Why do people think there is a giant “hidden” planet somewhere in the depths of our solar system?

Question

Why do people think there is a giant “hidden” planet somewhere in the depths of our solar system?

In: 5

Answer 1

Space is *ridiculously empty*. Even within our own solar system, there’s so much empty space that an entire planet could be out there past Neptune and we’d still never see it unless we specifically knew where to look for it.

There are [a bunch of weird things in the solar system](https://en.wikipedia.org/wiki/Planet_Nine#Evidence) that could be explained by another planet existing out there, but it’s still not certain whether or not that’s actually the cause.