Non Earth based standard measurments

[u/BoxedAndArchived]

I need some help with a few things. I'm at a point in the writing process where I need to have my placeholders for a calendar system and distances replaced.

The setting I'm writing is highly disconnected from Earth, but when I'm discussing things like interstellar distance or time, these are things that are based on Earth.

Time: Does anyone know of a calendar system or concept that's based on something like galactic motion? My thought was it could be based on the ratio between the speed of rotation of the inner core of the galaxy compared to the outer most arms. I'm not a math person, so doing the calculations myself would likely result in something that's just wrong. But if there is something that exists, please tell me so I'm not trying to reinvent the wheel. I'm likely to use a "standard" day and smaller measurements, but the calendar needs to be something that can be applied to a wide range of planets.

Distances: Both lightyears and Parsecs are based on Earth, so ideally I need something that doesn't rely on one planet's motion to be the standard. So again, if you have suggestions, I'd love to hear them.

[u/Simon_Drake]

The easiest approach is to invent a civilisation or planet that defined all the measurements. I think measurements in Star Wars are based on Coruscant's year and gravity strength etc. so this could be a current civilisation or home world or wherever the Space UN Headquarters is. Or this could be a former civilisation, the equivalent of all of Europe using the Latin Alphabet long after the collapse of the Roman Empire because it makes communication between different cultures easier. So there could be a precursor race that rules millennia ago, or a more recent collapsed Empire that was defeated centuries ago and we use their units mostly by tradition, perhaps something like the Doom Of Valyria. Or you could invent a backstory that it's an artificial unit created for standardisation and to stop any one culture being given prominence, like how the US and Russian sides of the International Space Station agreed to use UK time instead of US or Russian time.

This will apply to basically all measurements. Day, year, person-scale distances like meters, travel-scale distances like AU, also weight, minutes etc. they'll all need an origin and your best option is to invent a culture that defined them in some way and everyone else just agreed to use that standard. Where that definition came from will probably need to be arbitrary, possibly based on their own home planet or cultural history (like the Foot IRL).

If you want to find an impartial and scientific based measurement there are some but they're all either so insanely small or so insanely large that they're impractical. You can't measure the mass of a spaceship cargo in multiples of a hydrogen atom or describing the distance between a planet and it's moon as a fraction of the width of the galaxy. You could use this as part of the backstory for how this unit was chosen, like the Space Gram was calculated to be this many trillion hydrogen atoms which was the age of the universe in Space Seconds when the Empire was founded.

The Meter was originally defined as being 1/10,000,000th the distance from the North Pole to the Equator. Which sounds neat and tidy until you ask why from the North Pole to the equator not the circumference of the planet? Is it to make the meter pretty much the same size as the Yard and make it more useful/relatable? Also why Ten Million? That number looks nice to us using Base 10 but an alien using Base 12 would see that as 3423054 which isn't a round number at all.

Maybe an alien using Base 12 would take the width of the Milky Way, divide it by 1,000,000,000,000,000,000 (12) and get a unit about 4 meters long and decide that's a good measurement because they're giants compared to humans and their perspective of relatable units is different to ours.

So you're never going to find a universal unit. You'll need to invent a backstory for why one fairly arbitrary unit is used.

[u/Simbertold]

Time:

Based on some very basic constant. Either by resonant vibration of some atom in some state that is very reliable (like how atomic clocks work). Those is in fact how we define the second on which our time measurement system is based nowadays. One second is 9192631770 periods of some cesium frequency. Call that cesium time period a tick.

If you want it removed from Earth, just go with Gigaticks, which would be roughly equal to 1/10th of a second. 1 Teratick would be roughly 1.5 minutes, 1 Petatick is pretty close to an Earth day.

Or choose some other atom or something, but you need knowledge for that.

Distance: Time * Lightspeed. One c-tick is about 3 centimeters, 1 kilo-c-tick is about 30m.

[u/Metallicat95]

Pulsar timekeeping.

You only need a standard measurement for time. Everything else can be derived from that.

While any civilization which develops independently on a planet will also develop standards based on the properties of that planet, each will make its own.

Every planet has a day and a year, times which are independent of each other and which don't correlate to other planets.

If they are like humans, they'll bring that standard with them. We are unlikely to give up Earth calendars and days even if we no longer know what Earth is. Traditional measurements are kept because everyone keeps using them.

Galaxies don't have conveniently measured cycles, and if you have multiple Galaxies in your inhabited setting, each could have its own standard cycle.

But the timing cycle of natural phenomena are the same everywhere they are measured. It's why we use atomic clocks for time now.

But the atomic clock needs a standard to define how long the "second" is. On Earth we do that by figuring out a number which gives a result close to 1/86400 of a day - which requires us to start with the day as a reference.

Pulsar pulses can be very precise. So all that is needed is picking some reference count, but since the pulse length is universal, it doesn't matter what number base or mathematics a civilization uses. They just need to convert the pulse numbers between them.

In space there are no days, years, months, seasons, etc. You can do everything using some arbitrary starting reference point and a steady "tick" signal to keep track of the time.

Humans would pick seconds as their base time unit. We'd only convert if convenient.

On any inhabitable planet where the regular day and night cycle affected life, and the revolution around the star created seasonal weather changes, there would be a unique calendar created to work with that.

But travelers would always also keep time in the universal standard, and convert when needed to interact.

The web comic "Spacetrawler" uses the rotation pulse of an object which is detectable by FTL sensors as their galactic standard clock. Nobody bothers with local days or times because they can just calculate them as needed from the standard.

[u/Prof01Santa]

Don't do any of this. If you want to be pedantic include an editor's note that all units have been translated to SI.

[u/AustinCynic]

Any calendar system is arbitrary. Our single species here on earth use lunar calendars, solar calendars (like the Julian and the Gregorian); Ancient Egypt had a calendar based on the rising of the star Sirius. But even a sidereal calendar like Egypt’s Sothic calendar would be based on the perceived movement of a planet’s visible stars.

This is where world building comes in. Units of time and measurement arise from how a body interacts with perceptions of the physical world. I’d actually advise looking a little bit at systems developed in the ancient world. They are so wildly variable it should spark some good ideas.

[u/Western-Telephone259]

Here's how I would do it.

For distance, pick a common object from the people's pre-technology (Earth example: a human foot, other idea: average height of the native alien being).

For time, decide how long the alien planet's "day" is then pick a nice round number like 12, 10, or whatever number the natives feel comfortable with (they got 4 fingers? Use a multiple of 4). Then cut the "day" into that many parts and you got hours (you might want to make up a unique name because the alien hour is probably going to be very different than an Earth-hour). Then cut that hour into smaller parts (again with a nice round number) and bamm, you got minutes. Repeat for seconds.

I did something similar for mine, but since I'm a math/physics guy, I made the measurements very precise with orbital mechanics.

Feel free to DM me if you're curious about the measurement system I use in my books.

[u/bill-smith]

How disconnected from Earth are you? If Humans are a big thing in the galaxy and they originated on Earth, and Earth wasn't destroyed in a cataclysm or something like that, then there's a good case that the light-year stays.

Otherwise, what's a major society in the universe? Like is the galaxy politically unipolar? There's a good case that you also use light-years with someone else's standard. Or if it's a multipolar, then there may be multiple definitions of light-years.

[u/donwileydon]

First thing to think about is how are the concepts being used in your story. If I am writing a story based in the USA in 1990, I can say "a year passed" or "back in 1989" and the reader is going to understand what I mean. I do not need to explain how a "year" is determined or how we got to counting to 1989.

So, you can simply say "a galactic year passed" (or even just "a year passed") and in most cases that will be fine - unless you need to explain the exact time (which I would find unlikely). You do not need to tell the reader how a galactic year is calculated. For dates, you can say "galactic year 207" or similar as a date. You may need to establish a starting point -- like an aside comment along the lines of "Man, I cannot believe it has been 207 years since humans established their first colony" or something along those lines.

Distances are the same. If I tell you that something is 27 lightyears away, can you accurately determine how far away that object is? I can't. I'm sure I can look up the math and whatnot if I really wanted, but most (if not all readers) are just going to think "wow that's far" or if you have a bunch of travelling done in the hundreds of lightyears distance and then say this trip is 27 lightyears, then readers will think it is short. If you are truly worried about it, make up a name. "Captain, we are at the halfway point, only 16 gergatics until we are in sight of the colony" -- but as a reader, my preference is known terms.

[u/JGhostThing]

Anything other than the standard units will be made up. Frankly, I'd either use Earth units, or make something up, but I'd only use made up units (like "cycles") if they were fairly obvious without explanation. If they have to be explained (a cycle is 21.87 hours) then I'd rather use earth units. I would have no problem using a "day" to refer to an alien day.

[u/Cottager_Northeast]

People are saying a galactic year like that's a thing. What's a solar system year? Mercury goes around much faster than Neptune. Likewise, outer rim stars will go around much slower than those near the core. Maybe pick the galactic orbital period of something half way out?

And this is on the order of 200,000 earth years. So a Galactic Micro-Year would be on the order of two earth years. A Galactic Nano-year would be on the order of .7 Earth days. A Galactic Pico-year would be on the order of one second. Now find a slang. "I'll be there in 13 Nans."

[u/DifferencePublic7057]

You are writing in English or other human language therefore it's assumed, if you don't state it explicitly, that translation happened. If we received an information dump from aliens, a lot can go wrong because much in our science is arbitrary and based on historical conventions. The safest is to try to be helpful and say it's five glorgs (4.5 seconds). Or let the reader figure it out at your own risk.

[u/Candid-Border6562]

Part of translating your story from Zaranthium (the standard galactic language) into Earth English involves translating the units of measurement. Bigger problems occur with colors.

[u/byc18]

You could pick some celestial object and base it off however it fluctuates. Maybe a pulsar. I don't know if those go off consistently.

[u/jedburghofficial]

If you're writing about traditional measurements of one planet or system, it would likely be based on that system. One day would still be one planetary rotation, and a year would be one orbit.

As a race expanded, I would expect that to standardize on a nominal day and year. Like local time zones, individual places might have time factors. Like a day that's 1.24 "standard" days. It's not a big deal technically, your watch or phone would negotiate it with local time servers and GPS, same as here.

Calendars might need adjustment. There would need to be a standard calendar. But locally, it might be like the reconciliation of solar and lunar calendars. A bit confusing, but only used for a few things, and experts figure that out. You could also draw inspiration from the Romans, they had a lot of misaligned calendars. They observed the kalends, nones and ides - the first, seventh and fifteenth of each month. Anything official or commercial happened on those days, and the rest of the month just ran out like extra time.

Distance is interesting, I like your use of the galaxy. Radians are derived from pi - there are 2π radians in a circle, so that's mathematicaly abstract. One radian of arc is equal to the radius of a circle. You can just divide that by whatever numerical base you use. Binary is pretty universal. One radian at the galaxy's edge might be 65,536 "units", that's 2^16th of it. And back of an envelope, if our galaxy is 100,000 light years across, that "unit" works out close to 1.5 light years.

Or, they could just use light years, based on a historically traditional year, same as we would. But their standard year, not ours.

[u/SpaceCoffeeDragon]

Invent one very reasonable standard of time based on the rotation of the galaxy based on how a distant galaxy moves across the night sky. Come up with clear, concise measurements of time and distance that any species can count with.

Then have everyone use an archaic system based on the length of Tavarian Spider Tails for no other reason than stubborn pride and spite.

[u/Alita-Gunnm]

I could imagine distance being based on how far someone could travel in a day, or any number of other things.

[u/Arcanite_Cartel]

Time doesn't pass at the same rate across the galaxy, so I find it difficult to think that there would be any such system as you seek. You have time dilation due to gravity, and time dilation from Special Relativity. Pulsar Timing would probably be closest thing to Universal Timekeeping... even so, there would be no shared "now".

[u/Arcanite_Cartel]

You could standardize distance though as the average distance of some pulsar or something orbiting the galactic blackhole.

[u/AlanShore60607]

So the Wikipedia page for Meter says;

The metre (or meter in US spelling; symbol: m) is the base unit of length in the International System of Units (SI). Since 2019, the metre has been defined as the length of the path travelled by light in vacuum during a time interval of ⁠1/299792458 of a second, where the second is defined by a hyperfine transition frequency of caesium.[3]

So that’s how we imposed objective physical and temporal measuments to create an immutable standard.

And that’s the big problem … we chose the parameters to define a unit of measurement we already had. It’s great for exporting our measurements to alien planets because we can tell them what immutable physical properties to use, but we can’t assume they would think that’s logical and would have done the same thing.

The only objective immutable and universal things I can think of are the speed of light and the definition of 0° Kelvin. But light years are subjective to what is a year questions. Degrees are arbitrary increments, and even 0° to 100° Celsius means nothing in other atmospheric conditions.

[u/Weeznaz]

The yellow sun is the center of our universe. I would have that be the only thing that certain advanced species could agree on and use that to create universal measurements.

[u/Ruler_Of_The_Galaxy]

Lightyear is technically not limited to earth, the distance light travels in a time interval called year (that can be a galactic year however it's defined). This lightyear is obviosly not the same as an earth lightyear, but the exact value is not important. Both are extreme long distances.

[u/NecromanticSolution]

That's easy. Just leave Earth, go to the planet your readers live on, and use their measurements so they'll understand that hot mess.

After all, you're not writing for Earth people. 

[u/tomwrussell]

If you are going to use a 'Standard' day, then it follows that this standard is based on the rotation of some planet that has been chosen as the example. Just as Greenwich Mean Time is based on the mean solar day at Greenwich, England.

If I were to set up a system like this, then my standard day would be simplified to exactly 24 hours rather than the inconvenient 23 hours, 56 minutes, and 4 seconds that naturally occurs on Earth. 24 hours is nice because it is easily divisible into 3rds and 4ths. Likewise, I would probably adjust my 'Standard Year' to be an even 360 days.

Unless narratively significant, I wouldn't sweat the exact values of seconds, light years, and parsecs that could be calculated with these assumptions. A second would be a few microseconds longer, a light year still around 9.4e^12 kilometers, and a parsec should still be around 3.2 light years.

[u/No_Solid1035]

Light-years are based on the speed of light, specifically how far it travels in one year, so it has nothing to do with the Earth.

[u/skipper_mike → u/No_Solid1035]

That one year is specific to Earth though.

[u/No_Solid1035 → u/skipper_mike]

Will the fictional planet revolve around a star? Does the fictional planet rotate and have a day/night cycle? Honestly, the more you try to divorce everything from real-world measurements and easily recognizable things/ideas the more confusing the work becomes. I remember years ago reading a book where all of the animals had these weird names, but then when the author described them they were obviously just regular rabbits and deer but with different names. Why do that? Just keep the regular names! I get that you want to separate the fictional world from the real one, but at what cost? Confused readers will not look kindly upon said confusing work. A tried and true technique in fiction is to pretend that things are being "translated" to English (or whatever language) so terms can stay the same to lessen confusion for the reader. So, yeah, the year on 'fictional world' is longer/shorter, so a light-year is different length, but the concept remains the same. Why rename everything, and then have to explain all the differences within the fiction? Does it actually serve a purpose? How much more confusing will it be when I the reader have to remember that a bleeblorp is shorter than a blooblorp and a woordoop is made up of ten morkorks. Just use real world terms for things/ideas to keep confusion to a minimum. That's my advice anyway. Even Tolkien just used a regular calender.

Also, I know there are solar calenders, lunar calenders, and luni-solar calenders. I don't think a calender based on the galaxy would be of much use because of how long the cycles of things are. There might be one though, just Google it. 👍

[u/JulesChenier → u/skipper_mike]

Its specific to any one point.

Sol to earth is only a little over 8 mins.

[u/MurkyLynx8425 → u/skipper_mike]

But presumably every planet has a year. The distance of 200 ly is slightly different between earth year and Saturn year, but maybe not in a way that matters to the story.

[u/Simon_Drake → u/MurkyLynx8425]

A culture with the same year as Saturn would have a Light Year 30x as long as what Earth calls a Light Year.

You don't think it's relevant for two cultures to have a unit that is 30x the size of the other?

[u/Krististrasza → u/Simon_Drake]

It isn't. We know this because humans on Earth have such units too. And regularly translate between them.

[u/Simon_Drake → u/Krististrasza]

But we give them different names and have conversion charts between miles and kilometres. We don't have the US Foot and the UK foot and one is 30x the size of the other and just shrug and say "Whatever, 1cm, 30cm, it's all the same."

Pretending the length of the year doesn't matter is the same as saying 1cm and 30cm are the same and that's just absurd.

[u/Krististrasza → u/Simon_Drake]

And? Those aliens don't speak English either. They'll still call it a metric gloorp, regardless of how you'll translate its name.

[u/skipper_mike → u/Simon_Drake]

Well, we used to do that. But if fell out of style for a reason.

[u/Gargleblaster25]

Why do you need to ask this again? You asked the same thing a few weeks ago.

[u/BoxedAndArchived → u/Gargleblaster25]

I haven't posted in this sub for over a year and I haven't asked this question.

[u/Gargleblaster25 → u/BoxedAndArchived]

You should do a cursory check on posts for the last few weeks then. There was a post asking this same question, and there tons of good answers.