Re: [FT] sensors

On Friday 03 December 2004 21:17, Steve Pugh wrote:
> On 3 Dec 2004 at 19:44, Samuel Penn wrote:
[...stuff on black holes...]
> Look, Hawkings came up with this, I did a degree in physics and I
> just about understand the very simple version....

Didn't he also recently loose a bet that information was destroyed
by black holes? Now it's thought that information that goes into a
black hole is preserved.

I never did a degree in physics.

> > Basically, black holes evaporate given
> > enough time. A *lot* of time is needed, but micro black holes formed
> > at the time of the big bang have had long enough to evaporate by
now.
> > No idea how big a 'micro' black hole is however.
>
> One of the key points is that smaller black holes lose mass via this
> method faster than big black holes. So if you're a small black hole
> you get stuck in a vicious circle and end up going 'poof'.

Having now had a chance to look up micro black holes, their mass
is put at less than 10^14 kg (black holes as big as this last longer
than the current age of the universe, but would be about the size of
an electron). A cubic kilometer of water is 10^12kg (which, I think,
would accelerate you at 0.06g if it was 100m distant and squashed
into a black hole as part of our mythical space drive). For any
decent acceleration, I don't think evaporation is going to be an
issue, however I don't think it's going to be very black.

-- 
Be seeing you,				   http://www.glendale.org.uk/
Sam.					jabber: samuel.penn@jabber.org