of science. But most don't have his gift. I think it's because when you learn to write for scientific journals you learn to remove all emotion from your writing, because scientific research must be based on objective fact and devoid of emotion, which is by its nature subjective. Speaking for myself, it took at least two years after grad school before I was able to expunge that horrible, passive, dull writing style from my brain and begin to write stuff that I found interesting to read (nevermind anybody else). I still write long, convoluted sentences that my copy editor always has to hack into shorter, more active pieces. So experts are certainly helpful and they provide us with a lot of material but it still takes a lot of writing work to bring their material to publication in a way that our visitors will enjoy it and respond to it.

--Emily

[Guest_Richard Trigaux_*]

What you say about science writing is very true, emily.
With the only paper I have ever published (in economy) I had to expurge any emotion and most of philosophy/society implications (however there are much in economy). It is a bit sad, and on my site I rather presented the results in the form of a game, of novels, while summarizing up in some sentences, which are enough to explain it to the layperson.

In physics it is the same, and in space exploration there is also a high emotional content. I remember when I was a child, Mars was stil represented with the Schiaparelly maps (with the "channels") and Titan or Venus were just names, about which we knew exactly zero. Now we are getting out of our Earth craddle and exploring the wold!

Beyond the ordinary appearances such as a peaceful sun bathed afternoon among meadows and trees, there is this fantastic cosmos, baffling distances, incredible temperatures, other strange worlds, astounding time at the source of our lives, and we can abruptly feel the difference when suddenly the Sun hides behind the Moon (I whatched the 1998 eclipse). Then the day disappears as if a lamp was switched off, there are no more peaceful meadows but incredible masses of stone moving into the cosmos at unconceivable speeds, there is no more friendly sushine but a thermonuclear furnace which its red flames around the moon... And the guies who came with expensive telescopes and cameras just left them down, and gaze at this unforgettable view.

And then, as quickly as it came, it is over, the abyss door closes, the sky becomes blue again, the birds resume singing, only a chill remains of the strange vision.

Wow

[dvandorn]

I can also really relate to Emily's discussion of writing technique. My natural writing style is rather like Emily describes hers -- long sentences with conversational-tone punctuation. And sentence fragments. For effect.

At least, in my case, there is some sort of switch I can throw in my brain, and I can just start cutting the sentences down as I write them. And I can go through what I just wrote, give it a short once-over, et voila, short, action-verb sentences.

My first drafts are usuallly in final draft or next-to-final-draft shape. I just have this little problem with typos -- in specific, with hitting the space bar just a fraction of a millisecond early. One of the worst examples of this is when I write the short connecting phrase "to the"... it tends to come out "tot he."

Ever tried to use a spell checker to find something like that? When the words "tot" and "he" are both perfectly valid English words? Considering the subject matter I'm usually dealing with, though, I can just do a word search on "tot" and find every instance...

-the other Doug

[ljk4-1]

SETI@home killed off ?

Placed in sarcophagus rises again

http://www.theinquirer.net/?article=27885

By: Nick Farrell

Wednesday 23 November 2005, 07:18

DISTRIBUTED computing experiment SETI@home will be switched off on
December 15 as it becomes part of the Berkeley Open Infrastructure for
Network Computing (BOINC).

BOINC has been developed at UC Berkeley as a framework for volunteer
computing projects like SETI@home.

According to a press release, those who are currently using SETI@home are
being asked to visit here for instructions.

The workunit totals of users and teams will be frozen at that point, and
the final totals will be available on the web.

The BOINC site will allow boffins to build other volunteer computing
projects in areas like molecular biology, high-energy physics, and climate
change study.

A spokesSeti said that those who want to keep looking for aliens can do
so, but they will also be able to donate computer time studying climate
change or other BOINC projects.

[dvandorn]

Hmmm... upon reading this thread last week, I went ahead and started running SETI processing again. I've got a much better system now than I did back when I ran it a few years ago, and I figured it would be more useful now.

When I went out to the SETI@Home site to download the software again, I got the BOINC client. It's been running fine for me over the past week and a half or so.

So, a lot of people are already using the BOINC client, it would seem. It's sort of a nice name, too...

-the other Doug

[Guest_Richard Trigaux_*]

What does this means?

If I understand well, the work will continue, but in place of processing only SETI we will have to compute any other data from other experiments, without being given the choice.

Historically, as far as I know, what is now the BOINC was first developped for SETI, and after used by other experiments.

Is this just a technical/commercial move, or another tortuous mean to twart SETI? If someone has more precise info, please tell, at least to dissipate any doubt.

[jaredGalen]

What does this means?

If I understand well, the work will continue, but in place of processing only SETI we will have to compute any other data from other experiments, without being given the choice.

It's okay, , the whole process of distributed computing projects has been streamlined I guess you could say. The BOINC client now supports processing data from other projects, some of which are mentioned above.

A user simply picks which project they want to work on, or multiple projects and allocate processor time as they want. If you do 2 projects you can allocate time 80% to one and only 20% to the other if you want.

It's really quite good I think, makes everything much better rather than having a client for each number crunching application you want to join.

[Guest_Richard Trigaux_*]

It's okay, , the whole process of distributed computing projects has been streamlined I guess you could say. The BOINC client now supports processing data from other projects, some of which are mentioned above.

A user simply picks which project they want to work on, or multiple projects and allocate processor time as they want. If you do 2 projects you can allocate time 80% to one and only 20% to the other if you want.

It's really quite good I think, makes everything much better rather than having a client for each number crunching application you want to join.

So it's OK, not something bad for SETI. Anyway I heard that there are many other interesting experiments going on in other fields.
I was a bit alarmed, because there was in the past some unfair attempts to halt SETI. I hope this is really in the PAST now.

Alas I cannot join, my old computer is too slow for this. It took 1 month to process one SETI block... when they are considered lost after only some days and reprocessed elsewhere. (For reliability reasons they process several times the same blocks, but it is useless to send results months after)

[ljk4-1]

Scientists, be on guard ... ET might be a malicious hacker

The Guardian November 25, 2005

*************************

Richard Carrigan, a particle
physicist at the US Fermi National
Accelerator Laboratory, believes the
SETI@home project is putting Earth's
security at risk by distributing the
signals they receive to computers
all over the...

http://www.kurzweilai.net/email/newsRedire...sID=5064&m=7610

[Guest_Richard Trigaux_*]

Scientists, be on guard ... ET might be a malicious hacker

The Guardian November 25, 2005

*************************

Richard Carrigan, a particle
physicist at the US Fermi National
Accelerator Laboratory, believes the
SETI@home project is putting Earth's
security at risk by distributing the
signals they receive to computers
all over the...

http://www.kurzweilai.net/email/newsRedire...sID=5064&m=7610

There is at least one scientist who believes in extra-terrestrial intelligence!


Seriously, for an ET signal becoming an internet virus, need that the ETs know how our computers work. And anyway eventual ET signals (into the blocks the SETI@home program sends all over internet) are coded as analog signals, not available as digital codes. Even known internet viruses, coded this way, would be completelly inoffensive.

A more serious risk is that some intentionally modify many blocks. For this reason the SETI@home system sends every block to several computers, to detect any tempering of a block.

The only real risk is about an intelligible ET signal being spead over the internet. What would happen depends of "their" moral values or statement of intention. Many people will consider ETs as "superior" and thus accept their moral code as "better", whatever it is. (I am very affirmative, just look at what happens with the so-called "contactees"). If it is really better, it is a good thing. But if it is worse than ours... or only more subtle, many misinterpretations can occur.

After all, we tend to consider that ETs are more evolved, and thus better than us. But the only thing sure is that they avoided to destroy their planet with war and polution (a thing we are not yet sure to be able to do) so that they can last for long, and we have much better chances to encounter such a stable civilization than a civilization at the stage we are now.

[ljk4-1]

At least one SETI group is working under the assumption that ETI are using the Internet to understand humanity:

http://www.ieti.org/index.html

As anthropologists like to say, you learn a lot more about a culture by sifting through their junk than through their official records.

No wonder they haven't bothered to contact us.

[TheChemist]

At least one SETI group is working under the assumption that ETI are using the Internet to understand humanity

Darn, you blew my cover !!!
In order to prove my willingness to cooperate with the human race and avoid prosecution, here is a list of traitors that should be executed for high treason

[Guest_Richard Trigaux_*]

WE can seriously consider that, in the assumption some extra-terrestrial civilization is actually observing us, that they will try to connect to the Internet. After all, it is the best way to have a complete view of our anatomy that they will not find on TV

The most easy to observe from outer space are military radars and large power analog TV broadcasts. They could learn much about our technology level, and anamog TV is easy to decode into sounds and images. This could be done from 100 light years and more with the extra-terrestrial equivalent of the Arecibo telescope used for our SETI. But they will have to wait still some more tens of years for receiving us...

Receiving the internet signals is another story. These signals often travel by cables, and when they go in space, they are undecipherable and mixed altogether into packets, so what they could see only a randon mixture of millions of different pages, if even they manage to decode texts and simple gif images.

So to observe the Internet, an extra-terrestrial civilization would need to INTERACT with it: to receive and to SEND signals to it. For this, they will need a probe near Earth to achieve a connexion: the probe would have to simulate a cell-phone, Wi-Fi aparatus or something like that. This is possible only if the probe is near Earth, in order to reply in no more than some seconds: on a far orbit, on the Moon, at worse on the L1 Lagrange point. And it will have to use a narrow beam, and be itself radar-stealth and black. Or they may have somebody on Earth working for them...

Once on the Internet, they can observe all our pages (shame for many) and use Google for any search and study about our customs, languages or thinking. (It would be very easy to learn most languages using Google, I even use it as an orthography corrector)

Once I had in the stats of my UFO page "unknown origin"...

But it they do so, while keeping unoticed, they will simply have to connect using a free account with an ISP which do not check for identities: Yahoo, free.fr, etc... In this case, it will be very difficult to spot them. Only a large monitoring of the activity of all the accounts could allow to detect them.

So perhaps there is actually extraterrestrial agents studying this page...

But there are however so many large "if", that this idea is rather a scifi prospect than an actual concern.

[lyford]

Of course, they would need a compatible operating system... would ET be Mac or PC or
&$(#*$@nix or what?

http://www.billhusler.com/public/commercials/powerid4.mov

Not to mention the translation issues... just ask " It is quick the ?"

[Guest_Richard Trigaux_*]

Of course, they would need a compatible operating system... would ET be Mac or PC or
&$(#*$@nix or what?

http://www.billhusler.com/public/commercials/powerid4.mov

Not to mention the translation issues... just ask " It is quick the ?"

The strength of Internet since its very beginning is that it is OS-independent. They just need to get TCP-IP to make it work. So we could arrive one day to a galactic net with completelly mixed lists of links such as http:// for Earth, vegttp:// for vega, etc...

But we are not really yet here today, please wait still a while.


I do not tell you the download time if your page is located at the other end of the galaxy. With my opinion we need something faster than light.

[lyford]

Well, it started OS independent - but with all the bells and whistles that folks add on to make their pages look cool, things get complicated quickly - as even seen ON THIS VERY BOARD amongst this august company. And don't get me started on ActiveX.....

But your earlier point about proximity needed for "eavesdropping" is very salient. Based upon a sample set of one (our technological history), it would appear that the loud emission style broadcast age is short lived - we are switching to directed, cabled transmission and low powered wireless. Which would mean that you only get a "Honeymooners to Survivor" light bubble of about 50 years to catch someone before they get quiet in the spectrum again. I shudder to think that our species is being represented to the galactic neighborhood by Jack, Chrissy and Janet.

And forget about hearing anything from the REALLY advanced races out there....

[Guest_Richard Trigaux_*]

Well, it started OS independent - but with all the bells and whistles that folks add on to make their pages look cool, things get complicated quickly - as even seen ON THIS VERY BOARD amongst this august company.  And don't get me started on ActiveX.....

But your earlier point about proximity needed for "eavesdropping" is very salient.  Based upon a sample set of one (our technological history), it would appear that the loud emission style broadcast age is short lived - we are switching to directed, cabled transmission and low powered wireless.  Which would mean that you only get a "Honeymooners to Survivor" light bubble of about 50 years to catch someone before they get quiet in the spectrum again.   I shudder to think that our species is being represented to the galactic neighborhood by Jack, Chrissy and Janet. 

And forget about hearing anything from the REALLY advanced races out there....

Yes, it may happen that our powerful radio emissions will soon look like the steam locomotives age. We are certainly going toward a technology of discreete but all-pervasive broad spectrum radio network, very difficult to detect from abroad.

Just think that a recent radio coding system uses a fast random switching between many frequencies. And much more signals can mix that way into a given frequency range, than with the good old method -one frequency per signal-. But if you hear at such a frequency range, you get only a blank noise. Not to speak of the coding of fast digital signals, which very much looks like noise. So, in some tens of years, Earth will be noticeable only as a radio noise having an unusual spectrum (allocated radio bands, which are the result of conventions, not of physical processes).

And this still without accounting with completelly new technologies which would make radio useless for far transmissions. There are already teams in SETI who are working to detect laser pulses from near planets. And we can make prospective about using non-local quantum processes, which would work without the limitation of light speed (instantaneous like in the Aspect experiment) but which would be completelly unnoticeable for anybody else than the intended receiver. Not to speak about evolved civilizations which could go to a completelly spiritual state, without any technology.

Back to radio detection, rather than searching for spikes or discreete frequencies, SETI should try to find unusual radio spectrums in close stars (when it is possible to detect the emissions of an individual star). Eventually finding non-physically explainable rays in the spectrum of a star (or a whole galaxy) would indicate a smart radio network. The problem is that stars make much more radio noise than their civilizations (The magnetosphere of planets alone emits much more radio noise). But there are perhaps some "magical frequencies" allowing to get relevant spectrums. For instance a spectrum with regular spikes and gaps would indicate an intentionnal frequency allocation. All the more if these features exhibit doppler shifts in relation with the movement of a planet... But aren't radiotelescope sensitive enough to separate planets from their stars?


Back to Internet, it is really a pity that there are many interesting things we can do, but which work only with given OS... if not only one, you guess which. On my sites I already have to make a browser detection system in order to do simple things like a window size. So when we come to 3D worlds...

[lyford]

Richard, your points are all very good.

I am struck though by how contingent any search like this is upon our current state of technology - it wouldn't be so long ago that a SETI search would consist of looking for fires burning in geometrical patterns on the Moon or Mars....

It could be that Earth is being flooded with signals but in a technological medium that we can't even realize yet.

But it seems to even make the odds worse that we would be listening at the right time AND in the right way at the exact space/time coinciding with a species sending a message.

While I think it doesn't hurt to keep your ears, eyes, sensor platforms, etc, open, (and I do have SETI@home running on one of my boxes), now that I consider it I think I would rather donate my spare CPU cycles to a NEO hunt or something more practical if it existed.

[Guest_Richard Trigaux_*]

Richard, your points are all very good. 

I am struck though by how contingent any search like this is upon our current state of technology - it wouldn't be so long ago that a SETI search would consist of looking for fires burning in geometrical patterns on the Moon or Mars....

It could be that Earth is being flooded with signals but in a technological medium that we can't even realize yet.

But it seems to even make the odds worse that we would be listening at the right time AND in the right way at the exact space/time coinciding with a species sending a message.

While I think it doesn't hurt to keep your ears, eyes, sensor platforms, etc, open, (and I do have SETI@home running on one of my boxes), now that I consider it I think I would rather donate my spare CPU cycles to a NEO hunt or something more practical if it existed.  

There was not so long ago, there WAS proposals to burn fires in geometrical patterns, hoping to be seen by Moonians or Martians! Some will find this funny, I rather find this moving.

After some time of prospective reflection about future civilizations, the SETI search as it is done today may seem less useful. I say SEEMS. It may still be useful, if somewhere somebody uses large radio emissions for some purpose. But detecting the leakage of an Earth-like planet seems less probable for now.

But I still think their core job is very useful. What they do essentially? They develop techniques to extract relevant signals from noise, all along the processing chain: receivers, amplifiers, signal processing, analysis algorythms, search strategy... They are gathering an unequaled expertise in this domain. (Just like Google developed an inequaled expertise into finding content, which makes them leaders in this business for many years ahead). So, if in some years there is some technological breaktrough, new frequency range or more accurate suspicions at certain stars, their expertise will be indispensible. And it could make the difference.

My SETI suggestion right now would be to make a database of tiny unexplained features in star spectrum, in any electromagnetic range. Analysis of these could lead to select spectrums which could result of a frequency allocation.

Note also that the search for narrow spectrum spikes seems less useful now: broadband emission necessarily has a broadband frequency range, undiscernable from noise. Only the overal frequency distribution could hint at a frequency allocation, or at a source movement different of that of the star (in orbit around it). At least, this could perhaps be the best mean to detect Earth-like planets, as anyway planet emission are much stronger than civ emissions.

[ljk4-1]

SETI and Intelligent Design

http://www.space.com/searchforlife/seti_in...ign_051201.html

Many readers don't know that SETI research has been offered up in support of
Intelligent Design. Let's take a minute to fix this, shall we?

[Rakhir]

I think I would rather donate my spare CPU cycles to a NEO hunt or something more practical if it existed. 

More practical projects do exist.
http://boinc.berkeley.edu/

[Guest_Richard Trigaux_*]

SETI and Intelligent Design

http://www.space.com/searchforlife/seti_in...ign_051201.html

Many readers don't know that SETI research has been offered up in support of
Intelligent Design. Let's take a minute to fix this, shall we?

Yeah I take SEVERAL minutes to fix this.



First of all it is to be said that it is the ID (Intelligent Design) supporters who try to involve SETI as a support for their claim. SETI scientists themselves are not "guilty".

There is already a thread about ID here in this forum. On a science point of view, ID, the idea that the universe and living beings were designed by a god, is only a speculation, supported by faint evidences (such as anthropism) and counterbalanced by large evidences (the evolution of life). People should be free to do such speculation, but so long as they do not present them as "scientific facts". The problem is that ID is rather a large manipulation by "religious" integrists who try to take over a "scientific" speech to try to justify their "religious" dogmas. For this they raised a large reaction against them. Sane reaction, so long as it does not forbid in turn to make real science about an eventual divine origin of the universe.

As the article in the link explains, what SETI searches is evidences of intentionnal signals, or discriminating artificial signals from natural ones. There are some difficulties in doing so, but it is perfectly feasible. And this purpose is basically different if the manipulations of the ID proponents.


But if you look in depth, what the ID proponents say, like here http://www.spacedaily.com/news/life-01o.html is that there is NO extraterrestrial life NOWHERE, still for nut dogmatic "religious" reasons, the same they burned Giordano Bruno for.

So they do not lack some cheek, to be AGAINST the very purpose of SETI, while still USING SETI to back their views!! So it is clearly an attack against SETI, by confusing it with kook theories in the public's mind!

That SETI was impeded by rationalistist opponents to extraterestrial life, we are now accustomed to this. But that it is attacked by folks who claim to be spiritual, it is completelly weird.

[ljk4-1]

Paper: astro-ph/0512013

Date: Thu, 1 Dec 2005 03:28:14 GMT (229kb)

Title: Biological Effects of Gamma-Ray Bursts: Critical distances for severe
damage on the biota

Authors: Douglas Galante, Jorge Ernesto Horvath

Comments: 27 pages, 3 figure, submitted to Astrobiology
\\
We present in this work a unified, quantitative synthesis of analytical and
numerical calculations of the effects caused on an Earth-like planet by a
Gamma-Ray Burst (GRB), considering atmospheric and biological implications. The
main effects of the illumination by a GRB are classified in four distinct ones
and analyzed separately, namely the direct gamma radiation transmission, UV
flash, ozone layer depletion and cosmic rays. The effectiveness of each of
these effects is compared and lethal distances for significant biological
damage are given for each one.

We find that the first three effects have potential to cause global environmental changes and biospheric damages, even if the source is located at great distances (perhaps up to ~ 100 kpc). Instead, cosmic rays would only be a serious threat for very close sources. As a concrete example of a recorded similar event, the effects of the giant flare from SGR1806-20 of Dec 27, 2004 could cause on the biosphere are addressed.

In spite of not belonging to the so-called 'classical' GRBs, most of the
parameters of this recent flare are well-known and serve as a calibration for
our study. We find that giant flares are not a threat for life in all practical
situations on Earth, mainly because it is not as energetic, in spite of being
much more frequent than GRBs.

\\ ( http://arXiv.org/abs/astro-ph/0512013 , 229kb)

[Guest_Richard Trigaux_*]

This is interesting info. With this kind of data we can assess the probability of successfully completing the long duration evolutionary steps necessary to the appearance of life, multicellular life, and civilization.

Unfortunately if only one gamma ray burst is able to sterilize a whole galaxy, that makes this probability very weak. But they speak of environment change, not of complete disappearance (anyway only one side of a planet is directly illuminated). So there could be rather mass extinctions, or strong evolutionary pressure. The most critical period being between getting out of water and the appearance of civilization, which on Earth was fast, only 300 million years.
Anyway zone of intense stellar formation (propicious to gamma ray bursts) are the worse place for life. At the extreme only giant galaxies like Virgo (with only old stars) could shelter many civilizations, and we would be lucky or among the firsts in our galaxy, even if life started on many planets.

In a general way gamma ray bursts were more common in the past, and it may happen that only now life is beginning to flourish.

That giant flares are relatively harmless in on the other hand rather a good new, as many stars propitious to life are flare-prone. But is this study speaking of the effect of the flare on neighbouring systems, or on a planet of the star which is emitting a flare? If a flare is as luminous as the star itself, and lasts several days, it will heat a planet twice as usual!

[chris]

Unfortunately if only one gamma ray burst is able to sterilize a whole galaxy, that makes this probability very weak.

Richard,

Current theories suggest that GRB's can't sterilize an entire galaxy, as the radiation is emitted in two very narrow jets (See
Cosmological Gamma-Ray Bursts and Hypernovae Conclusively Linked). If you happen to be to get in the way of a beam, its bad news, but you have to be quite unlucky.

On a related note, I vaguely remember that the original extraordinary estimates for the energy output of quasars can be made much more reasonable by assuming that we are seeing down a beam (although longer lived and from an active galactic nucleus rather than a transitory event like GRB).

Chris

[Guest_Richard Trigaux_*]

Richard,

Current theories suggest that GRB's can't sterilize an entire galaxy, as the radiation is emitted in two very narrow jets

Chris

Not sure, still under discution. But this raises the probable number of civilizations by something like 1000!

In fact the beam feature changes nothing: it means that, the narrower the beam, for one beam we see, the more numerous we don't see. So the overal probability to have a planet killed by an hypernova or GRB does not depends on the radiation being focused or not!!

Again the probable number of civs is diminushed by 1000...

[ljk4-1]

Paper: astro-ph/0512053

Date: Fri, 2 Dec 2005 02:47:13 GMT (391kb)

Title: Atmospheric Biomarkers and their Evolution over Geological Timescales

Authors: L. Kaltenegger, K. Jucks, W.Traub

Comments: for high resolution images see

http://cfa-www.harvard.edu/~lkaltenegger

Journal-ref: CUP, IAUC 200 proceedings, 2005
\\
The search for life on extrasolar planets is based on the assumption that one
can screen extrasolar planets for habitability spectroscopically. The first
space born instruments able to detect as well as characterize extrasolar
planets, Darwin and terrestrial planet finder (TPF-I and TPF-C) are scheduled
to launch before the end of the next decade. The composition of the planetary
surface, atmosphere, and its temperature-pressure profile influence a
detectable spectroscopic signal considerably.

For future space-based missions it will be crucial to know this influence to interpret the observed signals and detect signatures of life in remotely observed atmospheres.

We give an overview of biomarkers in the visible and IR range, corresponding to the TPF-C and TPF-I/DARWIN concepts, respectively. We also give an overview of the evolution of biomarkers over time and its implication for the search for life on
extrasolar Earth-like planets. We show that atmospheric features on Earth can
provide clues of biological activities for at least 2 billion years.

\\ ( http://arXiv.org/abs/astro-ph/0512053 , 391kb)

[Guest_Richard Trigaux_*]

Paper: astro-ph/0512053

Date: Fri, 2 Dec 2005 02:47:13 GMT   (391kb)

Title: Atmospheric Biomarkers and their Evolution over Geological Timescales

Authors: L. Kaltenegger, K. Jucks, W.Traub

Comments: for high resolution images see

  http://cfa-www.harvard.edu/~lkaltenegger

Journal-ref: CUP, IAUC 200 proceedings, 2005
\\
......

\\ ( http://arXiv.org/abs/astro-ph/0512053 ,  391kb)

This work will be interesting, as it would provide us with some points in the Drake equation, at earlier stage than SETI can do. I recall that, after known theories, life should be common of planets (and planets common around stars) but this is still largely hypothetic: in fact we do not know.

These experiments will be able to detect planets at different stages: -massive microbian life (like Earth two billion years ago) -photosynthesis -evolved life (plants, and possibly animals and civilizations). This will provide us no less than three evolutionary points, on perhaps hundreds of planets.

If the results show that many planets are in the stage of microbian life, but few or not in the stage of evolved life, it will be that something hinders this transition. Perhaps Gamma ray bursts?

If the results show few or no planets with at least a microbian life, we shall have to envision a scarcely inhabited cosmos.

The two previous cases also lead us to few or no civilization, explaining that we never had any visit (even from agressive/colonizing/predatory civilizations).

In the case where the results show many planets with evolved life, we will able to conclude that many civilizations appear in our galaxy, but still from the absence of past visit, we shall have to conclude that these civilizations cannot last long, either they they self-destroy with war or pollution, or they have a different evolution than just increasing technology level and develop space faring technologies (if the later are possible, but it will be anyway possible to send interstellar probes and messages).

The view of civilizations self-destroying with war or pollution is not fully satisfying. For instance mankind can disappear from nuclear wastes, but nuclear wastes last "only" 10 million years, a glimpse in Earth history, which would allow many other attempts of appearance of a more clever civilization. Triggering an exponential increase of greenhouse effect, like we are doing today, is a much more serious threat: temperature rising at 80°C in some years would definitively remove any possibility of re-appearance of evolved life.

[Guest_Richard Trigaux_*]

Another interesting use of these (future) result will be to plot the number of planets according to the age of the star. Such a plot will allow to assess the mean duration of the longest evolutionary steps, such as oxydization of reductive materials (oxygen can appear only after this stage, which lasted more than 2 billion years on Earth) and the appearance of multicellular life (which took 3 to 4 billion years on Earth). If we were very lucky and these steps take usually more time, ther will be few civs around. If we were mean (or unlucky) there would be civs on every suitable planets. (On Earth the passage from plant covering, refered as the "red edge" in the article, occured only 0.44 billion years ago, so we can expect it is usually much shorter than the two previous).

Eventually this plot could allow to detect the past effects of a gamma ray burst, if only planets under a given age have life.

[ljk4-1]

Review: Life as We Do Not Know It
---
The nascent field of astrobiology faces a number of challenges,
including just how alien life on other worlds might be. Jeff Foust
reviews a book by a leading astrobiologist that tackles the nature of
life and its prospects elsewhere in the solar system.

http://www.thespacereview.com/article/516/1

[ljk4-1]

The Call That Is Important To Us All

Leigh Dayton

Science Writer

Earthlings haven't yet heard from ET, but leading questers for cosmic company are getting ready to take the call... just in case.

They've established an international committee to set the etiquette for inter-galactic contact. And Sydney-based cosmologist Paul Davies just took on the top job.

"We need to get the protocol correct and clarified," noted Professor Davies, with Macquarie University's Australian Centre for Astrobiology.

"If ET called tonight we'd be in a bit of a muddle about it all," he added, speaking prior to his first meeting as head of the Post-Detection Science and Technology Taskgroup.

The body is part of the International Academy of Astronautics and was founded by radio-astronomer Jill Tarter of the Search for Extraterrestrial Intelligence (SETI) Institute in California.

"We want the correct details about the discovery event and any interpretation made about it to get out there," commented Dr Tarter, in Australia for a lecture tour supported by Sydney University's Centre for Human Aspects of Science and Technology.

According to Dr Tarter - whose SETI exploits were portrayed by Jodie Foster in the 1997 film Contact - if a signal from ET is detected it must be verified quickly and the news spread widely to ensure it's not "co-opted" by interest groups or politicians.

"Another caveat is that (scientists) will not transmit a reply until there's a global consensus about whether to reply and what should be said," Dr Tarter claimed.

The rest is here:

http://www.theaustralian.news.com.au/commo...5E29098,00.html

[Guest_Richard Trigaux_*]

Review: Life as We Do Not Know It
---
The nascent field of astrobiology faces a number of challenges,
including just how alien life on other worlds might be. Jeff Foust
reviews a book by a leading astrobiologist that tackles the nature of
life and its prospects elsewhere in the solar system.

http://www.thespacereview.com/article/516/1

Interesting article.

Microbial life may appear quickly and thus be very common. But if it alway takes several billion years to develop intelligent life, and if it can be destroyed in much less time by events like star encounters, hypernovas and the like (see this thread "Near-future Extinction Event ?") this can explain that intelligent life could be rare in space (no past visit of Earth, no alien probe found orbiting in our system, no powerful radio beacons found by SETI) and thus solve the "dark sky" paradox in the beginning of this thread.

However as what other intelligent beings may be mandatorily very different of us (at least much different than TV series budget allows) is an extrapolation. There are somme mandatory common points. See:

-On Earth, only bilaterals primitive beings (with a right-left symmetry) were able to evolve toward intelligence. This does not rule out octupus-shaped intelligent beings, but makes bilaterals more probable.

-Any being will need to eat and evacuate residues, and so will have a variety of suitable orifices, the one for eating being necessary prominent and in relation with sensory organs and manipulating organs: a head. Even a fish head, but a head.

-any specie will need some kind of inter-member collaboration, and thus the members will have to communicate in a way and another (language), be able to be altruistic (or at least to do some kind of trade). So love and altruism are very likely to appear, except in very ant-like societies.

-The basic needs of all the species are the same: to gather food and resources, to shelter, to protect against hazards.

-All the species will require a genetic information coding.

-If a specie develops technology, it can nothing but develop the same than ours: stone walls, metals, steam engine, electricity, computers... They cars will not have the same shape or colours, but they will mandatorily have an aerodinamic shape, windshields of some kind, front lights (even if they use a sonar), four wheels, seats, doors, brakes, etc.

All this does not made mandatory that they are human-shaped and english speaking (sorry but for me this feature is very alien ) but it may happen that the variety of cultures and society organizations in space is not so much larger than on Earth.

[ljk4-1]

Paper (*cross-listing*): physics/0512062

Date: Wed, 7 Dec 2005 19:40:50 GMT (20kb)

Date (revised v2): Fri, 9 Dec 2005 17:55:41 GMT (20kb)

Title: A Solution to the Fermi Paradox: The Solar System, part of a Galactic
Hypercivilization?

Authors: Beatriz Gato-Rivera

Comments: Conference for general public given in the World Mystery Forum 2005,
Interlaken (Switzerland), November 2005. Latex, 16 pages. Footnote 8 added

Subj-class: Popular Physics
\\
I introduce the Fermi Paradox and some of its solutions. Then I present my
own solution which includes two proposals called the Subanthropic Principle and
the Undetectability Conjecture. After discussing some consequences of this
solution, I make some comments about brane world scenarios and their potential
to strengthen the Fermi Paradox. Finally, in the appendix I have included some
questions and answers that came up during this Forum.

\\ ( http://arXiv.org/abs/physics/0512062 , 20kb)

[Guest_Richard Trigaux_*]

Paper (*cross-listing*): physics/0512062

Date: Wed, 7 Dec 2005 19:40:50 GMT   (20kb)

Date (revised v2): Fri, 9 Dec 2005 17:55:41 GMT   (20kb)

Title: A Solution to the Fermi Paradox: The Solar System, part of a Galactic
  Hypercivilization?...

The Fermi paradox (what I call the black sky paradox) is that: "if civilizations are so numerous, why did we never received any visit?" The article reviews the different hypothesis (impossible space travel, difference of evolution level, space zoo, etc) trying to explain such a paradox.

We saw in the previous posts of this thread, that rare but very dangerous events (mainly gamma ray bursts) could occur several times in the time duration required to develop an intelligent civilization from microbial life. If this is true, we are very lucky to not having such event here since 4 billion years. If so, there would be many many planets with microbian life, but few with civilizations. But this is still not sure.

The article explains that Fermi stated this paradox in 1950, at a time where there was many UFO viewings and the idea as what UFOs would be spaceships was very new and with a strong support. Seing so many visits was obviously encouraging to think that there was many civilizations around practicizing space travel very easily so that we received many visits. The Fermi paradox could be thus summarized "Why do they don't conttact us??". Alas today any attempt to interact with the UFO phenomenon proved fruitless and deceiving, a gathering of weirder and weirder stories, so that more and more ufologists shifted to more bizare hypothesis, not alien spaceships. (Of course I mean by "ufologists" people trying to rationally study the phenomenon, not the so numerous kooks we hear today). So exit the numerous UFO visits from many friendly alien visitors.


However I still not agree that interstellar voyages are impossible. They are perfectly possible, even if much slower that in Starwars. Even today we could make interstellar probes, slow and unable to come back, but still able to reach close stars and get in orbit around. With a bit more technology, seed ships and self-reproducing factories allow for a slow colonization of the whole galaxy, in a matter of some tens of million years. Clearly, if a civilization emerged only one hundred million years before us, we should see traces of its past visits, and even eventually large traces such as huge sculptures on the Moon, visible with the naked eye.

But nothing such was found until today: civilizations are rare, either
-they do not appear, due to cosmic hazard or other difficulties
-they self-destroy,
-they quickly evolve in another state than our material state, so that they disappear from our universe. I develop this vision in two novels here

[ljk4-1]

National Geographic Channel - Monday, December 12, 2005:

WORLD PREMIERE - Naked Science: "Close Encounters" at 9P et/pt

Has planet Earth ever had close encounters with aliens? How did they
get here? Did any survive? Join us for a provocative look at whether
we've ever hosted visitors from outer space.

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This groundbreaking show creates two worlds that scientists believe
could exist in our own Milky Way galaxy - putting evolution in
motion to investigate what life-forms could survive there.

Is it Real?: "UFOs" at 8P et/pt

Numerous people believe they have spotted glowing alien spacecraft
hovering over Earth - and some even claim to have been abducted by
them. Scientists and astronomers dissect video footage and anecdotal
evidence as we consider the case for the existence of flying saucers
and UFOs.

Watch a preview.

http://ng.chtah.com/a/tBDnbqvASJ4TXAa$...R.ASJ-ROmH/ngs4

[David]

Interesting article.

-On Earth, only bilaterals primitive beings (with a right-left symmetry) were able to evolve toward intelligence. This does not rule out octupus-shaped intelligent beings, but makes bilaterals more probable.

Octopodes and other molluscs are just as bilateral as the rest of us; they do have tentacles arranged in a ring, but they have one eye to a side (and other, more basic structures that are definitely bilateral).

The fact that humans and every other plausible Terrestrial candidate for sentience, let alone intelligence, is bilaterally symmetric, is just a reflection of the extraordinary success of bilaterian fauna (which is a monophyletic clade by the way) in exploiting almost all niches for mobile macroscopic organisms. As the only non-bilaterian metazoans are things like sponges, jellyfish, corals, comb-jellies, hydras, sea anemones, cubozoans and other marine fauna, the result is that macroscopic land fauna are (to the best of my knowledge) 100% bilaterian. And while one can imagine intelligent sea life evolving, it's hard to imagine sea-creatures also having a body-shape that would be conducive to tool use and other desiderata of civilization.

[David]

Ward is famous—or perhaps infamous—for the 2000 book Rare Earth, where he and UW colleague Donald Brownlee argued that while simple microbial life might be commonplace in the universe, complex life (including intelligent life) would be highly uncommon. This conclusion raised the ire of many supporters of the search for extraterrestrial intelligence (SETI), which Ward says, “like the science fiction industry, depends on a belief in aliens for its economic viability.”

This seems like an incorrect assessment. I do not know what the various SETI searches require for "economic viability" but it seems to me that the people who are willing to support it are not people who believe religiously in the existence of aliens, but rather people who maybe hope that there might be alien intelligences, or who doubt that there are alien intelligences but are open to allowing the hypothesis to be tested.

As for science fiction, you can of course have a prolific fandom for things that nobody (or very few) people believe actually exist, like elves and hobbits. I think science fiction is mostly written and read by people who are not convinced that aliens exist, but find the concept of "the alien" to be a useful one in writing about lots of things that have very little to do with possibly real ETIs. The discovery of a real ETI would be a disaster for science fiction because there would suddenly be this stark contrast between the fictional foreshadowings and the real thing; SF writers wouldn't really be able to write about aliens any more.

The people I've talked to who really do believe in aliens wouldn't support SETI, because why bother searching for something you know exists? Nor are they terribly well versed in science fiction, or they would recognize a lot of their beliefs as poorly-made spinoffs of old pulp classics. The enthusiasts who have met aliens, conversed with aliens, and run alien contact societies are just not that interesting after the first fifteen minutes if you have read that sort of story before, and seen it better done.

[tty]

Not sure, still under discution. But this raises the probable number of civilizations by something like 1000!

In fact the beam feature changes nothing: it means that, the narrower the beam,  for one beam we see, the more numerous we don't see. So the overal probability to have a planet killed by an hypernova or GRB does not depends on the radiation being focused or not!!

Again the probable number of civs is diminushed by 1000...

Actually I don't see how a GRB could ever sterilize even a single planet since it only lasts a very short time, and can therefore never hit more than one side of a planet.

Even a supernova that lasts longer can only affect a whole planet if it is exactly in the equatorial plane, otherwise part of one hemisphere would always be shielded.

Even in this "worst case scenario" the planet would not be completely sterilized. Organisms living in deep water, caves or burrows would survive, as would organisms and seeds at some depth in soil, under rocks etc.
As a matter of fact the effect would probably be rather similar to the Chicxulub impact at the end of the Cretaceous, when the primary killing mechanism was probably intense IR radiation from re-entering debris (strong enough to cause world-wide fires and probably kill all animals that couldn't take cover).

The Gamma/UV radiation from a GRB or supernova would admittedly penetrate better but on the other hand it would usually be less world-wide. The secondary effects (NOx production, temporary destruction of the ozone layer, wildfires, erosion etc) would probably also be similar to but milder than the after-effects of Chicxulub.

I've tried to find a mass extinction that would fit with this scenario, but I can't think of one. As a matter of fact a "hemispheric extinction" by a GRB would probably be difficult to detect in the fossil record unless it happened fairly recently (in geological terms that is).

tty

[Guest_Richard Trigaux_*]

Octopodes and other molluscs are just as bilateral as the rest of us; they do have tentacles arranged in a ring, but they have one eye to a side (and other, more basic structures that are definitely bilateral).
 
  The fact that humans and every other plausible Terrestrial candidate for sentience, let alone intelligence, is bilaterally symmetric, is just a reflection of the extraordinary success of bilaterian fauna (which is a monophyletic clade by the way) in exploiting almost all niches for mobile macroscopic organisms.  As the only non-bilaterian metazoans are things like sponges, jellyfish, corals, comb-jellies, hydras, sea anemones, cubozoans and other marine fauna, the result is that macroscopic land fauna are (to the best of my knowledge) 100% bilaterian.  And while one can imagine intelligent sea life evolving, it's hard to imagine sea-creatures also having a body-shape that would be conducive to tool use and other desiderata of civilization.

Yes octopodes are bilaterals too, pardon my mistake. I was rather thinking to star fishes. But the fact is that only bilaterals could evolve into complex organisms, perhaps because they were alone to grow appendages such as fins of legs. But this does not make sure that bilaterals are the only solution. Perhaps this step of the evolution is difficult, and thus long. But once taken it eliminates any other possibility.

On the other hand, emerging from water seems easier, as it happened many times: fishes to reptilians, worms, molluscs, crustaceans to insects.

About evolved sea creatures, we unmistakenly think to dolphins. But dolphins are not true sea creatures, they have a hot blood and bthey breath air. A fish has a much lower temperature and oxygen content, so its brain cannot function continuously like the one of a dolphin.

Certainly dolphin are very unlikely to develop appendages like hands, and anyway they non't need them, as they are perfectly fit with their environment. (food everywhere, no need for shelter...) But they developped a complex social life (still undeciphered today, but implying mass "discutions" around a new object or hazard). So we can expect that such being may develop a civilizatio in the true sense of this word, but only into the cultural/artistic/spiritual domains. It is what I would call "animal civiliations". Obviously such civilizations are not discernible into the radio band!!! If they are the most numerous...

[Guest_Richard Trigaux_*]

Actually I don't see how a GRB could ever sterilize even a single planet since it only lasts a very short time, and can therefore never hit more than one side of a planet.

Even a supernova that lasts longer can only affect a whole planet if it is exactly in the equatorial plane, otherwise part of one hemisphere would always be shielded.

...

tty

The pessimistic statement "a gamma ray burst can sterilize a whole galaxy" comes from an articlequoted by ljk4-1 at the bottom of the page 4 of this thread. This source makes it something serious, but not a certainty. And in fact the article is not speaking of sterilizing planets, it is rather speaking of "severe dammages".

What I think is that, if we want to calculate probabilities of finding a civilization, we must not just count planets like in the Drake equation, we must also account with time: the probability of successfully achieving the different steps of the evolution of life, accounting with all the hazard and catastrophe which may occur: star increase, orbit change, large impact, close supernova, far gamma ray burst, etc.
Note that "severe effect on the biota" does not means that the evolution is stopped, on the countrary such events may speed it up, as with the Chixculub impact which allowed the supremacy of mammals, hot blooded animals which were able to develop intelligent brains, when cold-blooded reptilians could not.

Not that the maximum effect of the Chixculub impact was probably fires and soot, from many secondary impacts worldwide: the chixculub layer is everywhere around the Earth.

[Guest_Richard Trigaux_*]

The Call That Is Important To Us All

Leigh Dayton

Science Writer

Earthlings haven't yet heard from ET, but leading questers for cosmic company are getting ready to take the call... just in case.

They've established an international committee to set the etiquette for inter-galactic contact. And Sydney-based cosmologist Paul Davies just took on the top job.

"We need to get the protocol correct and clarified," noted Professor Davies, with Macquarie University's Australian Centre for Astrobiology.

"If ET called tonight we'd be in a bit of a muddle about it all," he added, speaking prior to his first meeting as head of the Post-Detection Science and Technology Taskgroup.

The body is part of the International Academy of Astronautics and was founded by radio-astronomer Jill Tarter of the Search for Extraterrestrial Intelligence (SETI) Institute in California.

"We want the correct details about the discovery event and any interpretation made about it to get out there," commented Dr Tarter, in Australia for a lecture tour supported by Sydney University's Centre for Human Aspects of Science and Technology.

According to Dr Tarter - whose SETI exploits were portrayed by Jodie Foster in the 1997 film Contact - if a signal from ET is detected it must be verified quickly and the news spread widely to ensure it's not "co-opted" by interest groups or politicians.

"Another caveat is that (scientists) will not transmit a reply until there's a global consensus about whether to reply and what should be said," Dr Tarter claimed.

The rest is here:

http://www.theaustralian.news.com.au/commo...5E29098,00.html

Interesting paper, ljk4-1.

The problem if "a signal is found" is twofold:
-avoid any mistake, and thus avoiding publishing before being sure
-avoid any censorship, and thus publishing as fast as possible.

This is contradictory, so it needs a special organization such as:
-contact many scientists under secrecy
-mobilize great science instruments in higher priority
-protect the evidences
-spread the information to the public by several different and numerous channels, especially internet sites in several countries

Hey hey SETI begins to look like a sci-fi story...

With my opinion, the first evidence of an extraterrestrial civ is very likely to be unintentionnal (from them). But if we find a probe orbiting around our sun...

The scenario in the "contact" movie is not realistic: if other civilizations reached a higher level, they are much more likely to have reached for long ago, not just in the same time than ours. So they are very likely to know our existence from very long too, not just discovering us when the first TV broadcast is send away. IF THERE ARE TECHNOLOGICAL EXTRATERRESTRIAL INTELLIGENCES, THEY KNOW OUR EXISTENCE. That they did not tried to actually contact us is a bit surprising. There is a wide range of very different explanations.

[tty]

Note that "severe effect on the biota" does not means that the evolution is stopped, on the countrary such events may speed it up, as with the Chixculub impact which allowed the supremacy of mammals, hot blooded animals which were able to develop intelligent brains, when cold-blooded reptilians could not.

That is a very simplified view. Mammals (synapsids may be a better word) are a very old group that was dominant before the dinosaurs and were outcompeted by them, persisting only in small-animal niches. The disappearance of the dinosaurs allowed them to diversify strongly, one of the results being us.
Also it is far from clear that dinosaurs were "cold-blooded", bird which are (highly derived) dinosaurs are rather more "hot-blooded" than mammals, and the difference between "cold-blooded" and "hot-blooded" animals was probably far from sharp back in the Cretaceous. As to whether dinosaurs could have become intelligen given another 65 million years of evolution, we will never know. Some late Cretaceous theropods had fairly large brains, and recent research suggest that the most intelligent birds (corvids and parrots) are about as smart as monkeys.
One thing is for sure. If that asteroid hadn't hit at Chicxulub 65 million years ago we wouldn't be here.

tty

[ljk4-1]

Interesting paper, ljk4-1.

The problem if "a signal is found" is twofold:
-avoid any mistake, and thus avoiding publishing before being sure
-avoid any censorship, and thus publishing as fast as possible.

This is contradictory, so it needs a special organization such as:
-contact many scientists under secrecy
-mobilize great science instruments in higher priority
-protect the evidences
-spread the information to the public by several different and numerous channels, especially internet sites in several countries

Hey hey SETI begins to look like a sci-fi story...

With my opinion, the first evidence of an extraterrestrial civ is very likely to be unintentionnal (from them). But if we find a probe orbiting around our sun...

The scenario in the "contact" movie is not realistic: if other civilizations reached a higher level, they are much more likely to have reached for long ago, not just in the same time than ours. So they are very likely to know our existence from very long too, not just discovering us when the first TV broadcast is send away. IF THERE ARE TECHNOLOGICAL EXTRATERRESTRIAL INTELLIGENCES, THEY KNOW OUR EXISTENCE.  That they did not tried to actually contact us is a bit surprising. There is a wide range of very different explanations.

The ETI in Contact were way ahead of us (see the novel especially). With 400 billion star systems to monitor, and we just started broadcasting about a century ago (in a galaxy that is at least 10 billion years old), it would not be that surprising if even an advanced ETI missed little old us.

I am also thinking of that first season episode of Star Trek: The Next Generation where an alien named the Traveler visits the Enterprise. When Riker asks why his kind never bothered to contact humans until now, his response was that we weren't interesting until then. I think there is a lot of truth to that statement. We might be of interest to an alien anthropologist, but what could we teach beings who can explore other stars with vessels?

And one more from Star Trek: The fourth film from 1986 had an ETI making contact with the most advanced species on Earth - and it wasn't us.

There is a series of images in the companion book and the film of Timothy Ferris' Life Beyond Earth that show the electromagnetic sphere surrounding our planet and spreading into the galaxy at the speed of light. As we move away from the sphere into deep space, it shows graphically how little we have really penetrated in this regard into the wider Universe.

http://www.pbs.org/lifebeyondearth/

So in addition to an advanced ETI probably having little reason to talk to or with us, we will not be obvious to most of the Milky Way for ages.

Of course you could argue that a species might examine every star with a reasonable chance of having planets with life, but since we now know that even red dwarfs might be friendly to life, that only adds to the time-consuming process.

But one thing I do agree with: If we detected an ETI signal now, humanity's reaction would be a muddled mess. But maybe it is just what we need.

[ljk4-1]

Paper: astro-ph/0512291

Date: Mon, 12 Dec 2005 19:19:49 GMT (74kb)

Title: Ultraviolet Radiation Constraints around the Circumstellar Habitable
Zones

Authors: Andrea P. Buccino, Guillermo A. Lemarchand, Pablo J. D. Mauas

Comments: 29 pages, 8 figures
\\
Ultraviolet radiation is known to inhibit photosynthesis, induce DNA
destruction and cause damage to a wide variety of proteins and lipids. In
particular, UV radiation between 200-300 nm becomes energetically very damaging to most of the terrestrial biological systems. On the other hand, UV radiation is usually considered one of the most important energy source on the primitive Earth for the synthesis of many biochemical compounds and, therefore, essential for several biogenesis processes. In this work, we use these properties of the UV radiation to define the bounderies of an ultraviolet habitable zone. We also analyze the evolution of the UV habitable zone during the main sequence stage of the star. We apply these criteria to study the UV habitable zone for those
extrasolar planetary systems that were observed by the International
Ultraviolet Explorer (IUE). We analyze the possibility that extrasolar planets
and moons could be suitable for life, according to the UV constrains presented
in this work and other accepted criteria of habitability (liquid water, orbital
stability, etc.).

\\ ( http://arXiv.org/abs/astro-ph/0512291 , 74kb)

------------------------------------------------------------------------------

\\
Paper: astro-ph/0512292

Date: Mon, 12 Dec 2005 14:46:55 GMT (56kb)

Title: Gas Flow Across Gaps in Protoplanetary Disks

Authors: Steve H. Lubow and Gennaro D'Angelo

Comments: 10 pages, 3 figures, 1 table. To appear in The Astrophysical Journal
\\
We analyze the gas accretion flow through a planet-produced gap in a
protoplanetary disk. We adopt the alpha disk model and ignore effects of
planetary migration. We develop a semi-analytic, one-dimensional model that
accounts for the effects of the planet as a mass sink and also carry out
two-dimensional hydrodynamical simulations of a planet embedded in a disk. The
predictions of the mass flow rate through the gap based on the semi-analytic
model generally agree with the hydrodynamical simulations at the 25% level.
Through these models, we are able to explore steady state disk structures and
over large spatial ranges. The presence of an accreting Jupiter-mass planet
significantly lowers the density of the disk within a region of several times
the planet's orbital radius. The mass flow rate across the gap (and onto the
central star) is typically 10% to 25% of the mass accretion rate outside the
orbit of the planet, for planet-to-star mass ratios that range from 5e-5 to
1e-3.

\\ ( http://arXiv.org/abs/astro-ph/0512292 , 56kb)

[Guest_Richard Trigaux_*]

Paper: astro-ph/0512291

Ultraviolet radiation is known to inhibit photosynthesis, induce DNA
destruction and cause damage to a wide variety of proteins and lipids. In
particular, UV radiation between 200-300 nm becomes energetically very damaging to most of the terrestrial biological systems. On the other hand, UV radiation is usually considered one of the most important energy source on the primitive Earth for the synthesis of many biochemical compounds and, therefore, essential for several biogenesis processes. In this work, we use these properties of the UV radiation to define the bounderies of an ultraviolet habitable zone. We also analyze the evolution of the UV habitable zone during the main sequence stage of the star. We apply these criteria to study the UV habitable zone for those
extrasolar planetary systems that were observed by the International
Ultraviolet Explorer (IUE). We analyze the possibility that extrasolar planets
and moons could be suitable for life, according to the UV constrains presented
in this work and other accepted criteria of habitability (liquid water, orbital
stability, etc.).

\\ ( http://arXiv.org/abs/astro-ph/0512291 , 74kb)

------------------------------------------------------------------------------

Ultraviolet plays two opposite roles, fostering and destroying life. Large stars are ultra-violet rich, small red dwarves are UV poor. So there is still many work ahead to be able to predict the probability of life versus the size of the star. Perhaps this can be done only by observation of planet spectrums.

Anyway an environment must receive UVs, but the energetic/reactive molecules produced by UVs must be able to gather into shelterd places. This implies a complex environment, with at least two mediums.

[edstrick]

One thing I have not seen much discussion of, at least in scientifically literate public reporting, is the interplay between atmosphere column mass and habitabality. A planet at Mars distance from the sun with (arm waving number) 2 atmospheres surface pressure would have a stronger greenhouse than Earth and be more temperate than a 1 atmosphere pressure global Alaska world.

A relatively high mass planet with a dense atmosphere could orbit F type star and have a fairly well shielded surface, though it might end up in a runaway greenhouse too soon as the star brightened on the main sequence.

At the other end of star masses, a high mass terrestrial planet with thick atmosphere, if one can accrete near a red dwarf, would be protected by the thermal inertia of it's atmosphere from flare-star activity, and have much better dayside --> nightside heat transfer than a 1 atmosphere mass planet (since it's presumably tidally despun)

While humans might not tolerate a planet with say 5 atmospheres of nitrogen (nitrogen narcosis is not recommended), the "locals" that might evolve would have no problem.

[Guest_Richard Trigaux_*]

One thing I have not seen much discussion of, at least in scientifically literate public reporting, is the interplay between atmosphere column mass and habitabality.  A planet at Mars distance from the sun with (arm waving number) 2 atmospheres surface pressure would have a stronger greenhouse than Earth and be more temperate than a 1 atmosphere pressure global Alaska world. 

A relatively high mass planet with a dense atmosphere could orbit F type star and have a fairly well shielded surface, though it might end up in a runaway greenhouse too soon as the star brightened on the main sequence.

At the other end of star masses, a high mass terrestrial planet with thick atmosphere, if one can accrete near a red dwarf, would be protected by the thermal inertia of it's atmosphere from flare-star activity, and have much better dayside --> nightside heat transfer than a 1 atmosphere mass planet (since it's presumably tidally despun)

While humans might not tolerate a planet with say 5 atmospheres of nitrogen (nitrogen narcosis is not recommended), the "locals" that might evolve would have no problem.

Yes this is the question of the "ecosphere" of a star, the zone where life-prone climate is possible. This zone can be much larger than just one orbit in a Titus Bode repartition: far planets may have a stronger greenhouse effect. And we can assume that, most of the stars (if not all) have planets in orbits in a more or less Titus-Bode way, so that we alway find several planets into the ecosphere.


We can even imagine Titan with just more gas: its temperature would allow for Earth-like conditions. The problem is that planets so far from their star don't have the massive solar energy input which, on Earth, allows for a large biosphere, many ecological niches and thus a faster evolution. Titan with an Earth temperature would have developped only primitive bacteria.

Still better, planets like Earth have a self-regulation of greenhouse effect. It is a complex system involving biological reaction, and also geoghemical reactions. In gross there is a constant source of carbon dioxid (volcanoes) which increases greenhouse effect, and chemical reactions (deposit of limestones, chemical or biological) which efficiency is strongly increasing with temperature, so that greenhouse effect decreases with temperature. (but too slowly to counterbalance industrial gasses). So that there is a regulation at the actual temperature (such effects are the basis of the "Gaïa" metabolism). This process will allow still much more worlds to have life-prone conditions at a variety of distance of their star.

Nitrogen pressure is not much of a problem, as local people will be accustomed to it from their very appearance. Look like andean and tibetan people adapted to rare oxygen in only some thousands years.

[ljk4-1]

Paper: astro-ph/0512221
Date: Thu, 8 Dec 2005 15:11:22 GMT (163kb)

Title: Abundance ratios of volatile vs. refractory elements in
planet-harbouring stars: hints of pollution?

Authors: A. Ecuvillon (1), G. Israelian (1), N. C. Santos (2,3), M. Mayor (3),
G. Gilli (1,4) ((1) IAC, Spain, (2) Observatorio Astronomico de Lisboa,
Portugal, (3) Observatoire de Geneve, Switzerland, (4) Dipartimento di
Astronomia, Universita di Padova, Italy)

Comments: 10 pages, 7 figures, accepted for publication in A&A. Figures with
higher resolution are available at www.iac.es/proyect/abuntest
\\
We present the [X/H] trends as function of the elemental condensation
temperature Tc in 88 planet host stars and in a volume-limited comparison
sample of 33 dwarfs without detected planetary companions. We gathered
homogeneous abundance results for many volatile and refractory elements
spanning a wide range of Tc, from a few dozens to several hundreds kelvin. We
investigate possible anomalous trends of planet hosts with respect to
comparison sample stars in order to detect evidence of possible pollution
events. No significant differences are found in the behaviour of stars with and
without planets. This result is in agreement with a ``primordial'' origin of
the metal excess in planet host stars. However, a subgroup of 5 planet host and
1 comparison sample stars stands out for having particularly high [X/H] vs. Tc
slopes.

\\ ( http://arXiv.org/abs/astro-ph/0512221 , 163kb)

------------------------------------------------------------------------------
\\
Paper: astro-ph/0512222
Date: Thu, 8 Dec 2005 15:16:52 GMT (42kb)

Title: Condensation temperature trends among stars with planets

Authors: Guillermo Gonzalez

Comments: 5 pages, 7 figures, MNRAS Letter in press
\\
Results from detailed spectroscopic analyses of stars hosting massive planets
are employed to search for trends between abundances and condensation
temperatures. The elements C, S, Na, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni and
Zn are included in the analysis of 64 stars with planets and 33 comparison
stars. No significant trends are evident in the data. This null result suggests
that accretion of rocky material onto the photospheres of stars with planets is
not the primary explanation for their high metallicities. However, the
differences between the solar photospheric and meteoritic abundances do display
a weak but significant trend with condensation temperature. This suggests that
the metallicity of the sun's envelope has been enriched relative to its
interior by about 0.07 dex.

\\ ( http://arXiv.org/abs/astro-ph/0512222 , 42kb)

[ljk4-1]

Paper: astro-ph/0412356

replaced with revised version Tue, 13 Dec 2005 00:49:09 GMT (226kb)

Title: How Dry is the Brown Dwarf Desert?: Quantifying the Relative Number of
Planets, Brown Dwarfs and Stellar Companions around Nearby Sun-like Stars

Authors: Daniel Grether (School of Physics, University of New South Wales) and
Charles H. Lineweaver (Planetary Science Institute, Research School of
Astronomy and Astrophysics & Research School of Earth Sciences, Australian
National University)

Comments: Conforms to version accepted by ApJ. 13 pages formatted with
emulateapj.cls

\\ ( http://arXiv.org/abs/astro-ph/0412356 , 226kb)


Paper: astro-ph/0512322
Date: Tue, 13 Dec 2005 13:03:32 GMT (71kb)

Title: Spectroscopic companions of very young brown dwarfs

Authors: Joergens Viki (Leiden Observatory)

Comments: Proceeding of ESO workshop 'Multiple Stars across the HRD' (Garching
2005). 6 pages, 4 figures
\\
I review here the results of the first RV survey for spectroscopic companions
to very young brown dwarfs (BDs) and (very) low-mass stars in the ChaI
star-forming cloud with UVES at the VLT. This survey studies the binary
fraction in an as yet unexplored domain not only in terms of primary masses
(substellar regime) and ages (a few Myr) but also in terms of companion masses
(sensitive down to planetary masses) and separations (< 1 AU). The UVES spectra
obtained so far hint at spectroscopic companions of a few Jupiter masses around
one BD and around one low-mass star (M4.5) with orbital periods of at least
several months. Furthermore, the data indicate a multiplicity fraction
consistent with field BDs and stellar binaries for periods < 100 days.

\\ ( http://arXiv.org/abs/astro-ph/0512322 , 71kb)

[David]

Yes octopodes are bilaterals too, pardon my mistake. I was rather thinking to star fishes.

Surprising as it may seem, starfishes are bilaterians too! Not only that, but the echinoderms are more closely related to vertebrates like us than to other bilaterians like molluscs and insects. Starfish larvae are recognizably bilaterally symmetric, but as they mature they acquire the pentaradial symmetry characteristic of echinoderms; the radial symmetry is a secondary development, not shared by the common bilaterian ancestor.

[Guest_Richard Trigaux_*]

Surprising as it may seem, starfishes are bilaterians too!  Not only that, but the echinoderms are more closely related to vertebrates like us than to other bilaterians like molluscs and insects.  Starfish larvae are recognizably bilaterally symmetric, but as they mature they acquire the pentaradial symmetry characteristic of echinoderms; the radial symmetry is a secondary development, not shared by the common bilaterian ancestor.

Ahem ahem

there must be some beings who are not bilateralians, at last?

[ljk4-1]

Paper: astro-ph/0512371

Date: Wed, 14 Dec 2005 18:29:41 GMT (49kb)

Title: Polycyclic Aromatic Hydrocarbons Orbiting HD 233517, an Evolved
Oxygen-Rich Red Giant

Authors: M. Jura (UCLA), J. Bohac, B. Sargent, W. J. Forrest, J. Green, D. M.
Watson (Rochester), G. C. Sloan (Cornell), F. Markwick-Kemper (Virginia), C.
H. Chen, J. Najita (NOAO)

Comments: 11 pages, 2 figures, ApJ Letters, in press
\\
We report spectra obtained with the Spitzer Space Telescope in the 5 to 35
micron range of HD 233517, an evolved K2 III giant with circumstellar dust. At
wavelengths longer than 13 microns, the flux is a smooth continuum that varies
approximately as frequency to the -5/3 power. For wavelengths shorter than 13
microns, although the star is oxygen-rich, PAH features produced by carbon-rich
species at 6.3 microns, 8.2 microns, 11.3 microns and 12.7 microns are detected
along with likely broad silicate emission near 20 microns. These results can be
explained if there is a passive, flared disk orbiting HD 233517. Our data
support the hypothesis that organic molecules in orbiting disks may be
synthesized in situ as well as being incorporated from the interstellar medium.

\\ ( http://arXiv.org/abs/astro-ph/0512371 , 49kb)

[ljk4-1]

Computer Security Expert Rejects Hacker Hypothesis

For Immediate Release

LITTLE FERRY, NJ.., 15 December 2005 -- A member of the grassroots, nonprofit SETI League has allayed fears expressed by some scientists, that malevolent signals from extraterrestrial civilizations could cripple Earth's computer networks. Responding to the so-called "SETI Hacker Hypothesis" articulated by particle physicist Richard A. Carrigan, Jr. of the Fermi National Laboratory, Canadian computer security expert Marcus Leech states "we test some of the elements of this hypothesis and find them to be unsupportable."

SETI science seeks evidence of advanced technological civilizations in space, primarily by monitoring electromagnetic emissions with optical and radio telescopes. Through the SETI@home experiment at the University of California, Berkeley, millions of personal computers worldwide have since 1999 been participating in distributed processing of data from one of those telescopes, the 305 meter dish in Arecibo, Puerto Rico. The SETI Hacker Hypothesis suggests that those computers could be at risk from malicious code deliberately sent Earthward by extraterrestrials. But in a recent paper available on The SETI League website at http://www.setileague.org/articles/hacker.pdf, Leech concludes that these fears are unfounded.

Carrigan's concerns were first voiced in a paper presented at a 2002 BioAstronomy conference, titled "The Ultimate Hacker: SETI signals may need to be decontaminated." Elements of that paper have recently resurfaced on the self-proclaimed nerd website SlashDot.org, been reported in the British newspaper The Guardian and elsewhere, and submitted to the prestigious scholarly journal Acta Astronautica. Carrigan states that "Biological contamination from space is a remote but recognized possibility. SETI signals might also contain harmful information." He argues for a decontamination process similar to that used when the first moon rocks were returned to Earth in 1969.

In response, Leech, formerly security area director for the Internet Engineering Task Force, makes the most generous assumptions possible in favor of the alleged ET hacker, and shows that such beings would be unable to trigger a buffer overflow, the known security flaw in computers most often exploited by terrestrial hackers. He allows that "while one cannot recommend a cavalier attitude with respect to software quality used by our SETI researchers, it's a near-certainty that computer viruses from outer space will not be one of the threats that need to be defended against."

"We conclude," states Leech, "with apologies to the film Independence Day, that SETI-hacker scenarios are only plausible within the fanciful confines of Hollywood, and then only when our ET hackers happen to be Macintosh ™ savvy."

Largely using radio telescopes and optical telescopes, SETI scientists seek to determine whether humankind is alone in the universe. Since Congress terminated NASA's SETI funding in 1993, The SETI League and other scientific groups have privatized the research. Amateur and professional scientists interested in participating in the search for intelligent alien life, and citizens wishing to help support it, should email join @ setileague.org, check the SETI League Web site at http://www.setileague.org/, send a fax to +1 (201) 641-1771, or contact The SETI League, Inc. membership hotline at +1 (800) TAU-SETI. Be sure to provide us with a postal address to which we will mail further information. The SETI League, Inc. is a membership-supported, non-profit [501©(3)], educational and scientific corporation dedicated to the scientific Search for Extra-Terrestrial Intelligence.

P.S. Tearsheets are always appreciated. Thank you.

-end-

--
H. Paul Shuch, Ph.D. Executive Director, The SETI League, Inc.
433 Liberty Street, PO Box 555, Little Ferry NJ 07643 USA
voice (201) 641-1770; fax (201) 641-1771; URL http://www.setileague.org
email work: n6tx@setileague.org; home: drseti@cal.berkeley.edu

[David]

Ahem ahem

there must be some beings who are not bilateralians, at last? 

That's just the problem -- bilaterians have been so successful that they haven't left much room for other animals!

Non-bilaterian metazoans include:

motile jellyfish of various kinds (scyphozoan, hydrozoan and cubozoan medusae, and siphonophore and chondrophorine colony animals), all of which are cnidarians, and comb jellies which are in a different clade, the Ctenophora;

sessile corals, sea anemones, sea pens, and hydroids (which look misleadingly like plants), all cnidarians; and sponges, which are in their own clade, the Porifera.

Then there are a bunch of microscopic animals, some of which form macroscopic colonies that look like sticky green goo.

That pretty much sums it up for metazoans; the next closest related group of macroscopic organisms are the fungi. I have some doubts -- small ones -- about the ability of fungi-like organisms to create a space-faring civilization, but I am willing to be convinced otherwise.

[Guest_Richard Trigaux_*]

That pretty much sums it up for metazoans; the next closest related group of macroscopic organisms are the fungi.    I have some doubts -- small ones -- about the ability of fungi-like organisms to create a space-faring civilization, but I am willing to be convinced otherwise. 

fungi? Yes they can. At a similar state of evolution, we were not better. Given equal chances, they may have evolved in intelligent beings.

Seriously, what, I think, gave the advantage to bilateralians is not the bilateral symmetry by itself, it is a set of innovations the other were deprived, such as nervous cells, or the coelome (sorry this is the latin name I don't know in english) or closed inner body cavity which allowed all the building of further evolution. The lombrics can move thank to coelomes (one per ring), and we still have three body cavities (or lombric-like rings) separated by muscles: chest, belly, and a smaller perinear cavity. Fungi seriously lack such structures, and corals have an open boby cavity for feeding (the opening serving ans both mouth and anus).

These body structures were first coded by a series of adjacent genes, called homeobox, each one coding for a body segment, and controling the growth of each segment. Further evolution complexified this scheme, but without altering the basic structure. It is the very unlikely appearance of such a complex structure which took many time and was the real breakthrough which allowed bilateralians to be the first. As such an event is rare, it does not happens often, only once in Earth history, and it is likely not to happen again, as the bilateralians now hamper any further evolution of the other clades.

beings like fungi are multicellular, but they don't have a homeobox-like system, and other system such as specialized cells. This allow them to grow rapidly, but with only simple structures.

Sime dates for Earth history:
-multicellular beings are traced from -600 millions years and likely existed 1 billion years ago
-bilateralians are known since 600 millions years only.

[ljk4-1]

Paper: astro-ph/0512445

Date: Fri, 16 Dec 2005 17:56:49 GMT (76kb)

Title: Planetary catastrophe risks cannot generally be inferred from the
Earth's formation date

Authors: Adrian Kent (Department of Applied Mathematics and Theoretical
Physics, University of Cambridge)

Comments: 2 pages
\\
Tegmark and Bostrom's provocative analysis of the chances of a "doomsday
catastrophe" [Nature 438, 754 (2005)] sets out an interesting idea, but
unfortunately contains a fundamental error which invalidates their conclusions.
The essential problem with their argument can be seen by considering the
assertion that "if [planet-destroying] catastrophes were very frequent, then
almost all intelligent civilisations would have arisen much earlier than ours".
This does not follow from Tegmark and Bostrom's assumptions.

\\ ( http://arXiv.org/abs/astro-ph/0512445 , 0kb)

[ljk4-1]

MONDAY, DECEMBER 19, 2005 - NGC

Naked Science: "Birth of the Earth" at 9P et/pt

How did Earth evolve to support such a diversity of living creatures,
including humans, requiring special living conditions to survive? An
imaginary "human" time traveler takes us on a journey back to the
moment our solar system was born.

Watch a preview.

http://ng.chtah.com/a/tBDpv6HASJ4TXAbRKOPA...R.ASJ-RO8d/ngs2


Naked Science: "Super Volcano" at 10P et/pt

A super volcano explosion is a million times stronger than the
atomic bombing of Hiroshima. Scientists have discovered an active
super volcano under Yellowstone National Park. What would happen
if it erupted? Could the United States survive?

[tty]

fungi? Yes they can. At a similar state of evolution, we were not better. Given equal chances, they may have evolved in intelligent beings.

Seriously, what, I think, gave the advantage to bilateralians is not the bilateral symmetry by itself, it is a set of innovations the other were deprived, such as nervous cells, or the coelome (sorry this is the latin name I don't know in english) or closed inner body cavity which allowed all the building of further evolution. The lombrics can move thank to coelomes (one per ring), and we still have three body cavities (or lombric-like rings) separated by muscles: chest, belly, and a smaller perinear cavity.  Fungi seriously lack such structures, and corals have an open boby cavity for feeding (the opening serving ans both mouth and anus).

These body structures were first coded by a series of adjacent genes, called homeobox, each one coding for a body segment, and controling the growth of each segment. Further evolution complexified this scheme, but without altering the basic structure. It is the very unlikely appearance of such a complex structure which took many time and was the real breakthrough which allowed bilateralians to be the first. As such an event is rare, it does not happens often, only once in Earth history, and it is likely not to happen again, as the bilateralians now hamper any further evolution of the other clades.

beings like fungi are multicellular, but they don't have a homeobox-like system, and other system such as specialized cells. This allow them to grow rapidly, but with only simple structures.

Sime dates for Earth history:
-multicellular beings are traced from -600 millions years and likely existed 1 billion years ago
-bilateralians are known since 600 millions years only.

Actually Hox genes are not specific to Bilateria since Cnidarians also have them, though only two each (homologous to the anterior and posterior Hox groups of e. g. arthropods). Sponges do lack Hox genes.

Multicellular organisms (algae) are known bact to at least 1200 mya (million years ago). Bilateria are known back to about 600 mya (earliest Edicaran faunas), but molecular data suggest they are at least 100 my older. This incidentally means that they originated at about the time of the extreme Neoproterozoic glaciations which may have turned Earth into a "snowball", or nearly so. The mass extinction these must have caused may have "made way" for new life-forms, including ultimately us.

tty

[Guest_Richard Trigaux_*]

Actually Hox genes are not specific to Bilateria since Cnidarians also have them, though only two each (homologous to the anterior and posterior Hox groups of e. g. arthropods). Sponges do lack Hox genes.

Multicellular organisms (algae) are known bact to at least 1200 mya (million years ago).  Bilateria are known back to about 600 mya (earliest Edicaran faunas), but molecular data suggest they are at least 100 my older.  This incidentally means that they originated at about the time of the extreme Neoproterozoic glaciations which may have turned Earth into a "snowball", or nearly so. The mass extinction these must have caused may have "made way" for new life-forms, including ultimately us.

tty

Thank you tty for your interesting precisions.

(For people not informed, I recall here the extreme climate changes which happened on Earth 600 million years ago. At that time, the continents were gathered along the equator, lefting place for two large polar oceans. This situation allowed a climate trick: large parts of this ocean were freezing in winter, and, as ice reflects most of sun heat, it cooled the climate. This process went increasing and increasing, until all the Earth was frozen, with ice all over the oceans and glaciers on the continents. Fortunatelly volcanoes were still emitting carbon dioxid, increasing greenhouse effect until the temperature increased enough to revert the icing process and melt all the ice. But at that time Earth had suddenly to sustain very high temperatures, 50°C or more, untill the self-regulation of temperature operated, bringing back Earth to a more ordinary temperature. This balance happened several times, making many oceanic form of life disappear. There was no life on the continents at this time.)

What I think is that it is the very evolution of the Hox sytem which produced all the clades, bilateralians, cnidarians, etc.
Bacteria have only genes which react to various chemical conditions to sustain the life of the bacteria. Primitive multicellular had system reacting to external chemical signals to trigger various sets of behaviour for the cell. This is enough for primitive multicellular, mushrooms, sponges, etc. which get their shapes from the grow process, like a mathematical rule can grow shapes in a fractal game.
But to have a real body structure needs 1)a kind of "map" of this structure, 2)coding various sets of behaviours from the cells, 3)a mean to specialize cells. These multiple conditions explain why about 500 million years were necessary to pass from simple masses of jelly to really organized bodies. But it was a necessary result of many simpler steps, the evidence is that plants evolved in a similar way and time, although in complete independence from animals.

The basic map was the Hox system, and we can say, I think, that it is the very process of appearance and setting of this Hox system which created all the clades.
Further steps gave the advantage to bilateralians, such as the coelome (closed inner body cavity) which allowed for real movement, not just swimming with a flagela like cnidarian larvae.

That all this happened into a period of extreme climate stress also tells us that such catastrophes (meteorite impacts, climate change) are an accelerator of evolution. A simple Darwinian view (as Darwin himself observed) implies slow processes which make two species of one specie separated in two populations. But more modern views suggest that there was many "punctuations", short periods of accelerated evolution, when a few number of individuals are constrained to find innovating solutions to an environment change. Humans themselves are the descendants of a very little groups of individuals, perhaps some hundreds, or even less.

Of course if such a global freezing occured today, 500 million years of evolution would be lost. Or there would be very few survivors, but what would be the result?

[Guest_Richard Trigaux_*]

Paper: astro-ph/0512445

Date: Fri, 16 Dec 2005 17:56:49 GMT  (76kb)

Title: Planetary catastrophe risks cannot generally be inferred from the
  Earth's formation date

Authors: Adrian Kent (Department of Applied Mathematics and Theoretical
  Physics, University of Cambridge)

Comments: 2 pages
\\
  Tegmark and Bostrom's provocative analysis of the chances of a "doomsday
catastrophe" [Nature 438, 754 (2005)] sets out an interesting idea, but
unfortunately contains a fundamental error which invalidates their conclusions.
The essential problem with their argument can be seen by considering the
assertion that "if [planet-destroying] catastrophes were very frequent, then
almost all intelligent civilisations would have arisen much earlier than ours".
This does not follow from Tegmark and Bostrom's assumptions.

\\ ( http://arXiv.org/abs/astro-ph/0512445 ,  0kb)

hmmm...
The effect of planetary catastrophes ending any life on a planed much depends on if this catastrophe occurs only on a planet (impact, climate, star death, gamma ray bursts sending beams...) of if a catastrophe can really end up life in all a galaxy (large gamma ray bursts spreading death all around them).

That a gamma ray bursts sterilized our own galaxy certainly not happened since at least the formation of our planet (otherwise we should not be here). But it could have happened just before. If so, we can expect to find only younger or equally old inhabited planets. In this model the probability of an inhabited planed decreases sharply with ages superiors to 4-5 billion years. If we were slow, there could be many civilizations. If we were faster, there could be few or not.

Other types of more local catastrophes imply that the probability to find an inhabited planet in a given system decreases with the age of the system, in a monotonous way. That too implies that this probability decreases with the achieved level of evolution. But in this case we are more likely to find an intermediate number of civilization.

As we can see, we are getting parts of the puzzle of the Drake equation, but we still lack far too many to be able to assess figures, even extreme (between billions of civilizations and only one). How to get out of this? With theoretical studies of the evolution of planetary systems and planet climate, and also, with observation, such as above, with the spectroscoping study of signature of evolved life on planets. SETI already bite into the error box, in detecting no large network of powerful civilizations.

[ljk4-1]

Partial Ingredients for DNA and Protein Found Around Star

NASA’s Spitzer Space Telescope has discovered some of life’s most basic ingredients in the dust swirling around a young star. The ingredients – gaseous precursors to DNA and protein – were detected in the star’s terrestrial planet zone, a region where rocky planets such as Earth are thought to be born.

The findings represent the first time that these gases, called acetylene and hydrogen cyanide, have been found in a terrestrial planet zone outside of our own.

"This infant system might look a lot like ours did billions of years ago, before life arose on Earth," said Fred Lahuis of Leiden Observatory in the Netherlands and the Dutch space research institute called SRON. Lahuis is lead author of a paper to be published in the Jan. 10 issue of the Astrophysical Journal Letters.

http://www.spitzer.caltech.edu/Media/relea...6/release.shtml

[deglr6328]

I think its JUST a bit of a stretch to say that partial ingredients for DNA and protein were found when really all they found was HCN and C2H2. Almost like saying "environment suitable for polar bear habitat found on Enceladus"! Interesting nonetheless though.

[Guest_Richard Trigaux_*]

I think its JUST a bit of a stretch to say that partial ingredients for DNA and protein were found when really all they found was HCN and C2H2. Almost like saying "environment suitable for polar bear habitat found on Enceladus"! Interesting nonetheless though.

I think that our actual DNA and proteins components are not necessarily the only solution for life; but they appeared as they appeared because they were created from available compounds, which themselves appeared from basic compounds like HCN and C2H2 because they were first available. But, of course, as you say, there are many steps between HCN and life, and the first does not necessarily implies the later, many other conditions are needed. But this observation is interesting, because it shows that the very first prerequisites for the appearance of life (accretion disk temperature and chemistry) are very common (if not mandatory) in solar systems, giving a very high value to the first term of the Drake equation.

[Guest_Richard Trigaux_*]

Back to the idea of gamma ray bursts (GRB) able to sterilize a whole galaxy.

First, even if GRBs are really dangerous, I have some doubts that they are really able to sterilize a whole galaxy.

Second, I note that GRBs occured in a distant past, perhaps at an epoch where the metallicity of stars was lower. As far as I know, the most recent GRBs are 3 billion years old, and the peak activity was 10 billions years ago. And they are not as numerous as we can think. (If we assume one detection per day, and 130 billion galaxies, that makes about 2.8 GRBs per billion years in a given galaxy, 10 billion years ago)

So we can figure this out: 10 billion years ago, GRBs were very numerous, and, if they were really able to sterilize a galaxy, this happened every 360 million years in average, much too short a time to allow for evolved life to appear.
But the activity of GRBs gradually subsided, and is quasi-zero today. So we may find most galaxies where there was no GRBs since 3, or 5, see 7 billion years.

Applied to our galaxy, this makes about the age of the Earth, and an elegant solution to the black sky paradox (life is expected to appear on many planets, but we yet detected no evolved civilizations): we would be amont the firsts to appear.

Places which are expected to have stopped any GRB activity for longer than our galaxy would be giant elliptic galaxies like Virgo. This is the best place to search for giant Type III civilizations (After kardanchev a Type III civilization is using the energy of its whole galaxy). So this is the place where we can more expect things like Dyson spheres, engineered stars, etc (if any such things can exist, but this is not what seems the most likely to me)

[ljk4-1]

On December 15 former Senator William Proxmire of Wisconsin died at the age of 90. Proxmire was no friend of the space program, and in 1979 he gave one his famous “golden fleece” awards for wasteful government spending to NASA for its research in the search for extraterrestrial intelligence (SETI). A few years later he was instrumental in stopping government support for SETI.

But Proxmire also provided The Planetary Society with one of its greatest victories, and consequently earned the respect of Carl Sagan and the organization for his willingness to listen.

The rest is here:

http://planetary.org/news/2005/1216_Societ...ETI_Critic.html