Physicists may have finally found hard evidence for the existence of dark matter.
And reports from the American Association for the Advancement of Science in Bostonsay the announcement could come within the next fortnight - if the data holds up.
Dark matter is thought to be the invisible 'stuff' which makes up the bulk of the universe's mass. In fact it's supposed to outnumber regular matter by six to one - even though we can't see it (or at least so far).
Its existence was first proposed in the 1930s, to explain the way that galaxies expand and move in clusters. Later studies of galactic expansion, rotation and distribution added weight - literally - to the idea that dark matter may be needed to explain how the universe works.
(Nasa has a great explanation of the complex idea of dark matter - and the separate concept of dark energy - here.)
Despite the theory, it hasn't yet been possible to directly observe dark matter or even know of what it's made, but the first results from a new instrument - the Alpha Magnetic Spectrometer - are now due.
And the rumour is they could be a game-changer.
"It will not be a minor paper," said Samuel Ting at MIT, lead investigator of the experiment.
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