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"The average density of a supermassive black hole (defined as the mass of the black hole divided by the volume within its Schwarzschild radius) can be much less than the density of water for very large mass black holes (the densities are similar for 108 solar mass black holes). This is because the Schwarzschild radius is directly proportional to mass, while density is inversely proportional to the volume. Since the volume of a spherical object (such as the event horizon of a non-rotating black hole) is directly proportional to the cube of the radius, average density decreases for larger black holes, being inversely proportional to the square of the mass."

I get how the density determined by the Schwarzschild radius should be inversely proportional to the mass, but it still seems so counter-intuitive to me, with so much weight bearing down upon the center of the black hole. Could someone give me an explanation as to which forces counteract the huge gravitational forces driving the volume of the black hole towards a point, and allowing it to have a density less than that of water?

Thankyou.