An international team of astronomers have made the most precise test of gravity outside our own solar system.
By combining data taken with NASA's Hubble Space Telescope and the European Southern Observatory's Very Large Telescope, their results show that gravity in this galaxy behaves as predicted by Albert Einstein's general theory of relativity, confirming the theory's validity on galactic scales.
In 1915 Albert Einstein proposed his general theory of relativity (GR) to explain how gravity works. Since then GR has passed a series of high precision tests within the solar system, but there have been no precise tests of GR on large astronomical scales.
It has been known since 1929 that the Universe is expanding, but in 1998 two teams of astronomers showed that the Universe is expanding faster now than it was in the past. This surprising discovery—which won the Nobel Prize in 2011—cannot be explained unless the Universe is mostly made of an exotic component called dark energy. However, this interpretation relies on GR being the correct theory of gravity on cosmological scales. Testing the long distance properties of gravity is important to validate our cosmological model.
