Scientists have been looking for gravitational waves for 11 years to no avail, putting into question what is currently understood about black holes and galaxies.
Proposed as part of Albert Einstein's general theory of relativity, gravitational waves are appealing to scientists because they are believed to carry information that will aid in generating a better understanding of how the universe began. There have been strong circumstantial evidence pointing to gravitational waves but no one has ever been able to provide direct proof that they exist.
A study published in the journal Science sought to find evidence of gravitational waves, with scientists expecting a background "rumble" produced as galaxies merged across the universe. However, the scientists, led by Ryan Shannon, were not able to detect anything using the Parkes telescope from the Commonwealth Scientific and Industrial Research Organization (CSIRO).
Shannon said that while gravitational waves were not detected, their study prompted the scientists to push the limits of the telescopes available to them, offering other means of understanding how black holes and galaxies work. Still, the lack of gravitational waves on the cosmic front throws out what scientists think they know about black holes.
According to Einstein, gravitational waves are produced as two black holes spiral around each other when their galaxies merge. His general theory of relativity has been able to withstand every test thrown at it except for detecting gravitational waves directly.
Why haven't scientists detected gravitational waves until now?
Shannon and his team offer several reasons, one of which may be that black holes are simply merging too fast, spending little time dancing around each other and producing gravitational waves. Another reason proposed is that there could be gas around black holes, which leads to friction that carries energy away.
The scientists failed to detect gravitational waves by timing millisecond pulsars, small stars that produce regular sets of radio pulses and function like clocks in space, but their failure will not affect ground-based efforts like the Advanced Laser Interferometer Gravitational-Wave Observatory since these look for out sources like coalescing neutron stars.
Shannon is affiliated with the International Center for Radio Astronomy Research, a joint venture between The University of Western Australia and the Curtin University supported and funded by the Western Australia's state government.