How attempting to break the theory of general relativity has migrated beyond the limits of the Milky Way

Reported by Robert Lea

Testing Einstein’s geometric theory of gravity, or general relativity (GR), was never going to be a straightforward task. At the heart of GR are the effects that massive objects such as planets, stars and even entire galaxies cause on the fabric of space. Such tremendous masses aren’t easily replicated in the lab, especially before the debut of complex computer simulations. In the century since its introduction, physicists have moved GR experiments into space, out past the limits of the Solar System and even beyond our galaxy.

“Space is the most ideal laboratory for testing general relativity, as its effects in and around the Solar System are so minuscule ,” Vivek Venkatraman Krishna n, an astrophysicist at the Max Planck Institute for Radio Astronomy, Germany, explains. “The effects of GR are significant only around objects that have strong gravitational fields – such as neutron stars and black hole s – which makes them ideal laboratories for testing.” During this journey , scientists have studied some of the most powerful and mysterious objects in the universe.

“GR was revolutionary because it jettisoned the New tonian concept of gravity as an attractive force between massive bodies. It replaced it with the idea that space and time – or space-time – is warped or curved by the presence of massive bodies, and that it is this curvature that leads to the orbital motion of stars and planets and the fall of an apple from a tree,” Cliffor d Will, professor of physics at the University of Florida and author of Was Ein stein Right? says. “This was a strange and radical conception, and many physicists, especially experimentalists, reacted strongly against it. The main challenge was that the effects predicted in the Solar System were tiny.”

Upon its introduction in 1915, Einstein knew that his new theory would have to account for the phenomena of gravity at least as well as Newton’s law of universal gravitation, which had served science just fine for over 200 years. But matching its predecessor’s level of experimental verification would be a challenge to say the least. To this end, the physicist calculated three tests that could be used to verify his new theory of gravity. The first of these involved doing something Newton’s theory couldn’t – explaining a strange ‘wobble’ in the orbit of Mercury.