10 Simple Questions That Still Totally Baffle Scientists

7. Why Is There Gravity?

Seeing as Newton got the whole gravity apple rolling in the 17th century, we've had a while to try to figure it out. Like electromagnetism, gravity is one of the four fundamental forces in the universe, but it is by far the most mysterious. For a start, we don't even have a particle for it, whereas we have one for the others. The "gravity particle" or graviton has remained stubbornly hypothetical as it continues to elude physicists.

The other thing about gravity that keeps physicists up at night is its frankly weird behaviour. It's actually a mind-blowingly weak force, demonstrated by the fact that your puny muscles can resist the gravitational pull of the entire Earth, but its effects extend interminably into space, holding moons in orbit around planets, planets in orbit around suns and so on. We know that objects with mass bend spacetime and that essentially generates the effect of gravity.

Unfortunately, we don't really know why massive objects should do that in the first place. This is similar to our problem with magnets as it attempts to answer a fundamental principle with and even more fundamental one.