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entropy after bigbang
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by
on 2006-10-13 03:42:11 |
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Let's say that a house has less entropy as a pile of bricks, and that a rock has less than sand. In the example of the big bang, immediately after the explosion there are a bunch of individual particles and stuff which then clump together into rocks, stars, masses of gas and junk. Though it's an expanding system stemming from a one point universe, in the time immediately after the big bag wouldn't the process of forming things be considered a loss of entropy in the whole universe?  |
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Re: entropy after bigbang
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by
on 2006-10-13 08:34:34 |
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1. the big bang is less of an explosion, and more of a "holy shit space-time started existing". it cannot always be compared directly to a thermal explosion. 2. particles did NOT form IMMEDIATELY after the big bang. as the different fundamental forces began to differentiate from one another, the various particles we know today (electrons, protons, neutrons, photons, positrons, muons, etc.) came into existence in some sequence, but not all at once. see here for a good chronology of events. 3. Cosmic inflation laid down the "structure" for the universe as it exists today. This is to say, the universe was a balloon which was blown up quickly, and all the irregularity that existed at the quantum level blew up to form the super-strings we see today. This is not a gain or loss in entropy, it is a magnification in size. However, my explanation here is flawed since I am still thinking of the universe as a 3-d object, while it is really a 4-d object, i have to think about it more. shit, im late for work. will edit later. 
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Re: entropy after bigbang
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by
on 2006-10-13 10:19:27 |
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@Gendou: You were thinking of the universe in a 4d sence because you were pointing out a change in the 3rd right? I can't imagine an object 3d or otherwise without using the 4th demention Yeah I wasn't sugguesting the big bang was a thermal explosion because I can't really understand what universe grids flattening and such really means so I picked the setting immediately 'after the big bang' (We can say we are still in it?)- which I don't see how the fundamental forces differentiating really negates my previous delema but let's set the time to after Nucleosynthesis, Wiki P. says: "Protons (hydrogen ions) and neutrons begin to combine into atomic nuclei." occurs at this time. Is this a reduction of entropy? I read the section on 'nuclear fusion' and some fusion releases energy and some absorbs- does that have anything to do with it remaining a gain in entropy? This is the first example to come up with what I was getting at. We can safely say that junk did form from a bunch of smaller things sometime after the 'bang', that's what I was really asking about. Wiki P. Says: "Structure formation in the big bang model proceeds hierarchically, with smaller structures forming before larger ones." which is contrary to this 2d+4d graph. New junk came from that: a) Ice melting shows entropy increasing, which is one way to see that time is moving forwards and not backwards. In Wiki P. it describes the movement in time in the early stages of the 'bang' can be seen with the change in temperature, which is cooling. WTF mate? b) The cooling of the universe in itself is not a loss of entropy? If the system which is explanding and forces seperating makes it so the temperature of the universe appears to be cooling, isn't it still a loss of entropy? c) The fundamental forces differentiating may start at different times but W.P. didn't say they stopped. If they continue forever and one force approaches infinity and one of the others approaches zero (not negative I hope) wouldn't that set it up the universe's bomb? |
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Re: entropy after bigbang
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by SuicidopoliS
on 2006-10-16 12:16:11 (edited 2006-10-16 12:41:26)
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If you're asking questions about the moment right-right-right... after the Big-Bang, at this time the answer is pretty simple: we don't know anything about it. The physical theories we've developped to describe the fundamental forces ruling the universe and stuff actually work pretty good for describing the world as we see it today, but the conditions right after the Big-Bang were so much diffrent we're not sure everything holds up till then. That's why they're doing all those accelerating experiments at CERN and Co, to try to recreate conditions as close as possible to the Big-Bang, in the hope to get to know more about the conditions that were ruling "the universe" back then. What I mean is: entropy is a notion that is meaningful in our actual world, but who knows it might be completely meaningless if you go back to such extreme conditions. And up till know, nobody ever managed to prove the Big-Bang actually really happened, it's just one of the possible theories. Admittingly the most likely one, but still not the only plausible one... Edit: forgot to add; the fact that the universe is cooling down isn't enough reason to say it's entropy is diminishing, since it's volume is increasing. Increasing volume means more possible ways for all the atoms in the universe to be ordened, means more "chaos", meanse more entropy... Also, I don't see how the image you linked to contradicts what preceeded ( that smaller structures formed before larger ones )? First, there just isn't much to see on that graphic, but some sort of milkyways that grow further and further apart from each other, and second, there had to be atoms first before there could even be milkyways... .oO° Life's THE CURE, the rest are details! °Oo. |
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Re: entropy after bigbang
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by
on 2006-10-17 16:12:34 |
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I have one question: how can an infinite thing increase in volume. That doesn't make any sense. The universe has been and always will be as big or small as infinity. Just the "stuff" inside the infinity has consumed a larger portion. That in it self is contradictory, you can fill no higher percentage of infinity no matter how much you add. I do however agree that the preciveable form of the univers has expanded in volume, mostly because if there is litteraly nothing there how can you define it other than the lack of anything You can imgine an object in the 3rd without thinking ofit in the 4th quite easily. what do you think you see at this very moment. You see an object at that particular moment in the 3rd only isolated from how it changes through time. I could be very wrong here, or very right not sure. In all reality your image helps support that idea more than be its contrary. Unless this is the fundamental problem of all images in that if they lack full explination they can be easily misinterpreted. |
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Re: entropy after bigbang
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by SuicidopoliS
on 2006-10-21 12:32:41
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Who said the universe is infinite? There's no way to verify that. I agree with you that our poor human brains are completely incapable of not looking at it that way, but the reality still is we just don't know what's out there, if already there is something out there. "But there's BOUND to be SOMETHING!". Nope, there simply isn't... Welcome to the world of Physics. But let's assume there is something out there, an infinity of strictly nothing, and our universe is expanding in that infinite nothing. Then I agree with you that in fact, there is no way of filling up a higher percentage of nothing... But that is only true if you look at the total picture. If we humans say our universe is expanding, then that means that it is growing bigger for us, from our point of view inside our universe. So for us, the universe can grow bigger. And wheter or not it is filling up a higher percentage of infinity isn't the question ( at least not the question relevant for the entropy question ). .oO° Life's THE CURE, the rest are details! °Oo. |
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Re: entropy after bigbang
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by
on 2006-10-21 13:09:49 (edited 2006-10-21 13:15:22)
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Suicidopolis: you are still thinking of the universe as a 3-D sphere, which it is NOT. i suggest that, before you ponder this further, you read up on the shape of the universe. only then can you visualize (albeit in a primitive way, as all humans are limited in this regard) what the expansion of space represents. Most importantly, and thus emboldened, the universe is not contained inside anything. if there were some infinite container around the universe, it too would be part of the universe! to escape this circular thinking and accept that the universe is, itself, infinite (in the sense that you will never come to a "dead end". let me be clear i do not mean to imply that the universe is or is not a compact space. i am talking about path geometry). if it were not, we would lead to the aformetioned contradiction, which is VERIFICATION that the premise (that universe is finite) is false!!!
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Re: entropy after bigbang
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by SuicidopoliS
on 2006-10-21 15:00:03
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*sniff*, I typed up this whole stuff, and apparently I took too long and got disconnected in the mean time :( Anyway, what I wanted to say is that, in a certain way, I feel we don't know enough about the universe to really be able to say anything about how the 2nd law applies to it ( let's be honest: there's more stuff we don't know, then stuff we do know about it ). And I fear that we're inclined to construct theories and think about the problem in such a way that we'll do justice to the 2nd law, just because we assume it to be true, 'cause we're so familiar with it, and it works just fine on earth ( and even beyond ). But let's face it: nothing actually proves the 2nd law *has to* hold for the entire cosmos. What if the entropy of the universe really is decreasing? Maybe it's just decreasing in such a slow way that we don't notice it? Or in a way we just can't notice it? I think Clausius and Kelvin and whoever else involved at the time, when they came up with the 2nd law, didn't really mean to talk about the *entire* universe, but rather "the universe = the system + the surroundings". They were studying the way certain processes happen spontaneously, and others don't, rather then asking themselves the question if the amount of disorder is increasing in the entire universe. I realize I'm a bit going in against what I said in my previous post, when I wrote something in the lines of "the univers is expanding, thus more volume, thus more entropy", but that only proves ( at least for me ) that we're inclined to turn the question around: we don't really ask ourselves whether or not the entropy of the universe is increasing or not, but rather we are asking ourselves how we can picture the expansion of the universe in such a way that it nicely answers to the 2nd law. .oO° Life's THE CURE, the rest are details! °Oo. |
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Re: entropy after bigbang
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*sigh* entropy is probably the most misunderstood topic in physics - possibly even less well understood than quantum mechanics - and all because of generations of high school and junior high school teachers too stupid to understand the concept and too lazy to find out. in a thermodynamic system, you apply heat to an engine that, as a result performs work. you can also reverse the process where the work a machine performs produces head. except that you can't perfectly reverse a thermodynamic process. every time heat is turned into work and then the work back into heat, some of the energy is lost - permanently. this permanently lost energy is called - ta da! - entropy!. now as for the question of the entropy of the universe - it all depends on whether the universe is an open or closed thermodynamic system. if it's a closed system and heat can't leak away anywhere, then the total net change in the universe's entropy is zero. the process that created the universe, the big bang, will reverse into a "big crunch" and all the energy of the original explosion will be recovered. on the other hand, if the universe is open, and heat can leak away, then the total entropy of the universe is actually dropping. heat leaks away to somewhere 'outside' the universe and when it contracts into a "big crunch" some energy will be lost forever, and the next expansion will be slightly less energetic than the last. eventually, the expansions and contractions of the universe will damp down until all the energy drians away. a third possibility is that there may be an external source of energy constantly being pumped into the universe. then, the universe will either reach an equilibrium where the energy lost to entropy will equal the enery being pumped in from outside (which begs the question, where is all this energy going and coming from?) if the universe gets too much of a charge of energy, there will be no "big crunch". it will expand forever. in that case the universe becomes open with its energy leaking away to ever greater distances also to be unrecoverable. in this scenario the universe becomes a place of ever dropping density of matter and fading radiation. |
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Re: entropy after bigbang
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by
on 2006-12-01 00:12:35 |
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yes but the universe could also continue expanding and never crunch together again. the net curvature of space-time is independent of the openness or closeness of the universe. since there is no "outside" for energy to escape to, i would think the universe is going to be closed! string theorists might argue with me on that point, but i would likely insult their mother and conclude they are jerks.
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