1. Welcome to the Fantasy Writing Forums. Register Now to join us.

measuring passage of time on a tide-locked world

Discussion in 'World Building' started by SMAndy85, Jun 20, 2017.

  1. SMAndy85

    SMAndy85 Minstrel

    I'm creating a fantasy world, which is tide locked to its star. I've done some research on this, and I'm happy with my results, so that's not up for debate.

    What is though, is how the inhabitants of said planet would mark the passage of time.

    Key points;
    the planet is tide locked. That means the same side faces the sun constantly. For the inhabitants, the sun barely moves in the sky.

    There is a small wobbly in the orbit, which means the extremes closest to the hot side and cold side experience some seasonal fluctuation. Essentially the seasonal shift means the edges of the habitable ring shift between hottest/coldest every 4 "weeks".

    A "year" is the equivalent of 8 weeks on Earth. i.e. the planet goes all the way around the sun and back to its starting point in 1,344 hours. This isn't particularly significant to anything, though.

    There is a moon, which would be in the same point in the sky every 24 hours, giving an easy to mark work/rest cycle.

    Medieval style technology, so it's feasible that they wouldn't even know the planet is going around the sun. Also, style-wise I'm going for old-english, so place names will fit to that effect. e.g. a town at the mouth of the river Bar* would likely be called Barmouth
    *randomly chosen word, read nothing into this.

    So. How would these people mark the passage of time? Names for these periods of time would also be a good thing to discuss. So far, my thoughts have been on the number of times the moon has passed them. I'm thinking it would be based on the number of times the moon passes, so ten-moon, or hundred-moon, perhaps. Let the discussion begin!
  2. KC Trae Becker

    KC Trae Becker Troubadour

    Though the fluctuations would seem small to us, experience is relative and so the fluctuations would likely take on a greater value for them. So I imagine these differences of seasons and years would be noticed and used to mark time. rather than a random number count, especially if the technology and mindset(?) is more medieval.
    SMAndy85 likes this.
  3. SMAndy85

    SMAndy85 Minstrel

    I can accept that. If that's all they see, that is all they would have to work with. If you accept an 80 year lifespan, which is 29,200 Earth days, that's 521 years for them.

    You're right in that the mindset would be more medieval. I'm already toying with Stone Circles being used to accurately mark a year, and settlements having a form of moon-dial, on which you compare the position of the moon in the sky with markings on the dial/altar.

    Thanks for the input!
  4. OfAllTheBars

    OfAllTheBars New Member

    Would such a world not have developed an entirely different concept for time? Time for us is as it is because the earth rotates giving day and night, because its tilted on its axis giving seasons, and because we have a moon like we have that gives us tides (and many other reasons). Take away the rotation, the axis tilt, and the moon, and the concept of time could be entirely different. Having said all that, in your world the stars would still appear to move across the sky as the year progresses, so that would be a suitable measure of time and seasons - exactly as the appearance of constellations in the evening sky marked spring for ancient civilisations on earth.
    SMAndy85 likes this.
  5. SMAndy85

    SMAndy85 Minstrel

    The problem there is for anyone in the habitable section of the world, there would be enough sunlight for the stars to be not visible. It doesn't make sense to travel up to a couple of thousand miles just to check what time of year it is by the stars. It is however feasible that one or two stars might be visible during the winter, but again, not for the parts of the civilisation closest to the hot edge. Those people would never experience anything like "night", during which the stars show.

    However, you've given me an idea. Given there is a bit of wobble in the orbit, I would suggest that on clear days, the sun would cast a shadow that would move down a wall, allowing them to see how much of the summer was left. Different methods could be used in different parts of the world, allowing the stars to be a marker on the dark edge.

  6. Viorp

    Viorp Minstrel

    The stars in the sky would cycle around troughout the year. But that helps only with the dark side.
    And you gave the answer yourself, there is seasonal fluctuation... to some extent.

    Plants and animals also would follow some type of cycle. Any type of time measurement would be based on what can be used as indicators for planting and harvesting plants.
    SMAndy85 and KC Trae Becker like this.
  7. SMAndy85

    SMAndy85 Minstrel

    So, it seems to me that the common consensus is for people to use what they have to hand. A year remains a year, even if it's short by our standards. So people on this world could live over 500 years (521.79 years on my planet is 80 Earth Years). This also makes adulthood roughly 100 years (roughly equivalent to 15 earth years).

    So that means the travel of the moon would be used to measure shorter time periods, but without accurate ways to measure it, it would likely be split only down to a half-moon (being roughly 12 Earth Hours).

    Ancient civilisations could have had fairly accurate ways of measuring it using stone circles, and water clocks, or sand clocks have been around for a fairly long time, allowing me to use them in towns and cities for accurate time keeping, reset fairly regularly against the rising of the moon.

    Those towards the lighter side could use something akin to a sundial, measuring the shadow against a wall, and those closer to the dark side might be able to see some stars, and use them as a form of measurement.

    Since it is fairly rare for people of that technological level to leave their home town, save for trade, I imagine it would work quite well for different regions to have different methods of time keeping. It would be easy for someone to marvel at the stars on their first trip to that edge of the world.

    Thanks for the input!
  8. CupofJoe

    CupofJoe Myth Weaver

    Are we talking about [basically] humans on this world?
    How do they deal with the constant daylight?
    Humans are built around a lot of cycles and rhythms.
    I've heard that some people can't get used to 24 daylight at polar stations.
    Even on the ISS they keep to a 24 hour schedule [which I think is Texas time] as they circle the earth every 90 minutes.
    Not wanting to derail the thread but I wonder how the people of this world think of it's shape?
    Their habitable world is probably a fairly long and relatively thin strip [favouring the daylight over the dark...], probably with lots of storms as the climate get stirred up by the heat differential. Would North and South mean anything? Would the talk about Sunward and Darkward?
  9. DeathtoTrite

    DeathtoTrite Troubadour

    So the habitable section would be a ring where the sun is low in the sky. The large, consistent temperature gradient causes extreme and regular weather. There's a great article here-


    I don't know if there is a paywall, but the most relevant section is-

    "One important issue is the concept of time. With no day-night cycles, concept of time will be
    difficult to come. On Earth right from birth, we notice that many phenomena in nature are
    repetitive. This is due to our most basic natural clock, viz. the rotation of the Earth, causing the
    rising and setting of the Sun, giving rise to alternative periods of light and darkness. All human
    and animal life has evolved accordingly, keeping awake during the day-light but sleeping
    through the dark night. Even plants follow a daily rhythm. Of course some crafty beings have
    turned nocturnal to take advantage of the darkness, e.g., the beasts of prey, blood—sucking
    mosquitoes, thieves and burglars, and of course astronomers.

    At least there might be no astronomers on a tidally-locked planet, as starry sky may not be
    known (except for some rumours about it by adventurer fellows daring to venture deeper into
    darker side of the planet). Secrets of the Universe − planets, stars, Milky-way, other galaxies −
    all these might remain very difficult, if not outright impossible, to unravel. Just imagine, it took
    us humans thousands of year to figure out that a few "wandering stars" are heavenly bodies
    (planets) in just our neighbourhood and all this happened in spite of the fact that a starry sky is
    daily visible most places for about half of the time (night). How will the inhabitants of a tidallylocked
    planet ever know about it when their everlasting "hot summer afternoons" never turn
    into cool evenings and dark nights?"

Share This Page