Hmm, I’m trying remember my school physics classes here. If I recall correctly, things have have mass (which means basically everything except the vacuum of outer space) attract other things. It’s one of the natural properties of the universe. Things that have *more* mass exert this force more strongly. The earth is so big, it attracts everything nearby so strongly we basically stick to the earth! It’s the same reason back holes suck things in – they’re *REALLY* dense and utterly full of mass – much more so than the earth – and so everything near black holes are attracted to them, and then they get sucked in and make the black hole even denser.