Scientific Method part 2

(By Dr.Duane Hampton)

Monday, after class, I was eating lunch with the Government Documents librarian, Mike. He told me he had heard that there was a recent article in “Science” about the origin and future of the universe. This article purportedly said that the universe expanded and contracted in successive cycles. Mike said he thought the author claimed to prove this was true. I told him that I didn’t believe that he had proved it, and that as a best case scenario, perhaps the author had established a hypothesis and then presented evidence to make a compelling case for the hypothesis. I said I was confident that the author could not have proved anything. How could I be so confident?

The answer has to do with understanding the scientific method. In this method, you establish one or more hypotheses, make predictions, and gather data to test these predictions. Some times the predictions are true. Often the predictions are not true, which means that the hypothesis is false. Then you know that the hypothesis needs to be revised to incorporate what you have learned. Very often the data do not disprove the hypothesis, but do not confirm the predictions either. This is merely a failed experiment. Successful experiments either disprove hypotheses, or corroborate hypotheses. Even if the prediction is confirmed, however, you have not proved that the hypothesis is true. You can never prove that a hypothesis is true. You can simply fail to disprove the hypothesis. When you do that enough times, you begin to believe the hypothesis is true. Then we show the hypothesis additional respect by calling it a theory (like Darwin’s theory of evolution). If we continue through many tests to show that the theory successfully predicts the future, without failure, we call it a law (like Einstein’s law of relativity).

The only thing that we can prove true is mathematical theorems, since these are within the realm of mathematical logic. Scientific hypotheses cannot be proven true, only shown to be false. Believe it or not, many physicists are still conducting experiments to try to demonstrate that parts of Einstein’s law of relativity are false. So far, nobody has succeeded in showing any part of relativity to be false. If someone succeeded in doing that, they would get the Nobel Prize in Physics for sure. But that is not the motivation for doing those experiments. The motivation is that when an experiment is done, we will hopefully understand better how the universe works in some way. That same motivation drives all scientific work.

So this new article in “Science” might make a case for a universe that expands and contracts cyclically, but could never prove that it is true. Furthermore, we know the universe is currently expanding, and analysis of the data suggests (i.e., we think we know) that the rate of expansion is increasing. Thus, it seems quite unlikely given what we know, and what we think we know, that the universe would stop expanding and start contracting in the future.

I should point out that our understanding of the universe’s beginning and future is very cloudy and tenuous. Dating of the “Big Bang”, the beginning of the universe’s current expansion, says that it began 13 - 15 billion years ago. Several astronomers (e.g., Alan Sandage) have dated individual stars and claimed they are about 20 billion years old. Clearly, stars should not be older than the universe in which they reside. We have some real problems to resolve in this area.

May 06, 2002.