tourist in Oxford: Please - what is time?
professor, after thinking for a while: That's a very interesting question, one
to which we don't have a definitive answer. However...
comes in different flavours. There's solar time, atomic time, universal co-ordinated
time, sidereal time, bedtime and harvest time - before we even start on those
created for science fiction.
We don't really know when mankind first started trying to tell the time.
Possibly it all began when womankind started telling mankind that he was late
and the children were hungry. The sun rose, the sun set. It stayed up longer in
summer than in winter. The moon grew and dwindled away in a regular cycle. The
burning skeins of stars made clear nights a time of beauty and wonder, their
patterns moving on by a barely perceptible step each evening.
What mattered was the hunting, and later on the farming - in a primitive
society, food comes before philosophical speculation. However, sooner or later
someone was bound to point out the obvious - the migrating geese, the ones that
were good eating, came at the same time every year. And every year, when the
geese came, the rising sun was just a little bit to the right of the tree on the
nobbly hill. It didn't take a genius to work out that if the whole tribe started
making arrows when the rising sun was still just to the left of the tree
it'd be raining campfire-ready geese a few days later.
A thousand little discoveries later, each one backed up by heaps of goose
bones, fields of corn or tons of smoked elk, astronomy was born.
There must have been an overwhelming sense of power running through the
early astronomers. For the first time someone could predict. By finding
regularities, counting off days and months, they could say that there would be
high tides on a particular night, or that the geese would arrive in three weeks.
For the first time the human race could grab control of its destiny.
Instead of accepting whatever the world chose to throw at them, the citizens of
our early society could know what was coming and prepare for it. In a real sense
this was what made them human. Passive
acceptance of fate was obsolete; this was the dawn of the age of engineering.
Of course nothing is that easy. The step-dance of the lights in the sky
was perfectly regular and utterly frustrating. A new moon appeared every
twenty-nine and a half days. Then one would be a day late. The ratios connecting
the movements of the sun, moon and planets weren't convenient, sensible numbers.
Puzzling them out needed better oberving instruments, followed by improved
systems of mathematics to reduce the observations.
Better instruments revealed even more complex patterns. Once pendulum
clocks were accurate enough to agree with one another, the strange behaviour of
the sun showed up. The sun gained and lost
time as well; solar time swung ten minutes either side of clock time
during the course of a year.
Even more interesting was the behaviour of the stars. Apart from the few
little dots of light that wandered around and were called "planets" -
from the Greek word for "wanderer" - most of the stellar background
was fixed. But night after night it stepped forwards a little.
Now it was time to find some explanations. The daily cycle of sunrises
and sunsets is caused by the rotation of the Earth. But at the same time it's
orbiting the sun every year. The earth has a tilt - its axis of rotation doesn't
stick straight up out of the plane of its orbit. The northern hemisphere points
in towards the sun in June. That's the British summer when we lose at cricket to
the Australians. The southern hemisphere points at the sun in December, the
Australians have their summer and we lose at soccer to any nation that's
passing. The Earth's orbit isn't perfectly circular, but an ellipse. The Earth
is closest to the sun around January and furthest away around July. This has an
effect on the seasons, small compared to the effect of the axial tilt, but large
enough to measure.
The Earth is both rotating and going around the sun. If you measure the
length of a day by how long it takes the stars to get back to the same places in
the sky, you don't get the same result as if you take the mean time from one
solar noon - when the sun is highest in the sky - to the next. The Earth goes
around the sun in the same direction as it rotates, so in a year that the sun
goes around the sky 365 times, the stars go around 366 times.
This is the difference between solar and sidereal time.
Solar time is measured by the sun, sidereal time by the stars. The sidereal day
is a little under four minutes shorter, so the stars rise and set earlier each
Things got much worse with the invention of the atomic clock. Good old
Greenwich Mean Time had been defined in terms of the movements of the sun as
seen from Greenwich. The various atomic clocks around the world all agreed with
one another - they could be synchronised by radio - and they all told the same
story. The Earth was speeding up and slowing down. Our definition of the length
of a second, based on observations from Greenwich, was built on foundations
about as solid as soft cheese.
This is why the world has changed from GMT to UTC. Now the length of a
second is defined in terms of the atomic clocks and from time to time "leap
seconds" are added or removed to keep UTC in step with the Earth.
Now we have enough information to start worldbuilding. We can tinker with
the parameters of an imaginary planet and see where they take us. For example:
eyes closed for a moment. "Eastern side and well in towards the galactic
core. Isn't there something odd about its orbit?"
Jane nodded. "No axial tilt to speak of - Greenworld doesn't have
any seasons. There's a temperate belt round the equator which is populated,
then it shades off into darker and gloomier forests as you head for the poles.
The trees grow with no annual rings, which makes the wood an expensive
There are two ways we can go from here. Either our imaginary planet is
part of a larger, interplanetary civilisation, or it's more or less isolated. In
the first case the inhabitants will want to try to share holidays and festivals
with other planets; they'll want the sense of solidarity that comes from
thinking that as we sit down here to celebrate Homeworld Day, cousin George on
St. Barbara is doing the same thing. Making this work will involve using a
calendar that's based on something other than the rotations and orbits of
individual planets. Greenworld again:
[Jane] "Atomic clocks. They work out which day comes closest to
Christmas on the theoretical Old Earth, what it would be if it hadn't been
nuked into a different spin in the long war. Then they build all the festivals
around that." She put her drink down and pressed buttons on her heavy
gold wristwatch. "We've timed it right. In about ten minutes it'll be
midnight, Old Earth, or nearly eleven in the morning here. The children will
come on and do a little play, then we all go through for lunch - which will
take most of the afternoon."
In this case the festivals will largely be created as commemorations of
people or events. It's then up to the government of your imagined planet to
decide who is worthy of being remembered and which events they want people to
have in their minds. Remember that this sort of festival will come at a
different time each year because it's based on a calendar that has nothing to do
with the orbits of the planets where the celebrations are.
Let's consider a starship carrying colonists to another planet. Even
though they'd travel in suspended animation, they'd take with them tins and
packets of food to eat when they arrived, because it would be a while before
they could produce their own. Sooner or later the stores would run out. It'd
either be a moment of release - they knew they were self-sufficient - or a
moment of terror if they weren't. I suspect that the instant of opening the last
tin would be a cause for celebration. It might even be caught on camera:
"We are able to produce a great deal of our own food in the
atmosphere domes. Not as much as we would like, which is why we've delayed
bringing the rest of our people out of suspended animation. It's been a
delicate juggling act, trying to make sure we could produce each commodity
ourselves before the supplies we brought from Old Earth ran out. Today we come
to the end of one of our stocks." Genevive held up the tin. "This is
the very last of the tins of condensed milk we brought with us from Old Earth.
And on this tray are the teacups belonging to the people who are working in
the domes." She pulled the ring on the tin and began to pour. "I can
stretch this tin to ten or so - no more." She picked up the teapot and
filled the cups. "Egil - if you'd like to take the tray out to
Egil Lund picked up the tray and left.
Genevive went on. "That leaves me with no milk for my tea." She
looked directly into the camera, a faint, prim smile on her face. "Or it
would, were it not for this." She reached out of shot and picked up a
jug. "Our own milk, from our own cattle kept in our own atmosphere
domes." She poured the tea and took a sip. "This is the moment of
transition. We are now free. Truly free." She froze, holding the cup.
From this little moment could come a sacred tradition:
And that's why if you're anywhere on the nine worlds of the Arcturian
Confederation on the first Wednesday in March - subject to the usual confusion
about calendars - you'll find that it's a public holiday called Homeworld Day.
Many businesses will be closed, but if you find one that is open, or you are
invited into someone's home, you'll be offered a small cup of hot, sweet,
milky tea with the words, "We are now free." To be polite take at
least one sip and reply, "Truly free."
There is another sort of holiday, the one that comes from the slow
turning of the seasons. Normally this would be restricted to the one planet
where it made sense, but I can see a possible future in which one planet is home
to the capital of a galactic empire and imposes its public holidays on everyone
else. Holidays of this kind would tend to grow out of the cycles of agriculture
and hunting, but they might persist long after most of the population has moved
away from direct involvement with the land. For example, the sun rises a little
further to the right each morning as we go deeper into winter, until around the
21st of December it stops. On the 25th it visibly moves to the left. This day
the Romans called the "birthday of the unconquered sun", and they
celebrated it as the beginning of the new year. Having no record of the date of
the birth of Jesus, the Christian church has borrowed the date from the pagans
as Christmas Day.
There is a little problem that comes from writing about a Galactic Empire
peppered with planets, each of which has a different length of year.
How do you know someone's age? Can the young lad who's just arrived from
another planet have a licence to drive a hovercar? Is the girl with him entitled
to be served in the bar? And are they old enough to be legally married? The only
solution I've ever found is this:for legal purposes everyone uses a clock and
calendar based on a theoretical Earth, but in fact derived from atomic timing.
Printed calendars use the local dating scheme which divides the year into days
and months. But underneath, in small type, is the theoretical Earth date. Of
course there'd have to be some fiddling; a planet with a twenty-three hour day
would have more days, and the same Earth date would sometimes be printed twice.
On a planet with a twenty-six hour day, two Earth dates might be printed for the
same local day. This way there's no ambiguity.
Our youngsters can simply state their birthdays in the Earth calendar;
the barman then glances at his local calendar and hands over two large
Rudesheimer beers. They could, of course, be lying about their ages - but that's
characterisation, not worldbuilding.
What remains is the flavour that holidays give to a civilisation.
They can impart a sense of fun, like Christmas cheer and Easter bonnets. Or they
can celebrate worthy things, such as getting the harvest in or the day the
hydroelectric dam was opened. At worst they can be the birthdays of dictators or
the anniversary of The Day We Enslaved The People In The Next Country. At best
they can point to hopes and dreams.
Now it's up to you. Decide
if your world is alone, like ours, or part of a vibrant, colourful galactic
culture. Choose the sorts of things your characters will celebrate,and that will
tell us a lot about them. Find reasons for the origins of their festivals, and
make up things worth commemorating. Look at the motivations of the people who
create or promote events: do you have an ambitious young priest looking for
reasons for more holy days because they'll bring offerings into the temple? Or a
kindly old one who adds new celebrations to give the farmhands a few days off
from back-breaking work?
Now build your world, and enjoy it.