We like to believe everything happens for a reason, maybe because it gives us a sense of

control in a world that can feel chaotic and unpredictable. So when really weird things

take place, we often can't believe it's

just a coincidence. We say, what are the odds of, say, being in a room with just two dozen

people and discovering two of them have the exact same birthday, as if determining those odds

is impossible. From KERA in Dallas, this is think. I'm Chris Boyd. Of course, it is not impossible

to calculate those chances or the likelihood of a lot of other weird and fascinating co-occurrences.

And if you open your mind to it, the hard numbers that prove these things are not magical

and take nothing away from how cool and interesting they are.

Sarah Hart is Professor Emerita of Geometry at Gresham College and Professor Emerita of Mathematics

at Birkbeck University of London. She's author of the book Once Upon a Prime and of the new

scientist article, The Surprising Math that explains why coincidences are so common. Sarah, welcome to

think. Thank you so much. Thank you for having me. I know your article is actually maths,

but I have such a hard time with that word that I just Americanized it, and I hope you'll excuse that.

That's fine. So you start your piece in the new scientist with this weird experience you had. Will you share that with us?

Yeah, so this was a little while ago I was visiting the beautiful English city of York with my daughter,

and we stopped off at a cafe for a snack.

And when I went up to order, I also asked, can I have the access to the bathroom to take my little girl?

And they said, yep, sure.

And then when I came to pay, I had to type in my PIN number, you know, to pay.

And just after that, the young lady at the counter handed me a piece of paper and on it was my pin number. And this made me

just be slightly anxious for a moment. Then I realized, no, this is a coincidence. The pin number

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