If an apple was magnified to the size of the Earth, then the atoms in the apple would be approximately the size of the original apple.

To test whether you have learned an idea or a definition, rephrase what you just learned without using the new word.

The highest forms of understanding we can achieve are laughter and human compassion.

From a long view of the history of mankind the most significant event of the nineteenth century will be judged as Maxwell's discovery of the laws of electrodynamics.

In those days, in Far Rockaway, there was a youth center for Jewish kids at the temple.... Somebody nominated me for president of the youth center. The elders began getting nervous, because I was an avowed atheist by that time.... I thought nature itself was so interesting that I didn't want it distorted like that. And so I gradually came to disbelieve the whole religion.

Philosophy of science is about as useful to scientists as ornithology is to birds.

Why make yourself miserable saying things like, "Why do we have such bad luck? What has God done to us? What have we done to deserve this?" - all of which, if you understand reality and take it completely into your heart, are irrelevant and unsolvable. They are just things that nobody can know. Your situation is just an accident of life.