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Eternal Inflation and it's Philospohical implications

  1. Apr 9, 2003 #1
    As anlternative to some other pre-Big Bang theories (like the Hawking-Turok Instanton pea model) there is a model of Eternal, Chaotic or Open inflation, in which Inflation reproduces itself eternally.
    The merit of this model of inflation is that there is no requirement for a "beginning of time". Once inflation starts, it keeps reproducing new space-time bubbles, each inflating space-time bubble representing a new universe coming out of a big bang.
  2. jcsd
  3. Apr 9, 2003 #2


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    Eternal inflation is very similar to the old steady state universe, even though proponents of the theory would like to downplay the similarities. Each "bubble universe" is created from a pre-existing space-time, but the universe as a whole may be eternal, as you've said. But the problem is, the pre-existing space itself is expanding. For a universe finite in size, logically it follows that the volume of space would be smaller and smaller the further back in time you look. Eventually at some time in the past, the entire universe (or multiverse, if you will) shrinks down to a point of infinite density. So even an eternal inflation universe would have a beginning. Andrei Linde admits even the self reproducing universe may start off with a primordial singularity.

    But with an infinite volume of space, there may indeed be no beginning at all. However, philosophically there is something very unsettling about an infinite volume of space that has been expanding for an infinite amount of time. Maybe it's because there is comfort in the finite, or maybe it's just because infinity is such an ugly concept. Should analysis of the WMAP survey find conlusive evidence that the universe is actually finite, then this model will be in the toilet. That is, unless someone develops a model of inflation based on extra dimensional space that has a minimum of 4 spatial dimensions.

    But ignoring WMAP for a moment, try to compare an infinite chaotic inflation universe with the old steady state models. Hoyle invisioned an infinite universe that had been expanding forever, but with matter continously being created from the vacuum to fill in the great voids. Later models dropped the perfect cosmological principle (that idea that the universe looks the same everywhere and at all times) and included the ideas of mini big bangs arising from the vacuum. Though the math and mechanism for these later models were obviously different than inflation, the basic concept is very much alike. They both involved infinite space, and both involved an infinite regress.

    At any rate, it seems the issue again comes down to the concept of infinity. Other models such as the cyclic universe, based on M theory also includes a universe that is infinite in space and time, so it seems to be an unavoidable topic these days.
  4. Apr 9, 2003 #3
    Just as the concept of paradox is increasingly unavoidable. Although, why you think infinity is "ugly" is beyond me. Certainly it is not nice and neat and easily defined, but personally I enjoy abstract art as much as any other kind. :0)
  5. Apr 9, 2003 #4


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    It's probably a mental thing, as the idea of an infinite number of galaxies, infinite stars, etc. is unsettling. Maybe if the damn universe was static it might be easier to swallow, but expansion throws that out the window.

    In physics, infinity is often a sign a certain theory is wrong, such as in the case of attempts to formulate a theory of quantum gravity.
  6. Apr 9, 2003 #5
    I agree that more often than not that is what it means, but it also means big things are likely in the wind. Newton used infinity to create an incredibly useful theory of motion and calculus. M-theory is now using it to reconcile a rift between mathematics and physics that has grown for over a century. If infinity can't lead to the next big thing in physics it may be that more profound paradoxes are required and that could be a great deal more difficult to resolve. :0)
  7. Apr 9, 2003 #6
    M-/string Theory does a pretty good job (IMO) in describing how the universe can continue to expand forever. You see, instead of saying that it will continue to alternate between expansion and contraction, it postulates that it (the universe) is always doing both. It all has to do with forms of measurement, since the measurement of the distance between "wound" strings is inversley proportional to the measurement of the distance between "vibrational" strings.
  8. Apr 9, 2003 #7
    I can for sure think of uglyer concepts as infinite.

    What about a finite space. When a spacetraveller arrives there, he will find the sign "End of space. Stop here, or you'll be nowhere!".

    Or things like begin or end of time. What would it be, if all of a sudden the universe would simply stop. Just before that, a big sign would be written in the sky: "End of time", and then everything would come to a halt and ceased to be.

    By the way, it is a good thing that the universe as such isn't consciouss about al things that go on in the universe. Else, it would already have ceased to be, or never even have begun to be. For sure!
  9. Apr 9, 2003 #8


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    The beauty of curved space is that the universe can be finite yet be unbounded and have no edges. A traveller could go in straight line forever, and though he pass where he started from several times, he would never reach an edge. So finite space seems a much more pleasant alternative.

    Finite time on the other hand, still does not seem so straight forward. However, if time is literally an extra spatial dimension (as with the no boundary proposal) the point is moot. The universe would only seem to have a beginning, while space-time as a whole would be eternal. The past present and future would exist as a 4 dimensional, static eternal universe. This eliminates the need for an infinite regress, and offers to solve the antinomy of both time and space. But this idea is counter-intuitive, and has it's own fair share of problems.
  10. Apr 9, 2003 #9
    So, the singularity of finite time is more attractive than infinite space? Both just sound paradoxical to me.
  11. Apr 9, 2003 #10


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    Carefull with the word singularity here. In physics, it means a point of infinite density with zero volume.

    With a 4D universe, everything would literally be space. Time would be an illusion. Unless you find geometry to be paradoxical itself, there doesn't seem to be any problems of that nature here.
  12. Apr 9, 2003 #11
    I would suggest this is a temporal singularity. Just as occurs with a physical singularity, the passage of time slows to zero when inside and no distinction between either kind of singularity is possible to measure. Thus, by physical standards they are one and the same thing.

    No matter what, it definitely qualifies as a paradox. It not only defies experience in much the same manner as Zeno's philosophy, it defies reason and logic. Just where did this "geometry" come from? If cause and effect don't apply because time doesn't apply, then logic and reason most certainly do not.
  13. Apr 9, 2003 #12


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    I don't see how that would be a paradox. Where did it come from would be a non question, since it would be non contingent. Of course it defies experience, and is one of the reasons this idea isn't likely to catch on. But there is nothing paradoxal or logically inconsistent about it, or at least no such problems have been found.

    The notion of an uncaused, eternal universe that just IS may sound hard to swallow, but that alone does not make it an illogical or unreasonable proposition. As I've stated before, there is nothing logically inconsistant about something existing without being created by something else. That is, unless you know of something philosophers have missed.
  14. Apr 10, 2003 #13
    To say something is infinite is to say it has no limits, which, in itself is to assert a limit. This is a contradiction philosophers have known about since the invention of philosophy. So absurd has the very idea of infinity been considered that Aristotle himself asserted there is no such thing as an actual infinity, just potential ones. He then successfully banned the use of actual infinities and other paradoxes from academia.
  15. Apr 10, 2003 #14


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    What does infinity have to do with the no boundary proposal?
  16. Apr 10, 2003 #15
    Don't get that logic. If something has no limit, then it just asserts it doesn't have limit.

    Same is the fact that the use of the term "nothing" is not making it into "something".

    On the other hand the concept of infinity is contradictionary. It is a contradiction f.i. that the infinity exist of finite parts.

    "Infinity is a contradiction, and is full of contradictions. From the outset it is a contradiction that an infinity is composed of nothing but finites, and yet this is the case. The limitedness of the material world leads no less to contradictions than its unlimitedness, and every attempt to get over these contradictions leads, as we have seen, to new and worse contradictions. It is just because infinity is a contradiction that it is an infinite process, unrolling endlessly in time and in space. The removal of the contradiction would be the end of infinity. "

    [F. Engels, Anti-Duhring (1877). V. Philosophy of Nature. Time and Space]
    Last edited: Apr 10, 2003
  17. Apr 10, 2003 #16

    Exactly my response. Bravo.
  18. Apr 10, 2003 #17
    Exactly. In this case, the concept of infinity itself contains the finite within it as well in that it denies it has limits. To say something has no limits is to impose a limit, the limit that it has no limit.

    The two terms are not wholly seperate and distinct, but instead, define each other. The finite and infinite, nothing and something, up and down, back and front, inside and outside all define each other. Attempting to speak of one without referring to or at least implying the other leads to semantically meaningless mumbo jumbo.

    In the case of infinity, when we do refer to its opposite it leads to contradiction. In other words, paradox. General semantics goes into more detail on this issue. Essentially, to assert infinity is real is to imply an infinitely valued logic in contrast to Aristotle's finite true/false logic.
  19. Apr 10, 2003 #18
    Yes, this semantic nightmare has been pointed out many times before in a hundred other threads about Paradox. It is a point that never seems to be understood. I would suggest getting back to the orginal topic of this thread. It was very interesting until it was pulled off track to step on a dead horse.
  20. Apr 10, 2003 #19
    Sorry about that, didn't mean to pop anyone's bubble or derail the conversation. Merely to point out the semantic and aesthetic difficulties people were bringing up. :0)
  21. Apr 10, 2003 #20
    I don't understand everyone's confusion with the limit of limitlessness. Do you think it's possible for something that is limitless to have a limit? And yet, if there is something that is impossible for this [limitless] entity, then it has a limit (whatever it is that is impossible for it is it's limit).
  22. Apr 10, 2003 #21
    Don't worry, you are not alone. This has been an infinitely confusing issue for millennia. Just ignore it, it'll go away. :0)
  23. Apr 10, 2003 #22
    But don't you think it's possible to explain it?

    Seriously, what was wrong with my explanation?
  24. Apr 10, 2003 #23
    Don't agree on that logic. Not having a limit, means that there isn't a limit, which doesn't impose a limit.

    Using your kind of reasoning also one could say that something undifned is self-contradictionary, cause it would be defined (as 'undefined').

    But this reasoning is absurd.
  25. Apr 10, 2003 #24
    No it's not, and your illustration is as good as any, for proving Wu Li's point.

    I do not, however, approve of Wuliheron's use of the word "infinity" instead of "limitlessness". I agree that there is a paradox, when speaking of something as being "limitless"; but "infinity" in mathematics and physics can just be endlessness in two directions, it doesn't have to imply limitlessness (and rarely, if ever, does).
  26. Apr 10, 2003 #25
    Why certainly you can explain infinity, just as you can explain paradox and the irrational. But your explanation needs to address the heart of the issue more directly instead of relying on finite classical Aristotelian logic alone. Heusdens' quote is more on the money:

    Infinity is a double negative and, thus, a positive as this quote makes clear. It is a logical tautology and as such lends itself better to more poetic expression. The passage above touches on the poetic and the most famous western poetic passage to date on infinity is that of William Blake:

    Because infinity is tautological and lends itself to poetic expression, these are widely considered the most satisfying and clear ways to express the concept.
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