ELI5: Explain Like I'm 5

Dark fluid

Dark fluid is something scientists believe exists in the universe. It's like a magical substance that we can't see or touch, but it's there and has some strange properties.

Think about a swimming pool. When you pour water into it, you can see the water fill up the pool. You can even splash around in it or feel it with your hands. But if you pour in some air, you can't see or feel it, can you? That's because air is invisible and intangible just like dark fluid.

Scientists believe that dark fluid makes up a big part of the entire universe, even more than regular matter (like stars, planets, and you and me). They can't see it, touch it, or detect it using normal instruments because dark fluid doesn't interact with light, which is how we usually observe things in space.

And here's the even more interesting part: scientists think that dark fluid might have the opposite effect of gravity - instead of pulling things together, it might be pushing things apart. This would mean that the universe would actually be expanding faster than we currently believe, and in a way that our current understanding of physics may not fully explain.

So, while we can't see or touch this magical substance called dark fluid, we believe it's out there and might be shaping the entire universe in ways we don't fully understand. Pretty cool, huh?