Wednesday, 14 June 2017

A briefer history of time

I'm reading Greg Jenner's A Million Years In A Day (subtitled A Curious History Of Everyday Life From The Stone Age To The Phone Age) at the moment. In the blurb, Tom Holland, himself no slouch in the popular history department, writes that Jenner is "as witty as he is knowledgeable." After a page or two, I was inclined to agree. After a couple more pages, the constant gags were getting a bit irritating.

I can see why he did it - nobody wants to sound po-faced and boring, but, for me, he tried to lighten the mood too much.* Not that I'd have done much better - if I tried to write something along these lines I'd probably have fallen into the same trap.

Still, Tom Holland's right about the "knowledgeable" bit. The first chapter, inspired by the alarm clock going off at the start of the day, was about how humans have recorded time. There was interesting detail on stuff I was already hazily aware of (mechanical clocks being invented mainly so that monks and nuns could say their prayers at the right time, the French Revolutionary calendar and the adoption of a standardised time zone across Britain being driven by the needs of railway timetables).

But the best bits were the things I had no idea about. For example, I had no idea how the ancient Egyptians dealt with the changes in day length over the seasons. Today we'd say that a midwinter day at, say, the latitude of Alexandria lasts about ten hours, while in midsummer, Alexandria has about fourteen hours of daylight. For the ancient Egyptians, a midwinter and midsummer day would have had the same number of hours - rather than measuring time in fixed units, they used seasonally adjustable hours which could last for only 45 minutes in midwinter, or stretch out to 75 minutes in midsummer.

It isn't just the adjustable hours that makes ancient Egyptian timekeeping look strange to our eyes - there were no seven-day weeks in the land of the pharaohs, but 36 ten-day weeks in a year made up of three four-month-long seasons, rather than our familiar four three-month-long seasons. Given the local climate, the seasonal thing makes sense, but it's a good lesson about how our way of measuring a continuous thing isn't the only way.

We might see ancient Egyptian time-related notions as quirky and counter-intuitive, but, as Greg Jenner points out, some of ours look just as odd to outsiders. Take the simple English word "day", for example. In English this can refer two completely distinct things. First, the approximately 24 hours it takes the Earth to rotate once on its axis.** Second, the daylight part of that 24 hour cycle, which can last from 24 hours to no time at all depending where in the world you are, at what season.

Other languages reflect this distinction - in Dutch, Dag means "day" as in "when it's light outside" and Etmaal means "day" in the sense of "a 24 hour period."***

In fact - and I didn't know this, either - English does have a specific separate word for "day" in the 24 hour sense. But it's a Greek loan word and so ridiculously obscure that hardly anybody knows it. And the word is:
Which, according to Greg Jenner, sounds like a Finnish heavy metal band.  To be fair to Greg, it does sound pretty cool, albeit in a rather nerdy way and, yes, I could just about picture the word emblazoned in gothic-style characters on a black tour T-shirt. With an umlaut above the "o", natch...

Anyway, I'm on to chapter two of Greg's book now, which is all about going to the toilet, so I'm not expecting the jokey style to calm down any time soon...

*I think this style would have worked far better if this had been a radio series, or a series of podcasts, rather than a book.

**Let's not get into solar versus sidereal days, unless you really want to.
***Although, AFAIK, languages which make this useful distinction are in the minority, so I'm not picking on English here.