## Monday, 20 October 2014

### Echoes of the Past

What are the chances of someone you know having the same birthday as you do? My basic maths skills aren't bad, but when it comes to probability and equations, I tend to find safety in words rather than numbers.

The birthday paradox is a neat way to work out how many people in a room might have the same birthday as each other. I say neat... what I mean is, to anyone who isn't a mathematician, it's a bit of a complicated maths problem that I find somewhat difficult to process. However, there is a formula, and it does make sense. Honestly. Check it out and you'll see.

Now, what are the odds of two family members having the same birthday? In this article, four siblings were born on the same day (although, granted, two of them are twins), at odds of over 133,000 to one.

That's pretty impressive. And, as most families know, it's not something that usually happens.

But recently, my family discovered that, despite all the jokes and the ideas about joint parties, it does happen. Because why not?

My sister and I have very close birthdays; I'm 3rd July, and she's 7th July (with two years separating us). We've always thought that was pretty impressive of our parents (although our parents would probably have preferred a little breathing space between celebrations, thinking about it). But now, the next generation has gone one better.

My daughter, Alice, was born on 10th October 2010 (yes, a 10/10/10 baby). It's a nice, round date, and although she was over two weeks late, it all worked out pretty well. When my sister announced she was expecting, and her due date was the same as Alice's had been, we laughed about it. What a coincidence! How strange!

And then her pregnancy went on. And on. And it suddenly dawned on us all that actually, the coincidence might go even further. What if... Only my sister was taken into hospital on 8th October to be induced, and everything started kicking off pretty quickly. Okay, we thought, those girls are going to have very close birthdays, just like their mummies - how strange!

Then the labour slowed down. It slowed riiiiight dooooown.

8th October came and went. 9th October came and went. 10th October came... and right in the middle of Alice's birthday celebration, we heard the news - Tabitha Violet had been born!

Now, what are the chances of that?

Happy birthday 10/10 girls!