I've asked this before and haven't gotten an answer. I've emailed askaphysicist, NASA, Hayden Planetarium, etc and gotten no reply.
If the universe spawned from a quantum fluctuation, and required a gravitational field to provide negative energy to accomplish the needed zero net energy, where did the gravitational field come from in the absence of space time and mass to warp it?
2013-08-07T11:55:27Z
A common concept being pushed in physics recently, as popularized by Lawrence Krauss' book "A Universe From Nothing" and Steve Hawking's book "The Grand Design" is that the universe literally popped into existence from a quantum fluctuation event (presumably the singularity itself). A quantum fluctuation has a proportional relationship between the amount of energy it contains and how long it persists for implying that this could not be the case. Hawking and Krauss argue that this can be easily resolved by balancing out the positive energy with the potential negative energy provided from a gravitational field making the total net energy zero, and allowing the universe to persist.
So my question is: If particles with rest mass did not emerge until the quark epoch, then the singularity should have disappeared as fast as it appeared. Without spacetime and mass, there is no potential for gravity, and no potential for zero net energy. Where did the gravitational
2013-08-07T11:57:54Z
field come from, that two such prominent physicists use as a solution?
2013-08-07T12:36:57Z
@Chris: Quantum fluctuations do not require gravity, but one with that much energy would disappear as fast as it appeared unless it had a net energy of zero which requires a gravitational field to provide potential negative energy to balance it out.
2013-08-07T13:46:01Z
@Cursus: I emailed Krauss too ... same result.
2013-08-07T13:47:11Z
I even prefaced the question with, "This is not a challenge, I'm not a theist trying to argue. I'm just hoping there is an answer to my question."
2013-08-07T13:56:44Z
@Cursus: The closest thing to even a possibility I have heard is gravity from another universe. However, that's wild speculation as we have no idea if we live in a multiverse, or if they can affect each other if we do.
At least it was an attmept at "maybe".
Cursus Moribus2013-08-07T13:29:00Z
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I actually asked a physicist this same question about 3 weeks ago. He said he wasn't familiar enough with Krauss' work to answer me, so I'm supposed to follow up with him. I also sent Krauss an email through his university account and haven't received anything back.
"If particles with rest mass did not emerge until the quark epoch, then the singularity should have disappeared as fast as it appeared." This is exactly my train of thought. A quantum fluctuation is possible only if it's coupled with the uncertainty principle, and can therefore only exist momentarily, as illustrated by Feynman diagrams.
Anyway, I hope you receive an answer, but this may be one of those questions that we are simply unable to answer at this time - which I think it is.
EDIT: He's a busy man and I'm sure he's overloaded with emails. He is, after all, one of the most notable cosmologists in the world now. I'm sure he will address these questions in his next book, which he's probably working on - he publishes a new book every two years or so.
The multiverse theories are interesting, but I'm almost entirely unfamiliar with them - I'm a philosopher, not a physicist. It's all very fascinating though.
I have read Steven Hawking's "The Grand Design", but not Lawrence Krauss' "A Universe From Nothing". Stephen Hawking does not give any detail; he uses the term "quantum fluctuations" without a clear definition.
I assume it means something like the continual creation and vanishing of virtual particles. Tiny, short lived virtual particles are more likely than larger ones, but in theory a cheese sandwich could spontaneously appear for no reason at all. The odds against it involve a number with so many zeros that it probably could not be written down even if all the matter in the known universe was turned into paper, but it is possible. If micro universes are popping into existence all the time, some extremely tiny proportion of them must be big enough to have a gravitational field.
I have some questions, though. Virtual particles appear in space, which already exists. If quantum fluctuations are creating universes, then are they sitting in some kind of hyper-space? It is hard to fathom. I find the timeless vision of Julian Barbour or the evolutionary ideas of lee Smollen more reasonable; (though at least one of them must be wrong!) After spending a little time researching your question I have put Krauss's book high up on my list of books to read.
Incidentally, I do not think it is possible for a singularity to expand. The equations of general relativity predict singularities at the centre of black holes and at the start of the big bang. They are points where the equations predict infinite density. The most likely explanation is that general relativity breaks down at some point, so singularities do not actually exist. If universes are popping into existence all the time, they must start with some size.
In your question you make assumptions that are not clear. "If the universe spawned from a quantum fluctuation, and required a gravitational field to provide negative energy to accomplish the needed zero net energy" What EXACTLY do you mean by "spawned from a quantum fluctuation" Physics is a very EXACT science and without claryfying all the terms used in your assumptions, the discussion is meaningless (each side - the person who asks and the person who answers - have something different in mind from the begining) That MIGHT be a reason you did not get any responses.
The idea that the "universe spawned from a quantum fluctuation" is pure speculation at this point and is not supported by any evidence and is nor part of any, actual, detailed scientific theory. It is merely a way for physicists to avoid saying "I don't know" when confronted with the question "What caused the Big Bang?" (physicists hate saying "I don't know"; I'm one of the them).
You seem to think quantum fluctuations require gravity. This is not supported by any current theory or evidence. Either you misunderstood what someone was saying, or that someone is being wildly speculative.