Posted on 05/24/2006 3:59:24 PM PDT by LibWhacker
Scientists use quantum gravity to describe the universe before the Big Bang.
Scientists may finally have an answer to a "big" question: If the Big Bang was the beginning of the universe, what could have caused it to happen?
Using a theory called "loop quantum gravity," a group led by Penn State professor Abhay Ashtekar has shown that just before the Big Bang occurred, another universe very similar to ours may have been contracting. According to the group's findings, this previous universe eventually became so dense that a normally negligible repulsive component of the gravitational force overpowered the attractive component, causing the universe to "bounce" apart. This big bounce is what we now know as the Big Bang. The group published its analysis in the April 12th issue of Physical Review Letters.
"These equations tell us that in fact there is another pre-Big Bang branch of the universe, and then we tried to understand what it looks like," Ashtekar said. "[Surprisingly], the universe again looks very much classical.
"So there is another universe on the other side which is joined to our universe in a deterministic way," he concluded.
Coauthor Parampreet Singh, a postdoc at Penn State, said that Einstein's theory of general relativity describes the current universe very well, but it breaks down when it encounters the extreme density of the universe around the time of the Big Bang.
"[General relativity] gives physical singularities when we ask questions about the physics near the Big Bang," he said. "Unless this problem is solved, or unless a solution of this problem is known, we do not have a complete description of the universe."
Physicists have developed theoretical systems, such as string theory, to unite general relativity with quantum mechanics and explain the very early universe. In the late 1980s, Ashtekar published the first paper on loop quantum gravity, a theory which applies quantum mechanical principles to examine the spacetime continuum. According to his model, there is no continuum: Smooth, continuous space is only an approximation of an underlying quantized structure, one that is made up of discrete units.
Loop quantum gravity also predicts a small repulsive component of gravitational force, which is a non-factor in other theories. At most densities, even the extremely high density of an atom's nucleus, this component has no significant effect. But as density increases, approaching 1075 times the nuclear density, this repulsion begins to dominate. According to the Ashtekar's equations, this appears to be what happened to the universe before ours: As it collapsed, it became so dense that gravity started to, in a sense, work backwards, birthing our universe.
Singh, Ashtekar's postdoc, noted that the group's conclusions are eerily similar to findings published by Princeton researcher Paul Steinhardt two weeks ago. Using string theory, Steinhardt concluded that the universe may be cyclic, with each crunch leading to a bounce.
But Steinhardt said the two papers are only distantly related:
"It is an idealized set-up which does not connect smoothly to realistic cosmology," he said via e-mail about the Penn State paper. "By contrast, our scenario is designed so that it connects smoothly to Einstein gravity and standard Hubble expansion, so that it reproduces the astronomical conditions we observe today."
Ashtekar acknowledge that his work addresses the idealized situation of a homogeneous, isotropic universe, one that is uniform in space and uniform in all directions—the model does not account for heterogeneities such as galaxies.
"This picture does hold up in kind of simple generalizations," he said. "The key question is really if this prediction is going to hold up with more and more realistic models."
The old universe junkyard?
In fact, as Reactionary (#55) has mentioned
Nietzsche thought it self-evident
since a finite universe only can have a finite number of states.
I've got to get that article written, and now I suppose I'll have to include the cyclical universal creation and destruction cycle as well!
DING DING DING, we have a winner. When the physicists can explain that one I will give up my belief.
Even the hydrogen could have been through one or more stars in the past.
Have you accepted the Spaghetti Monster as your personal Lord and Savior?
The command was "LET ... THERE ... BE ... Light. Spoken to a zero variable spatial expression in a gel of constant present. The resonance created between the point and the gel brought about a summing of the energy and the subsequent expression of linear then volume space and past then future temporal ... a bang followed by a linear rush followed by a planar burst followed by a slow dance.
It could, I suppose, although I would think that each trip through a star would make it more probable to get converted into a heavier element. In other words, I don't think that hydrogen would pass through multiple lifetimes of stars without being made into other stuff, i.e., the total quantity of hydrogen in the Universe will decrease over time as other heavier elements increase.
This is a sophisticated attempt to revive the old pagan notion of an eternally existing material universe.
Since the observable universe shows every evidence of having a beginning (no surprise to monotheists of any of the strains derived from the ancient Near East, but a great discomfort to atheistic materialists), the eternally existing material world must simply be unobservable, and partitioned into 'other universes' by states dense enough that the physics we can experimentally verify breaks down.
Notice that in doing this, the materialist abandons any rightful claim to being more scientific than the theist, since by definition 'another universe' is as unobservable as an initial divine fiat. Theism gains the advantage, though on the basis of Occam's Razor: one transcendant God is fewer unobservable entities than the infinity of 'other universes' this theory needs.
Personally, I quite like Hawking's null-initial condition proposal: there is *nothing* before the beginning, not even a 'before'. It's a nice mathematical model for a universe created ex nihilo, even getting the nihil right.
Try this thought: think of dimension space as having three variablity expressions, linear, planar, and volume; now posit dimension time as having three variability expressions, past, present, and future (corresponding roughly to the three expressions of dimension space; to ask about 'eternity before a present' is to ask the wrong question ... temporal existence takes place in one of three variable epxressions, past, present, or future, eternity being a subset of future.
That looks about right..
The same science that can not explain how aspirin works ...
I think our Medical Professionals understand this quite well. Would you like me to point out some web sites for you?
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Oh good, mystery solved at last - I had given up. Now about that second universe...
Not recently but I've come to accept the fact that loons accept Popper as their lord and saviour except when they don't. You really should consider the grapefruit hypothesis, it seems to fit in well with your definition of science.
You are quite correct. Every atom in our bodies, except for the hydrogen, has been through a star at least once.
. . . what was God doing for the eternity before that?
Getting very bored. He only keeps us around for laughs...
>>>Observational data seems to indicate that the rate of expansion is slowing, which eliminates number one.
Actually, the expansion seems to be accelerating (increasing rate), hence the postulation of "dark energy". Dark energy would presumably be antigravitational. If I am not mistaken, string physicists suggest this could be an effect of gravitational particles from an adjacent universe or p-brane, leaking into ours.
Here's one question I have (perhaps the answer is elementary for the average garden variety cosmologist, but, I'm not a cosmologist of any rank - I haven't ever even been to a cosmologist).
Anyway...How does an explosion (of volatile matter, much less volatile dense gases) result in the formation of solid matter? From what I understand, say, in an underground nuclear explosion - the end result is a big hole, not a monolith.
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