There was an interesting show on
TLC about spacebourne
debris. Typical space junk travels at thousands of
miles per hour, and to be called "
dangerous" only has to be a few
millimeters in size. A
satellite (or other
spacecraft) can be
destroyed or
damaged by a piece of space junk. Either way, more space junk will probably be broken off the damaged craft and become trash, due to the
collision.
This brings up the possiblity of a
chain reaction, where space junk from damaged spacecraft flys about only to damage other spacecraft, generating more junk, etc.
It becomes more interesting when you think of how many satellites are already orbiting up there, and the fact that a project called
Teledesic wants to add around 300 more. If a satellite "chain destruction" were to occur, the Earth would be surrounded by millions of little orbiting spacecraft bits whizzing about at hundreds of miles per second.
It could form a sturdy
barrier making space travel from earth impossible, and sending out a strong "GO AWAY" message to any
visitors of Earth.
Astronomers are not thrilled about this.
To top it all off,
Teledesic is a pet project of
Bill Gates.
See also
a preposterous flotilla of deadly orbiting space-junk