If I could name my favourite number, it would be pi or π. It is irrational. I mean, not irrational like my sister, but because it is a decimal that goes on forever and cannot be expressed as a fraction. It is also transcendental. That is not some yogi term. A transcendental number is a number that is not the root of any non-zero polynomial equation with rational coefficients. Say what? We cannot reduce it algebraically.

I have chosen to talk about π in honour of The International Day of Math aka Pi Day: March 14, that is, 3.14. And just to put the icing on the cake or maybe the ice-cream on the pie, March 14 is also the birthday of Albert Einstein. Wait, there is even more. Steven Hawking died on March 14. Coincidence? Perhaps. Nevertheless, it is certainly a day to be remembered.

## What is Pi?

π is the number of times that the diameter of a circle fits around its circumference. No matter how big the circle, the ratio of the diameter to the circumference will *always *equal pi.

So, the dude that came up with this number was Archimedes of Syracuse (287-212 BCE). I mean, what else is there to do when you don’t have WIFI? He approximated Pi by inscribing polygons on the inside and outside of a circle. In fact, he was so obsessed with pi that he got mad at a soldier who was messing up his circles and this soldier ended up murdering Archimedes. Too much pi can be a bad thing – for some, at least.

## Pi in our Lives

What is really interesting is that π comes up in real life in may different ways, not just with circles. Astronauts, architects and electricians all use Pi. They probably all eat pie too. In science, pi is important for many things, from modelling waves to economic statistics. Pi is even found in measurements of the Great Pyramid at Giza. Pi is used to calculate the deviation of light by the sun (this was in Einstein’s theory of general relativity). Double serving of pie! Pi also show up in Hawking’s equation for Black Hole radiation. Wow. Triple pie all **round**!

One of the most interesting ways Pi shows up is in showing the way rivers meander. The way that a river twists and turns through the earth is called its sinuosity. The sinuosity of a river is defined as the length of its winding path divided by the length of the river in a straight line. The average river has a sinuosity of 3.14.

Ok, one more fact to blow your mind. The mirror image of 3.14 is PIE!

Hungry yet?

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