If you compress any amount of mass, it becomes denser. If you compress it enough, it will become so dense that light can no longer escape it—this size is the object’s Schwarzschild radius. An object that is compressed smaller than this radius is a black hole. This tungsten sphere has exactly the same radius as the Schwarzschild radius of Earth. If you compressed all of the mass of Earth into the volume of this tiny sphere, it would be so incredibly dense that you would not even be able to see it. Photos here are prototypes and the final version will have a polished surface.
Radius: 8.87 mm
Stand included for display.
Every object has a Schwarzschild radius: Earth’s is about 9mm, Jupiter’s is 2.62m, and a hamburger’s is smaller than an atom. Karl Schwarzschild calculated this property in 1916 using Einstein’s recent field equations.