It's almost that time of year again, the last Sunday in October, when the clocks go back and we get an extra hour in bed. The good ol' British version of Daylight Savings Time is coming to an end for this year.
This got me thinking about time, and why it is how it is. What's so mean about Greenwich Mean Time? Why did it become the standard? And how long is a day?
The mean in Greenwich Mean Time means the same as a mean in mathematics. The astronomers in Greenwich would measure the time at which the sun was at it's zenith, and over the course of the year, the measurement was averaged out to give us a Mean Time for noon, as noon as measured by the sun does not occur at the same time each day.
The UK gradually adopted it as the standard from 1847, and by January 1848 the legal time for Great Britain was GMT. But why? Everyone around the country was capable of working out the time, albeit with some variance between them depending on where you were. The answer is that the rail network was growing, and it was impossible to coordinate time without a single standard time that everyone was using. No good saying that a train left Mansford-Thirtysixbrough at 10:16 and arrived in Wabsnazm at 10:21 if those times were believed to be the same moment in those localities!
GMT is no longer used as the standard time. UCT (Universal Coordinated Time) is now the standard and set by atomic clocks. This keeps the time correct within 0.9 seconds. Constant correction is required as the day is not always the same length. It's always slightly under or slightly over 24 hours.
Interestingly, before 1925, the astronomical convention was to call noon 00:00 and midnight 12:00.
So there you have it, GMT only became the force it was because of the railways.
Subscribe to:
Post Comments (Atom)
2 comments:
Universal Coordinated Time is usually abbreviated to UTC. Blame the French.
You know, I was thinking that every time I wrote it. But every time I corrected myself, I changed it back.
I hadn't realised that UTC was a compromise between "coordinated universal time" and "temps universel coordonné." Until now.
Post a Comment