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, e^{πi }= -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.)

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March 17, 2013 at 11:30 am |

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.

March 17, 2013 at 11:42 am |

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