[X] My Assistant

[Guest_Richard Trigaux_*]

Reading back the article on the "wow signal", I found that the one-time large candidate signals could be reflections of Earth radio sources onto space debris or satellites. Such signals would be very strong, narrow frequency, they would match the antenna pattern like with the wow signal, and seem to come from space. But they are not from ET origin. This is likely why one-timers are all rejected by the SETI protocols.


From where the idea, to avoid such false detections, to send the SETI antenna in space. Easy to say, but large radioastronomy dishes are tens of metres large, see hundred metres, and very heavy. A simple solution would be to send an array of dipoles mounted on something ressembling a spider web, rotating to keep its shape. Phase shifts on every dipole would allow to change the direction of reception. Such an apparatus would weight only some tons and could be folded into a common rocket upper stage.

But if this is useful for SETI, it can be usefull too for any other use of radioastronomy dishes, observation or deep space network as well. And it would be free of any Earth interference, a growing problem today. And the cost? we anyway save the cost of a large dish.

[dilo]

Nice idea, Richard... but I have a couple of observations on it.
First, I fear that widely spaced, small dipoles would have a small effective area, so resulting antenna would have small gain/sensitivity (but potentially very good beam width / resolution).
Second, I think that you should go very far from Earth (far lunar side?) in order to drastically reduce artificial interferences...
Anyway, I recall of some projects on inflatable antenna dishes which should solve the problem.

[Guest_Richard Trigaux_*]

Nice idea, Richard... but I have a couple of observations on it.
First, I fear that widely spaced, small dipoles would have a small effective area, so resulting antenna would have small gain/sensitivity (but potentially very good beam width / resolution).
Second, I think that you should go very far from Earth (far lunar side?) in order to drastically reduce artificial interferences...
Anyway, I recall of some projects on inflatable antenna dishes which should solve the problem.

Yes, it would need MANY dipoles, ideally as close as each other than the wavelength. This could be done easily, if we use the technique of striplines between two conductive planes, and slots in one of the planes. This way we obtain a cheap and large kind of sheet which can easily be rolled, then expanded and kept rigid by centrifugal force, and with yet excellent gain and excellent sensitivity.

Also the idea of placing it behind the Moon is good, there is here a Lagrange point, but it is unstable.

The two ploblems of such a structure is that it has a limited bandwidth, and it cannot easily be oriented (it behaves like a giant gyroscope). Orienting it would require much energy, and oscillations would need days to settle. It would be perfect, for instance to ensure a high data rate link between two planets, but not for astronomy observation.

So the idea of an inflatable parabolic antenna looks more appealing... But how to ensure an accuracy of some millimetres over hundreds of metres? What about the inflatable structure being punctured every day by micrometeorites? It could be left in place once inflated, for instance by using a polymer which hardens with sunlight. But then, when we change the orientation of that dish, the little force needed acts on a frail structure, so that it deforms and could need days to recover its correct shape.


At last, nice simple-looking ideas but not so easy to put into practice. We may be unable to pass the step of setting large rigid structures into space, like with the truss builder that the NASA envisionned for the ISS.

Or we could use a structure inflated by electric fields, not by a gas. The advantages are:
-insensitivity to puncturing
-possibility to locally adjust the field to accuratelly set the shape when building, or to cope with further deformations.
-very light weight structure, ideally two films of polymer with electrodes printed on them.

in addition to the advantage of an overal very light weight, large bandwith and no gyroscopic effect.

the only inconvenience is the need to adjust the electic fields when they more or less interact with each other. But this is a computer problem, not unlike the ones on telescope to compensate for atmospheric distorsion.

[Bob Shaw]

Back in the 1960s there were several balloon satellites other than the Echo series - one USAF test used a 10.5m structure built by Goodyear which was inflated in orbit, but then the plastic balloon material disintegrated under the influence of solar UV to form a rigid but very thin open aluminium structure, a so-called grid-sphere balloon. The vehicle was launched on July 13, 1966 from Vandenberg aboard an Atlas booster. Orbit altitude was 620 miles and tests revelaed that it was able to reflect radio waves five times more efficiently than a traditional balloon.

This sort of technology might well be applicable to large orbital antenna farms.

Bob Shaw

Attached image(s)

 

[Bill Thompson]

I am very suspicious of anything written or supported by G. Gonzalez,
as he is pro-Intelligent Design and co-author of the book The Privileged
Planet, which essentially states for theocratic reasons that Earth is the
only world in the entire Universe with life and that the Universe itself
was made just for humanity's use.

I can see why people would be suspicious. But people do a lot of strange things for the purpose of making money. I can understand why someone might write such a book because it is something that a lot of people might want to buy.

At the same time, we all have our warts. I am not defending him but good ideas can come from people who have made what we might regard as mistakes in the past.

As for not being contacted by ETI, it is possible that most alien life is
no more advanced than microbes, but with 400 billion stars in our
galaxy alone, how can you or anyone presume that ETI would even
know we exist to contact or stand out in any way when our electromagnetic
signals have barely traveled 100 light years into a galaxy that is
100,000 light years across?

I think the answer to this is found in Enrico Fermi's observation. I have heard people say "just because there is not an ET sitting at the coffee shop at the corner does not mean that there isn't one on the other side of the galaxy". But I disagree. I think this is precisely what Fermi meant:

Fermi's Paradox on The SETI Institute Part I
Fermi's Paradox on The SETI Institude Part II
Fermi's Paradox on The SETI Institude Part III

I understand thinking in a galaxy with 400 billion stars we could be the only folks like us is hard to believe, but, at the same time, there has to be a first one. If anything is possible, it is possible that we are the first.

[ljk4-1]

I can see why people would be suspicious. But people do a lot of strange things for the purpose of making money. I can understand why someone might write such a book because it is something that a lot of people might want to buy.

But does that make it good science? When what is considered "good" science is due
to how much the general public thinks it is "cool" or something similar, that is when
we are all in trouble. And I already see trouble brewing in all sorts of areas here.

At the same time, we all have our warts. I am not defending him but good ideas can come from people who have made what we might regard as mistakes in the past.

Gonzolez's views are not mistakes from his past, he continues to hold them and
certainly does not view them as mistakes. But it is obvious that his fundamentalist
beliefs have gotten in the way of what is supposed to be objective science. He can
believe/worship whatever and any way he wants, but when it comes to his science
work, the bias has to stay out as much as possible. Yes, I know, that is often quite
a difficult thing to do, but his biases are way too obvious and strong in the book.

I think the answer to this is found in Enrico Fermi's observation. I have heard people say "just because there is not an ET sitting at the coffee shop at the corner does not mean that there isn't one on the other side of the galaxy". But I disagree. I think this is precisely what Fermi meant:

I understand thinking in a galaxy with 400 billion stars we could be the only folks like us is hard to believe, but, at the same time, there has to be a first one. If anything is possible, it is possible that we are the first.

What evidence is there that we are first? Don't worry, it is mostly a rhetorical
question.

I cannot find the paper at the moment, but one astronomer recently published his
study that Earth-sized planets in the Milky Way galaxy are on average 1.1 billion
years OLDER than our world. This is based in part on the average ages of G-class
suns in our galaxy, the type our Sun is.

If biological evolution proceeded in a similar fashion as on our Earth, including
intelligent life, then such beings have had quite a start on us. They may be so
far ahead of us, to say nothing of so different from us, that they wouldn't bother
trying to get our attention any more than we do with insects and microbes.

Study us, yes; talk to us, probably not. As one old SF novel once said about a
seriously advanced supercomputer that was essentially an Artilect, having it explain
one of its more complex ideas to us would be like trying to explain taxes to a dog.

As for one idea as to why SETI has yet to produce positive results, see here:

http://arxiv.org/PS_cache/astro-ph/pdf/0506/0506110.pdf

I still maintain that beings (humanity) who have just begun to explore their own solar
system, developed technological communications systems just over a century ago,
and who live in just one spot in a galaxy with 400 billion stars 100,000 light years
across are not going to be drawing the attention of any ETI unless they happen to be
very nearby. And then one has to hope they are able, willing, and interested in
talking to us.

At this point you might rightly ask, well why bother looking for ETI if they won't talk
to us and have nothing in common with us mere humans?

Besides the main criteria that studying and searching the unknown to make it
known is one of the hallmarks of science, there is always the possibility that there
are ETI who are searching for others in the galaxy just like us and willing to talk
and learn. We're doing it, even if it is on a still fairly small scale, right? And
presumably most beings have to go through a growing curve before becoming
Artilects. And SETI is a relatively inexpensive way to search with rewards that
will far exceed their investments.

And even if ETI won't talk to us, we may still be able to find them in other ways.
An infrared glow in areas of space that seem otherwise empty could designate
a Dyson Shell or other similar construct by beings who know how to really harness
the energy of stars (we let 99% of the Sun's light slip past Earth into space every
second of every day - what a waste).

SETI has finally begun to mature. In the last decade, scientists have finally realized
that using lasers to communicate is more efficient for advanced societies than radio
and have begun conducting Optical SETI (just ask The Planetary Society). Some are
also realizing that if you can see a star, it probably doesn't have anyone advanced
enough to talk yet (of course we are an exception and there are probably others).
And there may be structures of such a grand scale in the galaxy (or other galaxies)
that we galactic novices don't even recognize them as artificial yet. They may even
have probes in our solar system, but that one is still stuck in the pseudoscience stigma
stage for many folks. Which is sad, because that might be the easiest/best way to
find and talk with them, especially in our lifetimes. But I am waiting for real scientific
evidence, not anecdotes.

But we need to search - that is what counts. Whether we find alien beings or not,
either way the answers will be profound for us. But as the 1959 Nature paper on the
subject concluded, if we don't search, the chances of finding out are zero.

http://www.coseti.org/morris_0.htm

[Guest_Richard Trigaux_*]

I can see why people would be suspicious. But people do a lot of strange things for the purpose of making money. I can understand why someone might write such a book because it is something that a lot of people might want to buy.

I understand too why you are suspicious. There is simply no theological basement as what other civs would exist or not: if you read the Gospels, it is even not mentionned, simply off topic. At this epoch the idea that other planets could be inhabitable was simply non existent (if we except Democritus). There are some hints into Jesus speaches at "other skies" which were recently interpreted as "other planets", but such an evidence is rather frail, don't you think so? The catholic church's idea as what there would be no other civilizations arose only in the Renaissance, at the time of Giordano bruno, and likely only because these guies were narrow minded, seing anybody else as ennemies, or slaves to conqueer. So this "religious" idea of earth being the unique creation is just a kook idea among all the other kook ideas on ETs.

I think the answer to this is found in Enrico Fermi's observation. I have heard people say "just because there is not an ET sitting at the coffee shop at the corner does not mean that there isn't one on the other side of the galaxy". But I disagree. I think this is precisely what Fermi meant:

Fermi's Paradox on The SETI Institute Part I
Fermi's Paradox on The SETI Institude Part II
Fermi's Paradox on The SETI Institude Part III

I understand thinking in a galaxy with 400 billion stars we could be the only folks like us is hard to believe, but, at the same time, there has to be a first one. If anything is possible, it is possible that we are the first.

As I said earlier into this thread, there is an apparent contradiction between what we know of the formations of planets and life (life should be common) and the raw result: there is no trace of landing on Earth, today or past. Such kind of contradiction often hint at something important that we don't understand, such as, as you suggest, a matter of timing. But now we can only speculate. And increase SETI power...

When we shall be able to detect a cell phone at 1000 light years, and still find none, yes we shall be right to say that civs are very rare.

As to our "right" to colonize the whole universe, that curiously reminds be similar debates some centuries ago, about our "right" to colonize other parts of Earth. Certainly the problem is not exactly the same, but I don't like that from the very beginning some put forward "our right" in front of the rights of others.

[Bill Thompson]

What evidence is there that we are first? Don't worry, it is mostly a rhetorical
question.

I cannot find the paper at the moment, but one astronomer recently published his
study that Earth-sized planets in the Milky Way galaxy are on average 1.1 billion
years OLDER than our world. This is based in part on the average ages of G-class
suns in our galaxy, the type our Sun is.

To me this is an indication that Enrico Fermi's observation was accurate.

[Guest_Richard Trigaux_*]

... I think this is precisely what Fermi meant:

Fermi's Paradox on The SETI Institute Part I
Fermi's Paradox on The SETI Institude Part II
Fermi's Paradox on The SETI Institude Part III

I understand thinking in a galaxy with 400 billion stars we could be the only folks like us is hard to believe, but, at the same time, there has to be a first one. If anything is possible, it is possible that we are the first.

I read this only after writing what I wrote previously. The Fermi paradox is really what I was speaking about.
Usually pessimists explain the Fermi paradox as "we REALLY are alone" when optimists need to add some special hypothesis, as what we would be in a kind of "zoo", or that ETs would be wise beings respectuous of our evolution. Pessimists reply that this is just adding ad-hoc hypothesis. They are true that the hypothesis "we are alone" is simpler, and thus more attractive, if we don't feel a strong regret from such a situation. But this simpler pessimistic explanation gets in turn complicated if we consider that all what we know on formation of planets and appearance of life tell us that ET civilizations should be many. So we are still in the situation of adding ad-hoc hypothesis to explain what happened to us so special that we are the only ones, or the very firsts. So the Fermi paradox don't really favours the pessimistic hypothesis: Why should we be alone, or the firsts, when theory predicts that civs would be common and ancient? This situation looks a bit like the anthropic principle.
But we must retain this: the Fermi paradox is not an evidence that we are alone. It is only an evidence that there is something important that we don't understand. It reminds me of the dark sky paradox: why the sky is dark when there are stars everywhere? The answer was that stars exist only for a limited time.

Today the only convincing pessimistic solution to the Fermi paradox is that, until recently, gamma ray bursts forbad any evolved life in our galaxy, explaining that we would be among the firsts. Optimistic explanations, such as the zoo, or wise ETs, are still untestable.
This is why me must still continue SETI and all the other searches on planet formation and astrobiology.

After the hypothesis of the end of the GRBs age, the best place to search for ET civs would be the giant elliptic galaxies in Virgo galaxy cluster. Eventually theory predicts that these galaxies should be type III civs. This would be testable, not at finding radio emissions of individual stars, but as a diffuse radio noise without astrophysical explanation. Eventually, according to their technical standards, this radio noise would have a peculiar spectrum, with recognizable spikes, each signing for a given galaxy.

[Bill Thompson]

The wrath of Xenu is an explaination why we seem to be alone. I am joking, of course.

But seriously, one possible explanation might be that the gaps in the steps of microbial evolution where we do not understand how something self replicating evolved from non replicating polymers is that it was enormously great luck and planet Earth is the recipient of winning (for lack of a better term) a cosmic lottery. Maybe life is a game of chance and the odds of winning are 400 billion to one.

Or has this been proven to be wrong?

[Guest_Richard Trigaux_*]

The wrath of Xenu is an explaination why we seem to be alone. I am joking, of course.

But seriously, one possible explanation might be that the gaps in the steps of microbial evolution where we do not understand how something self replicating evolved from non replicating polymers is that it was enormously great luck and planet Earth is the recipient of winning (for lack of a better term) a cosmic lottery. Maybe life is a game of chance and the odds of winning are 400 billion to one.

Or has this been proven to be wrong?

As I already explained somewhere else, the probability of a thing to happen at a given time can be translated in a time in which this thing MUST happen. This has been modeled in tumor growth, explaining why all tumors ressemble each other, even if each individual tumor arises from unique and very unlikely mutations. Or if you play every week to a lotery were wining is one millionth odd, you MUST win after 20 000 years. (statistical average, of course). If you play every minute, you win after two years.

This translates into duration for every step of the evolution of life. We don't know when life started, but likely at the beginning of Earth. 3 billions years ago, there was already a long history of DNA code, and chlorophylle (stromatolithes). But two more billion years were necessary to pass to multicellular beings. After this, nervous cells, digestion, muscles, all appeared in relatively short times. So it is clear that some evolutions steps are more difficult than others. We can even infer with some reasonable accuracy the probability of each step.

The step you speak about, the very first, from inanimated molecules to te first self-replicating things, is the most unknown, in fact. We simply don't know when it started. And we also don't know how many time was needed for the second step: the appearance and organization of the DNA code. But these two steps took at most 1 billion years. So they are not the most difficult to achieve of all, but not the simplest too.

But from this duration we can infer that the appearance of life is not very unlikely. Of course it is difficult to make statistics with only one case, but there are things to say even in this situation: If life was really something very unlikely to happen, it would be also very unlikely that it started right at the beginning of Earth.

So, yes, life could be very unlikely, and we would be in a very unlikely situation. But we MUST be in this situation, however rare it is. this reminds me of the anthropic principle. To say that life is a likely process is more "occam razor friendly".

Remains this contradiction: if life was likely, why we don't observe it everywhere???

From here the interest of the search of life on Europa and Enceladus. Even if we find only primitive things such as self-catalytic chemistry, it would give us unvaluable clues on the probability to find life on other planets.

[Bill Thompson]

As I already explained somewhere else, the probability of a thing to happen at a given time can be translated in a time in which this thing MUST happen. This has been modeled in tumor growth, explaining why all tumors ressemble each other, even if each individual tumor arises from unique and very unlikely mutations. Or if you play every week to a lotery were wining is one millionth odd, you MUST win after 20 000 years. (statistical average, of course). If you play every minute, you win after two years.

This translates into duration for every step of the evolution of life.

This is something where there are many integration marks still remaining. I am an engineer and not a biologist but the biologists I have spoken to have confirmed that there are gaps in our understanding of how microbes have evolved.

How much of this is a natural progression and how much of it is luck that has been playing favorably just for our planet is not known. Even though it is not mentioned often in the study of biology, there are steps along the evolutionary trail where the way one single cell organism adapted a special characteristic is not understood.

If the odds are that some things only happen once in 4 billion years for only one in 400 billion stars system then chances are we are alone in the galaxy.

[Bob Shaw]

As I already explained somewhere else, the probability of a thing to happen at a given time can be translated in a time in which this thing MUST happen. This has been modeled in tumor growth, explaining why all tumors ressemble each other, even if each individual tumor arises from unique and very unlikely mutations. Or if you play every week to a lotery were wining is one millionth odd, you MUST win after 20 000 years. (statistical average, of course). If you play every minute, you win after two years.

Richard:

I may well regret this, but that interpretation of probability is *not* as I understand it. I don't want to set one of those interminable discussions going on the subject, but suffice it to say that I disagree - there's no 'must' about probability, except when dealing with very large numbers (and that's still only a 'probably' - ask Sir Roy Meadows).

As regards SETI, there's so much in the way of pre-biotic material, energy and habitable zones out there that I'd be really surprised if life doesn't exist somewhere fairly close by - if not in our immediate locality, then within similar parts of our own galaxy. Intelligence is quite another matter - humanity is an extreme case in terms of the history of Earthly species, where for the vast majority of geological history intelligence has been pretty thin on the ground. If man persists on Earth then I hope we will send AI probes to the stars, which in due course may spread intelligence, but not life, throughout at least the nearby galaxy. The fact remains, though, that there's no sign of anybody else ever having done so (any 're-boot' events must have been a long time ago and very far away and would likely have destroyed the evidence, so it may have happened but would be invisible to us).

Large-scale robotic exploitation of the Asteroid Belt, comets and the Oort Cloud are exactly the sort of stepping-off points that would be required for a slow interstellar AI panspermia and would equally serve our descendents well!

Bob Shaw

[Guest_Richard Trigaux_*]

Bill and Bob, be reassured, I don't want too to start one of these interminable discution, and I shall not further reply to any argument in the kind "we don't know how it happened so it did not happened elsewhere" or "we are the unique example known so we must be unique" or "we are special so we are unique". Such arguments are simply of no help and out of place in a science forum.

Yes we can say "must" in statistics, when great numbers are involved. The decay of radioactive elements is an example: a completelly random process, even not time-dependent, and however it is the best clock we have for past events. And for instance Al26 "must" have disappeared from Enceladus. So you understand that rare events "must" happen with enouh time.

So "my" vision of appearance of life and its evolution as a series of random steps, which can go all the way from prebiotic molecules to intelligence and further (yes the further step is alrready engaged on Earth, and it may explain why we don't find other technological civs), this vision is not just a dogmatic vision, it is based on statistics, and on well documented real world models such as the "evolution" of tumors by random mutations. each tumor type depends on a series of mutations, and, if we compare each tumor to a planet, it is remarkable that all the tumors of the same type evolve in the same way, even in dependance of completelly random events, and in total independance of each other. There is even a diret relation between the size reached by the tumor and the happening of each mutation.

I agree with you Bob that, even if microbes are very common, the appearance of intelligence must be much more rare, as it depends of the availability of more specific conditions, and of enough time (four billion years on Earth) without deadly perturbations. So we cannot expect to find intelligence in the Europa ocean, even if there are plenty of microbes since four billions years. Similarly we cannot expect to find intelligence on large stars, as their life span is too short. And one of the main constrain known today, to add to the Drake equation, is the account of deadly events such as large meteorite impacts, gamma ray bursts, close supernovas, etc. This makes of star clusters bad SETI candidates and Virgo elliptic galaxies best canditates (better than ours). This problem is the simplest solution to the Fermi paradox, but it needs to be proven before being brandished as "the truth".

I would like to continue this discution, but so long as there are no definitive statements as above.

[ljk4-1]

The Planetary Society's Optical SETI Telescope at Oak Ridge Observatory
in Harvard, Massachusetts, has begun its search. Three news items here:


Planetary Society Opens World's First Dedicated Optical SETI Telescope

New Search for Extraterrestrial Intelligence Begins

Pasadena, CA, —Today, April 11, 2006, The Planetary Society dedicated a new optical telescope at an observatory in Harvard, Massachusetts -- one designed solely to search for light signals from alien civilizations. Read more.

Opening ceremonies for The Planetary Society's Optical SETI Telescope featured Project Director Paul Horowitz of Harvard University; Planetary Society Chairman Neil deGrasse Tyson, director of New York's Hayden Planetarium; and Society Executive Director Louis Friedman.

"With the launch of The Planetary Society's Optical SETI Telescope," said Friedman, "we are proud to be part of a new voyage of discovery with this great Harvard team."

The new telescope is the first dedicated optical SETI telescope in the world. Its 72-inch primary mirror is larger than that of any optical telescope in the U.S. east of the Mississippi River.

Under the direction of Horowitz and his team, the optical SETI telescope will conduct a year round, all-sky survey, scanning the entire swath of our Milky Way galaxy visible in the northern hemisphere.

Full article here:

http://planetary.org/about/press/releases/...rlds_First.html


Looking for alien lasers, not radios

NewScientist.com news service April 11, 2006

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

The first optical telescope
dedicated to the hunt for alien
signals, the Planetary Society's
Optical SETI (OSETI) telescope at
Harvard's Oak Ridge Observatory, has
opened. Once running, OSETI's
processors will carry out a trillion
measurements per second, in a
year-round survey of the sky. It
will be able to pick out flashes of
light that are...

http://www.kurzweilai.net/email/newsRedire...sID=5458&m=7610


Harvard's new telescope to boost search for alien life

Will scan heavens for flashes of light

By Douglas Belkin, Globe Staff | April 12, 2006

To quote:

Horowitz compared the previous generation of the Optical Search for Extra-Terrestrial Intelligence, or OSETI, to searching the skies through a soda straw -- viewing only a very narrow spot of the heavens at once. This telescope, built for about $400,000, scans a broad line in the sky.

As the Earth moves, the stars pass through that line. In about 200 nights the scope can observe the entire sky visible from the northern hemisphere.

The pace of observation: 100,000 times faster than any previous scope.

To analyze the massive amount of data being sucked in through the scope's 72-inch mirror, a team of graduate and undergraduate students built a computer able to wade through 1 trillion bits of information per second -- about as much information as is contained in every book in the Library of Congress.

''The technology is absolutely on the cutting edge," said Louis Friedman, executive director of the Planetary Society, a nonprofit group of scientists and space enthusiasts that funded the telescope. ''It feels like the Wright brothers working out of their bike shop; they're using chips never seen before."

Friedman compared building the scope to launching a space ship. The stakes, he said, could not be higher.

Full article here:

http://www.boston.com/news/education/highe...for_alien_life/