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m74z00219
2009-Feb-03, 04:39 AM
Ok, let me set the stage. I understand that light (energy), just like mass, can bend spacetime. There's even a theoretical event known as a kugelblitz; this is just concentrating light enough in a particular volume such that it collapses into a blackhole.

What if you had a beam of light (laser) that could be powerful enough (I'm guessing the energy densities are not actually obtainable) to reach the critical energy density across part of its length (so, accounting for dispersion, refraction, etc)? Would this form a black hole that is temporarily cylindrical or ellipsoidal? Would it shift into a spherical conformation or stay the same shape??

Long live BAUTF!

m74

Tensor
2009-Feb-03, 05:04 AM
Ok, let me set the stage. I understand that light (energy), just like mass, can bend spacetime. There's even a theoretical event known as a kugelblitz; this is just concentrating light enough in a particular volume such that it collapses into a blackhole.

What if you had a beam of light (laser) that could be powerful enough (I'm guessing the energy densities are not actually obtainable) to reach the critical energy density across part of its length (so, accounting for dispersion, refraction, etc)? Would this form a black hole that is temporarily cylindrical or ellipsoidal? Would it shift into a spherical conformation or stay the same shape??

Long live BAUTF!

m74

Probably not. Your question is related to the Hoop Conjecture (http://en.wikipedia.org/wiki/Hoop_conjecture). Formulated by Kip Thorne in 1972.

astromark
2009-Feb-03, 07:13 AM
Probably not. Your question is related to the Hoop Conjecture (http://en.wikipedia.org/wiki/Hoop_conjecture). Formulated by Kip Thorne in 1972.

I would except a ellipsoid shape for a high rotation velocity black hole...
Could enough mass to trigger a BH be found in a laser beam.? No. Could it create a cylinder.? No. The gravity of its mass is what a black hole is... So much mass as to prohibit the escape of anything...
A stupendous laser beam shooting into a black hole... would have nil effect.