A question concerning Evolution

I hope no one minds if I move just a little off topic and ask a related question. If all the matter of the entire universe once existed in a space smaller than the size of an electron, thereby creating a gravity well from which neither matter nor energy could escape (in other words, a black hole), then how did the Big Bang happen?--Percy

PercyStatistical quantum fluctuation? Maybe the universes therapist thought it should get out more often?

Actually, "statistical quantum fluctuation" is a possible answer. The energy content of the Universe appears to be near zero, and may be exactly zero ... in which case an arbitrarily large long-lived quantum fluctuation is allowed by the undcertainty principle.(The potential energy of two masses an infinite distance apart is zero. The potential energy decreases as you bring the objects closer to each other. Therefore gravitational potential energy is negative and cancels the postive energy of mattter. This is actually a hand-waving argument with one serious hole, but the real math gives the same result and is much harder to understand).

I kind of remember Roger Penrose explaining this in The Emperor's New Mind. If the the entropy is extremely low, then the matter will not be trapped in the "black hole" but will expand out of it. The original universe seems to have been "created" in a state of fantastically low entropy.

are NOT the same kind of mathematical object.People always seem to get this fact wrong.A black hole solution in GR is embedded in an exterior spacetime. You need an exterior spacetime to define the concept of event horizon.A Big Bang singularity has NO exterior spacetime for an event horizon to be defined in. Thus it is a source for all particle worldlines which, of course, does not apply to a black (or white) hole solution where worldlines don't have to intersect the singularity.

Thank you Eta, we are getting more and more in need of some real expertise rather than a number of us making up answers.

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Common sense isn't

NosynedI think the therapist theory is probably the best being as this is one CRAZZZYYY universe.

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"I am not young enough to know everything. "
Oscar Wilde

I absolutely agree!The big, long term, probably unanswerable question I have is:
"Will we ever be able to understand it?"I don't mean me, of course. I mean the best and brightest of us represented here by Eta and the other researchers. If they have to dumb it down for me I'll be happy with that. But it does seem to get wierder and stranger as we keep pushing deeper.from:http://darwin.ws/...llySpeaking/rationally_speaking%20N1.htm

quote:

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But remember the immortal words of physicist Richard Feynman: "If you think you understand quantum mechanics, you don't understand quantum mechanics."

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I don't think this relieves the conundrum. Imagine a time very shortly after the beginning of the universe when it is only a foot across. Take any sphere of space within the universe of diameter a half foot. The matter within this sphere will still have a density so great that it will form a gravity well from which no matter or energy can escape.Hmmm. Don't reply to the above, though. I can already see that the matter inside this sphere is affected by the matter outside the sphere. With matter fairly uniformly distributed across the 1 foot universe, the net gravity at any given point will be roughly 0. Does this sound like the right answer?I'm also wondering if the energy required to overcome gravitational attaction and move two objects apart is the same whether it occurs through the exertion of normal forces or through the expansion of space. If the same, then where does the energy for an expanding universe come from?--Percy

Interestingly, it is now believed that there is a universal repulsive force, being labeled as "dark energy". Although it was too weak at the beginning to be the answer to the question you are asking, this repulsion increases as space expands. It is believed, if I remember the article in Science correctly, we are now in an era where the repulsion is greater than the gravitational attraction.

I believe (in that this was an explanation of expansion I read) that the 5 forces (or 6) didn't exist at the time of the big bang. Particles had to "freeze out" as the expanding universe got cool enough. Presumably when gravitons froze out (& gravity came into being) the brakes went on, but at that stage it was too late to stop the expansion.Mark

PercyIn answer to your statement. Would it not be due to the mass present since the two are equivalent as per E=MC*2?

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"I am not young enough to know everything. "
Oscar Wilde

There were a couple responses to my question about where the energy comes from when two objects move apart against their gravitational attraction due to an expanding space. I'm no expert and can't say with any autority whatsoever that the answers are wrong, but they just don't feel right to my layman's eye. So let me describe the issue in just a little more detail.There are two cases:

1. Two objects increase their distance apart in space by an amount X due to explicit visible forces. For example, let's say the two objects are planets a million miles apart, and they increase their distance apart to two million miles by using thousands of giant rockets on each planet.
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2. Now imagine the same two objects that increase their distance apart in space by an amount X because space is expanding, and not due to any explicit forces. Using the same example of the two planets, let us say they increase their distance apart from one million miles to two million miles because space doubles in size.

In the first case, the energy comes from the chemical bonds in the rocket fuel that give up their energy when the fuel burns. Where does the energy come from in the second case?--Percy

This is where we need Eta's help. H E L P !(good question btw)

The expansion of spacetime is a global cosmological solution to a FLRW metric. It is not local.Locally we solve GR by say the Schwarzchild solution. There is no expansion of spacetime here.So the common answer is that your two objects are not expanding away from each other.Cop out answer, right?In reality the metric of the Universe cannot be approximated by these well known analytic solutions.So there is probably an expansion of spacetime in the background so to speak but the effect is negligible. Sort of like the Earth's orbit shifting an atomic width over the lifetime of the solar system.If we had a situation like your example 2) then the energy would have to come from whatever field was powering the exapnsion itself.This brings me roundabout to a comment or two on the 'dark energy'.What is it?Is it a cosmological constant related to the vacuum energy density - maybe but the math doesn't add up by current theory.Is it not constant but some new force a la quintessence models?Is this quintessence a decaying field left over from inflation? Who knows.Probably the biggest mystery in physics today is the nature of the dark energy. We have so little to go on - and I doubt it is solved soon.