I've just registered for online appointment booking at my local doctor's surgery. I gave them my date of birth and the guy pulled up my record immediately without even asking my name.
"Am I the only person with that birthday?" I asked.
"Yes," he said. "And we've got 80,000 people registered here now."
"Wow, what are the odds of that?!" I wondered aloud, guessing that 'one in a million' wouldn't even be close. Remember the probability of two people sharing a birthday is greater than 50% with a group of just 23. Imagine the odds of being a loner in a group 4,000 times that size! I immediately rushed to the office and punched numbers into an online big number calculator.
This gives roughly 1.14e95 - basically a one with 95 digits after it before the decimal point. That's within a factor of a million of being a googol! "Within a factor of a million," I hear you say. "That's hardly impressive." And no, you're right, it isn't. But it does mean I'm one in more than the number of subatomic particles in the universe which goes some way to explaining my continued lack of success finding a life partner on OKCupid.
Of course it's perfectly possible that our perceptive receptionist was using other information to identify me, such as gender. I like to think I'm obviously male, to the casual observer at any rate. Even so, assuming a 50/50 split (and of course according to anecdotal evidence about male attendance at the doctor this may be wildly inaccurate) 1/((365/366)^40000) gives me a solid 3.8e47 which makes me about as unique as any single atom in the Earth.
I won't lie, this is the point at which I started to suspect that this wasn't actually the case. I looked up the population for the entire borough and found it's roughly twice 80,000. I could easily believe that only half the residents of Hammersmith and Fulham are registered with a GP so that suggests the 80,000 is for the entire borough, not just for my local surgery. On top of that it seems likely that, upon performing a search, the system would prioritise people based not just on gender but on whether they are registered at the same medical centre, possibly even showing only locally-registered results as a first step. So it's entirely possible I'm only one in, say a few thousand and that actually I have plenty of celestial twins within the borough at large. But I am highly amused by the idea of having my own unique birthday, as if I'm quarantined away from the other 79,999-odd patients. Or maybe I'm just being over-sensitive and self-pitying. Who can tell?
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