From: Doug Jones (random@qnet.com)
Date: Sat Mar 18 2000 - 10:39:34 MST
"Robert J. Bradbury" wrote:
>
> This raises a raises lots of questions in my mind.... [Its early,
> I can be over the edge].
>
> 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.]
The numbers are a long ways out there- you'd need yoctosecond pulses of
yottajoule energy, focused into picometer volumes. Eeek!
> 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?
Synchrotron radiation is pulled from the kinetic energy of an
accelerated charged particle, but the rest mass is unaffected.
> 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?
Temperature is just a measure of the average kinetic energy of a medium,
so as it is ionized, the average molecular weight goes down- for
instance, hydrogen gas has MW of 2 (one mole of H2), atomic hydrogen is
MW 1 (two moles of H), and ionized the MW is .5 (2 moles p+, 2 moles
e-). The electron velocities are about 43x that of the protons, since
the ratio of masses is 1846. If they are in thermal contact with the
protons, they are all at the same temperature despite having different
velocities.
Temperature is unrelated to density, only to kinetic energy per unit
mass. Low density gas clouds can be far from equilibrium if the energy
is pumped up by an external source and the radiative processes are
inefficient- thus the solar wind is very hot, but the planets immersed
in it are much cooler. The thin hot plasma is essentially transparent,
and cools only very slowly because ion-electron interactions are rare,
and must occur to allow the gas to cool by radiation.
I'ver glossed over a lot of details, but I hope this gives you the
idea...
-- Doug Jones Rocket Plumber, XCOR Aerospace http://www.xcor-aerospace.com
This archive was generated by hypermail 2.1.5 : Fri Nov 01 2002 - 15:27:29 MST