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Our Sun Is A Star !
Guest_PhilCo126_*
post Feb 21 2006, 03:51 PM
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A very simple topic title because everybody knows that our Sun is a Star ( lectured to 8 year olds all over the world wink.gif ... )

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 wink.gif
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kwp
post Feb 21 2006, 04:49 PM
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QUOTE (PhilCo126 @ Feb 21 2006, 08:51 AM) *
But which scientist/Astronomer actually found out this 'simple' fact ?
( 17th Century CHristiaan HUYGENS studied the Sun, 19th Century Angelo SECHI even studied Sunspots )


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
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Guest_Richard Trigaux_*
post Feb 21 2006, 05:52 PM
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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"...
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dilo
post Feb 21 2006, 06:29 PM
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PhilCo, I think you are talking of Father Angelo SECCHI...


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ljk4-1
post Feb 21 2006, 08:48 PM
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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/~h...ristarchus.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


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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djellison
post Feb 21 2006, 09:42 PM
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I've often wondered what constellation we might be in as viewed from say, Sirius or Alpha Centuri.

Doug
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Guest_Myran_*
post Feb 21 2006, 09:50 PM
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Sol would be in Cassiopeia as seen from Alpha Centauri.
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ljk4-1
post Feb 21 2006, 10:42 PM
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QUOTE (Myran @ Feb 21 2006, 04:50 PM) *
Sol would be in Cassiopeia as seen from Alpha Centauri.


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

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


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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jamescanvin
post Feb 21 2006, 11:03 PM
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QUOTE (djellison @ Feb 22 2006, 08:42 AM) *
I've often wondered what constellation we might be in as viewed from say, Sirius or Alpha Centuri.

Doug


Always worth putting a link to Celestia up every now and again. A fantastic bit of software, especially with all the Add ons (be prepared to loose many hours!). See the night sky from 100,000 stars!

James


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Guest_Richard Trigaux_*
post Feb 22 2006, 09:04 AM
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QUOTE (ljk4-1 @ Feb 21 2006, 09:48 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/~h...ristarchus.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



WOWWW! ohmy.gif


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!!
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Guest_PhilCo126_*
post Feb 22 2006, 09:43 AM
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dilo that's correct, Vatican head-Astronomer Angelo SECHI ... I believe he might found it out !
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Guest_Richard Trigaux_*
post Feb 22 2006, 09:52 AM
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QUOTE (ljk4-1 @ Feb 21 2006, 09:48 PM) *
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



DOUBLE WOW ohmy.gif ohmy.gif ohmy.gif
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?
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Jyril
post Feb 22 2006, 10:03 AM
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QUOTE (ljk4-1 @ Feb 22 2006, 12:42 AM) *
Here is where Sol would be from the vicinity of Sirius:

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


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!


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Guest_Richard Trigaux_*
post Feb 22 2006, 11:50 AM
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QUOTE (Jyril @ Feb 22 2006, 11:03 AM) *
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.


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.




QUOTE (Jyril @ Feb 22 2006, 11:03 AM) *
It was known fact that Earth was round even in the Middle Ages,

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





QUOTE (Jyril @ Feb 22 2006, 11:03 AM) *
but some(?) Chinese believed that Earth was also located in vacuum and it orbited the Sun!

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.
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Guest_Myran_*
post Feb 22 2006, 12:05 PM
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QUOTE
Jyril said: There was no any mean to prove who was right


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.
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