I have talked before about how much I love the fact that the standard meter is "the same length as some stick in Paris". Sadly this isn't actually true. It's been redefined a couple of times, both in terms of the speed of light, and in terms of wavelength of some particular light.
I was today years old when I found out that it's not just some random coincidence that, in the metric system, the acceleration due to gravity is almost exactly the same as pi squared.
Before the standard meter stick, there was a proto-meter that was defined as the length of a pendulum that swings once every second. The formula for simple harmonic motion is defined in terms of theta - the angular frequency and acceleration. Because of radians theta is 2 x pi x frequency. If you solve the SMH equation for a pendulum with f=1, you get l = pi squared.
It's squared because you need to differentiate twice to get from acceleration to speed to distance.
The meter used to be defined so that, if you know how long a second is, and you're sitting in a nice comfortable gravitational field at Earth's surface g=pi squared meters per second per second.
The name "meter" seems to make more sense now as well.
Richard "Blame it on the Metrologist" B
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