2025-05-22
43 分钟I've been doing a lot of travelling this week.
I've flown all the way to South America and back, a total distance of just over 20,000 kilometres.
You'll find out why in a later episode of Babbage.
But for now, you should know that on the way back to London,
the flight took 13 hours and 41 minutes.
That's 49,260 seconds.
I'm taking all those measurements for granted, by the way.
I know that when I say I flew 20,000 kilometres,
you know what a kilometre is and are similarly amazed by the massive distance.
Same with minutes and seconds.
When you're on a plane, you know that you can easily pull up information on how fast you're going,
what the outside temperature is, and even your exact location using GPS.
None of that would be possible without knowing precisely what a meter or a second is.
It might be surprising to learn then that our modern system of weights and measures is relatively recent.
A Roman mile, for example,
was equal to a thousand paces that the empire's soldiers might march together in formation.
In the early 12th century,
English King Henry I defined the yard as the distance from the tip of his nose to his extended arm.
200 years later, King Edward II declared that the inch was the length of three grains of barley.
arranged from end to end.