"Clive Abramovich Delmonte" <c.delmonte@tesco.net> wrote in message news:GXuHc.288$9w1.74@newsfe3-gui.ntli.net...

Let me thank everyone who has offered a contribution in response to my
posting.  I have learned a great deal from these messages and am reassured
that our Earthly transmissions cannot reach distant aliens.

Hostile predators would not have reached us here yet, in any case, since we
have only had radio traffic for about 100 years.

The background noise in the Universe will protect us, as I see now.  If it
might need a terawatt power source to reliably reach a neighbouring star,
any alien that picks up our present transmissions would have to be very
close already.  Likewise it seems unlikely that intelligent aliens would be
pointing a power source of that magnitude out into their surrounding space
or towards us, except as part of some sort of search strategy.

Once again, I thank all who sent in messages.

Clive Abramovich Delmonte

Incidentally, the same background noise (and inverse-square law) makes
is very hard for us to detect ETI signals here also. So we are up against a challenge.