Scientists may be poised to make a major announcement that will open a new window on the universe.
A US team is rumoured to have caught the first glimpse of gravitational waves, ripples in space time predicted by Albert Einstein 100 years ago.
An update on the search for gravitational waves is due to be released on Thursday, but a tight lid is being kept on the information until then.
Gravitational waves are theoretically generated by cataclysmic cosmic events such as the collision of black holes or super-dense neutron stars.
As the waves spread out, they compress and stretch spacetime.
Scientists hope to detect them using laser beams capable of measuring minute changes in the lengths of two four kilometre long pipes situated in Hanford, Washington and Livingston, Louisiana.
Together they make up the Advanced Interferometer Gravitational Wave Observatory (Ligo).