Show of hands: who here likes a good alternate reality story?
So do I (which may or may not surprise some of you). What has recently occurred to me, however, is that a fairly typical alternate reality plot–one in which the main character discovers, for good or ill, what his or her life would be like under dramatically different circumstances–has a huge stumbling block of logic working against it.
Odds are, in any given alternate reality, the main character won’t exist.
Bear with me here, and all will be explained.
For purposes of the argument, let us use a model where every choice, no matter how mundane, splits off a new alternate reality. It’s the same scenario that they use over in Marvel Comics most of the time. For a main character, to keep the math simple, we’ll be going with someone who grew up as a single child, knowing both parents. So as to keep the grammar (and pronoun issues) simple, this character will be called You.
If Your parents never met, then You were never born. Since this is an either-or proposition, there is a 50% chance that You will not exist in any given alternate reality. Maybe Your parents did meet, but circumstances in the alternate timeline caused them to separate before You were born. Now You’re limited to existing in 33% of all possibilities. If Your parents do stay together, but remain childless? 25%. And if they child they have is not your gender, we’re down to a 20% chance of You existing. If they have twins instead? Well, neither one could honestly be said to be You, even if one of them shares Your name, so we’re down to a 16% chance that You’re around.
I could demonstrate how much worse the numbers get once we start adding in the odds of Your grandparents existing, but I will leave that as an exercise for the reader.
Just something to think about the next time you watch a mirror universe Star Trek or alternate timeline Stargate episode, and all the main characters appear in recognizable form.