10 Simple Questions That Still Totally Baffle Scientists

5. What Is The Universe Made Of?

Right, this is kind of embarrassing, but we don't appear to know what 96% of the universe is made of. Atoms, the things that make up you, the chair you're sitting on and everything else only account for around 4% of, well, everything. One of the first clues we got as to the fact that most of the universe appears to be missing was back in the 60s and 70s, when astronomers observed that the velocities that stars were moving at would cause them to rip the galaxy apart, because our then calculations for the amount of matter in the universe did not generate enough gravitational pull to keep them together, and yet they're pretty stable. This means that there must be something that we can't detect accounting for the amount of mass needed to hold the universe together.

With all this extra gravity flying around, we're presented with another problem. Namely that it should be causing the expansion of the universe to slow down and eventually reverse. The universe, in its characteristically uncooperative fashion, has other ideas and is actually speeding up. This means that there is some kind of force out there that is counteracting the effects of gravity, but we can't detect it.

These two mysterious phenomena are what physicists currently refer to as "dark matter" and "dark energy". Unfortunately, this is just to make their calculations work and doesn't actually solve anything. It's basically scientist-speak for "F**ked if I know".