Messing with time

Cross-posted from The H Word blog, first posted on 31 March 2013, the first day of British Summer Time.

Analogue clock

It’s hardly surprising that I’ve become very aware of time and how we measure it since beginning work at the Royal Observatory Greenwich. What has really struck me is how much we, on the one hand, are resentful at any suggestion that we alter the way we measure time and, on the other, have done just that many times over the course of history.

Although it’s useful publicity for the Observatory, I never cease to be amazed that the change of the clocks, which happens twice a year ever year like … err… clockwork, is always a news story. Suggestions that we might do away with British Summer Time, or shift to what is euphemistically called Double Summer Time (aka Central European Time) are huge debating points. The fact that we do, or the fact that we might cease to, add leap seconds are stories that both receive many column inches.

Although the introduction of BST was a very 1900s notion of making better – that is, more healthful and productive – use of our long summer days*, history suggests that it takes something like a world war to implement such seemingly radical changes. There is often a sense that diverting from whatever it is we are used to is, somehow, unnatural. It certainly seems unnatural when we are ripped untimely from our beds but, even before the arrival of this annual ritual, there was nothing natural about the way we measured time.

Take GMT, which traditionalists are keen to defend by rejecting summer time and by adding leap seconds to ensure that we do not drift too far from having the midday sun above the meridian at Greenwich at noon. In the scheme of things, it is almost as much of a novelty as BST. It only became official standard time in Britain in 1880, even if it had been used in specific contexts, like railway timetables or in navigation, some time before. Its use as a standard to which international time zones are aligned was a matter of slow adoption from the late 19th century onward.

The implementation of a national standard time, which might be some 20 minutes different from your local time, should you live in the west of the country, was seen by some as an unnecessary novelty. There were those who made a stand, and even today the chimes at Christ Church in Oxford still stick to local time. As can be imagined, the idea being floated at the end of the 19th century that there might be a universally-adopted International Time was much mocked, resented or worried about.

But the national or local times that seemed more meaningful to people are, of course, also artificial products. They are expressed as mean time, which is an averaging out of Sun’s the apparent motion that was adopted in deference to the introduction of a new technology – the clock. Clock time is produced by an artificial system that imperfectly mimics “real” time, which is a product of the Earth’s daily rotation and annual orbit.

The difference between mean time and “real” or apparent time is expressed by what’s called the Equation of Time. This was first calculated in the second half of the 17th century, when the introduction of pendulum clocks made the business of artificial timekeeping sufficiently precise. The fact is, the Sun is rarely at its highest point over the Greenwich meridian at the moment our watches show noon.

Things get even more complex when we start looking into how calendars have been calculated and established. These are fascinating histories that are intertwined with everything from the story of astronomy to how we live and order our lives. Our time has been messed with for centuries and it is not, forgive the pun, a clock that can be turned back.

* Personal gripe: many people seem to think that putting the clocks back in Winter is “daylight saving” and is designed, somehow, to give us more daylight. Guys: “daylight saving” is used in Summer and nothing, but nothing, will create more daylight in Winter.


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