As a child, Joseph Priestley noticed something that would influence the rest of his life: If you keep a bug in a jar for too long, it will die. At the time Joseph Priestley didn’t understand why that was true—nobody did. No one really studied the air; it was something everyone took for granted.

In 1927 a Roman Catholic priest and scientist Georges Lemaitre proposed what later became known as the Big Bang theory of the origin of the Universe, based on work by Edwin Hubble who theorized and then proved that the Universe was getting bigger and bigger. Many scientists have discovered other...