"Chris L Peterson" wrote in message
...
On Sun, 22 Feb 2004 22:58:21 GMT, wrote:

I have a question.

We would probably get some warning about a comet or an asteroid - but
what
about a pea size black hole? If one hit the moon would it be like a
match
to paper and suck the entire moon into itself even if it took some time?
Could an invisible small black hole just show up over the Sierra Nevada
and
no one would have foreseen it and it would destroy the earth? Would it
destroy the earth instantly or would there be some fantastically horrible
slow whirlpool of matter into a small black hole so that we would all
have
time to feel intense fear?

First, I don't believe it is possible to have such a small black hole.
Anything
this small (1e33g) would have formed only during processes very early in
the
Universe, and would have evaporated by now. If there remain any natural
processes capable of producing such low mass objects, they are presumably
very
rare, as would be our chance of encountering one such a black hole.

That said, the effect of such an object striking the Earth (or the Moon)
is
difficult to judge. If this black hole were in an Earth crossing orbit
around
the Sun, it would strike at typical meteor speeds. While the mass is
around 50
times that of the Moon, the momentum is very high, and I think it probable
that
only a relatively small amount of energy would actually be dissipated. The
object might simply crash through the Earth and out the other side, doing
relatively little damage. It certainly wouldn't swallow the Earth up. If
the
black hole was passing through from somewhere else, it might have just
about any
velocity. The most interesting case would be if its approach was at a low
speed.
Then, it would strike the Earth at about our escape velocity (11.2 km/s).
It
would probably end up in an orbit around the Earth's center of mass, but
that
orbit would actually be inside the Earth. Although it would take a very
long
time to swallow up all the Earth's mass, the gravitational effects would
be
devastating.





This is very interesting. It is interesting to think of the world's cities,
not to mention its lifeforms, if the gravity suddenly went up some huge
fraction of what it is now. I can see it pulling all the skyscrapers
colllapsing straight down into the ground like spears. Or maybe the
structures are overbuilt but the gravitational pull sucks the file cabinets
though the floor panels along with the water coolers down into the basement?
And while you might be ok supported by your car seats, and the car
suspension might be able to handle slow driving - what happens when you step
out of the car and you now weigh triple what you joints and bones are use
to?

What a way to go. I wonder if the dinosaurs wouldn't have had an easier
time with the asteroid?

I wonder what would happen to planes in the air? Would the gravity make the
atmosphere now three times as dense so that the planes, while weighing three
times as much, would have that much more lift on their wings? I guess the
wings might just rip off?

Thx for the info.