# Is there only one big bang.

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Lord Vasago, Sep 10, 2009.

1. ### Lord VasagobcdRegistered Senior Member

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I know that i'm not up to date to all this universe things but there is one question that i've been thinking about for years now. I hope it doesn't make me look like a morron

But what if the big bang that created our currently known universe is just a small part of a even bigger thing.

could it be possible that our bigbang could be compared to our solar system in the milky way. and billions of bigbangs occur ????? :shrug:

3. ### prometheusviva voce!Registered Senior Member

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There's no way to see outside our universe or our own big bang if you like, so what you propose may be true or not, but we can't test it.

5. ### Lord VasagobcdRegistered Senior Member

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I know but the way to discover planets is by looking at the gravitatinal pull they have on their star.
the multiple bigbangs idea came to me when i read a article on the accelaration of the expansion in our universe and the 3rd law of motion. (speed being constant unless there is a outside force). then this could mean that our universe is expanding faster because of gravitational force. some bigger big bangs pulling our galaxies toward them.

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8. ### quantum_waveContemplating the "as yet" unknownValued Senior Member

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Prometheus is telling you that current theory has it that the earliest moment, 10^-30 seconds after t=0 in Alan Guth's view of Inflationary Theory, there was faster than light expansion ("The Inflationary Universe", Alan Guth, Chapter 1, p 14). Light from anything in our universe that formed from those portions that are moving away from us faster than the speed of light will never be observed, hence an event horizon.

That is what Prometheus claims when he says we can't see outside our universe and can't test it. His view is based on theory, the current consensus of BBT with Inflation. Is it possible for the consensus to be wrong? Of course.

Observations of patches of apparent accelerated expansion are from data accumulate by WMAP in the scattering of X-ray emissions that seem to show a "dark flow" like you suggest, but such observations are not considered to be caused from outside the universe; they are currently thought to more likely come from anomalies in the initial superluminal expansion than from any great attractor outside of our observable universe.

From this thread: "The dark flow is just fluctuations in the cosmic microwave background detected in the 3 year WMAP data. The data captured is detected in the CMB "generated by the scattering of the microwave photons by the hot X-ray-emitting gas inside clusters", according to this abstract."

9. ### prometheusviva voce!Registered Senior Member

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From the moderator: Derogatory remark deleted. Be nice now. Next time will get you an official warning.
Things cannot recede faster than the speed of light because that is forbidden by relativity.

Also, playing the "just a theory" card is neglecting to mention the experiments that have tested the big bang theory extensively and found it to be in agreement with what we observe.

Last edited by a moderator: Sep 10, 2009

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11. ### fedr8081100101Valued Senior Member

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Actually whats interesting is that right after the big bang happening the universe and space actually expanded FASTER than the speed of light. Apparently going over Einsteins speed limit.

BUT, the very nice thing is that Einsteins theory states that nothing IN space can move faster than the speed of light, but space itself CAN move faster.

12. ### D HSome other guyValued Senior Member

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In this case, both of you are wrong.

prometheus: You are ignoring general relativity and the expansion of space. Things can recede faster than the speed of light. In fact, "superluminal recession is a fundamental part of the general relativistic description of the expanding universe." See "Superluminal Recession Velocities," Davis & Lineweaver, http://arxiv.org/abs/astro-ph/0011070.

quantum_wave: You too are ignoring general relativity and the expansion of space. See the article cited above.

Here's a simple example. Assume a finite universe with a constant linear expansion rate and a simple cartesian metric. At some point in time, a person at point A at the edge of the universe aims a beam of light from toward a point B at the point on the edge of our toy universe diametrically opposed to point A. The beam of light of course moves at a constant speed c with respect to local space. (Taking this back to our real universe, the speed of light is constant with respect to local space.) Will this beam of light ever reach point B? The answer is yes, even if point B is receding from point A at a (constant) speed that exceeds c.

Denote t=0 as the time at which the beam of light is emitted, s as the expansion rate of this universe (s is much greater than the speed of light), and d[sub]0[/sub] as the diameter of the universe at time $t=0$. In this simple universe, where s is much greater than the speed of light. The diameter of the universe, and hence the distance between points A and B, at some time t is

$d(t)=d_0 + s t = s(t+d_0/s)$

Suppose that instead of a beam of light we are talking about a spaceship moving from point A to point B. Somewhere along the way the spaceship takes a rest stop, rest meaning velocity=0 with respect to local space. Because local space is moving with respect to the point of origin, the spaceship's speed with respect to the point of origin is non-zero. Denoting the distance between the point A and the current location as x(t), this expansion velocity with respect to the point A is

$\dot x_{\text{rest}}(t) = \frac {x(t)}{d(t)} s = \frac{x(t)}{t+d_0/s}$

The beam of light of course never rests; it's speed with respect to local space is always c. Denoting the beams position with respect to point A as x(t), then

$\dot x(t) = \dot x_{\text{rest}}(t) + c = \frac{x(t)}{t+d_0/s} + c$

Sparing the nasty details, the solution to this differential equation is

$x(t) = c(t+d_0/s)\ln\left(t\frac{s}{d_0}+1\right)$

Solving for $x(t)=d(t)=s(t+d_0/s)$ yields

$t_{\text{end}} = d_0/s\,\exp(s/c-1)$

This is of course but a toy universe. The real universe does have an observability limit, but it is not the point at which the recession rate becomes superluminal.

13. ### quantum_waveContemplating the "as yet" unknownValued Senior Member

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I guess I got it wrong. I mentioned Inflationary Theory by Alan Guth and quoted from that book where here said that the period of inflation began at 10^30 seconds. During that period there was superluminal expansion.

Perhaps someone can correct my wording where I said that, "Light from anything in our universe that formed from those portions that are moving away from us faster than the speed of light will never be observed, hence an event horizon."

I just want to get the wording right. I think Guth points out that there are portions of the universe that existed at the instant of exponential expansion that due to inflation of space, will never be observed due to the event horizon. I was assuming that there would be structure formation in those far reaches of our early universe similar to the observable portion that would radiate and from which we would never see the radiation. I could be wrong about that or I could be saying it wrong. Can anyone help?

14. ### Fraggle RockerStaff Member

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The Big Bang can be described as a temporary decrease in entropy: a universe with no order suddenly having order. Physics tells us that entropy invariably increases, but only because of the law of averages. It is possible for order to occur spontaneously due to coincidence. The probability of this coincidence is so small that it might require rather a lot of mathematical notation to express it, but it is not zero. If space-time is infinite, then there's no reason that any event with a non-zero probability could not occur.

In fact it could occur more than once.
* * * * NOTE FROM THE LINGUISTICS MODERATOR * * * *

I am really frustrated with the community of scientists for being so sloppy with their terminology. The Big Bang should be called a hypothesis, not a theory. A theory is a hypothesis that has been proven true beyond a reasonable doubt, and the Big Bang has not achieved that status.

15. ### AlphaNumericFully ionizedRegistered Senior Member

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I'd disagree. An hypothesis is an explaination/model put forward which has little or no experimental support yet but has the possibility of being a good description of the thing it is trying to describe. A theory is what an hypothesis 'graduates' to once a significant number of experimental tests have been done to show the proposed model is, to within experimental bounds, an accurate description of said phenomena.

There is a difference between 'proven true' and 'verified to within experimental bounds'. For instance, Newtonian mechanics was a theory of mechanics which was verified to within experimental bounds for centuries, before being pushed aside by relativity. Newtonian mechanics was never 'proven true beyond reasonable doubt', it was 'verified to a good accuracy', where 'good' is short for 'better than any other hypothesis' and/or 'sufficient to use when attempting to build something where the phenomena which the hypothesis describes are significant effects'. Relativity is 'verified to experimental bounds' but its not proven. Infact we know it's not 'true' because its not a quantum theory. But we've tested it to parts per trillion and it's passed. Similarly, QED is incomplete (it possesses a Landau pole) but its been tested to parts per trillion and passed.

The BB model makes predictions about how the universe should be, including such big things as the power spectrum of the CMB, indeed the very existence of the CMB, which were verified to within experimental bounds by many different telescopes and arrays and whatnot. It is a testable and tested hypothesis which, as yet, remains unfalsified. Most people would call that a theory.

16. ### quantum_waveContemplating the "as yet" unknownValued Senior Member

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But let's apply the question in the OP to the BB model. Lord Vasago asked the question in the OP:

What happens to BBT (or BBH if we acknowledge FRs view) if the BB with its event horizon is not all there is? How do you answer Lord Vasago's "what if"?

17. ### prometheusviva voce!Registered Senior Member

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In science terms, it's a poorly posed question - ie, one that can't be answered in a way that could be measured in experiments.

No - When t was close to zero the universe wasn't just a very dense state that sat in space. Space itself was very small. Now space is a lot bigger you can't have a second big bang. If there is some region outside our universe there might be more BB's or not - it doesn't matter because we'll never know. I could make something up completely like outside our universe is where the titans live and it doesn't matter because we'll never be able to test it.

I agree with AN and would only add that it frustrates me a great deal when people pontificate on subjects they know nothing about as if they somehow have the right to. A hypothesis (or a theory) can only be proven wrong, never right so making this sort of artificial separation is pretty pointless. This about as fundamental to the scientific method as it gets.

18. ### quantum_waveContemplating the "as yet" unknownValued Senior Member

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Lord Vasago might not have realized that his question would have to meet the "measurable" requirement. If you check his profile you could think of it as a question to the Jedi Council. Foolish questions there are none. Brave you are to ask the council anything.

19. ### prometheusviva voce!Registered Senior Member

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Isn't it obvious that any question posed has to be measurable? If your question has no consequences for our universe then it's a question that cannot be answered and the answer is completely irrelevant

20. ### D HSome other guyValued Senior Member

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Piling on here, because this misrepresentation of the scientific process deserves it.

Firstly, nothing can be proven absolutely true in science. The best scientists can do is prove something to be consistent with known facts.

Secondly, as far as astronomers and cosmologists are concerned, the basic premise of this theory, that the universe was incredibly small and hot 13.7 billion years ago, has indeed achieved the status of "true beyond a reasonable doubt."

Thirdly, most astronomers and cosmologists use the term "big bang model".

21. ### kanedaActual CynicRegistered Senior Member

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Only because they refuse to debate any alternative and laugh down, insult or censor anyone who says otherwise. If it was true beyond reasonable doubt, there would be no need for them to FEAR debate and derail it in any way they can.

22. ### kanedaActual CynicRegistered Senior Member

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AlphaNumeric. The elephant is still in the BB room.

23. ### Fraggle RockerStaff Member

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I understand. I borrow the legal wording "beyond a reasonable doubt" because the average layman can relate to that after watching a thousand hours of police and courtroom dramas.

Nonetheless the word "theory" is used sloppily in science, and some of the things we call theories have not yet been proven true beyond a reasonable doubt. I have seen a more rigorous paradigm in which what I call a "promising hypothesis" is called a "theory" and what I call a "theory" is called a "canonical theory."

From a pedantic viewpoint it's at least consistent and well defined. But everyone seems to drop the adjective "canonical" when speaking to laymen. As a result many laymen think that doubts about the theory of evolution--which is canonical--are just as reasonable as doubts about string theory--which I would call a hypothesis.
I like that. As I've mentioned here a number of times, we have entered an era in which the boundary between physics, mathematics and philosophy is getting mighty blurry and they're all merging into this new discipline called "cosmology," which is as much about the models we construct to understand the universe as it is about the universe itself.