wrote:
Musing....

The earth is many orders of magnitude older than the time humans - or
even mammals - have been here.

And who knows what the future may bring.

As far as I can tell, any thought that we are not the first to inhabit
this planet belong in the realm of science fiction - but we may not
last, and there could therefore be other sentients after us.

If we wished to leave a notice that we'd been here, the best place
might be in orbit; by the time another sentient form reached that
level, they might be able to decipher and understand whatever we
decided to leave.

Low orbits decay - I assume higher ones do as well, just more slowly.
Could we place a satellite such that it would still be up there, say,
a million years from now? How about 100 million years?

Cool idea. One of the Earth/Moon Lagrange points, L4 or L5, ahead of or
behind the Moon along its orbit around Earth might be a good choice. It
would be someplace some future astronomer might look for captured
asteroids in Earth orbit. Such an extraterrestrial time capsule would
be more likely to be found, and stay in orbit. Also, that high up it
would less likely to get nailed by some other satellite crossing its path.



Shawn