# What is the Schwarzschild radius actually?

I am currently writing a detailed essay about black holes, the history of their discovery and their characteristics and I can't find the appropriate literature online and in my local libraries (I even looked in the uni libraries specialized for astrophysics, the books are just way too old) which explain in more detail what the Schwarzschild radius is.

I'd like to understand it more rather than copying those short wiki explanations and accepting the calculations just the way they are.

I'd really appreciate the explanation from the core of the definition of the Schwarzschild radius in order to understand the rest of the complex mechanism of black holes.

• How much mathematics do you want in the answer? The Schwarzschild radius $r_S$ is the radius of a black hole's event horizon. (More precisely, $2\pi r_S$ is the event horizon's circumference). There are several questions about this on the Physics stack, eg physics.stackexchange.com/q/191013/123208 – PM 2Ring May 21 at 13:49
• I looked up the link you gave in the comment and it helped me understand it more, but I'd like to know a little more of the theory behind the calculations. – Alice May 21 at 15:19
• Ok. In that case, your question is probably more suited to the Physics stack. But to understand the theory, you really need to start studying General Relativity (and before that, you need to be fairly confident with Special Relativity) and Stack Exchange can't teach you that, although we can assist you, to some extent. You may find this tutorial helpful: math.ucr.edu/home/baez/gr/gr.html – PM 2Ring May 21 at 16:24
• A bit of history never hurts: en.wikipedia.org/wiki/Karl_Schwarzschild Special relativity implies that black holes are possible, but it's unclear (at least to me) who came up with the idea of black holes first, or, now that I think about it, a physicist did come up with the idea well before Einstein, but it remained a speculation. Schwarzchild worked out the math behind relativistic orbits which includes non-rotating black hole radii, and the term was named after him. – userLTK May 21 at 17:34
• What exactly do you need to know? Specifically, what in en.m.wikipedia.org/wiki/Schwarzschild_radius needs clarification? – Rob Jeffries May 21 at 19:43