Scientists have confirmed one of Albert Einstein’s century-old theories by witnessing a phenomenon with the Hubble Space Telescope that he thought would be impossible to see, researchers declared Wednesday.
Astronomers have now glimpsed for the first time a distant star’s light bending and revealing its mass when an object passes in front of it, known as “gravitational microlensing,” said the report, which was published in the journal Science.
“Einstein would be proud. One of his key predictions has passed a very rigorous observational test,” wrote Terry Oswalt of Embry-Riddle Aeronautical University, in an accompanying Perspective article in Science.
This gravitational microlensing was seen in 1919, when starlight curved around a total eclipse of the sun. At the time, the discovery offered some of the first convincing proof for Einstein’s theory of general relativity — a law of physics that describes gravity as a geometric function of both space and time.
“When a star in the foreground passes exactly between us and a background star, gravitational microlensing results in a perfectly circular ring of light — a so-called ‘Einstein ring,’” said Oswalt.
But Einstein believed that it would not be possible to see the phenomenon with stars other than our sun. In a 1936 article in Science, he wrote that because stars are so far apart “there is no hope of observing this phenomenon directly.”
Of course, Einstein could not have predicted that the Hubble Space Telescope would be launched in 1990 and offer unprecedented views of faraway stars and planets.