First, we don’t know Earth is the only habitable planet. However, until we have some proof, we have no way of knowing for sure. That’s why we’re searching so hard for extraterrestrial organisms.
Second, who says the universe has to have a use? It just is. Similarly, you could say what’s the use of living if you die in the end. That kind of view doesn’t do anyone any good. Just go with it and enjoy the exploration and discovery life offers us, like whether or not life exists elsewhere in the Universe.
I don’t see either as being dependent on the other. In other words, you can believe in God and not in extraterrestrial life. Many religious people do in fact hold that view. On the other hand, you can believe in extraterrestrial life and not believe in God. I know many people who hold that view.
So I don’t see a paradox at all. According to the Google dictionary, a paradox is “a seemingly absurd or self-contradictory statement or proposition that when investigated or explained may prove to be well founded or true.” I fail to see a contradiction that two different people can hold either view. It’s all theory.
In reality, we do not know for sure that life exists anywhere other than Earth because we have never found any evidence of life, although we continue the search. We have yet to find even a fossil of a microbe from space. However, the laws of mathematical probability suggest that with billions of planets in this galaxy and billions of other galaxies, it is likely that there is at least microbial life somewhere, if not something more advanced. We just haven’t the proof yet.
Similarly, except for subjective experiences, there is no proof that God exists either, although people believe that God exists. Maybe both exist. Maybe neither exists. I suppose it’s a question of faith in either view.
Just as soon as we can solve the problem of only going 20 times slower than 1 tenth the speed of light, our fastest speed to date. Sadly, the ability for humans to send humans to other stars will most likely never happen.
Mechanical, intentional interstellar travel is unlikely since the distances are far too great to imagine. The best anyone could achieve is interplanetary travel within one’s own solar system. Therefore, if we pass the buck and say life didn’t start here but started somewhere else and arrived here, it would have had to arrive on a rock or asteroid as a microbe and somehow survive a fiery entry through Earth’s atmosphere and it would have had to survive the vacuum and temperature extremes of space. If the rock came from outside the solar system it would have had to survive a long, long time.
We don’t know. Some people think we know, but a real scientist will agree with my first sentence.
The theory, still unproven, is that life evolves from dead matter. We’re still searching for life on other planets to prove this wet-dream of scientists, but still we have no proof of concept – just a concept – to the chagrin of science. We are frankly disappointed we haven’t found life elsewhere than Earth.
Evolution starts with creation of stars that create elements like the ones we have on Earth. We think when conditions are right that the chemicals develop amino acids (this is proven), which are the basic building blocks of life.
From there, eventually by combination and permutation it develops into something that could be called life.
Again it’s not proven but widely accepted. We don’t know for sure, hence my first sentence.