This tutorial explains the theory of black holes, dating back to the first scientific hypothesis of their possibility from the eighteenth century. The most basic definition of a black hole is an object whose gravitational force is so great that nothing—not even light—can escape its pull. Are such objects possible? Even if possible, do they in fact exist?

To begin answering these questions, we first consider the concept of escape velocity, which specifies how fast an object must move to escape the gravitational force of another object.

Then we learn how the speed of light, and Einstein's theories of Special and General Relativity, determine the parameters of black holes.

Moving from theoretical possibility to scientific evidence of black holes' existence, we review the life cycle of stars: how they form, maintain equilibrium, and eventually die leaving behind immensely compressed compact objects, which may form the core of a black hole.