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.