An illustration shows gravitational waves emanating from merging black holes. Photo by Swinburne Astronomy Productions/NASA
CANBERRA, Australia, Sept. 24 (UPI) -- Einstein predicted the presence of gravitational waves as part of his theory of relativity. Although they haven't been directly detected, a number of scientific studies have implied the presence of the spacetime ripples.
Over the last 11 years, a team of astrophysicists have been looking for direct evidence of gravitational waves. But their efforts have proven fruitless.
Astronomers expected to pick up the enigmatic waves rumbling out across the universe from galactic mergers -- instead, crickets.
"We heard nothing. Not even a whimper," lead researcher Ryan Shannon, an astronomer with CSIRO and the International Centre for Radio Astronomy Research, said in a press release. "It seems to be all quiet on the cosmic front -- at least for the kind of waves we are looking for."
Einstein's theory of relativity predicts that the merging of two supermassive black holes would result in gravitational waves. Researchers estimate that if gravitational waves exist, they would show themselves by bending the bursts of radio waves sent out into the universe by pulsars.
So for 11 years, Shannon and his colleagues -- with the help of radio telescopes -- monitored pulsar waves as they passed Earth, looking for anomalies. But they came up empty-handed.
Scientists now think black holes may merge too quickly to send out gravitational waves during their brief death spiral.
"There could be gas surrounding the black holes that creates friction and carries away their energy, letting them come to the clinch quite quickly," said Paul Lasky, a postdoctoral research fellow at Monash University.
The new study, published in the journal Science, won't end the search for gravitational waves. Scientists theorize the waves may have a variety of other sources -- not just galactic mergers.
A number of ground-based gravitational wave surveys are currently looking for the phenomena at a higher frequency.