Ever seen the show “Sliders”? It is kind of hokey. The story is about 4 people who “slide” from one dimension into another parallel dimension where they often find copies of themselves.
A book by Paul Melko, “The Walls of the Universe” describes a similar situation.
Heinlein and many others have written about these "Parallel Earths".
Maybe they exist. Probably not.
String theory supports the idea of a multi-verse composed of multiple “string” universes, which we call “dimensions”, inter-twined with each other. Kind of like a thick rope twisted from multiple strings. Okay, not exactly, but, kind of.
Some people believe that new dimensions are created every time we make a decision, as if the individual thoughts of a single person were capable of the act of creation. Not very likely in my opinion.
Personally I think it is pretty arrogant to believe that our individual thoughts control the multi-verse. For me, our human arrogance and ignorance is very entertaining. Far more entertaining than hokey fiction.
I believe that, IF the multi-verse exists, each universe “evolves” in an individual isolation.
There may be natural physical occurrences which “split” a string into two sub-strings and then reconnect, or not. Under these circumstances it MAY be possible that both of the sub-strings are equal to the string they split from. In this case it MAY be possible that two “versions” of a person may exist simultaneously.
I think that is very unlikely. In fact I think it is unlikely that the Earth exists in any other dimension much less billions of copies of all of us.
If the universe splits the two strands are not necessarily identical. In fact, I think it would be as unlikely as identical twins being identical. They may look very similar and have the same DNA, but, the two people are very different.
However, I believe there are millions of worlds with unlimited resources available to those who can travel between dimensions.
There is another issue, the “infinite monkey theory”. The Infinite Monkey theory states that intelligent life is as inevitable as the fact that an infinite number of monkeys pounding on an infinite number of type writers will eventually pound out every literary work ever produced.
The problem with that is the distance between these works. The average book has about 80,000 words and many have as many as 1,000,000 words. The odds of a monkey pounding one out is 1/101^80,000. Every keystroke is at random so 1 out of 101 with a 101 key keyboard. It takes between 80,000 and 1,000,000 correct strokes to create a literary work. So the monkey has to beat the 1 in 101 odds 80,000 times.
That is a pretty BIG number and we can use it to represent the distance between manuscripts by multiplying the BIG number by the average distance between stars. Wow, really BIG numbers.
Not exactly. Inter planetary travel is possible. Inter-dimensional travel is theoretically possible. If we travel inter-dimensionally through enough universes, our BIG number of universes, we will eventually run into a planet with intelligent life.
Still, the odds of finding intelligent life are directly related to the odds of intelligent life developing on a planet.
From a scientific viewpoint, if God exists the odds of two intelligent life forms coming into contact are pretty good.
If God does not exist and life is a random event which occurs with a statistical regularity. Because there is only one life form on Earth intelligent enough to control it's environment to the point where we can build vehicles capable of interplanetary travel we can assume that the possibility for the development of intelligent life exists and that typically only one intelligent species develops per planet.
This may or may not be true.
Dolphins and whales are fairly intelligent even though they do not possess the mechanical dexterity to control their environment. It may be possible that two different intelligent species can develop without one destroying the other.
That is not very likely if Darwin's “survival of the fittest” is correct.
Animals typically wipe each other out regardless of their position on the endangered species list. In fact animals have wiped out far more species than people have.
It is a shame we very probably don't have an infinite number of nearly identical copies of ourselves out there in different universes.
It does make for interesting fiction though.