I recently read a Scientific American article on the subject of parallel universes. Interestingly this statement was made:
"The simplest and most popular cosmological model today predicts that you have a twin in a galaxy about 10 to the 1028 meters from here. This distance is so large that it is beyond astronomical, but that does not make your doppelganger any less real. The estimate is derived from elementary probability and does not even assume speculative modern physics, merely that space is infinite (or at least sufficiently large) in size and almost uniformly filled with matter, as observations indicate. In infinite space, even the most unlikely events must take place somewhere. There are infinitely many other inhabited planets, including not just one but infinitely many that have people with the same appearance, name and memories as you, who play out every possible permutation of your life choices."
Article Link
I think it would be interesting to discuss the reasoning behind the existence of parallel universes.
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(I noticed that there is another forum on this same topic, but it hasn't been posted to in a couple of years and I thought it would be better to start fresh.)
Edited by Ender, : Removed theological mumbo-jumbo