On October 3, the Nobel Prize in physics was awarded by the Royal Swedish Academy of Sciences to physicists Rainer Weiss, Kip Thorne and Barry Barish for their direct detection of gravitational waves – something predicted by Einstein more than 100 years prior.
One of Einstein’s predictions, in relation the theory of general relativity, was that the universe is a fabric made of space and time, and such fabric would bend due to massive objects such as planets and stars. This prediction was proved correct when it was discovered that the Sun could bend the light coming from other stars, resulting in Earth observers being able to “look through” the Sun to the stars behind it.
So, if space-time was a defining feature of our universe, Einstein predicted that when two massive objects interact, they will cause a ripple in the space-time fabric. These ripples are known as gravitational waves, and Einstein believed they would be detectable if there were an instrument sensitive enough.
This instrument came to fruition in the 1970’s when Rainer Weiss proposed a design which he believed could detect gravitational waves. His initial idea was then built on by multiple researchers, including Thorne and Barish, into what eventually became LIGO (Laser-Interferometer Gravitational-Wave Observatory).
LIGO consists of two identical L-shaped detectors in Washington state and Louisiana, each measuring roughly four kilometres end-to-end. Each detector is equipped with lasers and mirrors used to measure tiny changes in space-time made by passing gravitational radiation. It is currently the most sensitive measuring device on Earth. LIGO first detected gravitational waves in 2015, when the two-sprawling detectors heard a faint chirp caused by the collision of two black holes from more than a billion years ago. Since this extraordinary detection, three more waves have been detected. To date, all four detections have been the result of colliding black holes but it is expected that scientists will soon capture waves due to merging neutron stars or from supernovae.
Since LIGO’s first announcement of the detection, we have gained invaluable insight into the cosmos. We can now detect celestial events which are otherwise unseen due to little or no observable light.
“We have now witnessed the dawn of a new field, gravitational wave astronomy. This will teach us about the most violent process in the universe, and it will lead to new signs about the nature of extreme gravity” says Nils Martensson of the Nobel Committee
Nobel prizes are often given to researchers many years after their discoveries. As the gravitational waves detection breakthrough occurred only a little over two years ago, the prize committee must be confident that the work started by Weiss, Thorne and Barish is going to transform the study of astronomy and our understanding of the universe.
Find out more about the detection of gravitational waves in the video below.