TonyState

Q. What if everyone actually had only one soul mate, a random person somewhere in the world?—Benjamin Staffin

A.WHAT A NIGHTMARE THAT would be.

There are a lot of problems with the concept of a single random soul mate. As Tim Minchin put it in his song “If I Didn’t Have You”:

Your love is one in a million;

You couldn’t buy it at any price.

But of the 9.999 hundred thousand other loves,

Statistically, some of them would be equally nice.

But what if we did have one randomly assigned perfect soul mate, and we couldn’t be happy with anyone else? Would we find each other?

We’ll assume your soul mate is chosen at birth. You don’t know anything about who or where they are, but—as in the romantic cliché—you recognize each other the momentyour eyes meet.

Right away, this would raise a few questions. For starters, would your soul mate even still be alive? A hundred billion or so humans have ever lived, but only seven billion are alive now (which gives the human condition a 93 percent mortality rate). If we were all paired up at random, 90 percent of our soul mates would be long dead.

That sounds horrible. But wait, it gets worse: A simple argument shows we can’t limit ourselves just to past humans; we have to include an unknown number of future humans as well. See, if your soul mate is in the distant past, then it also has to be possible for soul mates to be in the distant future. After all, your soul mate’s soul mate is.

So let’s assume your soul mate lives at the same time as you. Furthermore, to keep things from getting creepy, we’ll assume they’re within a few years of your age. (This is stricter than the standard age-gap creepiness formula, but if we assume a 30-year-old and a 40-year-old can be soul mates, then the creepiness rule is violated if they accidentally meet 15 years earlier.) With the same-age restriction, most of us would have a pool of around half a billion potential matches.

But what about gender and sexual orientation? And culture? And language? We could keep using demographics to try to narrow things down further, but we’d be drifting away from the idea of a random soul mate. In our scenario, you wouldn’t know anything about who your soul mate was until you looked into their eyes. Everybody would have only one orientation: toward their soul mate.

The odds of running into your soul mate would be incredibly small. The number of strangers we make eye contact with each day can vary from almost none (shut-ins or people in small towns) to many thousands (a police officer in Times Square), but let’s suppose you lock eyes with an average of a few dozen new strangers each day. (I’m pretty introverted, so for me that’s definitely a generous estimate.) If 10 percent of them are close to your age, that would be around 50,000 people in a lifetime. Given that you have 500,000,000 potential soul mates, it means you would find true love only in one lifetime out of 10,000.

from "what if? Serious Scientific Answers to Absurd Hypothetical Questions" by RANDALL MUNROE