Re: A partial black hole?

sigidunum@[EMAIL PROTECTED]
 wrote:

> 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...

Possibly something along those lines, though that would only really work 
if a single quark were absorbed by the hole, since pulling hadrons apart 
won't result in free quarks, but rather more hadrons.

>> Freefall time is ~10^-5 s per solar mass of the black hole.
> 
> Really!  Huh.  Where does that come from?

_Gravitation_ by Misner, Thorne, and Wheeler, e.g., p. 863.

>> 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.

That's correct.  Remember the twin paradox; a geodesic is the path the 
maximizes proper time.

-- 
Erik Max Francis && max@[EMAIL PROTECTED]
 && http://www.alcyone.com/max/
  San Jose, CA, USA && 37 18 N 121 57 W && AIM, Y!M erikmaxfrancis
   Walking in space, man has never looked more puny or insignificant.
    -- Alexander Chase