Besides, in the context of science fiction, the question isn't whether it will happen, but whether it's plausible that it could. That's what science fiction is about: possibilities, not certainties.
Hard scientific evidence tells us that the universe is filled with planetary systems. It seems highly likely that there are many Earthlike planets elsewhere in the galaxy. Studies of life on Earth tell us that life can thrive in an enormous range of environments, essentially anyplace where there's water, carbon, and energy. We don't yet know for certain whether the spontaneous emergence of life is a rare or common event, but we do know that some species of bacteria can survive the vacuum and radiation of space, and that it's physically possible for such microbes to be blown off one planet and drift through interstellar space to be deposited on others. All told, there is very, very good scientific reason to consider it probable that life exists elsewhere in the universe.
As for interstellar travel, we know it to be difficult, but not impossible. FTL is probably unattainable, but there are plenty of slower-than-light ways of travelling between the stars: fusion rockets, antimatter rockets, laser-driven lightsails, particle beam-driven magnetic sails, self-replicating Von Neumann probes, etc. All of these concepts are the products of solid scientific and engineering research and the groundwork for them is being developed in earnest. So there is very, very good scientific reason to consider it a certainty that it is possible to travel between stars, even if it takes hundreds or thousands of years to do so.
Therefore, the concept of humans meeting alien life in the flesh is not an absurd or impossible one. It's true that it probably won't happen in our lifetimes, but all that matters for science fiction is that there's no reason why it couldn't happen, either within our lifetimes or within the lifetimes of characters living centuries or millennia in our future.
Hard scientific evidence tells us that the universe is filled with planetary systems. It seems highly likely that there are many Earthlike planets elsewhere in the galaxy. Studies of life on Earth tell us that life can thrive in an enormous range of environments, essentially anyplace where there's water, carbon, and energy. We don't yet know for certain whether the spontaneous emergence of life is a rare or common event, but we do know that some species of bacteria can survive the vacuum and radiation of space, and that it's physically possible for such microbes to be blown off one planet and drift through interstellar space to be deposited on others. All told, there is very, very good scientific reason to consider it probable that life exists elsewhere in the universe.
As for interstellar travel, we know it to be difficult, but not impossible. FTL is probably unattainable, but there are plenty of slower-than-light ways of travelling between the stars: fusion rockets, antimatter rockets, laser-driven lightsails, particle beam-driven magnetic sails, self-replicating Von Neumann probes, etc. All of these concepts are the products of solid scientific and engineering research and the groundwork for them is being developed in earnest. So there is very, very good scientific reason to consider it a certainty that it is possible to travel between stars, even if it takes hundreds or thousands of years to do so.
Therefore, the concept of humans meeting alien life in the flesh is not an absurd or impossible one. It's true that it probably won't happen in our lifetimes, but all that matters for science fiction is that there's no reason why it couldn't happen, either within our lifetimes or within the lifetimes of characters living centuries or millennia in our future.
