 For any given body, this critical stage of unavoidable collapse occurs when the object has collapsed to within its so-called Schwarzschild radius, which is proportional to the mass of the body. Our sun has a Schwarzschild radius of approximately three kilometers; the Earth's Schwarzschild radius is a little less than a centimeter; the Schwarzschild radius of your body is about 10-27 cm—ten times smaller than a neutrino and 1010 times smaller than the scale characteristic of quark interactions. This means that if you could collapse all the Earth's matter down to a sphere the size of a pea, it would form a black hole. 