An international team used telescopes all around the world to perform the most rigorous tests of Einstein’s general theory of relativity.

Professor Michael Kramer of the Max-Planck Institute for Radio Astronomy in Bonn, Germany, headed the research that proved that Einstein’s 1915 theory is still valid.

“The theory of general relativity describes how gravity works at large scales in the Universe, but it breaks down at the atomic scale where quantum mechanics reigns supreme,” said Dr. Dick Manchester.

“We needed to find ways of testing Einstein’s theory at an intermediate scale to see if it still holds true. Fortunately, just the right cosmic laboratory, known as the ‘double pulsar’, was found using the Parkes telescope in 2003.

“Our observations of the double pulsar over the past 16 years proved to be amazingly consistent with Einstein’s general theory of relativity, within 99.99 per cent to be precise.”

Two pulsars, rapidly rotating compact stars that emit radio waves like a cosmic lighthouse and create very powerful gravitational forces, make up the double pulsar system.

One star spins 45 times every second, whereas the other rotates only 2.8 times each second. Every 2.5 hours, the stars complete one orbit.

The tremendous accelerations in the double pulsar system, according to general relativity, strain the fabric of space-time and send forth ripples that slow the system down. In 85 million years, the two pulsars are expected to collide.

The impacts of this energy loss are difficult to identify since it occurs over such a lengthy duration. Fortunately, the spinning pulsars’ clock-like ticks are ideal tools for tracing the tiniest disturbances.

Another member of the research team, Associate Professor Adam Deller from Swinburne University and the ARC Centre of Excellence for Gravitational Waves (OzGrav), revealed that the ticks from the pulsar ‘clocks’ took roughly 2,400 years to reach Earth.

“We modelled the precise arrival times of more than 20 billion of these clock ticks over 16 years,” Dr. Deller added.

“That still wasn’t enough to tell us how far away the stars are, and we needed to know that to test general relativity.”

The study team was able to detect a minor wobble in the stars’ locations every year by combining data from the Very Long Baseline Array – a global network of telescopes – which revealed their distance from Earth.

“We’ll be back in the future using new radio telescopes and new data analysis hoping to spot a weakness in general relativity that will lead us to an even better gravitational theory,” Dr. Deller concluded.

Source: CSIRO

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