Born in Vienna, Austria, on May 22, 1920, Thomas Gold emigrated to England, where he attended Cambridge University, graduating in 1942. He received a master's degree three years later. In 1956 he came to the United States, worked for a year at Harvard University, and finally settled down at Cornell University. Gold was interested in a subfield of astronomy called cosmology, which deals with the structure and evolution of the universe.

Cosmologists hold that if we hope to understand the cosmos, we must make some assumptions about it. First and foremost, cosmologists assume that the universe is homogeneous--that is, it is nearly the same everywhere. The view of the sky as seen from the Milky Way galaxy shouldn't be radically different than the view from an entirely different galaxy. This assumption is called the cosmological principle.

In the 1920s, Edwin Powell Hubble observed that the universe appears to be expanding; galaxies are...