We often say that the earth is a sphere, but to be precise, the term sphere refers only to the surface. The correct mathematical term for the solid earth is a ball.

Every time a bit of information is erased, we know it doesn't disappear. It goes out into the environment. It may be horribly scrambled and confused, but it never really gets lost. It's just converted into a different form.

[Richard Feynman] truly believed that if you couldn't explain something simply, you didn't understand it.

Einstein, in the special theory of relativity, proved that different observers, in different states of motion, see different realities.

I did not come from an academic background. My father was a smart man, but he had a fifth-grade education. He and all his friends were plumbers. They were all born around 1905 in great poverty in New York City and had to go to work when they were 12 or 13 years old.

There is a philosophy that says that if something is unobservable -- unobservable in principle -- it is not part of science. If there is no way to falsify or confirm a hypothesis, it belongs to the realm of metaphysical speculation, together with astrology and spiritualism. By that standard, most of the universe has no scientific reality -- it's just a figment of our imaginations.

Science blogs bore me. When everyone is an expert, no one is an expert.