Yeah, if we ever actually received an alien signal, it wouldn't change much, other than some people going wild about knowing that extraterrestrial life exists.
We'd never be able to make meaningful contact. At best, we could send a high-powered signal aimed at where the aliens are, but by the time they received it, we'd likely already be extinct. Heck, they're probably extinct by the time we even receive their signal.
> Heck, they're probably extinct by the time we even receive their signal.
Many earthbound lifeforms have lifetimes in the tens of decades, and might be expected to survive as a species for thousands of years. And there are many "interesting" star-systems within 100 LY, so in those cases perhaps extinction isn't an issue. But I think humans would have difficulty when an exchange like "Earth to Aliens: come in please", "Aliens to Earth: receiving, go ahead" takes 2 lifetimes.
> And there are many "interesting" star-systems within 100 LY, so in those cases perhaps extinction isn't an issue.
No, in that case, timing is.
FWIW, I'm operating under a dystopian and pessimistic assumption that any civilization will destroy itself within a few thousand years of discovering radio. At some point, there will be massive wars over dwindling resources and eventually a weapon (or the combined power of multiple weapons) causes so much damage that it ends up wiping out all life on the planet.
This means that a civilization will only broadcast a signal for other planets to pick up for a few thousand years. In a galactic scale, that's incredibly short. It's basically the blink of an eye.
I share your view that broadcasting radio waves is a time-limited phase in human development; the airwaves are limited. But I don't agree with you that it could last "a few thousand years"; radio broadcasting depends critically on an electronics industry that only works at scale. Those industries depend on a stable, modern civilization, and I see no reason to think that modern civilization should last longer than earlier civilizations.
I completely agree that the duration during which a civililization can be expected to broadcast radio is extremely short, in galactic terms. So I think the likelihood is that if you do detect a radio transmission from outside the Solar System, by the time you receive it, the sender is dead; all his descendants have died; his planet's climate has changed, so that his species has been compelled to evolve (or die out); and his electronics-supporting civilization is long gone.
