And while we know a LOT thanks to science, there’s still so much that we don’t know.
These mysteries have stumped scientists throughout the ages—and will leave you scratching your head.
1. How did the universe form?

A few things we know about the universe: it’s infinite, it’s littered with black holes, and thinking about it can make your brain hurt.
And one of those things we don’t know: how it began. Even otherwise all-knowing Stephen William Hawking, PhD, theoretical physicist, cosmologist, and director of research at the Centre for Theoretical Cosmology in Cambridge, England, isn’t sure.
Some brilliant minds wonder if it even had a beginning at all, or if it was always there.
2. What happens inside a black hole

Black holes are places in space where gravity is so strong that even light can’t escape, so no one has ever been able to say what happens inside a black hole.
That said, Dr. Hawking has theorized that rather than being stored within the deep clutches of a black hole, information from “within” a black hole actually remains outside of it (in the “event horizon”) and is therefore theoretically accessible. (Still with us?)
Of course, since the event horizon is outside the black hole, the theory itself is a paradox.
3. The fate of the universe

Just as scientists haven’t figured out how the universe started, they haven’t figured out how it will end.
They do know that life on earth can’t continue forever, because life on earth is supported by the sun, which, like all stars, will eventually die.
And they do know the universe will end, but how that will happen depends on many unknowns (including the shape of the universe, its density, and the amount of dark matter within it).