The Effect of Mass on Gravity

To make a black hole, you have to take some mass and squeeze it into a tiny enough area. The more mass there is in a particular spot, the more space around that spot will curve and warp. That's why gravity is so much stronger around a big object like the Earth than around a small object like you or me. It turns out that if you put enough matter or energy in one place and make it compact enough, you will warp the surrounding space dramatically.