Sometimes it feels like scientists are getting pretty close to solving every mystery there is. We have theories on wormholes, dark matter, the beginning of the universe, and a whole map of how single-celled organisms evolved into human beings. We’ve solved some mysteries so complex that it boggles the mind to even think about them. Sometimes, it seems like there’s an answer to almost any question you can imagine.
But as it turns out, we don’t quite have everything figured out. There are extremely simple questions that nobody’s been able to figure out how to answer—some that sound so simple and obvious that you’d almost feel stupid asking them in the first place.