EINSTEIN'S THEORY of general relativity (GR), which describes how gravity is the result of mass, energy and the curvature of spacetime, has passed every test thrown at it since it was thought up in 1915.
But, despite its success, relativity isn’t expected to be the last word in gravity.
Although it makes superbly accurate predictions for everyday gravitational objects, relativity hasn’t been tested in more extreme circumstances.
You don’t get much more extreme than this pair. The larger object is a fairly unremarkable white dwarf star, but the smaller one, a newly discovered pulsar, is an extremely remarkable object indeed.
Imagine an object that could sit quite happily on the Isle of Wight and you could walk around in just a few hours – now imagine that bundled up inside it is enough atoms to make two Suns; its surface is burning away at millions of degrees and it shoots high-energy jets of radiations out into space at millions of miles per hour. That’s extreme.
The pulsar, PSR J0348+0432, along with its far less massive companion is part of a binary system that orbit each other every 2.46 hours. As they plough through space, they dig gravitational pits in the fabric of spacetime and push up gravity waves, which spread out into space.
According to GR, the binary will lose energy in the process of making those waves and, as such, their orbit will decrease.
This prediction has been tested by astronomers using the European Southern Observatory’s Extremely Large Telescope. They found that over twelve months of observations, the binary’s orbit slowed by eight millionths of a second, which may not sound like a lot, but it is exactly the amount predicted by GR.