BELIEVE ME NOT! - - A SKEPTIC's GUIDE
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As long as we're being relativistic, why not go all the way?
Suppose a very lightweight particle is in orbit around a very
heavy mass m, attracted only by gravity. A simple application
of Newton's Second Law yields the ORBITAL VELOCITY
|
(24.18) |
Taking this at face value, what happens when
?
For a given m, there is a radius called the
SCHWARZSCHILD RADIUS
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(24.19) |
for which anything close to the mass
cannot maintain its orbit without exceeding the speed of light.
Since this is impossible [I am being really sloppy and glib now,
but the conclusion is qualitatively correct] once anything gets
inside that radius it falls in the rest of the way and never
comes out. Even light. Hence the term, " BLACK HOLE".
Any mass m has its Rs; but usually the density
of a given lump of matter is not high enough to place sufficient
m inside a given r to cause a black hole to form.
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Jess H. Brewer -
Last modified: Wed Nov 18 17:31:11 PST 2015