BENGALURU: Exactly a hundred years ago, a group of astronomers led by Arthur Eddington conducted an observation during the solar eclipse, taking photographs of stars near the sun. Months later, the same photographs were taken again and it showed that the stars appeared to be in a different position the second time.
This landmark discovery verified the prediction of Albert Einstein’s theory of general relativity that gravity bends light. The Jawaharlal Nehru Planetarium arranged a special public talk on Wednesday, on the occasion of 100 years of the ‘Light Bending experiment’ which was conducted on May 29, 1919.
P Ajith, associate professor, International Centre for Theoretical Sciences (ICTS), addressed a crowd of students and science enthusiasts to mark the centenary of the discovery. “Einstein’s theory of general relativity predicted that gravity curves space and time. As a result, if the sun is between an observer and a star, the sun’s gravity would bend the light, and the position of the star would appear different to the observer. It was Eddington’s observation exactly 100 years ago with his team of astronomers in Africa and Brazil, that provided the first strong evidence for this theory and opened up a whole new field of astronomy called gravitational lensing,” explained Ajith.
There were several consequences and discoveries that came as a result of Eddington’s experiment.
“Gravitational lensing (distribution of matter such as a cluster of galaxies between a distant light source and an observer, that is capable of bending the light from the source as the light travels towards the observer) observations in the last few decades have enabled astronomers to detect planets outside our solar system.
They helped astronomers detect the presence of dark matter and understand the shape of galaxies and clusters,” said Ajith, adding, “It turns out that gravity not only bends light, but gravitational waves too. In 2015, gravitational waves which are elusive ripples in spacetime predicted by Einstein, were detected by LIGO ( Laser Interferometer Gravitational-Wave Observatory) and the discovery won the Nobel prize. This opened up a new branch of astronomy using gravitational wave observations.”Ajith said owing to Eddington’s first observation a hundred years ago, astronomers today are on the verge of detecting gravitational lensing of gravitational waves too.