Well, really advanced sapient life forms would be too busy and important to waste their time on trash like us. What forms of communication they might be using is anybody's guess. Backward life forms, even if sapient, might be undetectable due to their being primitive [how to detect from astronomical distances a post rider from, say, 15th century? And the 15th century is rather recent one].
> What forms of communication they might be using is
> anybody's guess.
Marconi wouldn't have been able to detect ETs on the moon,
if they were using GSM, TDMA or GPRS. Nonetheless, our
culture, 100 years later, is still using some AM that even
Marconi could detect. But will we in 200 years? 500? 1000?
Our signal encodings on earth are increasingly looking
more and more like low power noise, and are often
deliberately encyrpted to prevent casual receivers
from extracting information. What will our wireless look
like a few centuries hence? Will it even be EM?
If ETs Out There are still using some legacy comms,we
just might detect one. As long as the funding for looking
is voluntary, or a trivial fraction of NASA's budget,
I have no problem with it. We'd really feel silly if we
didn't look, and later discovered that latent value was
there all along had we bothered.
But the odds, distances, noise, and time suggest no joy.
And the results to date are consistent with the estimated
odds.