Re: How did the universe begin?

Hi Jason,

When you ask which theory I believe in, I assume that you mean theory for the origin of the universe.

The criteria that scientists go by when deciding to adopt a particular theory over others are how well that theory explains what observers can see, and how simple it is. Put another way, we usually go with the simplest theory that can explain everything that we see. Of course, how well a theory explains the observations is open to debate, which leads to many of the disagreements that you may see among scientists as to which theory works best.

Specifically, for the formation of the universe, I, like almost all astronomers, believe in the Big Bang theory. So far at least, it has been the best theory for explaining the expansion of the universe, the existence of the cosmic microwave background radiation, the amount of light elements formed early in the history of the universe, and many other observations.

This isn't to say that other theories (the steady-state theory, for example) can't be made to explain the observations. But, none seem to do it as well or as simply as the Big Bang theory.

Most other theories are essentially modifications of the Big Bang theory. For example, the inflation theory postulates that the universe went through an early unstable period in which it expanded incredibly rapidly, which helps to explain some observations with which the simplest Big Bang theory has difficulty. Some other interesting variations of the Big Bang were discussed in a recent issue of Scientific American (the January issue, I believe).