| From: Zardoz ® | 04/11/2001
19:32:50 |
| Subject: re: COSMOLOGY FAQ | post id:
484057 |
| What
happened before the big bang? "Well, the first thing is there's no 'before.' Because time itself, as far as we understand time, was generated-and space-at the Big Bang." Nobel Prize winning Physicist Leon Lederman, of the Illinois Institute of Technology. From: James R (Avatar) What was here before the big bang? Some would say there was no "here" for anything to be at, and no "before", so the question is kind of meaningless. Donald Terndrup, Faculty, Astronomy, Ohio State University The obvious answer is that all the stuff in the Universe would have been crammed into a small volume, and therefore would have been hot and dense. If you compute what would have happened, you would expect several things that are actually observed: the cosmic microwave background radiation, the basic composition of matter (about 77% hydrogen and 23% helium), and that there should be about a billion photons for each particle of ordinary matter. Since the expectations match the observations, astrophysicists are in general agreement that the Universe did indeed exist in a hot, dense state some finite time ago (about 12-16 billion years). That's the Big Bang in a nutshell. Like all theories, the Big Bang theory is about things we can observe, and we simply do not have any information earlier than the first tiny fraction of a second after the expansion started. If we could somehow deduce earlier times than that, then it would become part of the theory. http://www.madsci.org/posts/archives/jun2000/959868473.As.r.html Key Concepts
The generally accepted model of the creation of the Universe is called the Big Bang Theory. It says that everything was created in a vast explosion roughly ten billion years ago, and that the Universe is expanding because everything is still rushing away from the original explosion. Space and time themselves were created in the explosion, so it's meaningless to ask what was here before the Big Bang. The main alternative idea, the Steady State Theory, says that although the Universe is constantly expanding, new material is being constantly created within it to fill the voids left as everything rushes apart. The Steady State theory was popular until the 1960s, when radio astronomers discovered a weak glow, called the cosmic background radiation, coming from every part of the sky, at the very edge of the observable Universe, and therefore many billions of years back in time. The only convincing explanation for this radiation was that it is the afterglow of the Big Bang itself. Another alternative theory is that the Universe is cyclical - after billions of years, the expansion will slow to a halt, and it will collapse under its own gravity, to a Big Crunch, which will then become another Big Bang, creating a new universe. Although the cyclical theory is unprovable, and the Steady State idea discredited with most astronomers, the Big Bang theory is not by any means perfect - there are a number of problems with the evidence. The age of the Universe depends on exactly when everything within it coexisted at one point in space, and this is in turn dependent on the rate at which the Universe is expanding now. Most of our evidence for the expansion of the Universe comes from the red shifts of distant galaxies, and there is still some argument about the precise meaning of these red shifts. Even if this problem is ignored, the best estimates of the Universe's expansion rate are getting higher, meaning astronomers keep lowering the age of the Universe. Some recent estimates put it as young as 8 billion years old - but meanwhile stellar astronomers are putting the ages of the oldest stars up to 10-12 billion years old! How can stars be older than the Universe itself? Other problems with the Big Bang involve explaining exactly why the Universe is how we see it today. In order to explain the large scale structure of the Universe, and the domination of certain types of matter within it, the Big Bang theory has been modified several times. http://www.sciencenet.org.uk/database/Physics/Cosmology/p00704c.html |
|