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Posted by: PhilCo126 Feb 21 2006, 03:51 PM

A very simple topic title because everybody knows that our Sun is a Star ( lectured to 8 year olds all over the world ... )

But which scientist/Astronomer actually found out this 'simple' fact ?
( 17th Century CHristiaan HUYGENS studied the Sun, 19th Century Angelo SECHI even studied Sunspots )

I do know that 20th Century Fred HOYLE did a lot of calculations on the destiny of Stars but we might go back way earlier to know who found out that our Sun is a Star

Posted by: kwp Feb 21 2006, 04:49 PM

Huygens used the comparative brightness of the Sun and Sirus (using a pinhole to reduce the former
and his memory of the latter) and calcualted that Sirus is 27,000AU away (off by a factor of 20, but when you consider
that Sirus is 8x brighter than the Sun -which Huygens couldn't have known- he was only off by a factor of 2.5;
pretty damn impressive). Thus clearly it was known that the Sun is a star prior to the end of
the 17th century. Indeed, the lack of apparent parallax indicated that the stars were very far -and thus
Sun-like in their brightness- well prior to Copernicus. But agreed, it is an interesting question as to who
made the first compelling argument that the Sun is a star.

-Kevin

Posted by: Richard Trigaux Feb 21 2006, 05:52 PM

For us it is easy, but back in the past, it was not obvious, as the Sun and stars look very different. Only when thinkers became aware of the huge distances of the stars it was possible to infer their enormous luminosity. Well though at that time.

It would be even more impressive if some antic thinker had such an idea, but I never heard of that.

Another difficulty is that, until recently, everybody was thinking at stars as being fixed on a sphere, all at the same distance, thus explaining that they don't have a parralax even if they were not much further than the planets. So the idea that stars were not all at the same distance and not all the same size had to be discovered before.



Anyway the fist physical evidence was only very recent, the end of the 19th century, with the discovery of spectroscopy, which allowed to really see that the sun has the same composition and temperatures than stars. And nailing down whose scientist I don't remember his name, who stated just a year before that "we shall never know what are the stars"...

Posted by: dilo Feb 21 2006, 06:29 PM

PhilCo, I think you are talking of Father http://en.wikipedia.org/wiki/Angelo_Secchi...

Posted by: ljk4-1 Feb 21 2006, 08:48 PM

Aristarchus of Samos was one of the first in history to theorize that
the stars are similar to Sol, only very far away. You will recall he
was also among the first to claim that Earth orbited Sol and not
the other way around, like most others thought.

http://en.wikipedia.org/wiki/Aristarchus_of_Samos

http://www-history.mcs.st-andrews.ac.uk/~history/Mathematicians/Aristarchus.html

Among the many advanced ideas of Democritus was that the
band of the Milky Way consisted of many stars which were
faint because they were so far away.

http://en.wikipedia.org/wiki/Democritus

Posted by: djellison Feb 21 2006, 09:42 PM

I've often wondered what constellation we might be in as viewed from say, Sirius or Alpha Centuri.

Doug

Posted by: Myran Feb 21 2006, 09:50 PM

Sol would be in Cassiopeia as seen from Alpha Centauri.

Posted by: ljk4-1 Feb 21 2006, 10:42 PM

Here is where Sol would be from the vicinity of Sirius:

http://hubblesite.org/newscenter/newsdesk/archive/releases/2005/36/image/c

Posted by: jamescanvin Feb 21 2006, 11:03 PM

Always worth putting a link to http://www.shatters.net/celestia/ up every now and again. A fantastic bit of software, especially with all the http://www.celestiamotherlode.net/ (be prepared to loose many hours!). See the night sky from 100,000 stars!

James

Posted by: Richard Trigaux Feb 22 2006, 09:04 AM

WOWWW!


That antic thinkers were so close of the marvelous astronomy truth makes me glad for them, but also sad, because there was such a long time of oblivion and ignorance after!!

Posted by: PhilCo126 Feb 22 2006, 09:43 AM

dilo that's correct, Vatican head-Astronomer Angelo SECHI ... I believe he might found it out !

Posted by: Richard Trigaux Feb 22 2006, 09:52 AM

DOUBLE WOW
the intuitions of Democritus were incredible, he not only though of the atom, but also for their arrangement into molecules, explainig the variety of differnt matters, solidity, taste, etc...

he even went so far as considering the atoms as being "void" as in the quantum concept... or was he in contact with Buddhist thinkers? There was actual contacts from Buddhism toward Greece, but later, when the India emperor Ashoka sent an ambassy toward Greece (a little known fact, but important for the appearance of certain ideas into Antiquity)

Democritus was also the first to explain that there could be many inhabited worlds..


I noted an article in a french popular science review (sorry don't recall the reference and title) that the 5th century BC was a king of special, witth he appearance of many "modern" great thinkers, including Zoroastre, Pythagore, Buddha, etc. We should add Democritus to the list. So these scientists were asking the question: what happened so special into this century? Why so much intuitions and thinking system appeared at that time, and not further? For about a millenia, Antiquity lived onto these intuitions, without adding really new things, until catholic fanaticism put an end to it in the 5th century, bringing the heaviest setback of human evolution. Why so much progress in this 5th century BC, and not a linear following after the 1000 years it was still possible?

Posted by: Jyril Feb 22 2006, 10:03 AM

Only because of the selected viewpoint...

------

Democritus had some clever ideas, but so had for example Aristotle. The only difference is that Democritus was right and Aristotle much more popular. There was no any mean to prove who was right; so although Democritus' ideas sound awesome, they weren't that useful or popular in ancient times. Just some ideas among others.

It was known fact that Earth was round even in the Middle Ages, but some(?) Chinese believed that Earth was also located in vacuum and it orbited the Sun!

Posted by: Richard Trigaux Feb 22 2006, 11:50 AM

Yes there was no mean to prove who was right, from for instance heliocentrism and geocentrism. But if knowledge had evolved regularly, such means would have appeared soon after, say 2 to 1st century BC. In place of this, Antiquity did not made real great moves and stagnated into dogmatism, before it was put an end to it in the 5th century AC. This is also true in many other domains, and the cause is perhaps dogmatiscism and lack of real reasoning capacity: in Antiquity everybody was trusting their masters, not their reasonings. This is perhaps why the Antiquity was not able of a real evolution like today science. Perhaps only the appearance of mathematics, logic and reasoning allowed science to take off in hte time of Galileo.

What is curious anyway is this fascinating 5th century BC where so much great ideas and thinking systems appeared all over the world, and only at that time.





This seemed not a problem, as it is not contradictory with heliocentrism.






At what epoch? The Chinese had to bear an evolution similar tou our Antiquity, but on several millenia rather than one: great ideas, but too many dogmaticism (especially in confucianism) and social conformism to be able to really question the "teachings of the ancestors". It was even said recently that the Chinese were able to tour the world some tens of years before Magellan. But when they were back to their country, the new emperor had ordered to forbid further travels, dismantle the ships and scrap all their science results... and they all did, from obedience.

Posted by: Myran Feb 22 2006, 12:05 PM

Yes in many cases they lacked the tools to check and test their ideas, one of the few they could test was if the Earth were round looking down wells in Greece and Egypt and so were able to calculate the diameter with one amazingly good result, only slightly off.
What they did have was scientific discourse, even though the term wasnt invented back then (they most likely had another word for it though). Regardless many of these amazing ideas these philosophers presented had been discussed at length with their students and fellows, very littl of that is preserved, so we really dont know how they actually reached the conclusions.

Posted by: ljk4-1 Feb 22 2006, 06:21 PM

I highly recommend Lucretius' On the Nature of Things, which
is conveniently online thanks to thousands of years of patient
innovations and technological developments:

http://classics.mit.edu/Carus/nature_things.html

http://en.wikipedia.org/wiki/Lucretius

Posted by: David Feb 23 2006, 12:51 AM

My, my, what a long long way we've come.

Posted by: AndyG Feb 23 2006, 09:48 AM

It's an intriguing point - did Democritus invent or use a low-power telescope? We are told Lippershey invented the refractor in the 1608, but I think the evidence for its use goes back much further than that.

The early-mid 13th century saw huge interest in the scientific study of optics. Robert Grosseteste (a contemporary of Albertus Magnus, and teacher of Roger Bacon - the populariser of glasses for those with long sight) said, in De Iride:



Reading the above, I can't believe that Grosseteste wasn't aware that two convex lenses placed together make a simple refracting telescope: it's hardly rocket science, after all - and this over 350 years before Lippershey.

Grosseteste in a different work goes on to repeat Democritus' comment (which he may or may not have been aware of) that the Milky Way is made up of the light from many small, close stars: a statement also made by Albertus, and something you could easily ascertain with even a bad refractor of binocular-levels of magnification.

So: Medieval telescopes? I think possibly, yes.

Andy

Posted by: Richard Trigaux Feb 23 2006, 10:41 AM

Two possible explanations:

1) the ancients made a small telescope. This is not completelly impossible, after all, in the Middle Age and even in the time of Democritus. But why we shall not know of this? For the same reason we ignore most of the achievements of the ancient: -themselves granted little attention for science matters, except for some philosophers or artisans -many technical skills were kept secret, for corporative reasons (this was even true in the Middle Age) and lost once their keeper was dead. -most of the knowledge on Antiquity was lost in the 5th century, with barbarian pillaging and catholic fundamentalism, and in the 6th century with the subsequent economical recession. -The ancient did not capitalized on their discoveries, as do modern science, so that an interesting result was not taught at school, but just made a legend or forgotten. -the ancient were very conservative and social conformism, for instance the idea of heliocentrism was considered a "blasphemy" even in the open minded Greece. As an evidence of this, there are other examples of astonishing antic realizations, such as the "Badgad batteries" in the 2-3th century BC, or the Anticytheria machine, found in a sunken ship, and which was a bronze mechanical Moon age calculator featuring dials, gears, and even a differencial. No litterature was never found about it, but it however seems a common navigation device on a greek ship.


2) we have no idea of this in our modern countries with our skies polluted by the lights of many cities, but looking the sky at night in nature or Antiquity town revals a rather different spectacle: we can count thousand of stars even with the naked eye and a normal eyesight. We can see at least five Pleiades and many more things. Then it is easy to notice that there are many faint stars in the direction of the Milky Way, and not in other places. More, playing on central/lateral vision make often appear groups of faint stars as nebula (in lateral vision) so that it is not difficult to infer that true nebulas such as the Milky Way are made of a great number of faint stars.


So that there is nothing realy unexplainable in Democritus statement about the Milky Way, at least much less than about his incredible intuitions on atoms, molecules and void.

What is astonishing again is that at a precise epoch, the 5th century BC, there was all over the world so many great intuitions in physics and spirituality, and much less after. What hapened at that epoch?

Posted by: AndyG Feb 23 2006, 12:40 PM

http://www.coda.com/greek.pdf using an original Greek pottery shard would agree with you. :-)

Andy

Posted by: ljk4-1 Feb 23 2006, 03:45 PM

He appears to be looking through the "telescope" via the side of
his head, but ah, those ancient Greeks were good at figuring out
such things, I am sure they solved that problem, too.

Regarding real ancient lenses and the possibility of very old telescopes,
check out the Nimrud lens from the 8th Century BCE - which you can
do if you are in London:

http://farshores.org/telesc.htm

http://www.thebritishmuseum.ac.uk/ane/anecofaq.html#lens

http://www.archaeologyanswers.com/some_original.html

http://www-groups.dcs.st-and.ac.uk/~history/HistTopics/Light_1.html


That Renaissance smart guy Leonardo da Vinci also wrote about
using lenses to magnify objects. To quote:

"Leonardo certainly realised the possibility of constructing a telescope and in Codex Atlanticus written in 1490 he talks of

"... making glasses to see the Moon enlarged.

"In a later work, Codex Arundul written about 1513, he says that

... in order to observe the nature of the planets, open the roof and bring the image of a single planet onto the base of a concave mirror. The image of the planet reflected by the base will show the surface of the planet much magnified."

There is no evidence that he actually built a telescope and conducted
astronomy with it, but these quotes show he certainly knew of and
understood the principles of such optics. Full article here:

http://www-history.mcs.st-andrews.ac.uk/~history/Mathematicians/Leonardo.html

Posted by: Richard Trigaux Feb 24 2006, 12:38 PM

Even at the epoch of leonardo, such great discoveries were considered of no interest and lost. Fortunatelly we still have Leonardo's books, otherwise we shall ignore everything of this genius.

It is often said that science started with Galileo, who was the fisrt to use the experimental method, still at the base of today science. But, much less noticed are some other very contingent conditions which allowed science to really start and become a society feature and not an alchemist secret:

-The invention of PRINTING which allowed knowledge to spread much further that only a circle or very interested people (manual reproduction was tedious and very expensive)

-Galileo published in ITALIAN and not in latin, allowing for a much larger audience of open-minded people that just the conservative establishment

-In the RENAISSANCE there was a large interest into discoveries, exploration, studying ancient knowledge, etc...

-The weakening of the ideological grasp of the catholic fundamentalists, and generally more open-mindedness, not to just reject everything new as "blasphemy". Perhaps we owe this to the protestantism which first dared to question the christian spirituality, but I think it is rather a part of the mystery of the renaissance. What happened exactly at this time?

-around Galileo formed an informal team of scientists and mathematicians

-some tried to formalize the science methods (Descartes)

-Persons interested in science were often philosophers interested in politics. From where their involvement brough them in the spheres of power.

-Governments were convinced of the interest of science results (weapons, navigation, great works...) and founded the first professionnal academies.

We know the following...


But, in the time of Democritus, even if he was a genius like both Leonardo, Galileo and Descartes, in this time there as no printing, no communities of open-minded peoples, and no governments interested into fostering science... it was just a lightning of knowledge, after which darkness fell again, for two millenia...

Posted by: David Feb 24 2006, 03:26 PM

To be fair, Galileo wrote in both languages (both of which he was an acknowledged master of). The Sidereus Nuncius, for instance, is in Latin. Writing in Italian may have made his writings more accessible to Italians, but Latin made them more accessible to the wider world. Latin was a part of primary education in all of Western and Central Europe at the time, and so what Galileo wrote in that language could be read from Portugal to Poland and from Scotland to Sicily. I think most of Galileo's Italian writings, such as the Due Nuove Scienze were also translated into Latin.

Posted by: Canopus Feb 24 2006, 03:35 PM

Wow, REALLY?

Posted by: Bob Shaw Feb 24 2006, 05:43 PM

Even Descartes was too early for his own good, as an effective transport infrastructure was lacking in his time - hence the old saying about putting Descartes before des horse.

Bob Shaw

Posted by: tty Feb 24 2006, 08:34 PM

I doubt these medieval or older telescopes for several reasons.

First telescopes have such obvious military and naval applications that it seems highly unlikely that they would ever have been "forgotten". Once they were invented they spread very quickly.
The same thing is true about spectacles which were invented early in the fourteenth century (at least that is what contemporary sources say) and also spread quite rapidly.

Second there are quite a number of optical works from the Middle Ages and early modern times, none of which describes a telescope in unequivocal terms.

I know it seems strange that it took 300 years to progress from spectacles to a refractor, but there are any number of inventions that could have been made centuries or millenia earlier from a technological point of view if only somebody had had a bright idea. Take the hot-air balloon or the windmill or the stirrup for example.

tty

Posted by: ljk4-1 Feb 24 2006, 09:05 PM

I recall reading about the early history of the telescope that when
Hans Lippershey started investigating its workings, the device was
known as and considered to be a child's play toy. So this may explain
why scientists and governments of the era did not delve into it until
roughly 1609.

The only wheeled vehicles ever found in Aztec culture were also
children's toys. Is this just more proof that when we grow up, most
people lose their wonder and natural inquisitiveness about the world?
That only those who don't go on to be the inventors and scientists?

The ancient Greek Heron invented the steam engine, but nothing major
came of it for ages. And a Roman actually built a small model of a bird
that flew around on a string using steam power, but the 747 did not come
right after that for at least several weeks.

I highly recommend the book The Ancient Engineers by de Camp and
Campbell.

Posted by: Richard Trigaux Feb 24 2006, 09:47 PM

To add to the example quoted by ljk4-1, there are also incredibly modern looking aircraft models found in antic egyptian tombs. Toys, again...

Military? The militaries are as dumb as the others and as much subject to social conformism and fear of what is new. What distinguishes the ancient from us, I think, is that they had an incredibly strong pigheadnesness idea about what should be or not, especially about customs, morals, etc (which did not forbad them to break moral rules at least as often as us, anyway, as having an opinion is a thing, to embody it is another). More subtly, they were lacking some concepts which seem obvious for us today. When we see an unknown new apparatus, we think "it is science" and we immediatelly look what we can do with it. The ancient, I guess, were rather thinking "it is magic, it is a trick, it is not in the order of things, so it is bad, I should not use it, its appeal is a trick of the devil" (don't we were thinking in this way still recently? I remember when I was a child, elder people were reluctant about new inventions...). So, imagine that a glass worker found inadvertently how to make a magnifying glass. He build several, and finds how to make a telescope. If he is not simply afraid of it, he will speak of this to only little people, otherwise he knows he will be procecuted, whipped and killed for blasphemy. At best, he will have some disciples, and write some words about what he saw (milky way made of many stars). Even if by chance, a general finds the telescope, and uses it for battle, he will use it for himself, and keep is secret, by fear of being accused, or by interest simply.

So this difference of mind can explain that science did not appeared in the Antiquity, where however many conditions were set for it to appear.

The difference is that we have EVOLVED and that society features and concerns such as science, human rights, social care, democracy, appeared "spontaneously" when this evolution allowed it.

When an overal society evolution allows it, features arise and spread, in much the same way as in a nuclear reactor. But if the conditions are not yet present, any discovery or insight is bound to degenerate and disappear, as in an under-critical reactor where a reaction follows a decreasing chain. If it is really under-critical, a fission can produce one or two other fissions, but no more.

Posted by: David Mar 9 2006, 05:44 AM

The technical breakthrough is, I think, the quality of the lenses and the ability to grind them. Using ordinary spectacle lenses of the time I doubt that a magnification better than 2x could be obtained. Lipperhey apparently experimented with a great enough variety of lenses to get the magnification up to about 3x; his contribution stemmed from having, as a spectacle maker, a lot of lenses on hand, and the willingness to play around for a while with different combinations to produce a better image. 3x is good enough for some basic spyglass work, and got people interested in the instrument as a tool rather than a toy, for which Lipperhey deserves credit. But Galileo deserves even more credit for bringing the instrument to a higher state of efficacy and making it useful for astronomical study.

Posted by: Richard Trigaux Mar 9 2006, 06:10 AM

Indeed 3x magnifying spectacles are not very useful in astronomy. I have a 10x50 spectacle, it allows to see Moon craters and shadows on limb, I guess Jupiter's satellites and Venus crescent, but it would not be very convincing in 1610. Even if soon after Galileo there was serious progresses in telescopes, they had to wait a while to be taken seriously by everybody, and there was still peoples writing that "if we see things in the telescope, it is that we put them into the telescope". In the beginning astronomy was as well considered as UFOs today. Progress required better instruments, of course, but also a better state of consciousness allowing to think "we discover that things are like we observe" and no more "we know how things must be, and any evidence of otherwise is a devil's trick".

Posted by: Adam Mar 9 2006, 04:35 PM

I've heard of a working steam engine used during the reign of Trajanus, but it was only used to open temple doors (behold, the great god opens the door!). It's interesting nobody saw the potential, says alot about that time.

Posted by: Richard Trigaux Mar 9 2006, 09:26 PM

Yes indeed. Perhaps if somebody proposed to use steam power at work, the slaves trade unions would have yelled for the loss of their job. More seriously it was said by economists that machines were not economically interesting in Antiquity, when slaves were numerous and cheap. This was certainly one of the brakes to the development of industry and indirectly of science. In modern times in the countrary the will of the business class to develop technologies was a fuel for the development of science, for instance thermodynamics for the steam engine.


If this machine really existed, it was perhaps simply some leather pouch pushing the door when filled with steam, and releasing it when the fire was removed. I guess that many elements of a true steam engine where missing, taps, valves, rod and crankshaft, distribution cylinder, etc.


Your remark is relevant: there was in Antiquity many hints and opportunities to develop science and industry, but none seized them, or only as a trade secret lost at their death. On the countrary some basic devices such as pumps, railroads, cranes, etc appeared in the 18th century and even 17th century BEFORE the steam engine, so that using it appeared logical to everybody. As a recall of this, there is in France a little town called "la machine" a recall of mining times before the steam engine, there was here some crane or something which appeared huge for the epoch.

So it is a difference in the very psychology of the average person which allowed science and technics to develop in modern times and not in Antiquity, perhaps prior to any other political/economic conditions.

Posted by: ljk4-1 Apr 6 2006, 03:36 PM

IT'S THE SUN, BUT NOT AS WE KNOW IT (News in Science, 06/4/06)

Analysis of the first sample of lunar soil collected by Neil Armstrong has
thrown into disarray what researchers believe about the Sun, an
international team of scientists says.

http://abc.net.au/science/news/stories/s1606906.htm