"Jacques Cousteau, a famous marine biologist, described a scientist as "a curious person who looks through a keyhole." hat did he mean? When you look through a keyhole, you can't see everything,only a few things (Figure 1.2). An experiment is like looking through a keyhole. The results of each experiment give you a small amount of information, not the answers to all your questions."

A very good pdf file is in the link...