What if there exists another parallel planet in the other side of the universe where we can find humans or another similars species? Can scientifics really know that?

No, probably not. But I gotta say, that is a pretty good question. That would be dope though.

I have wondered the exact same question! I truly believe that there are other planets with humans or at least any other living thing. It might seem insane and strange but space is enormous we cant be the only planet with biotic factors! Who knows, there could be an exact replica of earth across the universe. Or maybe we're the replica of another planet like ours. There could be planets with mutant animals that were merged together with a different animal. We don't have the technology to travel to another galaxy and most scientist do say that intergalactic travel is impossible but the word impossible has possible in it! And who knows, sometime in the future maybe it will be possible and they will find a form of life in the universe.