SCIENTISTS believe they have found the first direct evidence of mysterious "dark matter" - invisible material thought to make up 22 per cent of the universe.
Observations of two colliding galaxy clusters 100 million light years away showed ordinary matter and dark matter being wrenched apart.
Hot gas produced by the 6.2 million miles-per-hour collision was slowed by a drag force, similar to air resistance.
But dark matter particles were not affected the same way, since they do not interact with ordinary matter except through gravity. This produced a separation of normal and dark matter, which raced ahead of the bullet-shaped hot cloud.
Astronomers used a technique called "gravitational lensing" which measures the way light is bent by the distortion of space caused by gravity.
No-one knows what dark matter is made of, but without it the universe could not exist as it does and there would be no life on Earth. Dark matter is thought to act as a "glue" holding galaxies together and creating order in the cosmos.