This brain swap may not be as far off for humans as one might think. In only a few decades, the computer revolution here on Earth has produced supercomputers capable of performing more than a quadrillion calculations per second. (According to research by Hans Moravec, an artificial-intelligence expert at Carnegie Mellon University, that rate trumps the human brain's estimated top speed of 100 trillion calculations per second.) Some scientists speculate that in a few decades, an event called the technological singularity will occur, and machines armed with computer brains will become sentient and surpass human intelligence. Civilizations equipped with technology light-years ahead of our own could have already experienced the singularity thousands, or even millions, of years ago.