As you may know, astronomers for several decades have been finding planets outside of our own solar system. The total number found so far is, I believe, over 400.
For reasons having to do with the discovery process, most of those are very large planets. Also, most of them are too close or too far from their suns to be able to have liquid water, which is believed to be vital to the existence of life. Therefore, so far there haven't been any earth-like planets found where life could exist (according to our understanding of how life can form and even exist). But even within our own solar system, some of the moons of Saturn or Jupiter might be able to support life.
In any event, it is probably only a matter of time before planets similar to our own Earth are found. Of course that does not mean that they will be found to have life, let alone intelligent or highly evolved life.
But also, astronomers have been speculating about intelligent life outside of our own earth for a long time; and the famous, late Carl Sagan in fact proposed a formula for calculating the likelihood of extraterrestrial life given the enormous number of galaxies, each with many stars, and many stars no doubt having planets.
So if you want to believe the speculation and calculation, they're out there--though we have not yet contacted them. (Some people of course believe they have visited us.)
Well, if we do ever confirm the existence of creatures like ourselves (or not) elsewhere in the universe, that will pose a problem for religion. Christianity holds that God sent his Son to Earth. Did God send the same son--or anyone else that he progenerated--to other planets? If not, why was Earth singled out? Can we assume that somehow Earth is special in God's sight and was singled out for the blessing of having His Son sent to us?
So the eventual discovery or confirmation of life elsewhere should, in principle, pose a problem for religion--at least for Christianity. But you know what? I think it will survive. Some sci-fi writers have even speculated that Christianity will simply send missionaries and export its religion throughout the universe, just as it did all over the Earth.
It is too strong to say that Christianity banned almost all sciences. The dispute was over the authority of scripture as interpreted by the church and the authority of observation.
There is a continuing controversy going on about the contributions of Christianity to the rise of science. On one side are those who claim that science became the dominant mode of thought for understanding nature only by breaking free from Christianity and on the other side are those who believe that scholastic philosophy in the hands of Aquinas and others set the stage for rational investigation of nature. It's hard to get an objective reading on this question.
The Galileo case is complex and open to different interpretations. One test of the Copernican geocentric system that would have verified it was parallax in the position of stars seen from earth at different points of its orbit. Galileo tried hard to discover this parallax and could not. His telecopes were not good enough and the parallax is quite small.
The result of his failure was that there existed scientific reason for doubting the Copernican system. Bessel found the parallax of 61 Cygnus only in 1838 and measured it at about 1/3 second of arc, not far from modern measurement.
There is no doubt that some Christian institutions safeguarded and maybe even advanced learning. There were the medieval monks who copied some classical manuscripts (while destroying some others that they regarded as pagan or heretical). And Renaissance Italian scholars learned Greek and translated some classical manuscripts. And Islamic scholars--maybe this is not relevant here but I want to give them their due--also did a lot to preserve and pass on classical learning.
On the other hand, there is quite an opposite tradition. Carl Sagan, in his great TV series Cosmos, talked about how a Christian mob in Alexandria killed the female philosopher and mathematician Hypatia (ca. AD 350–370–March 415). And, aside from any suppression of science or knowledge by the Pope and the Church more generally, when Ferdinand and Isabella of Spain completed the Reconquest of Spain from the Moors, one of the first things they did was to burn most Islamic manuscripts (except some medical treatises).
Not to mention so much medieval suppression of learning by the Inquisition when it was accused of being heretical.
Certainly the preservation of Greek science by Islamic scholars is an important historical fact that had great influence on later developments in science. Our word algorithm comes from the Persian mathematician Al-Kwarizmi, c. 825 AD, who gave the first complete solution of quadratic equations.
We have now sent a vehicle into interstellar space - Voyager. For you Star Trek fans - VGER. And, notwithstanding this "stellar" achievement, the majority of the members of that species responsible for this accomplishment believe in some sort of religion/superstition. Who's to say that when (and I am convinced it is a matter of when, and not if) we make contact with another species as described in Drake's Equation, they too will not have their own batshit version of religion/superstition? Why should we think we're the only species to be subjected to this?
The hope is that any sufficiently advanced civilization that is capable of such travel would be older, so people also assume that it would be more... Well "mature" for lack of a better word...
There certainly no reason to assume that it will be any older, more peaceful, or more reasonable; but people like to dream...
Well, if they meet us more than halfway, it doesn't seem too unreasonable to assume that they will be more developed than us. But here's the really frightening idea... You know how sci fi always has an "elder race"? Be it Vulcan or Protoss or whatever... What if we humans are the actual elder race of the galaxy? Scary, isn't it?
It is not reasonable to assume that they will be superior in any way but technologically. Having bigger, better toys, does not necessarily mean anything more than just that. However, if we learn we are the "elder race", we might as well just stick to this rock because the universe is doomed.
Travis, I agree that if we are the elder race the universe IS doomed!
Well, that seems to be where all the evidence points. It may have taken 200,000 years to get where we are, but I am comfortable believing we are more than halfway to the stars. If third generation stars like our sun have been around for billions of years, the less than half million years it will take to go from dawn of our species to interstellar voyagers is nothing. A margin of some 0.01%. The odds that there is a race older than us, but just a tiny bit so that we haven't heard from them yet, seems miniscule.
Lets see, the universe is 13.77 ± 0.059 billion years old according to our best estimates, and our solar system has been around about 4.5 billion. Humans have been around for what, about a couple of hundred thousand years or so? I really do not see there being any evidence that we are the apex species of the universe...
As far as us not hearing from them yet, you make the assumption that they would try to contact us, which isn't necessarily true. What reason should they believe we would be welcoming or have anything of any value to offer?
We live on a semi-dark ages planet where religion still holds enough sway to stigmatize theories that have better and more persuasive evidence than gravity. There are wars, murders, and just plain sadistic bullshit crawling out of the orifices of just about every single mainstream religion on this rock. We have polluted, destroyed, or exploited the majority of natural resources we have(lets not even go into global warming). And if that isn't bad enough, we have politicians.
What race in their right mind would WANT to have anything to do with us, we are the insane asylum of the universe! Hell, I would live on the moon if I could, but I am sure the crazies would make it there eventually, and it would start all over...
They might want to study us as examples of primitive life forms.