are we absolutley sure that there is no phenomenon in space that would permit these signals from being sent back through time to a time before
humanity even existed?
is there no known force in the entire universe that could act as an arc with any message going in, which comes out thousands, or millions of years
ago?
worm holes?
black holes?

Not directed at me, but I feel like answering anyways.
Yes, we're sure that there is no phenomenon in space (that's natural)
that would allow for radiowaves to exceed
C, which theoretically
would allow for time travel.
Worm holes, while theoretically possible, would'nt exist on a large
enough scale for a sufficient signal to pass through it, and than the
probobility of one existing in the radiowaves path is incredibly small,
unless you're producing an incredibly small full sphere signla, which
we generally don't.
And it may be that worm holes may not even alow for time travel.
As for black holes, well, they're just giant gluttonous singularities,
things go in, and get destroyed.
However, it could be that an Einstein-Rosen bridge could form,
however it would'nt exist long enough (naturally) for the signal to
pass through it, even if it was passed the event horizon, and than
the signal may very well come out in another universe.
[edit on 10/22/2006 by iori_komei]