Why do objects with mass attract each other?

[Yan_Dalton]

In most cases, we know why things happen. Protons can stick with each other because of the strong nuclear force. There's all kinds of forces and we know mostly about why they occur and how they are transmitted.

But I don't understand gravity. Why do objects with mass attract each other ? I know how to calculate it, but I can't seem to understand how it works.

 

[phyzguy]

If you're satisfied with the explanation, "Protons can stick with each other because of the strong nuclear force,", why are you not satisfied with the explanation, "Two massive objects attract one another because of the gravitational force." What's the difference between these two explanations?