Most of the universe is missing - here are 5 ambitious experiments that might find the rest

Everything that we see around us - planets, stars, nebulas, and so on - only makes up about 15% of the matter in the universe.

The other 85% of matter is missing. Scientists call this invisible stuff "dark matter" because we can't see it and, so far, no one has directly detected it.

We know dark matter exists only because all the matter that we actually can see can't explain the motion of stars and galaxies in the universe. Not even close.

It's become one of the biggest mysteries in physics. There are a lot of differing theories about what dark matter is made of, and how we might actually find it.

From deep underground caverns to laboratories in space, here are five of the coolest dark matter experiments that are attempting to solve this cosmic mystery.