I was watching a Vsauce video and learned that any two objects, like two baseballs, are attracted to each other because of their mass, and the bigger the mass, the more gravity an object has. What does mass have to do with gravity, and what causes gravity? Why does something just attract other things around it?
In: Physics
Serious answer: Because.
Science ulitimately describes and models. It’s a mistake to assume that the descriptions and models, however good, are what’s actually happening, or “explain” it – even though that’s the language we tend to use.
Newton said roughly what you did – that bodies attract each other according to how massive they are (and also how far apart they are). That was a good fit to reality, but not a perfect one (notably, using Newton’s rules alone didn’t quite work to explain Mercury’s orbit).
Einstein described things in terms of curved space and time. That gave a better fit, and if you want to explain things in those terms, that’s fine (other people in this thread will and have described things in those terms). But just because the description is better, that doesn’t mean it’s necessarily what’s actually happening – it’s just a good match. It’s also incompatible with another excellent description of the way things “are”, namely quantum theory. One or both will have to give at some point.
It’s perfectly possible that, tomorrow, someone will make an observation that indisputably flies in the face of Einstein’s explanation – or maybe find a different way of describing things that works even better, and isn’t at odds with quantum theory. And then, quite possibly, we’ll be describing and “explaining” it in some other way completely. Either way it will still ultimately be a shorthand for “The universe behaves, roughly, as if this were the case” rather than “This is what is actually happening”.
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