Many Physics discussions I have often conclude with:

Well you will then form a black hole...

My questions are:

  • Is there a general recipe for making a black hole?

  • If not, then can you list the families of black hole causes?

This means I can put a more rapid halt to many future Physics discussions.

  • 1
    $\begingroup$ A general recipe for creating a black hole requires a general solution of the Einstein Field equations - but this has not yet been created. $\endgroup$ – user28355 Jan 12 '14 at 23:30

Whenever an amount of mass (or mass equivalent in energy) finds itself inside a volume smaller than the event-horizon for a Schwarzschild black hole of that mass ($R = \frac{Gm}{c^2}$), then you have the necessary and sufficient condition for a black hole. In fact, the black hole may form before the matter reaches this point, provided that it will reach it some time in the future.

What kind of discussions are you having?

  • $\begingroup$ Cheers for this @lionelbrits, $\endgroup$ – hello_there_andy Nov 30 '13 at 17:48
  • $\begingroup$ It seems rather straightforward then, not sure why it hasn't been brought up. Here are some discussions leading to that: "how many photons can you fit into a unit of space", "what happens if superman punched you?", "what happens if you create a very loud noise? (more specifically the "fus do rah" in skyrim), and a lot of things involving high energy, time travel, curving space time. $\endgroup$ – hello_there_andy Nov 30 '13 at 17:56
  • $\begingroup$ This is the hoop conjecture. Which, as far as I know, is still an open problem. $\endgroup$ – MBN Dec 2 '13 at 11:26
  • $\begingroup$ I think what I meant would be a stronger requirement (a sphere) $\endgroup$ – lionelbrits Dec 2 '13 at 11:45

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