We use measurement everyday but have you given much thought how these definitions originated?
I’m currently reading The Measure of All Things about Delambre and Mechain's meridian expedition of 1792-1799 to calculate the length of the metre. It’s a great read as combines scientific discovery, history, politics and adventure as they were travelling in France measuring landmarks along the meridian during the French Revolution!
A story today from The Register details how the Kilogram is the only metric measure that still refers to a single reference object, a lump of platinum-iridium alloy in Paris, rather than a reproducible physical constant.
In comparison, the metre is no longer one ten-millionth of the distance from the north pole to the equator as originally defined. It’s now the length of the path travelled by light in an absolute vacuum during a time interval of exactly 1/299,792,458 of a second. The main reason is this can be measured anywhere there is light, no need to run back to Paris to check your ruler.
They now want to change the Kilogram to a “universal measure”. One of the reasons; "A meteor could strike Paris - destroying the prototype"!