ELI5: Is dark matter everywhere, or just in certain places?

Dark matter is mostly in certain places, like a big, invisible cloud around groups of stars called galaxies.

Imagine our universe is like a playground. We can see all the kids playing, those are like the stars and planets we see with our telescopes. Now, imagine there are also invisible grown-ups watching over the playground. You can't see them, but they're there, making sure the kids don't run off the playground and get lost. These invisible grown-ups are like dark matter.

So, is dark matter everywhere?

• Not really. You wouldn't find a lot of these invisible grown-ups scattered all over the park.
• Instead, they mostly hang out around the big groups of kids, making sure they all stay together.

Think of it this way:

• A galaxy is like a city full of people (stars).
• Dark matter is like a giant, invisible force field around the city.
• This force field keeps the city from flying apart because the people (stars) are moving around.