For centuries, it was assumed that our universe was static. Then, in the late 1920s, astronomers made a startling new discovery—from Earth, the light of distant galaxies appeared to be red. This meant those galaxies were receding from us, and a revolutionary realization was born: the universe is expanding. In The Red Limit, Timothy Ferris recounts the fascinating tale of this discovery, its far-reaching ramifications, and the passionately competitive astronomers who charted the past, present, and future of the cosmos.