Gravitational Waves Rock the Physics World

An aerial view of the LIGO site in Louisiana, showing 2.5-mile-long extensions of the experiment against the verdant countryside.

About 1.3 billion years ago, a pair of black holes suddenly spiraled in on each other and merged, creating a new spinning black hole—all in just one-fifth of a second. The immense energy released by this cosmic cataclysm generated waves that shook the very fabric of space and rippled out through the cosmos.

In 1916 Albert Einstein’s theory of general relativity predicted that events like this would produce such ripples in the fabric of space, which he called gravitational waves. They would, however, be so weak that he thought they would never be detected.

But Einstein was wrong. Today U of M researchers are among the 1,000 scientists worldwide celebrating the landmark discovery of gravitational waves from a merger of black holes as described above. The signal was so faint, its effect was to stretch and squeeze a 2.5-mile distance by less than one-thousandth the size of the smallest atomic nucleus. So Einstein was right about the weakness.

The discovery is generating its own ripples—strong ones—through the scientific community. Besides validating Einstein’s prediction, it opens the door to using gravitational waves to understand the Universe.