The Universe at 25 C

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albert_eimstymied

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Does anyone know how old the universe was when ambient temperatures were 25 C ?<br />How long would these conditions have existed for ?<br />Do you think terrestrial planets with life could have existed without suns ?<br /><br />
 
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green_meklar

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I'm not sure how old the Universe would have been at that time, no.<br /><br />As for planets, my guess is that at that time there weren't yet any rocky planets like Earth. 25 celsius, or 298 kelvin, is pretty high compared to the modern value of 3 kelvin, so it probably occured within the first one or two billion years after the Universe formed. At this time, almost all the normal matter in the Universe was hydrogen (it still is, but not quite as much as then...think 99% now as compared to 99.9999% then). The materials necessary for terrestrial life mostly formed later in some of the Universe's first giant supernovas. So I personally suspect that by the time there was enough carbon and oxygen and nitrogen and so on around to support life, the Universe had already cooled well below 0 celsius. <div class="Discussion_UserSignature"> <p>________________</p><p>Repent! Repent! The technological singularity is coming!</p> </div>
 
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albert_eimstymied

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Those are some very good points..<br /><br />However, wouldn't you suspect that elements of that nature could have been created in the big bang itself ?<br /><br />Im imagining that the initial shock wave of material would have created the heavier elements also (and perhaps for millions of years) , and that over time it too would have cooled to liveable temperatures.<br /><br />Maybe our existance thru supernovae is a secondary method of establishing living conditions, and the outer perimeter of our universe was once a habitable zone ?<br />
 
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green_meklar

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<blockquote><font class="small">In reply to:</font><hr /><p>However, wouldn't you suspect that elements of that nature could have been created in the big bang itself ?<p><hr /></p></p></blockquote><br />Well, during the period when the Universe was as hot and dense as the supernovas that fuse heavy elements, I'm not sure whether even hydrogen had formed yet. As far as I know, the evidence is that before the first stars coalesced and ignited, essentially all the atomic matter in the Universe was hydrogen. <div class="Discussion_UserSignature"> <p>________________</p><p>Repent! Repent! The technological singularity is coming!</p> </div>
 
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MeteorWayne

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The surrounding area or environment.<br /><br />A dictionary is one of the best investments a person can make <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
 
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green_meklar

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<blockquote><font class="small">In reply to:</font><hr /><p>What does "ambient" mean?<p><hr /></p></p></blockquote><br />Read. <div class="Discussion_UserSignature"> <p>________________</p><p>Repent! Repent! The technological singularity is coming!</p> </div>
 
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newtonian

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green_meklar - Observations confirm that part of the big bang model which predicts the only elements produced after the big bang but before stars were formed were hydrogen, helium and a small amount of Lithium.<br /><br />Main sequence stars like our sun, if average in magnetic properties etc, and assuming no collisions with brown dwarfs, etc., will go red giant and then will synthesize carbon in the triple alpha reaction - but that is much later.
 
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newtonian

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albert_eimstymied - On your original question, the answers seem to be concerning the temperature of the CMB, or cosmic microwave background radiation.<br /><br />The temperature of the universe is not uniform. As one dramatic example, the temperature of the IGM (= Intergalactic medium) is extremely hot - way hotter than 25C at this time.<br /><br />On terrestrial planets - do you mean earthlike planets?<br /><br />Before planets, stars would have to synthesize the elements that make up planets. <br /><br />There is current research on the earliest generation of stars, well before our sun was formed. <br /><br />I forget the details, but some were much shorter in lifespan than our sun - so elements were synthesized long ago.<br /><br />As for origin of life, I assume you mean life as we know it. For logical, scientific reasons I consider it logical to believe life was created rather than evolved by chance.<br /><br />Either way, though, you need an environment that would sustain life as we know it.<br /><br />Planets can, of course, escape gravitational capture by a star - so, yes, such planets could theoretically exist.<br /><br />I am not aware, however, of any observational evidence that such star-less planets exist.<br /><br />Such planets would be very cold unless, like Io if I remember correctly, tidal interactions with a larger planet cause internal heat to buildup - and then a thick insulating atmosphere holds said heat in.<br /><br />In other words, a planet that while it is star-less, nevertheless orbits a large planet.<br /><br />Hope that helps!<br /><br />
 
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green_meklar

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<blockquote><font class="small">In reply to:</font><hr /><p>Observations confirm that part of the big bang model which predicts the only elements produced after the big bang but before stars were formed were hydrogen, helium and a small amount of Lithium.<p><hr /></p></p></blockquote><br />Makes sense.<br /><blockquote><font class="small">In reply to:</font><hr /><p>On terrestrial planets - do you mean earthlike planets?<p><hr /></p></p></blockquote><br />What else would 'terrestrial planet' mean? o_O <div class="Discussion_UserSignature"> <p>________________</p><p>Repent! Repent! The technological singularity is coming!</p> </div>
 
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bobw

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Strangely enough, I stumbled across a book that says "When the universe was 15 million years old, the CMBR had a temperature of about 300 K, which is close to room temperature..." There is a little diagram which shows this temperature as the time when stars and galaxies began to form. <br /><br />http://www.nap.edu/readingroom/books/cosmology/1.html is the first chapter of the book. You can download the whole thing for free in .pdf format, if you tell them your e-mail and zip code, from the link below or you can read it online a page at a time if you wish. It is a little bit old (1995) so it doesn't have WMAP stuff, just COBE, but I think 15 million years to cool to 25C is probably still good.<br /><br />http://newton.nap.edu/catalog/9293.html#toc<br /><br />About your questions:<br />If the defining event at ~25 C was the beginning of stars and galaxies you could say that things haven't changed much. A little cooler now, more heavy elements, stuff is spread apart more. I would say that those conditions existed until very recently and the major change from then has been that expansion is accelerating now. <br /><br />I guess if life on Earth could have evolved underground or around black smokers then possibly life could exist without suns, but without the accretion disk from stellar formation where would the planets come from? Interesting thought, though. <div class="Discussion_UserSignature"> </div>
 
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