In December I watched a science program on TV about the idea of there being not only our Universe, but a lot of Universes, that we are part of a Multiverse. (The Fabric of the Cosmos: Universe or Multiverse? with Brian Greene).
I donâ€™t find the idea of a Multiverse impossible, but what I reacted against was, that in stead of focusing on the eventual proof of a Multiverse or on how such proofs could be found, the focus was on the possibility that each and one of us has a doppelganger in another Universe. This person is not only a look-alike, but a person who seemingly is identical to me. The reason for this speculation is that the Multiverse contains an infinite number of Universes and one of those should therefore be as our own and contain a person just like me.
Many years ago I listened to an organ concert in Notre Dame de Paris when I saw a look-alike sitting some benches in front of me. He was not an exact copy of myself, but alike enough and moved quite like myself. This shows there is a possibility of meeting close copies, but even identical twins are not identical, there are always differences between them.
Taking into account that we humans have developed here on Earth, it is of course possible that humans more or less like our species have developed on other planets in our Universe, and even more likely if we can count on infinite Universes. When I could find a person like me at an organ concert in Paris I could certainly find somebody who looked even more like me on the multitude of planets in the Multiverse, but would that be a copy of me?
The implication of such a parallelism should be that there is no freedom of will, that we human beings just are preprogrammed robots. If person a in World A thinks something, his doppelganger person b in World B is bound to think exactly the same. Of course this is a difficult question with philosophical implications, but I really believe that we have the possibility to, within given limits, make our own choices and form our lives.
However, without any philosophy, using only natural sciences, I find the possibility of twin people in twin Worlds impossible, in fact contradicted by Quantum Mechanics and the Heissenberg Uncertainty Principle. In case there should on two planets (in our own Univere or in Multiverse) be born a person genetically identical to me (in principle an identical twin), the way he would develop and what he should become would depend on the circumstances in which he is growing up. Only if those circumstances would be like the one in which I grew up, there would be a chance that I, aside for physical likeness, would recognise myself in him.
If we assume that I met a genetic twin growing up in the Stone Age, would he be like me? Not much. To be like me he had to grow up under the same circumstances as me. How big a chance is there that not only a genetic copy of myself, but a genetic copy of our whole society will exist on another place? And even identical twins growing up together are different.
I find that the focus in the TV program on us having doppelganger in other Universes unscientific and populistic and that the participating scientists have prostituted themselves to commerciality.