The Big Bang Theory is Unscientific

Discussion in 'Astronomy, Exobiology, & Cosmology' started by §outh§tar, Nov 25, 2004.

  1. phlogistician Banned Banned

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    Ah, boxes, what an interesting idea.

    Ok, if the Universe is infinitely old, is it also infinitely large? See, a Universe which doesn't have a finite size, or finite amount of matter/energy in it poses problems, doesn't it? And a finite sized Universe, that didn't have a beginning, well, thah begs the question, what constrains the Universe?

    So, let's examine these possibilities. There was no big bang, the Universe and everything in it has always been there, and we can 'extend the arrows of time infinitely backwards'.

    Hmm, so in this inifinite time, how come the Universe hasn't suffered 'heat death'? If energy moves, and coalesces back into matter, why hasn't it spread out evenly, and become infinitely diluted? Or isn't the Universe infinite, and if not, what constrains it? What's 'the box'? So, the universe must be infinitely large?

    Does it also, therefore, contain an infinite amount of matter? Because if it's finite, a finite amount of matter, spread out in an infinite Universe, well, that means, well, matter is spread out so thinly, it becomes CMB, and without anisotropy, we have heat death. So here's a metaphysical question for you, if you have an infinite amount of matter, and an infinite space to put it in, do you still have space between your matter, or is the entire Universe full of matter, with no spaces?

    So, what if matter and space are the same thing. That solves this question, but we're effectively talking about ether then. Matter being nothing more than waves in the ether?

    A steady state is not simpler, more elegant or more beautiful than a big bang then, and it doesn't solve the question of origins at all, rather just ignores that question. Probably the biggest question of all time! I know science doesnt have to provide satisfactory answers, that's not it's job, but not having this question answered certainly lacks the 'beauty' aspect a theory is supposedly to have.
     
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  3. marv Just a dumb hillbilly... Registered Senior Member

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    A BB requires a "before", which in turn then requires an "after". The BB also postulates an expanding universe which in turn requires an "outside". These then become mysteries that parallel the "creation", "final day" and "heaven/hell" in turn in religion. I think that this pretty much represents thinking in the box. The only difference is that religion is content to leave matters as "mysteries". But the mainstream science clergy marches on ignoring what may be a reasonable alternative.

    What is wrong with the concept of infinity? It's not that difficult to grasp. Mathmeticians do it all the time. Must everything have a boundary or beginning or end?

    An infinite universe, in both time and dimension, in which there is a continuing exchange between "space" and "matter" seems to be a reasonable, and I might add elegant, alternative to the BB. The only theory that needs to be proved, and it's already been offered, is that matter can "pop" in and out of "empty" space.
     
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  5. blobrana Registered Senior Member

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    @marv
    I don’t want to sound like a preacher but,
    I would disagree with most of what you have said.
    The bb theory does <b>not require</b> a before. As I’ve said before the infinite temperature, infinite matter compressed into a singularity is beyond our current mathematics to deal with. (<I>that</I> is the major detraction to the theory, IMHO)

    The Ekpyrotic Universe is <B>another theory</B> dealing with the big bang, but in its case, it gets around the infinities by using 5 dimensional membranes.

    The classical BB postulates an expanding universe which <b>does not </b> requires an "outside", because the big bang `creates` space-time that is expanding into a `region` that contains no space-time, a sort of <b>infinite void</b>.
    (<i>in this case, the infinities are not scary for the mathematician, because we don’t need to make any calculation on it for the theory to work – but generally, when infinities crop up in calculations then something is wrong</i>)


    These thing may seem strange to the layperson,
    and it is good that you do question them, (as any good scientist should),

    but when thousands of others have tried to find alternative theories to fit what we see, or find major flaws, and have failed (<i>so far</i>), we must tend to lean toward the idea that the theory is on the right track…
     
    Last edited: Nov 29, 2004
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  7. marv Just a dumb hillbilly... Registered Senior Member

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    What is being said here is that the singularity which "created" the BB is the "god" that created the universe. What's being offered are mysteries offered as answers to what are really simple questions. It seems that we are all too intent on complicating the trivial.
    • "...infinite temperature, infinite matter compressed into a singularity..." Why was it compressed, when, and what did it?
    • "The Ekpyrotic Universe...gets around the infinities by using 5 dimensional membranes." Unproveable theories needed to support unproveable theories is a red flag.
    • "...the big bang `creates` space-time..." Then where was the singularity except in some mysterious "nowhere, notime"?
    • ...a `region` that contains no space-time, a sort of infinite void...this is a contradiction , but I see a glimmer of hope in the phrase "infinite void"!
    This begs the question, "Where is the failure of an 'infinite space, infinite time' model of the universe." As theories go, why would that not be just as valid, as a theory, as the BB? I do see one advantage to the BB theory, however. It preserves the option of a theistic order to the universe.

    Thousands of scientists have invested careers, reputations, grant money and many decades in the BB. Although I've invested nothing in any theory, I can understand why they exhibit such vigor in holding on to the BB. I guess I would, too.
     
  8. mercurio 9th dan seppuku sensei Registered Senior Member

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    Couldn't agree more:

    http://mathforum.org/library/drmath/view/62486.html
     
  9. marv Just a dumb hillbilly... Registered Senior Member

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    I agree that infinities cropping up in math calculations pose a problem. However, the "infinity" discussed here deals with the nature of the universe.
     
  10. apolo Registered Senior Member

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    Hi Phlogistician ( That's a develishly hard word to spell. Does it mean something in some language ?)

    I was going to answer some of the strange selfcontradictory questions you posed in your reply to my post about a universe that is infinite in time and space. But I see that Marv (now there is a nice short handle) have already done so.
    However Blobrana's sentence " when matter was consentrated in one singularity we have no math to deal with it" caught my eye. And it seems to me that, that is precisely the reason (or one of the reasons) why the BBT cannot be taken seriously. Now, we know that math can be used to describe things that we cannot see or hear or touch. So if even math fails us, where are we? I'm reminded of a famous saying by Einstein "SO FAR AS MATHEMATICS REFER TO REALITY, THEY ARE NOT CERTAIN. AND SO FAR AS THEY ARE CERTAIN, THEY DO NOT REFER TO REALITY"

    As ever, kid regards from APOLO
     
  11. phlogistician Banned Banned

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    Apolo, no matter which model you prefer, there is still the 'where did it come from' question. Solid state Universe just ignores this point. It's like saying 'god did it', and drawing a line under your investigations. How did the matter/energy come into being in a solid state Universe?

    Marv hasn't answered my questions at all. He just threw out some more. The BB does not require a 'before'. Nothing caused the BB. The BB was the birth of space/time, the creation of dimensions.

    The problem here for people, is that our thinking is constrained by what we see every day. We see matter as solid, indestructible, and it's interactions predictable, and described by simple maths. We use terms like 'laws' to describe the ways in which matter behaves, and the mathematical models we use to describe those behaviours. That's a very Victorian mindset. Matter doesn't obey 'laws', it just is. It does what it does, and we observe, and model.

    On closer inspection, matter behaves in very complex ways, and requires some truly scary mathematics to describe those. But matter can still do whatever, it is not constrained by logic, rules, or mathematics. All of these things are derivatives _from_ the existance of matter, because we exist because of matter. mathematics and logic do not exists outside the Universe, they are inside it.

    So, in a void, before a Universe has sprung into being, what have you? Nothing, it's a void, remember. Try not to take too much of yourself into that void, you aren't there either. So, this void, what is is constrained by? Nothing. What can happen then? Well, logic says nothing, because we need a chain of events. Remember though, Logic is a product of the Universe, it does not exists outside it. So, what is constraining the behaviour of this infinite void? Nothing. So what can it do? Anything. Can matter suddenly spring from somewhere? Of course, what's stopping it?

    Of course, matter is made of energy, energy is a wave, with positive and negative parts to the waveform, hence waves, at the right time, and right pahse, can temporaily cancel out each other. So the sum of energy in a wave, over an even number of cycles, is zero. So what was created in the big bang? Nothing more than unbalance. A differential, between positive, and negative. a variation from Zero. Now, there are some interesting mathematical concepts, these being Zero, and Inifinity. In this Infinite void, suddenly we have something which is non-zero. An infinite amount of zero adds up to a 1. What is the 1? Our entire Universe. Everything that is. How big was it? It was just 1? Well, it got complex (maths pun for the initiated), which gave us dimensions.

    OK, so that last part was a rather abstract mathematical illustration. The physcial version is, we have no rules, so anything can happen. Anything did. Anything suddenly, was very different from nothing, and suddenly became the biggest thing. Luckily, something didn't collapse in on itself. nor expand in a uniform fashion, and formed a framework to support matter.

    Simple, elegant, beautiful.

    Now, explain where all the stuff came from in the steady state Universe, and maybe you have a model to rival the BB.
     
  12. mercurio 9th dan seppuku sensei Registered Senior Member

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    Phlogiston was the hypothetical 'fire-essence' that was supposed to make stuff actually burn.

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    http://en.wikipedia.org/wiki/Phlogiston_theory
     
  13. marv Just a dumb hillbilly... Registered Senior Member

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    Not exactly. The "infinite dimension, infinite time" model requires no begining or end by definition. Nor is ID-IT a static model, it only requires the interchangeability between matter and energy as Einstein conveniently proved and Hiroshima demonstrated.
    ...and no exotic theories to support a "creation". We may have no rules, but nature certainly does; it's simply a matter of uncovering them.
     
  14. phlogistician Banned Banned

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    But where does the matter/energy come from in your model? Can you explain that? Saying 'it was always there' isn't an answer! IF the 'Universe' has always been there, where did it's contents come from? THAT is a 'beginning' question.


    'nature' is defined by the Universe, as it exists now. Nature is part of our Universe. Nature does not exist outside, nor govern, our Universe.

    If our Universe sprang into existance from a void, that's nature.
     
  15. phlogistician Banned Banned

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    Correct, and a 'phlogistician' would be a made up name for someone who keeps fanning the flames, .....
     
  16. marv Just a dumb hillbilly... Registered Senior Member

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    Is it necessary for everything to have a begining or end as in the BB model? And where did this "void" that contained the singularity that gave birth to the BB come from?
    The "contents" have always been there. It's the ultimate re-cycling example of E=MC² and M=E/C².
    That's your opinion. Mine is that nature and the universe are one and the same. Nature is more than flowers and trees and fish. Nature is everything, everywhere, always.
    ...that "void" had to have been either finite or infinite. Which do you choose, phlogistician, to satisfy the BB theory in a non-theological manner?

    This comes close to an either/or argument. There are two choices:
    • universe from BB from singularity from void from ?????
    OR
    • universe!
    So that leaves us with....
    ...and "Marvin" is 'friend of the sea', that nasty stuff that trys to wash clean and put out fires.

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  17. blobrana Registered Senior Member

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    Hum,
    Well ultimately, you may be right.

    i.e., it’s possible that there is just one question.
    As in <b> universe----> BB->universe----->BB->universe</b> etc...

    However, perhaps asking that question is meaning less as our universe (our space-time) would be separate from any proceeding universe (which by definition means everything)

    <b> universe----> empty->universe----->empty->universe</b>

    The other universes would perhaps be very similar to our universe (with Darwinian principles involved) but they would be totally `cut-off` from our universe.

    Perhaps since we don’t have the mathematic to deal with infinities at the beginning, perhaps we could look at the other end…
    I.e., How can an expanding universe produces a big bang (er, quantum fluctuations)?

    Or perhaps we can just sidestep the infinities by saying that singularities are not bottomless pits, but have a finite size , albeit very, very small 10<sup>-42</sup> cm in size…
    Then we can use our normal everyday maths to make sense, and perhaps verifiable with observation of black-holes (singularity), or the creation of mini black holes in the next gen colliders.
     
  18. phlogistician Banned Banned

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    It's not just the BB model that has a beginning! In a 'steady state' model, the questions are still unanswered 'where did it all come from from' and 'how did it come to exist'. Handwaving over these questions and saying 'it was always ther' is NOT an answer!


    It didn't come from anywhere. A void, is a void. A void is not space. A void is a void is a void. It is nothing, it isn't really an 'it'!

    No, it doesn't leave us those choices at all.

    The choices are;

    The Universe sprang into being because there was no reason why it shouldn't.

    OR.

    The Universe has always been there, and everything in it wasn't actually ever created, but can still exist somehow, because we're ignoring the difficult questions.
     
  19. marv Just a dumb hillbilly... Registered Senior Member

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    Is that all that prevents us from considering the ID-IT model?
    To prove an end, you have to also prove a begining.
    ...please don't sidestep a legitimate proposition...I secretly suspect that the avoidance of the word "infinity" in any description of the universe has something to do with the association of the word with Judeo-Christian deities. Just a suspicion mind you.

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    No offense intended.
    Hmm. I can make pot stew taste like anything from grilled salmon to apple pie - as long as I adjust the ingredients and still call it "pot stew".

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  20. blobrana Registered Senior Member

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    Hum,

    "<i>to prove an end, you have to also prove a beginning</i>"
    i don’t know about that, that really starts to sound like philosophy...

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    "<i>sidestep the infinities</i>" - what’s the point of rhetoric questions?
    hum, perhaps i should have said <b>unbounded</b>, but as i implied before it’s the mathematics that dictates how we deal with it.

    (BTW Being a Pictish pagan, i do hope i don’t come across as a Judeo-Christian.)

    Anyway, i think your catching on, adjust the ingredients and certain "pot stews" will taste better than others...

    Hoyle leaves a bitter taste, while the bb tastes reasonable (just now), but ppl cook up new ideas all the time.
     
  21. marv Just a dumb hillbilly... Registered Senior Member

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    Well, not so much philosophy as logic. So I disagree that it’s the mathematics that dictates how we deal with it. Reason and logic are also required. Mathematics, unfortunately, can be used to "prove" almost anything. Just ask an accountant! And I'll be the first to admit that reason. as well as logic, can also err.

    I'm an atheist and not a mathematician, so perhaps that makes it easier for me to accept the concept of "infinity" in a real, physical universe. But when I discuss something like ID-IT, I get the sense in people that there is a real need for some kind of "creation" scenario. Most people I talk with seem, at least passively, to desire some sort of "higher power", something beyond human ken.

    For my taste, creation by a deity is pastey, empty, and cold like grits. BB is somewhat better, but it has too many ingredients and conflicting flavors like a Christmas fruitcake. For me, ID-IT is best of all with a simple, straight-forward and robust flavor like the BBQ pork ribs I did today.

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  22. apolo Registered Senior Member

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    First of all thanks to mercurio. When I read the word phlogiston, a little light went on in the back of my brain. So apparently we have a student of ancient greek history in our midst, How nice.

    Phlogiston. I read your response to my last post. And then I read it again. My first reaction was; what a bunch of absolute (I was going to say nonsense) but I'm serching for a kinder word, hard to understand piece of writing. First you keep asking for the umpteens time "the SST does'nt explain what was before the beginning of the universe and where did it come from. Marv and Southstar and I have repeatedly told you, that question cannot be asked about the SST. It is like looking at a globe and noticing the line of the equator and asking, but where does it start ? If some one were to keep asking that, he would soon be takin away by some men in white coats. Now listen Phlogiston. You are obviously a fairly intelligent human beeing, but you have a mental block when it comes to grasping the idea of the concept of infinity and no beginning and no end. Every hypothesis (which both the BBT and the SST is) starts with a basic cocept or postulate, and then every thing is built up from there. F.ex. Geometry starts with the fundamental axiom that; beween 2 points you can draw one and only one straight line. And then all the rules about triangle, circles a squares are built up from there. The SST starts with the assumption that the universe has always existed. It was'nt built or exploded or started by god, it was and is just there. And then the hypothesis is built on from there. You may try to falsify it, or find some compelling evidence showing that it cant work. But you cant ask how did it get started any more than you can ask; why we cant we draw more than one straight line between 2 points. You may wander into spherical geometry and say; I can so draw 2 different lines between 2 points. But if we are considering
    euclidian geometry, that's just the way it is.

    So please. Dont ask anymore, How did it start ?

    REGARDS APOLO
     
  23. blobrana Registered Senior Member

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    Hum,
    Here is a small summary of the evolution and beauty of the big bang theory. (As it has not really been properly outlined here).
    As I understand it, when the Time = 10<sup>-43</sup> seconds, and the Temp = 10<sup>32</sup>K (the Planck epoch), all four fundamental forces were unified and "particles" as we known them could not have existed. Beyond this point, the classical theory becomes meaningless, because our conventional physics breaks-down.
    (Sry, no apologies, for my lack of friendly layperson speak – but I have highlighted keywords in bold to be googled)
    At this time, it is thought that Gravity and the Strong Force are at the same scale. <b>1/R<sub>2</sub></b> is extremely large (R is very, very small), and particles can be created from the gravitational field into a 10 dimensional point.
    A couple of weird things can happen, for example, one particle can have all the energy of the Universe, and it could be same size as the Universe.

    Therefore, even if we had the mathematical tools, I doubt we could <i>really</i> understand that physics.
    Basically, quantum physics tells us that it is meaningless to talk in quite such extreme terms, it is better that we should consider the expansion as having started from a region no bigger across than the so-called <b>Planck length</b>(10<sup>-35</sup>m), when the density was not infinite but `only` 10<sup>94</sup> grams per cubic centimetre. (<i>These are the absolute limits on size and density allowed by quantum physics</i>)

    At this time, the theory can explain the mechanism; <b>quantum uncertainty.</b>
    The idea that the Universe may have appeared out of nothing at all, and contains zero energy overall, was developed by Edward Tryon, New York City University, who suggested in the 1970s, that it might have appeared out of nothing as a so-called vacuum fluctuation, allowed by quantum theory.
    Quantum fluctuations would form temporary quantum bubbles, (for example pairs of particles - such as electron-positron pairs) out of `nothing`, provided that they disappear in a short time. The more mass created, the shorter the virtual bubble could exist, and just inside these bubbles, <b>Higgs particles</b> released their energy as they decayed. Supersymmetry was breaking, making the bubble grow.
    When the symmetry is broken, forces are <i>decoupled</i> (a phase transition) in a specific manner so that the forces have now separate characteristic.
    This defines the physics of our Universe.
    It is thought that of the original ten dimensions, 6 compactified, leaving 3 macro-dimensions and one temporal dimension.

    (<i>The energy in a space-time gravitational field is negative, while the energy locked up in matter is positive. If the Universe is exactly flat, then the two numbers cancel out, and the overall energy of the Universe is precisely zero. It is also expected that the rotation, and charge, of the Universe is also zero.</i> )

    One problem, thought, was as the bubble was gradually filled with energy, and the bubbles of the "true vacuum" (with a nonzero Higgs field) percolate and grew, <b>baryogenesis</b> occuring at or near the bubble walls, the gravity would stop it expanding...
    It was a problem encountered with an early version of the theory: that if a <b>quantum bubble</b> (about as big as the Planck length) containing all the mass-energy of the Universe did appear out of nothing at all, its intense gravitational field would immediately crush it into a singularity.

    Luckily, development of inflation theory showed how to remove this difficulty and allow such a quantum fluctuation to expand exponentially up to macroscopic size before gravity could crush it out of existence.

    <b>Supersymmetry breaking</b> provided the energy for inflation, of course.
    For example, at the Planck time, 10<sup>-43</sup>of a second, gravity would be created/broken, and by about 10<sup>-35</sup> of a second the strong nuclear force.
    Within about 10<sup>-32</sup> of a second, the scalar fields would have doubled the size of the Universe at least once every 10<sup>-34</sup> of a second (some versions of inflation suggest even more rapid expansion than this).

    It would mean that in 10<sup>-32</sup> of a second there were 100 doublings. This rapid expansion is enough to take a quantum fluctuation 10<sup>20</sup> times smaller than a proton and inflate it to a sphere about 10 cm across in about 15 x 10<sup>33</sup> seconds. At that point, the scalar field had crystallized leaving the Universe rapidly expanding so that the influence of gravity would not pull everything back into a Big Crunch.

    This give the Universe an outward push (acting like antigravity) while it was a Planck length in size. Such a small region of space would be too small to contain irregularities, so it would start off isotropic and homogeneous. There would have been enough time for signals (travelling at the speed of light ) to have crossed the tiny volume, so there is no horizon problem. In addition, the expansion flattens space-time itself, in much the same way that a balloon becomes smooth, as it is blown-up. If we blow-up the balloon big enough, say the size of the earth, the surface will appear flat.

    At this time Supersymmetry breaking is also predicted to have created a few other oddities; cosmic strings are thought to be supermassive relics of this process, forming at phase transitions. Other relic objects from topological defects are also predicted, such as <b>monopoles</b>, textures and domain walls.
    In the case of monopoles there should be 10<sup>80</sup> of them out there...
    (but we don`t see any - see previous post ,on how inflation got rid of them)


    When the Time = 10<sup>-11</sup> seconds, and the Temp = 3x10<sup>15</sup> k (<b>The GUT epoch</b>) the other three forces remained unified. The small excess of matter that makes up the universe today must have been created during this epoch,
    Shortly after the Strong force separates, then the Weak force and the Electrostatic force (which hade the same magnitude.)

    <b>omega=1</b>
    If the Universe starts out with the parameter less than one, omega gets smaller as the Universe ages, while if it starts out bigger than one; omega gets bigger as the Universe ages. The fact that omega is between 0.1 and 1 today means that in the first second of the Big Bang it was precisely within 1 part in 10<sup>60</sup>. This makes the value of the density parameter in the beginning one of the most precisely determined numbers in all of science, and the instinctive deduction is that the value is exactly <b>1</b>.
    One important feature of this is that there is a large amount of dark matter or energy in the Universe. Another is that the Universe was made flat by inflation.

    [A common confusion is that inflation seems to violate the faster-than-light rule. Even light takes 30 billionths of a second (3 x 10<sup>-10</sup> sec) to cross a single centimetre, and yet inflation expands the Universe from a size much smaller than a proton to 10 cm across in only 15 x 10<sup>-33</sup> sec. This is possible because it is space-time itself that is expanding, carrying matter along for the ride; nothing is moving through space-time faster than light. Indeed, it is just because the expansion takes place so quickly that matter has no time to move, and the process captured the original uniformity of the primordial quantum bubble. As into what the universe is expanding into is also a bit confusing to the layperson; space-time expands (perhaps I should say `enhances into`) a region that contains no space-time, a region that contains absolute nothing, the Void.]

    The inflationary scenario has already gone through several stages of development during its short history. The first `classical` inflationary model was developed by Alexei Starobinsky, at the L. D. Landau Institute of Theoretical Physics in Moscow, at the end of the 1970s. It was a model based on a quantum theory of gravity, it became known as the "<b>Starobinsky model</b>" of the Universe.

    In 1981, Alan Guth, then at MIT, published a different version of the inflationary scenario. Guth came up with the name "inflation" for the process he was describing. There were obvious flaws with the specific details of Guth's original model. In particular, Guth's model left the Universe after inflation filled with a mess of bubbles, all expanding in their own way and colliding with one another. We see no evidence for these bubbles in the real Universe, so obviously the simplest model of inflation couldn't be right.

    In October 1981, the Russian cosmologist Andrei Linde presented an improved version, called "<b>new inflation</b>", which got around the difficulties with Guth's model.
    The next step forward came with the realization that there need not be anything special about the Planck- sized region of space-time that expanded to become our Universe. If that was part of some larger region of space-time in which all kinds of scalar fields were at work, then only the regions in which those fields produced inflation could lead to the emergence of a large universe like our own. This "chaotic inflation", because the scalar fields can have any value at different places in the early super-universe; it is the standard version of inflation today, and can be regarded as an example of the kind of reasoning associated with the anthropic principle (nothing to do with "chaos theory").

    The idea of <b>chaotic inflation</b> led to the next development of the inflationary scenario. A tackling of the singularity and, "before" the singularity. (<i>remember, time itself began at the singularity – so the `before` is not in a temporal sense</i>). Chaotic inflation suggests that our Universe grew out of a quantum fluctuation in some pre-existing region of space-time, and that exactly equivalent processes can create regions of inflation within our own Universe. New universes could bud off from our Universe, and our Universe may itself have budded off from another universe, in a process, which had no beginning and will have no end. A twist on this theory suggests that the process takes place through black holes, and that every time a singularity is formed it expands out into another set of space-time dimensions, creating a new inflationary universe - this is called the baby universe scenario.

    Even Darwinian principals can be applied to this process. As new Universes are formed, they (probability) take on the physics of the parent Universe. If the initial conditions are exactly right then the baby Universe will collapse back. This may explains why our Universe is so finely tuned.
    There are similarities between the idea of eternal inflation and a self-reproducing universe and the version of the Steady State hypothesis developed by Hoyle and Jayant Narlikar, with their <b>C-field</b> playing the part of the scalar field that drives inflation.

    One of the first worries about the idea of inflation (long ago in 1981) was that the process was so efficient at smoothing out the Universe, how could irregularities as large as galaxies, clusters of galaxies and so on ever have arisen? Quantum fluctuations could produce tiny ripples in the structure of the Universe even when our Universe was only 10<sup>-25</sup> of a centimetre across -- a hundred million times bigger than the Planck length.
    Observations of the background radiation by a satellite called <b>COBE</b> showed exactly the pattern of tiny irregularities that the inflationary scenario predicts.
    The theory said that inflation should have left behind an expanded version of these fluctuations, in the form of irregularities in the distribution of matter and energy in the Universe. These density perturbations would have left an imprint on the background radiation at the time matter and radiation decoupled (about 300,000 years after the Big Bang), producing exactly the kind of nonuniformity in the background radiation that has now been seen, initially by COBE and later by other instruments.

    After decoupling, the density fluctuations grew to become the large-scale structure of the Universe revealed today by the distribution of galaxies. This means that the COBE observations are actually giving us information about what was happening in the Universe when it was less than 10<sup>-20 </sup>of a second old.

    No other theory can explain both why the Universe is so uniform overall, and yet contains exactly the kind of "ripples" represented by the distribution of galaxies. This of course does not prove that the theory is correct.
    The theory also makes another prediction, that the primordial perturbations may have left a trace in the form of gravitational radiation with particular characteristics, and it is hoped that detectors sensitive enough to identify this characteristic radiation may be developed within the next ten or twenty years.

    Another big snag with the simplest inflation models, is that after inflation even the observable Universe is left like a mass of bubbles, each expanding in its own way. We see no sign of this structure, which has led to all the refinements of the basic model. Now, however, this difficulty has been turned to an advantage.

    It is suggest that after the Universe had been homogenised by the original bout of inflation, a <i>second burst</i> of inflation could have occurred within one of the bubbles. As inflation begins (essentially at a point), the density is effectively "renormalized" to zero, and rises towards the critical density as inflation proceeds and energy from the inflation process is turned into mass. Nevertheless, because the Universe has already been homogenised, there is no need to require this bout of inflation to last until the density reaches the critical value. It can stop a little sooner, leaving an open bubble (what we see as our entire visible Universe) to carry on expanding at a more sedate rate, into something looking very much like the Universe we live that can arise naturally, with no "fine-tuning" of the inflationary parameters.
    All done using the very simplest possible version of inflation, going back to Alan Guth's work, but applying it twice.

    In addition, you don't have to stop there. Once any portion of expanding space-time has been smoothed out by inflation, new inflationary bubbles arising inside that volume of space-time will all be pre-smoothed and can end up with any amount of matter from zero to the critical density (but no more)….

    Whoops got carried away there…and I haven’t even got to the <b>Ekpyrotic</b> version…
     
    Last edited: Dec 1, 2004

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