What would happen if SETI actually detected artificial signals from an extraterrestrial civilization? How would SETI verify them? Would we be able to know what’s in the transmission? What would be the effect on society? Religion?
Effect on religion: None. If religion could survive the rise of modern science, it’s not going to collapse because we find another civilization. I imagine a few new cults might spring up, though.
Effect on society: That depends on the nature of the contact. If it’s just a few beeps from 500 light-years away, not much. On the other hand, if we started collecting detailed information on the other civilization, it could be quite a bit, but what that is would be totally dependent on the kind of information we learned.
If the other civilization was close (say, within 20-30 light years), then I think you’d see a dramatically increased level of funding for large space telescopes, especially interferometry arrays, and maybe even interstellar probes.
Carl Sagan authored a novel on this, I think it was made into a film, but I didn’t see it, although I read the book. I believe the title was “Contact”, a good read.
The OP asked about “effect”, which is more subtle than a simple binary survive/die. Religion has hardly been unaffected by the rise of modern science.
And hey, if the aliens contact us with their cultural information and they mention a “Jezuz Chrizzt” as an important prophet, I think religion might be quite affected 
On the other hand, if the aliens in question clearly had massively superior science and technology, and if their philosophy/ies were based on hard core materialism completely eschewing any kind of supernaturalism, I would guess that this would have a devastating effect on religion.
It might not work the other way around; I know for that some fundamentalists already have a generic prediction in place to the effect that aliens might contact us someday, but they will in fact be satanic minions in discuige.
Re effects on religion: Christianity is built around a story-arc – fall of Adam and Eve, original sin, redemption by Christ – which is clearly specific to humanity on Earth. If another sapient species were discovered, Christians might be divided on whether they have immortal souls, whether they are born with original sin or not, whether they can be saved by Christ or need a savior of their own species. Could lead to some interesting schisms.
!!! Cite?
Speculations as to why? Perhaps their world-view just doesn’t have room for extraterrestrial sapients? Since the Bible does not mention such. (See above.)
http://www.hiddencodes.com/
http://www.mt.net/~watcher/angelicconspiracy.html
http://www.satansrapture.com/the4400.htm
Plenty - nay, myriads - more where they came from. Google “lucifer alien”. 
I wish I could link to the specific example I had in mind, but it existed on a messagboard (creationtalk.com) that has recently become defunct.
As to why… couple of potential reasons:
firstly, many of these people believe that Earth is the focus of God’s attention and man is the pinnacle of his creation; that doesn’t leave much room for other intelligent mortal beings.
But also, it’s an easy, safe and open-ended bet; if we never contact aliens, they lose nothing (or can still say “wait and see…”); if we do contact aliens and the message is something that undermines their worldview, they have an automatic ‘to you so’ reason to shun them.
Speculations as to why? Hmm. I think it’s because all these people are expecting the events described in the Book of Revelation to take place literally as written, and there are plenty of references in it (and elsewhere in the Bible) to angels, stars, beasts, and divers other tribulations “falling from heaven” or “coming down from heaven”.
Something that came down from heaven (the sky) these days would be regarded by most of society as an extra-terrestrial life form, but, as the Bible describes such entities as “fallen angels”, then that’s what they must be. Given that the Bible is literally true throughout, of course.
:rolleyes: And they revile skeptics as “humanists”!
Assuming the extraterrestrial civilization is discovered only through radio signals, and there is no indication they have an FTL drive – I guess, while the event would have a profound effect on the world-view of anybody willing to seriously confront the facts, the practical effects would be very limited. If we wanted to establish two-way communication with the aliens – that would take decades, for the signals to travel back and forth at lightspeed. In the meantime, a whole new branch of science would develop around interpreting those few signals SETI intercepted and trying to extrapolate, from them, the nature of these ETs and their society. But for most of us, life would go on as before.
I agree and I don’t want to divert this thread any further off-topic, but (speaking from personal experience), it is also the case that sometimes, hardcore religious types, having made bold claims and then seen them undermined, fall into a sort of pattern of denial where they’re not longer really sure what it is they believe, but must somehow defend the claims they made; at the expense of reason and fact.
For Christianity, anyway, the state of salvation would be the issue. We supposedly have original sin because of Adam and Eve, and thus have to be saved. But would aliens have had an Adam and Eve? Perhaps they are in a state of grace already? Blish’s A Case of Conscience is the benchmark sf book on this very issue.
I’d be more worried about science than religion. If the aliens were on the same level as us, there would not be much impact, except mutually useful collaboration. But considering the life span of races, that would seem to be as wildly improbable as the sitting next to some one on a plane born the same day, year, and minute as you. If they were more advance, more likely, much of physics would turn into learning and understanding where they are. We’d be students, and much of the creativity would disappear. I’d guess that there would be a boom in biology, where knowledge of their genetic makeup would give a lot of clues about how inevitable evolution and life is, while not teaching us much about our world.
What about politics? Would the world unify to talk to the aliens as one, or would things get worse as each system tried to be the leader?
I’m curious as to what questions dopers think we could ask of an extraterrestrial intelligence; I have started this thread in IMHO.
Very Good Book and Good Movie starring Jodie Foster. It was being made as he passed away. He & his widow liked the film. I would recommend it for anyone NetFlix Queue.
Distance will be the key factor as others have said. The odds would seem to favor there being no nearby radio civilizations and so unless someone is broadcasting their Abridged Library of Science and Philosophy it probably won’t matter much.
That said I sincerely hope we do make “Contact” with a race we can communicate with. I need to ponder **Mangetout’s ** question for a while.
Jim
And of course C. S. Lewis’s Out of the Silent Planet and Perelandra. In the first book, the protagonist finds to his surprise that Mars is inhabited by creatures in a state of grace, happily under the direct rule of what might as well be considered an archangel and his attendant angels. In the second, he visits Venus in time to meet the Venusian Eve before her version of the apple incident.