Why does gravity only pull things one way?

I was hanging a shelf last week and started wondering, why hasn't anyone ever found something that gravity pushes away? I know magnets repel, but with gravity it's always just pull, pull, pull. Has anyone else thought about this or is there some basic physics answer I totally missed?

2 comments

2 Comments

michaeld481mo ago

I mean, you were hanging a shelf and went straight to the physics of gravity? That's a pretty big jump. But sure, the simple answer is mass is mass, it always pulls. Magnets have two poles, gravity just has the one "stay close" setting. I guess questioning it is fine, but it's like asking why water only flows downhill. It's less a mystery and more the whole point. Maybe just enjoy that the shelf didn't fall on your head and call it a day.

lewis.terry1mo ago

Correct me if I'm wrong, @michaeld48, but I don't think it's quite as one-sided as that. Water flows downhill because of gravity, sure, but it also finds its own level, which is why it stops in a cup or a lake. Gravity's not just a "stay close" setting, it gets weaker with distance, and it's actually the weakest of the four basic forces. Magnets can push and pull because of positive and negative charges, but gravity only pulls, and we still don't fully know why mass does that. I'm not saying your shelf won't fall, I'm just saying the mystery is a bit bigger than "that's just how it works.