The 14th was Pi Day — for the mathematical constant whose decimal expansion begins 3.14 — and my grand-daughter’s school broke out in wild celebrations of π (hey, it’s a Montessori school), including π-themed costumes. Very sweet.

This moved me to consider another irrational constant, Euler’s number e, the base of natural logarithms: 2.718… That would make February 7th E Day.

(e, π, the imaginary unit i — the square root of -1 — and negative numbers come together in Euler’s identity, eπi  = -1)

Then there’s the golden ratio ɸ, whose expansion begins 1.61… — so that Phi Day would be January 6th, otherwise known as Epiphany or Twelfth Night.

(I note that a fair number of people have reinterpreted Pi Day as Pie Day and celebrated the occasion with the baking and eating of pies.)

2 Responses to “pi”

  1. Andy Sleeper Says:

    One aspect of mathematics that fascinates me is that we use an infinite set of rational numbers for many purposes. A rational number can be expressed as a ratio of integers. There are infinite rational numbers, but this is said to be a countable infinity.

    There is a much larger, uncountably infinite set of irrational real numbers.

    Despite our most sophisticated math operations applied to rational numbers, we must use irrational numbers like pi and e to describe some very basic physical truths, such as the circumference of a circle or the effect of compound interest.

    Language is similar. We have a countable set of words and symbols used to represent an uncountable set of ideas. We will never run out of new things to say and write.

  2. Wendy Thrash Says:

    Going to day/month dates, Pi day could be approximately 22 July.

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