A century ago, Albert Einstein hypothesised the existence of gravitational waves, small ripples in space and time that dash across the universe at the speed of light.
But scientists have been able to find only indirect evidence of their existence. On Thursday, at a news conference called by the US National Science Foundation, researchers may announce direct observations of the elusive waves.
Such a discovery would open the door to a new way to observe the cosmos and unlock secrets about the early universe and mysterious objects such as black holes and neutron stars.
Scientists from the California Institute of Technology, the Massachusetts Institute of Technology and the LIGO Scientific Collaboration are set to make what they bill as a "status report" on Thursday on the quest to detect gravitational waves.
It is widely expected they will announce they have achieved their goal.
"I believe in the next decade our view of the universe is going to change really quite dramatically," said Abhay Ashtekar, director of Penn State University's Institute for Gravitation and the Cosmos.
Einstein in 1916 proposed the existence of these waves as an outgrowth of his ground-breaking general theory of relativity.
"Gravitational waves are literally ripples in the curvature of space-time that are caused by collisions of heavy and compact objects like black holes and neutron stars," Ashtekar said.
Scientists have been trying to detect them using two large laser instruments in the US, known together as the Laser Interferometer Gravitational-Wave Observatory (LIGO), as well as another in Italy.
The LIGO work is funded by the National Science Foundation, an independent agency of the US government.
All the current knowledge about the universe comes from electromagnetic waves such as radio waves, visible light, infrared light, X-rays and gamma rays. But a lot remains hidden because such waves get scattered as they traverse the cosmos. That would not be the case with gravitational waves.
Neutron stars and black holes have proven tough to study but could offer ideal subjects if observations of gravitational waves are possible.
"It gives us a detailed picture of what's happening inside or around the object that's producing the waves," Allen said.
Gravitational waves also offer a way to study what the universe was like in its infancy. For the first roughly 200,000 years of its existence, light did not travel freely through the universe, Allen said, but "gravitational waves can travel freely, back to very early times".
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