Astronomy experiments could soon test an idea developed by Albert Einstein almost exactly a century ago, scientists say.

Advanced technology could resolve a long-standing puzzle over what is driving the accelerated expansion of the Universe.

Researchers have long sought to determine the mechanism behind the expansion of our universe.

Calculations in a new study could help to explain whether dark energy, as predicted by Einstein, or a revised theory of gravity are responsible.

Explaining gravity

Einstein’s theory describes gravity as distortions of time and space. This included a mathematical element known as a Cosmological Constant.

Einstein originally introduced it to explain a fixed universe, but discarded the idea after it was discovered that our universe is expanding.

Research carried out two decades ago showed that this expansion is accelerating.

This suggests that Einstein’s Constant may still have a part to play in an explanation of dark energy.

Gravity effects

Without dark energy, the acceleration implies a failure of Einstein’s theory of gravity across the largest distances in our Universe.

Scientists from the University have discovered that the puzzle could be solved by experiments to determine the speed of gravity in the cosmos.

Theory test

The researchers’ calculations show that gravitational waves – ripples in space-time in the universe - may hold the key.

If these are found to travel at the speed of light, this would rule out theories without dark energy. It would also support Einstein's Cosmological Constant.

If, however, their speed differs from that of light, then Einstein’s theory must be revised.

Advanced laboratory

The experiment could be carried out by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US.

Its twin detectors, 2000 miles apart, detected gravitational waves in 2015.

Experiments conducted at the facility this year could resolve the question in time for the 100th anniversary of Einstein's Constant.

The study was published in Physics Letters B.

It was supported by the UK Science Technology Facilities Council, the Swiss National Science Foundation and the Portuguese Foundation of Science and Technology.