Philosophers played a crucial role in past scientific revolutions, including the development of quantum mechanics and relativity in the early 20th century.Today a new revolution is under way, as physicists struggleto merge those two theories into a theory of quantum gravity a theory that will have to reconcile two vastly different conceptions of space and time. Carlo Rovelli of the University of Aix-Marseille in France, a leader in this effort, says, “The contributions of philosophers to the new understanding of
space and time in quantum gravity will be very important.”
Two examples illustrate how physicists and philosophers
have been pooling their resources. The first concerns the “problem of frozen time,” also known simply as the “problem of time.” It arises when theorists try to turn Einstein’s general theory of relativity into a quantum theory using a procedure called canonical quantization. The procedureworked brilliantly when applied to the theory of electromagnetism,but in the case of relativity, it produces an equation the Wheeler-DeWitt equation—without a time variable.
Taken literally, the equation indicates that the universe should be frozen in time, never changing.