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Interestellar Timekeeping
alexmakepeace
Member Posts: 10,633 Arc User
So here's something I've been pondering recently in the course of writing fiction. Suppose that we eventually reach out into space, establish colonies, meet other races and form a unified federation of planets. In this diverse nation, how do we keep time? The basic units we use now (days and years) are based on natural cycles particular to Earth. A day or a year on Mars is different from a day or year on Earth, which is different still from a world rotating around a star.
You could use local time for the basic "daily" cycles, but how do you synchronize planets with different year lengths? How do you know when to expect the next interstellar passenger shuttle, or when to celebrate the centennial anniversary of the formation of the federation?
And what about colonies where normal cycles don't apply, such as a planet with an atmosphere that blocks most light, or a colony on a satellite rotating a gas giant, or even a rogue planet flying off through space without a star? What happens if we eventually reach a state where we're not only an interstellar society, but an intergalactic one?
We could use the galactic cycles, but those are so incredibly long it seems like they would be unwieldy. In the time it takes for one galactic year to pass, Earth's continents could move from their current configuration to become a supercontinent. Would other celestial objects like pulsars make better reference points?
Any thoughts?
You could use local time for the basic "daily" cycles, but how do you synchronize planets with different year lengths? How do you know when to expect the next interstellar passenger shuttle, or when to celebrate the centennial anniversary of the formation of the federation?
And what about colonies where normal cycles don't apply, such as a planet with an atmosphere that blocks most light, or a colony on a satellite rotating a gas giant, or even a rogue planet flying off through space without a star? What happens if we eventually reach a state where we're not only an interstellar society, but an intergalactic one?
We could use the galactic cycles, but those are so incredibly long it seems like they would be unwieldy. In the time it takes for one galactic year to pass, Earth's continents could move from their current configuration to become a supercontinent. Would other celestial objects like pulsars make better reference points?
Any thoughts?
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Everything after that is just colloquialisms...which serve us much better than Metric time would, thank you very much (I'm American and therefore have an innate dislike of the Metric system). For interstellar purposes starships from a given stellar nation will probably just use the standard day of their homeworld.
Presumably if some kind of international standard was absolutely needed, we'd just use SI prefixes on the second:
Terasecond: 1,000,000,000,000 seconds (30,619.24 years)
Gigasecond: 1,000,000,000 seconds (30.62 years)
Megasecond: 1,000,000 seconds (11.57 days)
Kilosecond: 1,000 seconds (16.67 minutes)
Hectosecond: 100 seconds (1.67 minutes)
Decasecond: 10 seconds
Presumably the "hectosecond" would serve as one metric minute, and might be colloquially referred to as the "hex".
There's no convenient SI equivalent for an hour or day. We'd just have to get used to the idea of getting about 28.8 kiloseconds of sleep each night.
Actually, I'm fairly certain that the Apollo mission did use metric. That's standard for scientific applications.
But why a second? Seconds are just as arbitrary as minutes or hours. They don't correspond with any specific physical phenomena (as far as I know). Wouldn't it make more sense to base your unit of time on something with a fixed cycle? Unless it's more important to use a familiar system.
Edit: It occurs to me that changing the method by which time is measured also changes the measurement of distance because our standard unit is the light year: the distance light travels in one Earth year.
But since you guys mentioned it, and because I'm pro-metric, eh, maybe change it this way:
1000 milliseconds = 1 second (already exists)
100 seconds = 1 minute
100 minutes = 1 hour
10 hours = 1 day
Not sure if my math's correct, but that day would be 100,000 seconds as opposed to the current 86,400 seconds. Just an extra 3 hours 46 mins a day.
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Yes, they do correspond to a specific physical phenomena - I defined it in my post. One second is equal to 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 caesium 133 atom.
Why it is equal to 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom is something that's not known to me off the top of my head, but I'm sure there's some bright person around here who can tell you why.
The point being that anything you choose will always be arbitrary in some form. The gram is defined as the mass of one cubic centimeter of pure water at the melting point of ice. Why water? Why not mercury, or bromine? For that matter, the meter was originally one one-millionth of the distance between the equator and the north pole. It's currently defined as the length of the path traveled by light in vacuum during a time interval of 1/299,792,458ths of a second.
Measurement is always arbitrary. We have defined the second now, though, and so might as well keep using it, since the ground state of the caesium 133 atom presumably tends to undergo 9,192,631,770 periods in the same amount of time no matter where you are. Unless you're close to a very, very high gravity well, anyway, but in that case you're probably dead.
Actually the light year is informal. Professional astronomers use the parsec, the distance at which one astronomical unit subtends an angle of one arcsecond.
An astronomical unit is the average distance of Earth from the Sun; an arcsecond would take too long to explain, so I'll let Wikipedia handle it.
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What's more arbitrary is why a gramme is the mass of one cubic centimetre and not one cubic metre. A metre is reasonably large, a litre is reasonably large, the volt, candela, amp, etc. are all largish. So why are the gramme and bel so small?
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So why not a cubic lump of iron or something? Or gold?
Norway and Yeager dammit... I still want my Typhoon and Jupiter though.
JJ Trek The Kelvin Timeline is just Trek and it's fully canon... get over it. But I still prefer TAR.
#TASforSTO
'...I can tell you that we're not in the military and that we intend no harm to the whales.' Kirk: The Voyage Home
'Starfleet is not a military organisation. Its purpose is exploration.' Picard: Peak Performance
'This is clearly a military operation. Is that what we are now? Because I thought we were explorers!' Scotty: Into Darkness
'...The Federation. Starfleet. We're not a military agency.' Scotty: Beyond
'I'm not a soldier anymore. I'm an engineer.' Miles O'Brien: Empok Nor
'...Starfleet could use you... It's a peacekeeping and humanitarian armada...' Admiral Pike: Star Trek
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That's helpful. I'm familiar with AUs and arc minutes, but I wasn't familiar with the specifics of their use.
Here's part two of my question that delves more into culture and evolution than creating rational standards. How would a civilization developing on a Titan-like moon orbiting a gas giant measure its time? Could such a planet have seasonal variations of some sort? If your atmosphere is opaque, you can't measure the passing months by the stars like we do, and perhaps even sunlight would have difficulty penetrating your atmosphere.
A cubic meter of water weighs about 1000 kg, whereas the same volume of iron weighs about 7,874 kg.
Say nothing of 1 cubic meter of gold, which weighs about 19,282 kg!
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Norway and Yeager dammit... I still want my Typhoon and Jupiter though.
JJ Trek The Kelvin Timeline is just Trek and it's fully canon... get over it. But I still prefer TAR.
#TASforSTO
'...I can tell you that we're not in the military and that we intend no harm to the whales.' Kirk: The Voyage Home
'Starfleet is not a military organisation. Its purpose is exploration.' Picard: Peak Performance
'This is clearly a military operation. Is that what we are now? Because I thought we were explorers!' Scotty: Into Darkness
'...The Federation. Starfleet. We're not a military agency.' Scotty: Beyond
'I'm not a soldier anymore. I'm an engineer.' Miles O'Brien: Empok Nor
'...Starfleet could use you... It's a peacekeeping and humanitarian armada...' Admiral Pike: Star Trek
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Extra challenges will be for relativistic travel. And without relativistic travel and without faster than light travel, it's irrelevant to be able to translate something like the time of day - it would take millenia to travel.
What unit of measurements we use is mostly arbitrary. Some units existed before they were standardized, and the standard definition was chosen to be very close to typical values used before.
I suppose something like Planck time and Planck length, as well as the electron charge would be a more objective base for measurements - but also very impractical, if you always have to operate with Tera or Peta as prefix to talk about meaningful values in every day life.
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The number 9,192,631,770 was chosen simply because it was the integer amount that was closest in length to the previous definition of the second (1/31,556,925.9747 of the mean tropical year circa AD 1900).
Atomic-based time measurement has the advantage of being (theoretically) absolutely stable due to the whole quantization-of-energy stuff--there are no too-small-to-notice fluctuations in the duration of the transition--either it transitions between the two levels, or else it fails to transition or transitions to some other level instead. In fact, by our current understanding of physics, any variations in the duration of the transition are the result of a variation in the speed of time itself due to relativistic effects (motion, gravity, etc.).
***
Anyway, the whole issue with different planets having their own day and year length (and different civilizations having their own time units), plus relativistic effects, is why Starfleet uses the Stardate system for timekeeping instead of any given member civilization's traditional calendar. We don't know the in-universe reason for why one thousand Stardate base units equals approximately one Earth year (the TV production reason was for season progression--41xxx was 1st season of TNG, 42xxx was 2nd season, etc.). Perhaps it's the length of a standard Starfleet duty shift (between eight and nine hours)?
While for us the measurement of a second can be measured with great accuracy, what happens if you encounter a civilization that has never discovered Ceasium 133? all your measurements will be meaningless to them.
That's why I would personally use the universes natural clocks the pulsars! They are regular and regardless of the amount of our time quanta that we measure them in the amount of time between pulses will be the same for everyone. So all we and they have to do is say when a ship leaves planet 'A' that pulsar should pulse 'X' number of times before a ship arrives at planet 'B'.
Simples!
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By the way, humankind learned about the cesium-method BEFORE we discovered pulsars (pulsars were discovered in the 1960s!), so saying that we should use pulsars "because cesium is too high of a tech hurdle" doesn't really pan out.
Are there other celestial objects with a cyclic pattern? What about the rotation of the galaxy? It's too long to be a useful unit in and of itself, but we defined a year as 100,000,000th of a Galactic year?
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What if someone uses a different pulsar? They don't all pulse at the same rate, I don't think.
Not learning about cesium, even if it's rare on their planet, is vanishingly unlikely. It's an element, the existence and even some properties of which can be predicted when the aliens start assembling a periodic table of elements, something they'll have to do to start reaching advanced technology and studying their world closely - conversely if they're not the sort to go about investigating their world, this suggests that they're not the sort to try for space travel, either, and so colloquial methods of telling time would be sufficient to them.
Besides, astatine (atomic number 85) and berkelium (atomic number 97) are both very rare elements on Earth, but we know about them.
Mind, there's no particular reason that I'm aware of to use cesium-133 over any other radioactive isotope, further compounding the issue.
Tons of things, but none of them are unique and so there's no reason to assume that an alien race would pick one of them over any other, i.e., there's nothing that makes the pulsar Centaurus X-3 a better choice than Vela X-1.
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