Posted on 12/22/2002 6:07:08 PM PST by PatrickHenry
Space might end up dark, thick and boring.
The Universe is not as bouncy as some think, say two physicists. If a Big Crunch follows the Big Bang, it may get stuck that way for ever1.
A fluid of black holes would bung up space. There would be nothing to drive another Big Bang, and nowhere else to go. The Universe would be, you might say, stuffed.
In a bouncing universe, all the matter currently flying apart slows until it reverses and falls towards a Big Crunch. Some physicists think this could ignite another Big Bang, in an unending sequence of expansion and contraction.
An idea called M-theory suggests how the switch from crunch to bang could happen2. The details depend on the shape of space: whether it is infinite and flat, or finite and curved like the surface of a balloon or a doughnut.
Thomas Banks of Rutgers University, New Jersey, and Willy Fischler of the University of Texas at Austin have considered a flat, infinite space in which particles get ever closer and ever denser.
In a space with such features, the smallest kinks in density are amplified into black holes, the densest objects in the Universe. So the whole of space-time would congeal into a very lumpy soup - a black crunch.
"We don't really know what this fluid is made out of," Fischler admits. But he and Banks argue that it may reach a pressure at which it cannot become any denser. At this point, the speed of sound equals the speed of light. Deadlock results.
No theory can cope with a Big Crunch. Because of this, says Fischler, the analysis that he and Banks have performed remains speculative. And a doughnut-shaped Universe could meet a quite different fate, he adds.
References:
1. Banks, T. & Fishler, W. Black Crunch. Preprint http://xxx.lanl.gov/abs/hep-th/0212113, (2002). |Article|
2. Khoury, J., Ovrut, B. A., Seiberg, N., Steinhardt, P. J. & Turok, N. From Big Crunch to Big Bang. Preprint http://xxx.lanl.gov/abs/hep-th/0108187, (2002). |Article|
[See the original article for links in the footnotes]
Dear lurkers:
The answer given by MacDorcha (8.6 ft) was right, but only the good Lord knows how MacDorcha computed it. The simplest way is to look up the sine of a 60 degree angle. If you're not equipped for that, there's another way. The other angle is 30 degrees, and most can remember enough high school trig (sine of 30 degrees is 5) to know how far the base of that the ladder is from the wall -- an even 5 feet. So even without some handy trig tables (or a slide rule which has them built in), one could rely on the ol' Pythagorean theorem to bang out the height, as we already know two of the sides of the triangle.
I think we can safely conclude that it's Bush's fault for not following the Kyoto protocols.
Even $5 calculators have "SIN" buttons nowadays. But I'd give him the points: usually when a student pokes the "SIN" button, the answer he writes down is 0.8666666.
You wippersnappers have it too darned easy! Buncha button pushers! Snort, grumble, harumph ...
Sigh! See what happens when you post late at night after a long weekend! :-(
Should have read circumference. (feel like a fool! LOL)
The isotropic 2.7 deg. K Cosmic Microwave Backround radiation is consistent with a Universe that is expanding...
The recession of distant galaxies (again, isotropic), is consistent with an expanding Universe.
"sides" of the universe have nothing to do with it.
how do we know it isnt just some phenomonom that causes movements around us?
Because if it were a localized motion effect, it wouldn't be isotropic; we would appear to be moving away from some distant celestial objects, but towards others.
or... that this system is contracting?
Because we don't see any evidence for an isotropic blue shift.
saying it has no sides down plays the big bang theory
BB Cosmology says nothing about the Universe having "sides" (boundaries). An unbounded Universe is entirely consistent with BB Cosmology.
You passed Trigonometry?
RadioAstronomer, you are a class act.
Square root of three, divided by two will get you the ladder answer, exactly.
Hard to believe he passed English. Maybe he slept away in those classes too.
Who says? It all started spontaneously in the beginning, why couldn't it do it again huh?
ahem...
We see the DOE supported some of this work. Aside from that, would the assumption of an infinite, flat universe make this any more than an academic exercise?
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