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.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com