Gravitational waves were first observed on 14 September 2015. We had known Einstein’s theory about them for a hundred years, but only now was there proof they actually existed. Physicists and astronomers around the world were ecstatic. They knew that they had a new way to study the universe. Measuring gravitational waves could result in exciting discoveries, such as how black holes form and what happened just after the Big Bang. A new era in physics and astronomy has begun.
When stars collide, space vibrates
Extreme events in the most massive regions of the universe trigger vibrations in the fabric of space-time. That is the “elastic” stage on which all events in the cosmos take place. When a gravitational wave ripples past them, the distances between objects expand and contract by tiny amounts. These changes are imperceptible to us, but they can be detected using the world’s most sensitive instrument.
The gravitational wave of 14 September 2015 began as a collision between two black holes 1.3 billion light years from Earth. This went unseen by normal telescopes, but produced an unmistakable signal at LIGO, the Laser Interferometer Gravitational-Wave Observatory in the United States. In 2017 three researchers from LIGO’s collaboration with its European counterpart, Virgo, were awarded the Nobel Prize in Physics for their contributions to the detector and its observation of gravitational waves.
A new window on the universe
The first detection of a gravitational wave created a whole new field of research in physics and astronomy. As well as light and fast particles, scientists can now also observe ripples in space-time. They are the only kind of signal which cannot be deflected or blocked by matter in their path. No light is released when two black holes collide, but their gravitational waves are always measurable. As a result, physicists are now gathering new information about the nature of neutron stars, black holes and the universe immediately after the Big Bang.