- How likely are we to find extraterrestrial life?
I personally think there are good reasons to believe that we will find extraterrestrial life eventually. Although it may not be advanced enough to be technology. But keep in mind that humans existed for quite a very long time on earth before we became technological. In fact, we've only been seriously technology for a few hundred years. Prior to that time our "technologies
" would not be noticeable from beyond our planet. The aliens would need actually come here and look up-close and in-person to notice that we were here. So potentially other intelligent civilizations could exist very nearby us and we simply can't see them because we are looking for signs of technology like radio communications, etc.
- What empirical evidence is there that any extraterrestrial life exists?
For me the empirical evidence that extraterrestrial life most likely exists resides in the fact that living biological life on earth is made of common elements. There's nothing special about the earth that wouldn't be true for billions of other planets. Humans aren't made of anything special.
So the fact that the universe contains the same physics and elements as far as we can see is evidence that we should expect to see living creatures similar to what we see on earth throughout the universe.
- What are the implications if extraterrestrial life exists or do not exist?
Well, to begin with, we can't really even talk about whether life exists in other galaxies. They are simply too far removed in both distance and time. So it would be next to impossible to rule them out as potentially having technological life. For example Andromeda, one of the closest galaxies to us, is 2.5 million light-years away. This means that it could be teaming with technological life today, but the signals from those civilizations wouldn't reach us for yet another 2.5 million years. So we can't tell by looking at other galaxies whether there is life there or not. At best all we can say is that there doesn't appear to have been a lot of activity 2.5 million years ago.
In short, we could never determine that extraterrestrial life does not exist elsewhere in the universe. All we can ever say is that we can't see any evidence for technological civilizations that it had existed in the distant past. It's also extremely difficult to measure technological signals from far away galaxies. And signals created by extra terrestrials are going to be extremely weak compared to the natural noise created by natural objects.
So we will never be able to determine that we are alone in the universe. It will forever be a one-way question. The only way we can ever get an answer is if the answer is yes and we actually find signs of other life.
What would it mean either way?
For me it wouldn't mean anything other than telling us something about the statics of how probably it is for life to spontaneously arise.
It certainly wouldn't cause me to jump to any conclusions about an intentional creator. After all, if there exists an intentional creator why not create life throughout the entire universe? The idea that a purposeful creator would have only created life on earth doesn't make any sense to me. Why bother creating such a huge universe if that was the original intent. As Carl Sagan once said, (I'm paraphrasing here) "The cosmic stage is far too large for a drama focused solely on life on Earth"
If scientists can be convinced something exists when there is no empirical evidence for it, why would it be unreasonable for Christians to believe in something if there is (purportedly) no empirical evidence for it?
For me personally this idea is not even close to representing the actual situation.
Scientists have good reasons to suspect that life should emerge throughout the universe because there's nothing special about biology that should restrict it solely to Earth. So in a very real sense they do have evidence for the potential for life elsewhere. The universe is made of the same elements in the same abundance as far as our telescopes can see. And the laws of physics are also necessarily the same otherwise distance stars and galaxies wouldn't behave they way they do.
So scientists actually do have evidence to believe that life should be somewhat common in the universe. Precisely how common is yet to be understood.
However, Christian theology is not based on anything reasonable. It's very God is proclaimed to be a jealous God who becomes angry and wrathful with things don't go his way. Even if we ignore the myriad of problems with the mythology that the Christian Bible is based upon we still end up with a story about a God who has character flaws that even we as humans would like to improve upon.
So I don't see the comparison.
I think scientists have far more evidence that it's reasonable to expect to find other life forms in the universe, than Christian theologians have for justifying Hebrew mythology. So I see no comparison here at all.