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Colapse of the universe

  1. Jan 13, 2009 #1
    I know that there are many different subscriptions on how the universe will end, and I have a question. If the universe is expanding and is increasing in expansion than theroreticly it may fall in on it's self... That much I understand. (I am only refering to this theroy, because it confuses me. So after the universe snaps back on it's self would it create a supermassive black hole, or would there be so much mass involved that the singularity that it formed not beable to contain it's self and just rip back out creating the universe over and over again throughout time. Is this even a theroy or have I missunderstood what I have read?
  2. jcsd
  3. Jan 13, 2009 #2


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    This is my personal view on the questions you raise. I'm sure you know what skepticism is---holding back on belief, methodically examining the different possibilities without making a premature commitment to one or the other.

    All these things have to be studied. The different ways the U could have evolved and be going to evolve in future. I think you said you are a physics student---highschool, college whatever. You quite possibly don't have time to go into this methodically and do careful comparison of alternative models. You probably need to study your coursework, pass the tests, write the term-papers etc.

    You arent likely to miss out on much by focusing on immediate job at hand. Cosmology only recently became a precision science (with instruments like Hubble telescope and WMAP microwave.) It is also undergoing a revolution because of quantum cosmology, the possibility that the big bang was actually a bounce. These things are too speculative and tentative to be easy to study now. The problems are not going to be solved in a hurry either! The experts are really just getting started. The problems will still be there in 4 or 5 years.

    That said, I'm willing to make a stab at trying to answer pretty much any question about cosmology and quantum cosmology (QC). I don't do research, I just follow the scene as a spectator.

    Cosmologists business is to construct different math models of the universe and see which models fit the data best. But they also study a variety of less realistic cases just for understanding the range of possibilities. They run computer simulations of different cases to see what will happen. So it isn't all focused on one favorite or most likely model.

    they now have a lot of data. millions of data points. to fit their models to, and they have a best-fit LCDM model which is the current favorite ("lambda cold dark matter").
    If you ask a cosmologist to predict the future of our universe all he can do is tell you the future according to the best-fit LCDM model universe---the experts cant actually KNOW the future, they can only project using reasonably good-fit models.

    LCDM continues expanding forever and does not do a crunch, and does not do a "big rip" or anything dramatic and Hollywood like that. there is a gradual acceleration but the effects are not very remarkable. local galaxies merge into one large conglomerate galaxy which stays together indefinitely as the stars gradually burn out. more distant galaxies get so far away they effectively vanish from sight.

    Not to take this too seriously :biggrin: It's good science, given present knowledge, but eventually there will be new data, the favorite best-fit model will change, our prospects of the the future may change, based on a slightly different model. science keeps on getting better. instruments get better etc. new ideas gradually come to light etc.

    I personally think that in 4 or 5 years we will know a good deal more about the past surrounding and before the big bang. There will be more books about this, more research papers to read, more conferences. And people will have found ways to test the mathematical models that have a bounce. Because they will predict slightly different stuff that we can observe. and check to see if they are wrong or not.

    I personally don't expect the consensus vision of the future to change as much as how we picture events right before and around the big bang---if we are talking on a 4 or 5 years timescale. We will still have the LCDM, but it will probably be extended back a bit with some kind of QC bounce instead of a singularity.
    Last edited: Jan 13, 2009
  4. Jan 15, 2009 #3
    how about this. instead of expanding on and on. it stops at some point. and starts to shrink. o_O would everything go backwards. would time reverse itself.
  5. Jan 15, 2009 #4


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    People used to be interested in that, 15 or 20 years ago. They used to include it as one possibility and study that case. For the past 10 years there has been a lot less interest in that case though. The 1998 supernova findings make it less likely.

    One occasionally hears that idea put forward, but I don't know of any physical reason to support it. Don't know anything in that case that would cause time to reverse, or even if it is logically possible.

    With collapse not a very strong possibility anyway, I don't think I'd want to spend much thought on how collapse could cause time reversal.
  6. Jan 15, 2009 #5


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    Marcus, that answer must be the best i have ever seen, (the first one) thank you.
  7. Jan 18, 2009 #6
    Maybe the universe isn't expanding. Maybe it is collapsing and the point of collapse is farther than we can see. It's over there. The objects closest to the point of collapse would move faster and faster but to us they seem to be expanding. Objects behind us would seem to be expanding because we're moving faster than they are towards the point of collapse. That would seem to explain a lot of things.
  8. Jan 18, 2009 #7


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    It gives some rather bizarre results. Notably: if time reversed, then everything in it would also be time-reversed, including my living creatures trying to figure out what their universe is doing. As far as they are concerned, time is moving forward and their universe is expanding; there would be no experiment that could show otherwise.

    And, strangely enough, that has quite real consequences on us. If such a thing can exist, we could very well be in a time-reversed, shrinking universe right now and we would never know it.
    Last edited: Jan 18, 2009
  9. Jan 18, 2009 #8
    maybe jesus christ was really an ancient astronaut.
  10. Jan 18, 2009 #9


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    No time reversal in a t^2 interpretation.
  11. Jan 23, 2009 #10
    good question dude. i was also thinking that maybe the big bang created a super massive black hole in it self and that the universe maybe actually orbiting around it and it will eventually cause the universe to collapse in on itslef. and i was also thinking that as we get closer to it time will speed up and then as we hit the event horizon it will stretch and slow dramaticly or maybe it could do the opposit and speed up so much it will reverse time.

    haha im really just trying to entertain my brain and there isnt any proof to wat im saying. but if anyone can help me that would great.
  12. Jan 23, 2009 #11


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    How do it know? Time is what clocks measure. There is no 'superclock' to refer to, so we humans view the flow of time as a constant. It makes sense because all time related events march to the same drummer from our perspective. Find an observation that defies this premise and you might be onto something.
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