As part of my research into the theories of relativity and of black
holes (a project that J. Denker inadvertently helped me start; see the
thread "Singularity Temperature/Infalling material" that was active
around the first week of March), I encountered the following Microsoft
Encarta Online article:
The article is written at a pretty basic level, so I didn't learn much
that I did not already know. I did manage to catch a number of subtle
errors in the article, mostly having to do with confusion of the
velocity parameter (beta = u/c) with the Lorentz factor
(gamma = (1 - beta^2)^(-0.5)), and some carelessness in the
specification of the value of c. As a public service, I have already
alerted Microsoft (not with high expectations of seeing the errors
corrected; I don't think this is something that will increase the
company's bottom line). You might challenge your students (or
yourselves) to catch the bugs before they get squashed.
As J. D. suggested, I got myself a copy of Misner/Thorne/Wheeler's
Gravitation (relatively cheaply at Books-A-Million). Even in softback
(I couldn't find a new hardcover), it's something you'd not want to
drop on your foot. The chapters in the early thirties do a nice job of
explaining some of the event horizon-related phenomena that would keep
you from re-crossing it if you ever found yourself inside. There is
also an interesting theoretical calculation that estimates the maximum
proper time it should take for matter to be absorbed (scrunched?) into
the singularity after crossing the event horizon of a non-rotating,
uncharged black hole; it works out to <~15 microseconds times the mass
of the black hole (expressed in solar masses). For garden-variety
holes, even if the tidal forces didn't get you while you were still
outside, you wouldn't have much time to make observations (or
contemplate your fate) once inside.