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How will it end?

  1. Nov 22, 2004 #1
    According to most recent and most believed theories, how is the universe going to end? Of will it just keep expanding? How solid is the theory of the Big Crunch?

    thanks
     
  2. jcsd
  3. Nov 22, 2004 #2

    Garth

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    How long is a piece of string?
    The standard view that if the actual density is above the critical density then the universe will contract at some point has been thrown into some confusion because of the deduced accelerated cosmic expansion and the consequent role of the hypothetical dark energy.

    Whether the total density is this large or not depends on who you speak to. So,
    your guess is as good as anybody's!

    Garth
     
  4. Nov 22, 2004 #3
    When ever I feel like it.
     
  5. Nov 22, 2004 #4
    Speculation

    All theories on how the universe is going to end is pure speculation at this point in man's knowledge of the universe.

    Some suggest as you have that the universe may end in a big crunch. Others claim that the universe will expand or exist for an infinite amount of time in which the universe would die of a "heat death".

    I lean towards a cyclic universe in which the universe is constantly expanding and contracting. To propose a beginning and end to the universe is born from linear thinking.
     
  6. Nov 22, 2004 #5
    speculation indeed-

    given the new ideas like branes from M-theory and spin-networks from LQG- it could very well be that the evolution of the universe will unfold in ways we cannot even imagine- such as future collisions/intersections/mergings with random branes casuing unpredictible effects- or the matrix of spacetime could deform/transform in time due to the exponential increase in Dark Energy and expansion- who knows?

    and this doesn't even consider what role intelligence with technology developed to the limit of physics with zero-point energy and quantum computing may do
     
  7. Nov 22, 2004 #6
    Question: Do we know that the universe will end?
    Question: If yes, There's obviouly no way to advoid it. So what's the use of living when in several billion years, we will be a singularity? What is the point to life?
    Question: If no, what do YOU think will happen to the universe?
    Question: If you answer that you can't say for sure, then which one are you leaning towards?

    explain that more to me? Expecially the "role intelligence"
     
  8. Nov 23, 2004 #7

    turbo

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    We do not know that. The universe may be in a state of steady creation, for all we know.

    Wow! Most of us go through our lives (even doing little things like brushing our teeth and dressing ourselves) with enough commitment to make that a moot question. We can pose the question academically, but the fact that we (and other animals) act in ways that that enhance our self-preservation should be considered proof that life has value (at least to ourselves). Of course, even microbes seem to exhibit "behavior" that is self-serving, so perhaps we cannot blithely attribute value to such behavior - we're just hard-wired that way.

    The universe may coast along forever, creating new matter incrementally. It could die a long slow "heat death", or maybe collapse in upon itself. There are a lot of possibilities. Maybe we're here to try to find that out.

    The universe may coast along forever, creating new matter incrementally.
     
  9. Nov 23, 2004 #8

    Phobos

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  10. Nov 23, 2004 #9
    How is the universe creating new matter? Matter can't be just created can it? I don't see how that is physically possible.

    I read somewhere that Heat death is when the universe reaches maximum entropy. What does that mean exactly? That the disorder in the universe is too high be hold survival? could someone explain this some more?
     
  11. Nov 23, 2004 #10

    turbo

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    Matter can be created through Hawking radiation. The vacuum surrounding black holes is suffused with a sea of virtual particle/antiparticle pairs. Black holes can promote virtual particles of the quantum vacuum to real particles by capturing their partners. If the field of virtual particle pairs can be polarized by the presence of mass, black holes will be able to capture an excess of antimatter particles, thus promoting an excess of matter particles to "real" status. If CERN's Athena project detects a difference in the gravitational infall rate between hydrogen and antihydrogen (which they intend to produce in experimentally usable quantities) the mechanism by which the ZPE field can be polarized will be established.

    Warning: This model is not standard cosmology, by any stretch. The Hawking radiation model is quite widely accepted in some circles, but the consequences of Hawking radiation in the presence of a polarized ZPE field have not been examined, to my knowledge.
     
    Last edited: Nov 23, 2004
  12. Nov 23, 2004 #11

    Phobos

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    Virtual particles exist but I'm not so sure its "creating" matter like turbo-1 describes. But that's probably best left to a separate topic (check out some of the ongoing/past discussions by turbo-1). The mainstream theory does not point to a steady state universe.

    It's not disorder in the sense of the universe running wild. Instead, as entropy increases, energy is converted to less useful forms (e.g., lower and lower heat). Stars will burn out. Matter will fall apart. Black holes will evaporate. The sparse particles that remain will get farther apart with no significant interactions. Everything will have sunk to the lowest energy state.
     
  13. Nov 23, 2004 #12
    Thank you very much for the posts, I still have more questions though.

    So the black hole is actually radiating particles because within the black hole, there are particles being formed from "a sea of virtual particle/antiparticle pairs." How is this radiation able to excape the gavatational pull of the black hole? what do you mean by the word "virtual"?

    How is this different from the theoretical "Big Freeze"?
     
  14. Nov 23, 2004 #13

    turbo

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    In regard to the "heat death" model, perhaps its fair to say that everything that exists in our universe is an expression of energy differences. When everything in the universe has died, diffused, and cooled to the point that there are no energy differences left, existence is over. The fact that the universe may not yet be at zero degrees absolute is moot. As you say, the energy has been converted to "less useful forms".
    :smile:
     
  15. Nov 23, 2004 #14
    how can energy be destoryed? Or as you put it, the universe "dies"?
     
  16. Nov 23, 2004 #15

    turbo

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    The vacuum (empty space) of the universe is not really empty, according to quantum theorists. It is a sea of particle/antiparticle pairs that arise spontaneously and annihilate spontaneously within the parameters set by the Heisenberg Uncertainty Principle. The existence of the the quantum vacuum (sometimes referred to as the ZPE field as an acronym for zero point energy) has been experimentally proven by quite a number of experiments that have been designed to demonstrate the Casimir Effect (do a Google search on that!). Steven Hawking has described a method (Hawking radiation) by which one of these particles (which we call "virtual particles" due to their fleeting and normally self-negating existence) can be captured at the event horizon of a black hole. It cannot annihilate its partner, as it would in the "normal" (if we can call it that with a straight face) quantum vacuum, so it becomes a "real" particle, which will persist in our universe. Thus "new" matter is formed in our observable universe.
     
    Last edited: Nov 23, 2004
  17. Nov 23, 2004 #16
    does this mean that the black hole loses mass?
     
  18. Nov 23, 2004 #17

    turbo

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    In Hawking's model, yes the black hole loses mass because it has to give up some energy to promote the particle outside the event horizon to "real" status.
     
  19. Nov 23, 2004 #18

    Chronos

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    Current physics make steady state theory [continuous creation of new matter] a long shot in the competition for the title of 'Standard Model'. The first law of thermodynamics, which states energy cannot be created or destroyed, is still very popular and experimentally well supported. GR also predicts energy conservation, albeit the case is not ironclad. And energy conservation is also required by Noether's Theorem, as well as the Hamiltonian operator in quantum mechanics.

    More telling is the lack of a viable theoretical model for the creation of matter ex nilho. BBT, of course suffers this same problem. The difference is the problem only occurs one time - at the very first instant of the Big Bang - and under extreme conditions where the very laws of physics are poorly understood. Explaining the creation of matter ex nilho after the BB is much more problematic. We have a relatively thorough understanding of the conditions and physical laws that apply after the Big Bang, and there are no experimentally supported theoretical models for creation of matter ex nilho that satisfy these constraints.

    Perhaps such a model will someday emerge. At present, it just does not look promising. Do we need to specifically look for such evidence at present? I would say no. If the evidence is out there, it will be found as a natural consequence of our continuing to expand our knowledge of current theory. And that is a generally more productive and practical approach than firing what-if shots into the dark. People who make a career in research are not inclined to take a lot of low percentage shots.

    Heat death is just that. All the stars that can be formed will be formed, and will all eventually run out of fuel.
     
  20. Nov 23, 2004 #19
    I read this:

    Is this person talking about heat death? What is the difference between the Big Freeze and Heat Death?

    Chronos, you say that the BBT is more popular than the creation of matter ex nilho. What about your input on how the universe will end?

    How reliable is Hawking Radiation?
     
  21. Nov 24, 2004 #20

    Chronos

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    Personal opinion? How awkward. In a big freeze scenario, you pretty much recreate the conditions from which the Big Bang arose [a pervasive state of equilibrium]. In that case, I would guess if it happened once, why not again? Quantum theory suggests nature objects to such a state. Summary, another BB appears likely [perhaps inevitable] after the current universe thins out sufficiently.
     
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