Posts Tagged Hours

World Building Question: How Long is an Hour?

Has anyone else been thinking about the nature of time lately? Two weekends ago we lost an hour, an entire hour, as Daylight Savings Time began. Today is the vernal equinox, the transition point where days are once again longer than nights. I know I must think about time around this point of the year, because it was almost exactly a year ago that I started asking these World Building Questions, and started by asking What Time Is It? I’m going to move back to my questions about how time works on earth. So we lost an hour recently, but what is an hour?

Cesium

Cesium. For all your time telling needs. Can you see it performing hyperfine level transitions?

Alright, that’s an easy one. An hour is sixty minutes long. Each of those minutes is sixty seconds long. So an hour is 3600 seconds long. We know the length of a second because it was defined at the 13th General Conference on Weights and Measures, an occasional meeting that sets things like the international standards for metric measurements, and just how many yoctometers are in a yottameter (a hell of a lot). A second, per this SI definition, is “the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the [cesium] 133 atom.” Whipping out a calculator to do the math, an hour is thus 33,093,474,372,000 of…whatever the hell they’re talking about with transitions and hyperfine levels. I was never that great at the applied sciences. As I’ll one day demonstrate when I crowd source some physics questions for an upcoming novel.

This is clearly a modern definition. An extremely modern definition. A definition less than 50 years old with a clarification less than 25 years old that “[t]his definition refers to a [cesium] atom at rest at a temperature of 0 K.” Cesium itself wasn’t discovered until 1860. And yet the human race has had hours for far longer than this definition has been around. For most of the history of the hour it was defined as 1/24 of a day-night cycle. Actually, this is a subtle lie. For much of the history of the hour, it was defined as 1/12 of the period between sunup and sundown. The period between sundown and sunup didn’t get hours because no one was doing anything during them, so who the hell needed to know what time it was? Night was divided, if at all, into watches.

Why 12? I covered that one when I asked what time is it? For those who don’t want to do the back reading, the short answer is “the Egyptians.”

As a side note: back in that post I said “Once a society becomes more advanced, it needs more granular time,” without really going much into it. I’m not really proud of that statement, as my wanderings through history in the last year have smacked down notions of societies as more or less “advanced,” which is really a modern ethnographic concept. To employ better phrasing, the use of granulated time, which flows from broad chunks of the day to hours to half and quarter hours, relates less to the “advancement” of society as it is to the ability to easily know what time it is while on the go. If you’re bustling around Rome and not stopping to check the nearest sundial, all that matters are the periods before noon, noon itself, and after noon. When you stop at a sundial, you could see where the shadow fell and know more broadly what time it was, but the same could be gauged by looking overhead. It’s not until clocks are visible from multiple points in the city, and the advent of portable clocks we call “watches,” that the person on the go could quickly have a better notion of the actual time.

So, alright, an hour is 1/12 of the time from sunup to sundown. This was thanks to those sundials, which started working every morning when a shadow first appeared and stopped working every night when the last shadows slipped into total darkness. There’s a problem with this definition, however. The period from sunup to sundown is not a constant. Here in the DC area the winter solstice produces just 9 hours and 26 minutes (by modern reckoning using the cesium atom) of sunlight. During the summer solstice DC gets 14 hours and 54 minutes (cesium) of sun. Dividing each of those by twelve, the length of a classical hour here in DC would be 47.2 modern minutes on the winter solstice, 74.5 minutes on the summer solstice. This is a significant swing. Playing this out over a modern eight “hour” work day, this would mean working just 377 minutes in late December but 596 minutes during late June.

Which is why it’s fitting to talk about this today, one of the two equinoxes, when the modern definition of an hour is as close to the classical definition as it gets during the year. Actually, this isn’t quite right as most of the world is today experiencing a day of 727 minutes, not 720, but it’s as good as you’re going to get. This is less the day where we get equal amounts of day and night, and more the day that everyone gets an equal amount of day.

Later hours were defined not as 1/12 of the daylight, but as 1/24 of the period from sunup to sunup. This wouldn’t result in 45 minute swings in time seen by the old definition of an hour but would still drift ever so slightly and require clocks to be reset a little each morning. Using DC from March 20, 2013 to March 21 as an example, on the 20th the sun rose at 7:11, on the 21st it will rise at 7:10, resulting in a day that is a minute short, and hours that are each about 2.5 seconds off. Which doesn’t sound like much, until you turn that into 22,981,579,425 of the cesium things.

So when did hours become equal in length? Not until the 1400s. Why? It took that long for the combination of accurate time keeping and a willingness to move away from the previous sunup-to-sunup definition. Technology fighting the momentum of “that’s how we’ve always done it,” just as it will throughout human history on oh so many issues. This technology continues to push forward, and we now understand that what we once defined as an hour isn’t necessarily a constant. But I’d rather not get into that, because I’m far more likely to say something entirely wrong. Or more wrong than the wrong things I’m sure already litter this post.

I like to bring these posts back to world building, so let’s give it a shot. We’ve seen how the hour evolved on earth, and how it was originally tracked thanks to sundials. The sundial is an intuitive piece of technology, by which I mean it emerged independently at several points in human history. So let’s take it out of the picture. How does time keeping evolve on a planet where the light is diffuse, say through a constant cloud layer? There would be a clear morning and dusk as light grew and diminished in intensity, midday could be intuited as the midway point between the two, but no clear progress of shadows would be seen. How would hours be divided by a species who has a sleep cycle that doesn’t line up with the planet’s day/night cycle? Would two clocks develop? What if a culture developed under more extreme cycles, such as those seen in Iceland where the length of a day swings from 21 hours to 3 hours?

There’s one more bit I wanted to go into, but I’m already over 1200 words so I’ll hopefully get to it later in the week. It’s the related, but interesting question: What time is noon?

Cesium ampule picture released under Creative Commons Attribution-Share Alike 3.0 Unported license by the Dennis s.k collection. Find his other photos at his Wikipedia user page.

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World Building Question: What Time Is It?

Here in the United States, except for most of Arizona and Hawaii, we’ve gone into Daylight Saving Time, when we shift our clocks forward an hour so we can take advantage of more sunlight in the evenings after work.  You know what DST is, because while the whole world doesn’t use it, probably 95% of this blog’s traffic comes from countries that do.  However, DST is not universally applied internationally.  The US and the UK shift a few weeks apart, and Australia observes DST opposite the rest of the world due to flipped seasons.  It also picks different dates.  This video explains the history of DST and how things just don’t line up all that smoothly, and even the odd DST observing and non-observing enclaves within Native territories in Arizona:

So last week we here on the east coast of the United States were 16 hours behind Sydney, Australia, now we’re 15, and in another few weeks it’ll be just 14.  And just when it looked like we were catching up to the Aussies, it’ll all reverse and go back to 16 hours in a few short months.

Alright, so what’s my vague justification for talking about DST under the auspices of World Building?  It brings up an important question when it comes to non-earth worlds:  What time is it?  How granular is time?  In a less advanced civilization there may be just four broad times: morning, midday, evening, and night.  If you’re not trying to plan specific and detailed events, that’s all you really need, and it’s more about our perception of time than actual hours.  “Morning” changes by hours a year, to when it starts, when it ends, and how long it is, thanks to lengthening and shortening of a day and by ones latitude.

A more advanced society requires more advanced time keeping.  Broad subdivisions of time independent of the rising and setting of the sun come first.  We call these hours on earth, and arbitrarily divide a day into 24 of them.  There are 24 because the Egyptians liked to use base 12, and split the equinox day into equal halves, twelve portions of daylight, twelve portions of darkness.  Why 12 when we have 10 fingers?  Because they counted knuckles, not digits.  It’s handily a mathematically significant number because there are more factors of 12 than 10, but it’s largely arbitrary due to one culture’s affinity for a number and later cultures’ affinity for that culture.

Once a society becomes more advanced, it needs more granular time.  This won’t necessarily lead straight to minutes, but could be quarters of the longer time blocks, or perhaps eighths.  Even modern society we tend to use only halves and less frequently quarters for most of our daily activities.  Sixty minutes on earth come from old methods of hand counting from cultures that lacked calculators and needed ways of tallying numbers larger than ten using the digits on their hands.  It’s the old 12 knuckles on one hand, multiplied by 2, 3, 4, or 5 on the other.  Thumbs need not apply.  We further divide things into seconds, again with 60 per minute.  After that, time becomes decimal, belying the fact that smaller units of times than seconds weren’t really necessary until after the scientific revolution.  Thus we end up with milliseconds and picoseconds.

There are some who suggest that all of time should be decimalized the way subdivisions of seconds are.  A day would be 10 hours of 100 minutes of 100 seconds, which the length of each being determined by taking the period of revolution of the earth and dividing by the correct number.  While there’s a certain logic to this decimalization, there is so much cultural momentum to overcome that decimal time will likely never be more than just a novelty.  We see this here in the United States as various movements fail to convert the country from imperial to metric measurements.

We further complicated time of day with time zones, designed so that noon in each part of the world roughly represents the midpoint between sunrise and sunset, but rarely actually does.  There is some push to eliminate those just as there is a push for the decimalization of time.  This is more successful as there are already organizations, such as major world navies, who see the benefit of referring to an exact moment of time by the same numerical representation wherever you are in the world.  Thus 0300 Zulu is 0300 Zulu whether a ship is in the Atlantic, Pacific, or Indian oceans.  It’s handy for any organization attempting to synchronize around the planet, or even beyond it, something that wasn’t necessary or possible until very recently.

So let’s pretend we’re world building time on the earth.  The day was divided into 12 units (and the night an additional 12) because 12 was a culturally significant number for an early culture, in no small part because it represented the number of segments on the fingers of one hand.  Hours and seconds were divided five times farther because early cultures would use this counting-to-twelve method on one hand, then use the fingers on the other hand for the multipliers 2x through 5x.  Subdividions of seconds are the only units of time that are decimalized because they are only useful to scientists who prefer decimalization because it makes math easier.  These divisions have nothing to do with when the sun rises or sets, and even arbitrarily shift by an hour at a time.  The earth itself is divided into 24 major time zones (we won’t even start with the minor half and quarter hour zones) one per hour of the day for offset, though these are slowly going away in favor of a universal time.  And this is all before we’ve put down our first settlement on a planet that rotates at a different rate than earth, which will further complicate things.

So we’re back to the original question.  What time is it?  It’s a complex question that will deal with the history of your planet and culture, cultural norms, scientific advancement, and ultimately may cause debate and confusion on a planet shrunk by high speed communication.

And this is without even asking two far more complicated, but legitimate, world building questions: What day is today? And when is lunch?

Railway station clock picture by Wikipedian Petar Milošević, licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.  French decimal clock picture by Wikipedia Cormullion, and also licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

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