“But they’re also quite small, so you need very precise tests to see these small differences.”
The pulsars are both about 30 per cent more massive than the Sun but only about 24 kilometres across, meaning they exert huge gravitational influence on each other and the surrounding space.
CSIRO Astronomy and Space Science fellow Dick Manchester said the properties of the pulsars made them perfect to test general relativity.
“Such fast orbital motion of compact objects like these allows us to test many different predictions of general relativity – seven in total,” Dr Manchester said.
“Apart from gravitational waves and light propagation, our precision allows us also to measure the effect of ‘time dilation’ that makes clocks run slower in gravitational fields.”
The researchers spent 16 years measuring and analysing the data to make sure it was as accurate as possible, Professor Deller said, adding that they could have kept going but believed they now had the best data possible.
Ultimately, the behaviour of the pulsars conformed to everything predicted by Einstein’s equations, made all the more impressive by the fact that pulsars had not even been formally discovered when he devised them.
Professor Deller said, despite their experiment seeming to prove the theory is correct, he fully expected it to be eventually replaced with a different theory to explain the universe.
“The trouble with general relativity is that it is great for explaining how things work on a very large scale, but on a small scale, on the scale of atoms, it doesn’t work at all, and quantum theory takes over,” he said.
“One day, we will come up with something that physicists have been looking for a long time – the Unified Field Theory, which explains everything.
“So experiments like this push [general relativity] to its limits in the hopes of finding where it breaks down, and that will point the way to the next best theory.”
Professor Michael Kramer from the Max Planck Institute for Radio Astronomy in Germany was the lead researcher on the project, which utilised seven sensitive radio telescopes around the world, including the Parkes telescope in Australia.
The findings have been published in the journal Physical Review X.