there are an incalculable amount of planets between the incalculable amount of universes, the chance that life is on many planets is very great. Based on what we know is needed for life, the chances that life similar to earth is very great. Could you imagine if we somehow got access to get to one of these planets and they were in an age similar to what we experienced in the 1930s...I could imagine the possibilities and would be very interested in know the similarities and differences from our earth. We would be the martians to them. Incredible, I wish I were immortal to conduct research and stay around when it is discovered. Wow, the possibilities.
It would not be an alternate reality. For example perhaps if the Pangaea Theory is correct the countries separated in other ways no different wonders of the world animals evolved differently, humans evolved differently. Really exciting if you think about it. I'm into all that stuff though.