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 directionsthe 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."
What's my definition of science?
Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)
Dunno, what's my golf handicap?
"The "Hindu" and Buddhist cycle of creation and destruction." My thoughts exactly.
Loop quantum gravity strikes again.
I heard they've found where all the missing socks go, as well.
I do not claim to know your golf handicap.
I should have been born in the previous universes............
These people have been reading too much Asimov!
In order to offer a hypothesis on whether or not the universe will cease expanding, the guy doing the hypothesizing first has to know what causes the expansion and the nature of that force. To my knowledge, blue collar knowledge, nobody has those answers though it is posited that dark energy drives the expansion. What are the properties of dark energy? Your guess is as good as mine.
Sorry, not playing word games today. If you have something to say defending this article as "science", say it. My position is clear, this is no more science than your interminable use of the dreaded sphagetti monster is.
'kay, then. Have a nice day, and may his Noodly Appendage guide and protect you.
Tell you what, go get some graph paper and a calculator. Pick some random numbers to plug into this equation as "X" and plot the result. You'll see what I mean after a few numbers.
Y = 1/X
Anything divided by zero is infinity by definition so try some numbers that are very small like 0.0000001 and then try some that are very large like 1,000,000.
The graph of "Y" is said to be asymptotically approaching zero as "X" approaches infinity. That is every time you double "X", "Y" is cut in half but it only goes to zero when "X" equals infinity. To further confuse the issue "Y" also is asymptotically approaching infinity as "X" goes to zero. The graph of the function is said to have two asymptotes at Y=0 and X=0.
Regards,
GtG
I'm a former math major so I'm quite familiar with inverse relationships and assymtotes. Not sure what your point is, though. Mathematically, there are some functions that approach but don't get to zero. In the real world, however, you would have to show that there is some reason not to get to zero when a function is decreasing constantly. There might be some physical law in the universe that would constrain the function from reaching zero (and eventually negative if we are talking about the universe contracting) but I'm not familiar with why that would be.
why is it easier to believe that God was always there instead of the rest of the universe always being there?
The underlying assumption is that G-d exists in this dimension--in our reality. Maybe he does, but maybe he doesn't. Consider the possibility that what we call G-d actually inhabits another dimension, totally hidden from us, but has absolute control over this dimension and (perhaps) others.
I sometimes imagine G-d as a computer programmer and we are the program. The program exists only in the computer and can only process what it is fed. Simulated characters in the program cannot perceive what is outside of their virtual environment (unless the programmer wants them to). Ultimately, the programmer has total control over the program and what it does (assuming he doesn't make mistakes). In this context, the Big Bang is akin to G-d pressing the ENTER key.
Even if you buy this analogy, something, somewhere had to come first. There had to be a primordial creator. However, I believe the nature of that entity will remain unknowable unless and until he makes it known to us. Even then, if the truth were right in front of us, we may not be able to comprehend it. While I have the utmost respect for science and scientists, in this case, I think all it can do is scratch at the surface of the truth.
The universe might have done this trillion of times already, who knows.
Of course there still has to be something bigger, or something that created the whole mess in the first place; that would be God. Now when you try to explain how God came to be that's when the brain really gets fried!
No way to know how many times its been observed without a review of the scientific literature but enough to establish it as fact. Elements are synthesized inside stars. This will continue until the star runs out of fuel.
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