What is dark matter?

Explore the mystery of dark matter with our print-out-and-keep infographic guides (you don’t have to print it out, you can just look at it on your computer screen.. or phone… or tablet… the possibilities are endless!

Science is littered with concepts that seem custom-made to strain the limits of intuitive logic and high up on this list of scientific oddities is dark matter — a mysterious substance that accounts for about 85 per cent of all the matter in the Universe, yet is invisible and can only be detected by its gravitational effect on the matter we can see… but what is it?

To the ‘rational’ mind it might seem that dark matter is, at best dropped, the product of the fevered mind of a low-rent science-fiction writer, or, at worst, is something dreamt up by scientists to fill an embarrassing hole in their understanding of the Universe.

Dark matter’s existence was first suggested 80 years ago to explain anomalies in the behaviour of galaxies but is now accepted to be an essential component in the machinery of the cosmos. Without the gravitational input of dark matter, the Universe as we know it couldn’t exist. But, despite overwhelming evidence for its existence, science still doesn’t know what dark matter is made of.
​
The trouble with dark matter is that, although it interacts with the gravitational force, it is immune to charms of the electromagnetic force, which is why we can’t detect it directly. Since we are made of ‘normal’ matter, we interact with the world through the electromagnetic force — tables feel solid because the electrons in the atoms in our fingers are electromagnetically repelled by the electrons in the table’s atoms; and we can see objects because our eyes collect the visible electromagnetic radiation (light) they emit or reflect.

But how do you find something you can see? Scientists all over the world have devised experiments to detect these theoretical dark matter/matter interactions. Some, like STFC’s Boulby Laboratory, are buried in Earth’s deepest mines (using the many metres of rock to filter out ‘normal’ particles that interact more enthusiastically with matter) while others have been launched into space.

Meanwhile, also underground, scientists at CERN’s particle-smashing behemoth, the Large Hadron Collider are hoping to create their own dark matter. They hope that by smashing particle together and carefully watching the resultant particle debris for some missing mass, that missing mass might be evidence that a dark matter particle was created… kind of like looking for nothing to find evidence of something.

Story by: Ben Gilliland