# Mathematical Digest

### Short Summaries of Articles about Mathematics

in the Popular Press

"Number Crunching Cosmos," by Kathy A. Svitil. *Discover,* September 2002.

"Seth Lloyd, a quantum mechanical engineer at the Massachusetts Institute of Technology, proposes a completely different way to take the measure of the universe: by how much data it generates." Lloyd says, "The challenge lies in defining and quantifying this notion. In a conventional computer, binary digits flip from 0 to 1, or vice versa, to perform computations. In the universal analog, each flip in the 'computation' occurs when sub-atomic particles interact and change their quantum energy states, the most fundamental unit of physical change." Svitil summarizes, "By factoring in the amount of available energy and the speed of light, Lloyd estimates the universe could have performed at most 10^{120} logical operations since the Big Bang."

*--- Annette Emerson*