Originally posted by vivify Below is a video about Kugelblitzes, black holes made up entirely of light. Now this is only theoretical, but it's interesting.
[youtube]gNL1RN4eRR8[/youtube]
I do have one question: is there any limit to the amount of matter a black hole can contain?
There's no upper bound to the mass of a black hole. Basically take a stellar mass black hole and keep throwing planets and stars and things into it until you've thrown in all the matter and other black holes in the accessible universe; then the only thing stopping it growing more is the unavailability of more matter.
Originally posted by DeepThought There's no upper bound to the mass of a black hole. Basically take a stellar mass black hole and keep throwing planets and stars and things into it until you've thrown in all the matter and other black holes in the accessible universe; then the only thing stopping it growing more is the unavailability of more matter.
But according to that video, you would have to confine the light to a volume 1000 times smaller than a proton. That would seem to limit the lower frequency of light that would be able to be packed in such a volume. Can electromagnetic radiation even exist at that wavelength? So doing the arithmetic, the formula would be M=E/c^2 .
Originally posted by sonhouse But according to that video, you would have to confine the light to a volume 1000 times smaller than a proton. That would seem to limit the lower frequency of light that would be able to be packed in such a volume. Can electromagnetic radiation even exist at that wavelength? So doing the arithmetic, the formula would be M=E/c^2 .
The catch is that one would need more than one photon. The Compton wavelength of a particle is given by h/mc where h is Planck's constant (unreduced), c the speed of light and m the rest mass of the particle. This is roughly the dimension of the volume of space one would expect a particle to occupy. The Schwartzschild radius of a black hole is 2GM/c^2. If the Compton Wavelength of the particle is smaller than its Schwartzschild radius then it is a "single particle black hole" candidate, at least at this handwaving level of description. We get a "single particle black hole" if M^2 > h/2Gc. This is the Planck Mass. It is huge and photons are massless. So one would need several photons whose wavelength is smaller than the region to be in the region at the same time, the "photon ball" has a mass assignable to it. To put it bluntly, you'd need to focus something like a second's power output of a star into a space the size of a proton to hope to create something like this.
Originally posted by DeepThought There's no upper bound to the mass of a black hole. Basically take a stellar mass black hole and keep throwing planets and stars and things into it until you've thrown in all the matter and other black holes in the accessible universe; then the only thing stopping it growing more is the unavailability of more matter.
Originally posted by apathist The black hole expands as it feeds, yes?
Till it runs of of food, gasses, asteroids, comets, planets, stars eventually get all drawn in leaving a dead space and only occasional wanders will get captured after that.
Originally posted by sonhouse Till it runs of of food, gasses, asteroids, comets, planets, stars eventually get all drawn in leaving a dead space and only occasional wanders will get captured after that.
So when it eats the entire universe, I suppose we've found the upper bound to the mass of a black hole. Ha-ha! What just happened? We used to have a universe, but now its a black hole?
Originally posted by apathist So when it eats the entire universe, I suppose we've found the upper bound to the mass of a black hole. Ha-ha! What just happened? We used to have a universe, but now its a black hole?
Our universe may BE the other side of another universe's black hole.
08 Jul '16 18:09
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