Ultima Thule

In ancient times the northernmost region of the habitable world - hence, any distant, unknown or mysterious land.

Tuesday, May 23, 2006

Before the Big Bang there may have been a Big Shrink

By Aussiegirl

OK, everybody - thinking caps on -- and hopefully not set to the "stun" position. This is tricky -- but fun. And to add to the fun, let's add yet another dimension from Gerald Schroeder's fascinating book "Genesis and the Big Bang". Now Schroeder, who is a nuclear physicist, cell biologist AND applied theologian specializing in Hebrew and the ancient rabbinical study of the cabala, tells us that hundreds of years ago, both Nahmanides and Maimonedes described and interpreted Genesis this way: Before the creation time did not exist. In a quote from the book:

"...If space and time did not exist, how was the universe brought into existence? Some 500 years ago, the cabalists theorized that at the instant of creation, God, filling all eternity, contracted. Within that contraction, the universe expanded. To form the universe God chose from the infinite realm of the divine, ten dimension or aspects and relegated them to be held in the universe. These dimensions are hinted at in the ten repetitions of the statements, "And God said..." used only in the opening chapter of Genesis. The cabalists believed that only four of the ten dimensions are physically measurable in today's world. The other six contracted into submicroscopic dimensions during the six days of Genesis. Today we refer to those measurable dimensions as length, width, height and time. {...}With an amazing congruity, particle physicists now talk about String Theory, a unified description of our universe in ten dimensions."

Well, now -- how do you like them apples? The cabalists already had not only String Theory figured out, but the idea of a contracting universe which preceded the Big Bang. Pretty neat, huh?

Another universe may have preceded ours, study finds

Three physicists say they have done calculations showing that before the birth of our universe, which is expanding, there was an earlier universe that was shrinking.

The results stem from a theory that claims the fabric of space and time is made up of minuscule, indivisible bits, much as matter is.

The diagram represents our expanding universe as the right branch of the arc. The present time is at the right edge. According to Ashtekar's calculations, when looking backward throughout the history of the universe, 'time' does not go to the point of the Big Bang but bounces to the left branch of the drawing, which describes a contracting universe. High resolution version here.

Scientists believe our cosmos began in a sort of explosion called the Big Bang, when everything that exists—which just previously had been packed into one infinitely dense point—burst outward.

The universe is still expanding, according to this view, because it was born expanding.

According to some proposals, the Big Bang is a repeating cycle. Universes might expand, then shrink back to a point, then expand again. Thus the “bang” would be really more like a bounce.

The idea is appealing in some ways, but scientists have found it far from easy to test. Einstein’s General Theory of Relativity, a key basis for the Big Bang theory, is silent on what happened before that event.

“General relativity can be used to describe the universe back to a point at which matter becomes so dense that its equations don’t hold up,” said Abhay Ashtekar, director of the Institute for Gravitational Physics and Geometry at Penn State University in University Park, Penn.

To go further, physicists must use tools Einstein didn’t have, he added. Ashtekar and two post-doctoral researchers developed such tools through a combination of quantum physics—the science of subatomic particles—and general relativity, which describes the large-scale structure of space and time.

They found that before the Big Bang, there was a contracting universe. Other than the fact that it was shrinking, they added, it was similar to ours in terms of the geometry of its space and time, or spacetime, as cosmologists call it since Einstein found the two are interwoven.

“In place of a classical Big Bang there is in fact a quantum bounce,” said Ashtekar. “We were so surprised by the finding,” he added, that the team repeated the calculations for months to include different different possible values of some numbers representing the current universe. But the results kept pointing to a bounce.

The findings appear in the current issue of the research journal Physical Review Letters.

While the general idea of another, pre-Big Bang universe isn’t new, Ashtekar said, this is the first mathematical study that systematically establishes its existence and deduces properties of its spacetime geometry.

The notion that spacetime has a geometry involves the idea that it can be curved or flat. A “flat” spacetime is one in which geometry works as we normally expect; for example, parallel lines never meet. But Einstein found that material objects deform this flatness, introducing curvature.

To arrive at their pre-existing universe finding, Ashtekar’s group used loop quantum gravity, a theory that seeks to reconcile General Relativity with quantum physics. These two seemingly fundamental theories are otherwise contradictory in some ways.

Loop quantum gravity, which was pioneered at Ashtekar’s institute, proposes that spacetime has a discrete “atomic” structure, as opposed to being a continuous sheet, as Einstein, along with most us, assumed.

In loop quantum gravity, space is thought of as woven from one-dimensional “threads.” The continuum picture remains mostly valid as an approximation. But near the Big Bang, this fabric is violently torn so that its discrete, or quantum, nature becomes important. One outcome of this is that gravity becomes repulsive instead of attractive, Ashtekar argued; the result is the Big Bounce


At 11:09 PM, Blogger Brandon_T_Stanley said...

Great site. Nice to run into some cosmology and philosophy every now and then.


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