26 September 2009

Happy Birthday!

Today - 26 September - is Susan's birthday!

It is also that of approximately 18.579436949424012813404792706216 million other persons - give or take a few. Assumptions behind this calculation:

  • The world's population today is 6.786 billion
  • Babies are as likely to be born on any one day as on any other

The world's population figure must be correct, because it is taken from that impeccable source: Wikipedia.

The assumption about the probabilities of birthdays is questionable, but are you going to be able to prove me wrong? I don't think so!

I point out the (approximate) number of other persons (I don't vouch for all the decimal places; that just comes out of Windows Vista's calculator, when dividing 6.786 billion by the number of days in a legal year = 365.2425 (think about it - remembering that years divisible by 100 but not by 400 are not leap years; I'm sure you'll work it out) - I point out, I say (a long parenthesis back), the number because today is also the birthdays of:

  • Susan and my close friend Jenni Surrey
  • Our daughter Helen's husband Robert's

And Susan thinks this amazing. I have offered the to calculate the probability, given a number of friends, that some two - or three, or whatever - have the same birthday, but she has declined. This is lucky for me as I am by no means certain I could make that calculation (correctly, that is).

The world has become a more boring place. I just wondered whether Wikipedia (again) could tell me that probability. It can. Sad when the mystery goes out of life. But looking at that page, the maths seems sufficiently opaque as to ensure I would get tired of trying to understand it before having finished.

Tuesday last, the 22nd of September, was my birthday - and also those of Bilbo and Frodo Baggins - so there! I did not blog last week-end, and I could tell you that the reason was because on the Sunday - the 20th - we went up to Eddie and Eveline's for what was the official John and Susan Birthday Lunch. It is true that we went - and had a lovely time with them all - but it would not be true. I could have blogged on the Saturday but did not - because I forgot.

Actually I just read the Birthday Problem page and it turns out to be pretty simple after all - ah, well!

Sue and I will leave shortly (this Saturday afternoon) to stand as Godparents for Gerard and Delia Farrell's new daughter (whose name, I am informed, is Magdalena); then off to Little Thai Restaurant for dinner. Little Thai is the only proper restaurant (as opposed to Burger Fuel, where we go for takeaways) that we go to. The reason: both cater to Susan's no-gluten needs.

And let me take this opportunity to wish a hearty 'Happy Birthday' to all 18.579436949424012813404792706216 million (minus one) of the rest of you whose birthday is today.


Unitman said...

OK, I think your assumption about "any day is as likely as any other" for a birthday are hokey. Parrots and lots of other birds mate mostly in the late fall or early winter, so the eggs can hatch in spring, so offspring have a better chance of survival. And of course, that's the same explanation as to why schools start in the fall -- so "students" can "prepare" for duty in the late fall and early winter! Robin was the only one of us three born at the "right" time. Not sure whether that was Mom's or Dad's doin'.

Happy birthday, Susan.

Unitman said...
This comment has been removed by a blog administrator.
Unitman said...

The apparent problem is that mating in the fall would produce babies in late summer, since gestation is 9 months more or less. I say "apparent" because that just goes to prove that the mating cycle hasn't caught up to changes in gestation requirements, but it will -- soon, schools will be starting in July, and in fact in some in California that's already beginning !!

John Thayer Jensen said...

OK, Unitman, what are you, some kind of ecofreak?

I have always blamed my birth on the Japanese. The story I think I have heard is that mom and dad, having married in August, 1934, were kind of 'Depression Yuppies' - no kids.

Then Pearl Harbour happened. Mom told Dad, "You're going off to that war and you might not come back; I want a baby."

Nine and a half months later ... here I am!

I presume Dad came home on leave around April, 1943. And of course the war ended in August, 1945...


Trifonovitch said...

Well, this was certainly an interesting birthday announcement/greeting! Anyway, Happy Birthday to both of you and many more.

When are you coming to Hawaii for another visit?

Greg & Bev

John Thayer Jensen said...

Right after you come to New Zealand for another visit (or when we hit the Lotto big!) :-)

Blessings, Greg and Bev!