How to tell time
Moving off earth means a lot of things change. And if we not only get off earth, but manage to colonize other star systems, they change a lot.
On Earth we have our "simple" 24 hour clock, with 60 minute hours and 60 second minutes.
Those numbers are actually a lot better than most folks think. 24 is evenly divisible by 2, 3, 4, 6, 8 and 12. That makes it easy to split things up for shifts and the like. The sometimes suggested "decimal time" only lets you divide the day into 2 or 5 chunk without dealing with odd fractions.
And 60 is divisible by 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30.
So a standard day will likely remain 24 hours/ 1440 minutes/ 86,400 seconds.
Now, on Mars or some hypothetical planet around another star the length of the "solar day" is going to be different. And it's important to not get the local day and the standard day confused.
I'm going to assume that we will follow the lead of the folks monitoring the various Mars landers and use sol for the local solar day.
We will want to divide the sol into useful periods. And do some *evenly*.
Why? consider colonists on Mars. The sol is an important unit, because many/most outdoor activities are going to depend on sunlight.
One commonly seen proposal is that we just keep hours, minutes, etc. That's kind of doable, but a royal pain.
Consider Mars. A mean Martian solar day, or "sol", is 24 hours, 39 minutes, and 35.244 seconds.
The guys on graveyard shift are not gonna appreciate having that extra 40 minutes in their shift.
And once you have more than one base on the planet (unless they are very close to each other, you have to deal with timezones. So that make the extra "40" minutes happen at different times of day depending on your longitude. Ick. That make things worse.
I've seen folks suggest that the extra time always be inserted between 2400 and midnight.
That means that the time difference between different bases will vary with time of day! Yeah, computers could handle that, but it'd still be a pain.
We could just use centisols, millisols, etc. But that runs into the same problems that decimal time did on Earth.
So, we need to divide the sols into a *convenient* number of chunks. We *don't* want to call the chunks hours, minutes and seconds as there are far too many critical things that depend on those terms having a fixed duration.
For example, how long a power unit or air tanks will last. Don't want to have to worry about whether it'll last for 8 standard hours or 8 "Martian hours".
So we need a different term for the subdivisions of the sol. Long ago (I've been thinking about this for something like 30 years) I came up with "peri (plural: peris) from "period".
David Brin came up with dura/duras in his Uplift books.
We will eventually need *several* names, because there may be multiple inhabited planets in a system. And it'd help avoid confusion if each had their own name for their hour equivalents.
How many duras you want to divide the sol into depends on the length of the sol. You'll still want numbers that divide up easily for shifts. But you'll (probably) want to keep duras not *too* far off from hours. This is a bit of a balancing game, and I'll go into suggestions on that another time.
When the sol is really short or really long we may want to combine several actual sols into the "legal" sol, or vice versa. Consider Luna. 28 days is a bit much to deal with. making the "legal" sol 1/28th of the actual sol would be a lot more convenient.
Though, come to think of it, we might want a different term for these fraction & composite sols.
Now let's go in the other direction. We need a term for the local year. Latin and other Romance languages are out because they are too close to annum and annual, which are terms we need to keep the current meaning of.
Greek proves to be an acceptable choice. Etos is the Greek word. Not apt to be confused with anything else (unless you are a Greek. :-)
The length of months varies enough on the standard calendar that we may be able to get away with re-using the term.
Weeks are a different matter. There are consumables and other things that are rated in weeks. Plus "week" gets *way* tied into various religions (I'll deal with *that* can of worms in another post).
Which brings up another matter. synchronization.
Let's use Mars as an example. Say it's 0000 hours on Sunday at both a base on Earth and one on Mars.
7 sols later it'll be 0437 on Sunday on Earth.
14 sols: 0914 Sunday
28 sols: 1828 Sunday
40 sols: 0223 Monday
That 's right. In 40 sols, Earth is more than a day ahead of Mars.
So there *will* be local clocks and calendars on any planet where you go outside with any frequency and where dayligh makes a difference.
Places where that's not true can happily continue on UTC.
This entry was originally posted at https://kengr.dreamwidth.org/1076041.html. Please comment there using OpenID.
On Earth we have our "simple" 24 hour clock, with 60 minute hours and 60 second minutes.
Those numbers are actually a lot better than most folks think. 24 is evenly divisible by 2, 3, 4, 6, 8 and 12. That makes it easy to split things up for shifts and the like. The sometimes suggested "decimal time" only lets you divide the day into 2 or 5 chunk without dealing with odd fractions.
And 60 is divisible by 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30.
So a standard day will likely remain 24 hours/ 1440 minutes/ 86,400 seconds.
Now, on Mars or some hypothetical planet around another star the length of the "solar day" is going to be different. And it's important to not get the local day and the standard day confused.
I'm going to assume that we will follow the lead of the folks monitoring the various Mars landers and use sol for the local solar day.
We will want to divide the sol into useful periods. And do some *evenly*.
Why? consider colonists on Mars. The sol is an important unit, because many/most outdoor activities are going to depend on sunlight.
One commonly seen proposal is that we just keep hours, minutes, etc. That's kind of doable, but a royal pain.
Consider Mars. A mean Martian solar day, or "sol", is 24 hours, 39 minutes, and 35.244 seconds.
The guys on graveyard shift are not gonna appreciate having that extra 40 minutes in their shift.
And once you have more than one base on the planet (unless they are very close to each other, you have to deal with timezones. So that make the extra "40" minutes happen at different times of day depending on your longitude. Ick. That make things worse.
I've seen folks suggest that the extra time always be inserted between 2400 and midnight.
That means that the time difference between different bases will vary with time of day! Yeah, computers could handle that, but it'd still be a pain.
We could just use centisols, millisols, etc. But that runs into the same problems that decimal time did on Earth.
So, we need to divide the sols into a *convenient* number of chunks. We *don't* want to call the chunks hours, minutes and seconds as there are far too many critical things that depend on those terms having a fixed duration.
For example, how long a power unit or air tanks will last. Don't want to have to worry about whether it'll last for 8 standard hours or 8 "Martian hours".
So we need a different term for the subdivisions of the sol. Long ago (I've been thinking about this for something like 30 years) I came up with "peri (plural: peris) from "period".
David Brin came up with dura/duras in his Uplift books.
We will eventually need *several* names, because there may be multiple inhabited planets in a system. And it'd help avoid confusion if each had their own name for their hour equivalents.
How many duras you want to divide the sol into depends on the length of the sol. You'll still want numbers that divide up easily for shifts. But you'll (probably) want to keep duras not *too* far off from hours. This is a bit of a balancing game, and I'll go into suggestions on that another time.
When the sol is really short or really long we may want to combine several actual sols into the "legal" sol, or vice versa. Consider Luna. 28 days is a bit much to deal with. making the "legal" sol 1/28th of the actual sol would be a lot more convenient.
Though, come to think of it, we might want a different term for these fraction & composite sols.
Now let's go in the other direction. We need a term for the local year. Latin and other Romance languages are out because they are too close to annum and annual, which are terms we need to keep the current meaning of.
Greek proves to be an acceptable choice. Etos is the Greek word. Not apt to be confused with anything else (unless you are a Greek. :-)
The length of months varies enough on the standard calendar that we may be able to get away with re-using the term.
Weeks are a different matter. There are consumables and other things that are rated in weeks. Plus "week" gets *way* tied into various religions (I'll deal with *that* can of worms in another post).
Which brings up another matter. synchronization.
Let's use Mars as an example. Say it's 0000 hours on Sunday at both a base on Earth and one on Mars.
7 sols later it'll be 0437 on Sunday on Earth.
14 sols: 0914 Sunday
28 sols: 1828 Sunday
40 sols: 0223 Monday
That 's right. In 40 sols, Earth is more than a day ahead of Mars.
So there *will* be local clocks and calendars on any planet where you go outside with any frequency and where dayligh makes a difference.
Places where that's not true can happily continue on UTC.
This entry was originally posted at https://kengr.dreamwidth.org/1076041.html. Please comment there using OpenID.