Robert J. Bradbury, <firstname.lastname@example.org>, writes:
> a) What is the photonic density required to create a black hole
> and do any of the principles of photon interaction prevent
> this from focusing laser beams to produce a black hole?
> [I may have asked this before, but I'm too lazy to go check
> the archives.]
In our previous discussion, I think I found some references from
sci.physics which indicated that no intensity of photons would create
a black hole, if they are all going in the same direction. The answer
was complicated for other cases.
> b) If you have particles (electrons, protons, etc.) circulating
> in a syncrotron, emitting syncrotron radiation, shouldn't
> they eventually "evaporate" into nothing? Or is it always
> true that the photons they are emitting get replenished by
> the external power source?
An electron won't evaporate. The radiation it emits must be coming from
the EM fields accelerating in the synchrotron.
> c) Why do astronomers, esp. X-ray astronomers, often quote the
> temperatures of gas clouds in "millions" of degrees? If the
> atom/molecule densities are on the order of a few per cc
> I don't see how you can get temperatures like this. Temperature
> corresponds to vibration or molecule velocity, but what is
> the relationship between ionization state and temperature?
> Is the effect of increasing temperature -- atom ionization
> then acceleration of the ions? If so, then what would be
> the "temperature" of an electron gas?
I'm not sure about what this actually means, but presumably there are
two choices. (1) the gas cloud is emitting black body radiation and
really has a temperature of millions of degrees. (2) the gas cloud is
emitting non-thermal radiation of some sort, whose peak is in the range
that would correspond to a black body temperature of millions of degrees.
There is nothing in principle preventing (1) from being true, but it
is hard to see what energy source could get it so hot, since the Sun is
only a few thousand degrees. Perhaps some kind of magnetic interaction
could super-heat the cloud.
I would assume the temperature of an electron gas, or a plasma, could be
defined based on the kinetic energies of the particles just like for a
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