Science: Astronomy and cosmology: Dark Matter, What Is It. (Daily Telegraph)

What is dark matter?

Dark matter is an invisible substance spread across the cosmos which makes up the majority of the physical universe.

Observations show that dark matter in the Universe is distributed as a network of gigantic dense (light) and empty (dark) regions, where the largest dense regions are about the size of several Earth moons on the sky Photo: VAN WAERBEKE/HEYMANS/CFHT LENS

By Nick Collins, Science Correspondent

7:00PM GMT 09 Jan 2012  Daily Telegraph

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Incredible as it may sound planets, stars and everything else we can see in space only accounts for about four per cent of the matter in the Universe.

Up to 90 per cent is believed to be comprised of dark matter, a substance which is invisible but can be inferred through its gravitational force which holds galaxies together.

Despite being theorised almost 80 years ago, dark matter still remains deeply mysterious because it can not be detected directly.

Scientists believe that huge clumps of the stuff are spread throughout space where their gravitational fields attract what we know as normal matter.

Eventually this normal matter condenses into galaxies of stars and planets, making dark matter in effect the glue that holds the Universe together.

Learning more about the matter, which likely consists of various different types of particle performing different roles, could shed light on some of the most fundamental questions in science.

If it did not exist, as some scientists believe, we would need a new explanation for how Earth and everything else in the Universe was formed