What is dark matter? And have scientists finally found it?

What is dark matter?

That's a question scientists have been asking for a REALLY long time, and that's because it makes up nearly a third of the universe.

But a recent discovery might have brought them a lot closer to an answer.

Hundreds of scientists from different countries, including the UK, are taking part in the study.

It's a little bit of a complicated topic, but don't worry, we'll break it down together.

Read on to find out more about dark matter and this discovery!

There has been loads of big space news recently, like the Nasa telescope launched into space and the eclipses we saw this summer!

But this discovery is also BIG space news because scientists have made a possible breakthrough in the hunt for dark matter.

They could have observed hints of it during an experiment that's being done deep underground in the US - pretty cool, right?

In this experiment, the scientists saw something new that they cannot explain.

Lead researcher physicist Dr Sam Eriksen said it could be "the first step in understanding dark matter as a particle" BUT they're not getting too excited, it's not confirmed as actually being dark matter.

But other, independent scientists also need to check their work.

And it might be that there is a totally different explanation for what the scientists saw.

'Matter' is the name for anything that takes up space and that can weigh something, and a particle is an extremely small piece of that.

For two years, the team has been using one of the world's most sensitive dark matter detectors.

It's basically a big tank filled with a really dense liquid.

We spoke to Professor of Astrophysics Matt Nicholl to try and help explain this a bit more. He said to picture the tank of liquid like a giant snooker table.

And all the time there are particles, like snooker balls, passing from one end to the other, and usually they don't hit each other.

But every so often they do!

And the heavier the snooker ball, the bigger the bump would be if it hit another one.

He explained that it's like the scientists "have found one of their snooker balls got hit by a bigger ball".

And the one they saw has roughly the same mass as gold, but usually things from space are a LOT lighter.

So it seems likely that it's a particle we don't know about which COULD be dark matter.

Simply, dark matter is the invisible glue that holds the universe together.

Scientists have been finding clues about it for MANY years.

Prof Nicholl said one of the main discoveries was in the 1970s when astronomer Vera Rubin discovered that stars toward the edges of galaxies move too fast to be held there by matter we already know about.

So there must be something else, something we can't see. Something that adds gravity and acts like a glue.

That's what scientists call dark matter.

He continued to explain that you can understand dark matter really easily using some everyday things:

"Imagine you have a rope with a weight on the end of it and you're spinning it around.

The faster you spin it around, the stronger the rope needs to be to hold onto the weight and stop it breaking and flying off.

Well, dark matter is basically what makes the rope stronger!"

Scientists think that ordinary matter makes up only about 5% of the universe, while dark matter makes up about 27%. The rest is another mysterious thing, known as dark energy.

So, we don't really know what most of the universe is made of.

There are some parts we know loads about, like stars and planets, but if we add all of that up, it's actually just a little bit of the entire universe.

But this discovery hopefully has brought scientists closer to finding out.

Professor Henning Flaecher, who's one of the scientists on the study, said: "It's an incredibly exciting time, the kind of event every astro-particle physicist dreams of!"