Realitycheck Posted February 28, 2008 Share Posted February 28, 2008 because Big Bang nucleosynthesis models set tight constraints on the amount of baryonic matter present in the early universe. http://en.wikipedia.org/wiki/Baryonic I think that this is why we have concluded the presence of dark matter, because the estimated amount of matter in the universe is not close to what is being used in these models. Therefore, according to these models, the universe is definitely finite. What I was wondering is this. If we compacted the density of all of this matter to where all of the particles in the universe are joined in one big mass, how big would it be? I guess the only way to know that is if you know the numbers used in the models. Sure enough, this wiki does not give anything in the way of references. Link to comment Share on other sites More sharing options...
timo Posted February 28, 2008 Share Posted February 28, 2008 I assume that "amount" is to be read as "density" in the context of the quoted half-sentence, it seems to make more sense if BBNS is influenced by a local density rather than a total amount. Link to comment Share on other sites More sharing options...
Realitycheck Posted February 28, 2008 Author Share Posted February 28, 2008 Where have I heard that before? Link to comment Share on other sites More sharing options...
Dark matter Posted February 29, 2008 Share Posted February 29, 2008 By my opinion, it would not be very large at all, and in fact it may only a few thousand kilometers across. That would be (in my opinion) because the gravity would act as a paradox upon itself and crush the material, making in denser, and giving it yet more gravity, much like a black hole. That would continue until there is an equilibrium between all of the matter and finally the atoms are crushed to infinite volume and infinite length, infinite height, and infinite time. Link to comment Share on other sites More sharing options...
kaneda Posted March 8, 2008 Share Posted March 8, 2008 agentchange. If all the matter in the universe were in a ball, whether a molecule or a light year across, then it would stay like that forever. A singularity or black hole, whatever you want to call it. Big bangs do not happen for that reason. I don't like the use of the word "infinite" so definitely a finite universe. Link to comment Share on other sites More sharing options...
Realitycheck Posted March 8, 2008 Author Share Posted March 8, 2008 I think it would be a lot bigger than a few thousand kilometers across, as any black hole mass would be a lot bigger than a specific point. The question is why would it exist in such a form? All of the matter in the universe contained in an infinitely hot environment where matter is not even sure what form it wants to take and does not even remain in one form for long until something starts catching. It smacks of Big Crunch Theory but that is a pointless avenue because the cycle had to start somewhere. Why would matter have arisen in such a manner? I think the answer is hidden in an old Escher painting. Link to comment Share on other sites More sharing options...
kaneda Posted March 9, 2008 Share Posted March 9, 2008 Heavy elements are created in super-novae. The big bang is essentially the grand-daddy of all super-novae so should have created massive amounts of heavy elements rather than mostly hydrogen and helium. Link to comment Share on other sites More sharing options...
Klaynos Posted March 9, 2008 Share Posted March 9, 2008 Heavy elements are created in super-novae. The big bang is essentially the grand-daddy of all super-novae so should have created massive amounts of heavy elements rather than mostly hydrogen and helium. The big bang and super-novae are completely different phenomena. Link to comment Share on other sites More sharing options...
Martin Posted March 9, 2008 Share Posted March 9, 2008 http://en.wikipedia.org/wiki/Baryonic I think that this is why we have concluded the presence of dark matter,... the presence of dark matter was inferred earlier on other grounds (rotation curves). there is now much evidence for it of many different sorts---either for dark matter (constituting rougly 23 percent of total density of the universe) or some modification of the law of gravity having the same apparent effects. So far, except for comment by Atheist and Klaynos, I can't find any quantitative physics thinking in this thread. All seems verbal. No reason has been given for why we should assume the amount of matter in the universe is finite. Link to comment Share on other sites More sharing options...
Realitycheck Posted March 10, 2008 Author Share Posted March 10, 2008 Infinity is inherently an abstract. My assumptions on how the presence of dark matter was calculated were incorrect. Quantitative physics is a verbal term. Link to comment Share on other sites More sharing options...
Martin Posted March 10, 2008 Share Posted March 10, 2008 the lead post gives a bogus argument which says some stuff and then concludes "Therefore, according to these models, the universe is definitely finite." then just now, this gets reiterated again without justification: "Infinity is inherently an abstract." Agent you seem to have a thing about "infinite". All I can suggest is 1. learn some math, do relevant calculations to what you are discussing. Put relevant calculations into your posts, showing that you are thinking quantitatively. 2. back up your assertions with links to reputable sources. Don't make us hunt. When you quote something give the exact quote. And the page reference is your link is to more than one page. 3. ask more questions, state fewer opinions. I mean real questions, not making some statement and then saying ", right?" that is not a question. Try to act like you are able to learn, and that you are learning something. this forum is supposed to be educational. the main aim is for folks to learn. In that regard, this thread is not serving a constructive purpose. Link to comment Share on other sites More sharing options...
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