Re: A partial black hole?

On Feb 28, 11:19 am, Erik Max Francis <m...@[EMAIL PROTECTED]
> wrote:

> The Schwarzschild radius of a black hole varies with the mass, but the
> tidal forces at the Schwarzschild radius vary with the inverse cube of
> the radius, so the tidal forces vary with the inverse square of the
> mass.

Cool.

Of course, this raises an interesting point: for a very /small/ black
hole, the tidal forces would get superfantastically /large/.  (Albeit
only over a very tiny distance.)  Nuclei being ripped apart into
constituent quarks?  If you allow small black holes, the tidal forces
can get arbitrarily large...


> Freefall time is ~10^-5 s per solar mass of the black hole.

Really!  Huh.  Where does that come from?


> So that's a few days here.

I thought at first that this article

http://www.publish.csiro.au/?paper=AS07012

contradicted you, but it doesn't.  The freefall time from rest at the
event horizon to impact with the singularity is a fixed  maximum.  It
turns out that, if you don't start at rest -- if you cross the event
horizon moving in any direction -- then you can increase your survival
time by firing a reaction drive.  But only up to that fall-from-rest
maximum limit.


> In the comment above I was referring to generally to the idea of such a
> huge black hole (that would form naturally, at least as far as we know
> right now) that you could fall into, and live out an interesting,
> productive life without even realizing you're in a black hole, with your
> ultimate destruction against (or near) the singularity so far in the
> future that you can live in bliss.

So, we'd need to tack another four or five orders of magnitude onto
the size of the black hole.  A hole with a mass of a quadrillion suns,
10^15, would give you about 400 years.

Unfortunately the most massive elliptical galaxies are only around
10^13 solar m*****.  Assuming that's an upper limit for black hole
size (at least in our epoch of the universe), that would only give you
about 4 years.  Time enough to write your memoirs, but who will read
them?


Doug M.