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Quantum Equation Suggests Universe Had No Beginning
cyberspittle writes: The universe may have existed forever, according to a new model that applies quantum correction terms to complement Einstein's theory of general relativity. The model may also account for dark matter and dark energy, resolving multiple problems at once. "In addition to not predicting a Big Bang singularity, the new model does not predict a "big crunch" singularity, either. In general relativity, one possible fate of the universe is that it starts to shrink until it collapses in on itself in a big crunch and becomes an infinitely dense point once again. ... In cosmological terms, the scientists explain that the quantum corrections can be thought of as a cosmological constant term (without the need for dark energy) and a radiation term. These terms keep the universe at a finite size, and therefore give it an infinite age. The terms also make predictions that agree closely with current observations of the cosmological constant and density of the universe."
Equations and theories that not only explain current observations but bundle up and deal with things our other theories say we should observe that we don't are attractive from a neatness standpoint. I'm skeptical when they make exotic and complex predictions which we haven't seen any evidence of yet, but when they tie up all the loose ends without creating more I usually take that as a sign there's something fundamentally right about that path. Only time and accumulated evidence will add certainty to it, but I like the ideas in this one.
And as far as a universe with no beginning or end is concerned, what's the problem? I was dealing with infinite open shapes (lines, planes) in grade school, unending closed shapes are trivial (a circle, a sphere), and if you assume our universe is a 4-dimensional "slice" of an n-dimensional space it's not that hard to construct an arrangement where you can travel forever in any "direction" (since the time axis counts as a direction here) inside our universe without either encountering an edge or returning to your starting point. The math's brain-bending when you start, but it's like differential equations: migraine-inducing and you hate it with the burning fire of a thousand suns right up until they describe the General Method, at which point you blink and go "Oh. That's easy. Why didn't you mention this in the FIRST PLACE?!
OK, these guys are probably far smarter than I'll ever be, but... the universe clearly isn't staying at a finite size, and playing the universe's expansion in reverse would imply that it started at a single point. How do they account for this? I even went as far as to read the article, but it wasn't mentioned.
Are they saying that the universe fluctuates between a not-quite-a-singularity tiny point of density and a not-quite-eternally-infinite empty void, or that it simply was a not-quite-a-singularity tiny point of density for an infinite time before it expanded?
One of the many, big, unanswered questions concerning the origin of the universe is - where did the energy come from? Conservation of energy - the assumption that energy cannot be either destroyed or created - is a fundamental axiom in physics, which goes against the idea that there was a point in time before which the universe didn't exist, but after, it did. Unless, of course, one can conceive of a negative energy of equal size having been created at that same moment.
A naive consideration would say that if a mass, M, is created, then there must have an 'anti-mass', -M, as well; using Newton's equations, we would expect M and -M to repulse each other, while M would attract M and -M would attract -M (yes, doesn't make sense at stated, but follow my thought here, OK?) And, if one were to ramble on along those lines anyway, it seems tempting to look at the equations for how electric charges interact and think of electric charge as a kind of imaginary (as in complex numbers) mass. No doubt better people than I have already spotted this and worked out why it doesn't make sense, but I haven't seen their work yet.
All of these type of models about the universe have elegant math behind them.
But until they can any observable predictions which can be measured and possibly falsifiable, then we are really dealing with pure math and philosophy and not physics.
One can construct countless mathematical models which fit known observations, but very few make new falsifiable observable predictions.
This is my gripe with something like String/M-Theory, which has not made any legitimate predictions, and fails at stuff like monopoles which not been observed.
Suppose the Universe is filled by a Bose-Einstein condensate of gravitons with mass, and that the amplitude of the condensate's wavefunction spans the entire universe.
Turns out that when you derive the FRW equations from this, doing so inserts a cosmological-constant lookalike into the equation for a''
So plug the size of the Universe into the Yukawa equation and a graviton mass of 10^-32eV pops out. Plug this into the assumption that the wavefunction is a Gaussian the size of the universe (which makes d'Alembertian proportional to the wavefunction and gives you that nice constant) and you get a cosmological constant that's plausibly near to what we observe.
Inserting the universe-condensate also creates a second correction term which prevents the FRW scale factor from blowing up or collapsing either in the past or the future, which makes that nasty big bang singularity go away.
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It's worth noting that they invoke Bohmian quantum mechanics, which will immediately sketch out a lot of quantum folks...
What bugs me is that the massive graviton blows up the mass hierarchy problem. It's hard enough to come up with a non-contrived way to have particles whose measured mass ranges from 1eV to 170GeV, but to extend it by 30 orders of magnitude on the light side is just mean.
In music, there is something called a Shepard tone, which is a series of skillfully combined harmonics that, when listened to as a loop, appears to be constantly ascending.
Perhaps the "expanding universe" is something like that.
- Mike