Planetary ages (exoplanets)

[takadote26]

Long story short, in my storylines which are 'set' on different planets, characters seem much older than they are (for example I just learnt that on planet Mars a 'full year' consists of 687 days, whereas Earth only has 365 days in its rotation)- how to resolve this problem? Not to mention planet Saturn's years are even worse. Tldr; characters' ages are often very wonky because planets rotate differently around the sun- leading to a 56 year old character having the body AND stamina of a 30 year old (because Martian age)

Also, planet Mars is a totally and completely different setting to Earth because no trees and plants and also volcanoes everywhere.

 

[Madman Starryteller]

Can you have something like universal time in your stories? Based on say... Earth time? Or some other standard?

 

[Hammer]

You'll need to standardise time. Not really as drastic at it sounds - here in the UK we only used to have two times - time to go to work, and time for a beer. As we evolved we added bedtime and lunchtime. When trains could travel the whole width of the country in a couple of hours, we needed to synchronise our clocks - up until then it only mattered to mariners so that they could navigate by the stars...

Day length varies massively for different planets too - a day here on earth is, famously, 24 hours. On venus it's nearly six thousand.

You will need the equivalent of a metric hour and a metric month. We used to have Greenwich Mean Time here on Earth, but that is now called "Universal Standard Time" - you will need Universal Space Time...

 

[Homer Potvin]

What everybody else said... standardize time. That'll apply to everything, as length of day from sunrise to sunset will be different everywhere and may (or may not) be relevant. A planet with a six standard hour day for example, probably won't have normal sleep and working schedules. And there would probably be a standard GMT style clock needed for planets to talk to each other, if that's a thing.

 

[Naomasa298]

What everybody else said... standardize time. That'll apply to everything, as length of day from sunrise to sunset will be different everywhere and may (or may not) be relevant. A planet with a six standard hour day for example, probably won't have normal sleep and working schedules. And there would probably be a standard GMT style clock needed for planets to talk to each other, if that's a thing.

What he said.

Long story short, in my storylines which are 'set' on different planets, characters seem much older than they are (for example I just learnt that on planet Mars a 'full year' consists of 687 days, whereas Earth only has 365 days in its rotation)- how to resolve this problem? Not to mention planet Saturn's years are even worse. Tldr; characters' ages are often very wonky because planets rotate differently around the sun- leading to a 56 year old character having the body AND stamina of a 30 year old (because Martian age)

Also, planet Mars is a totally and completely different setting to Earth because no trees and plants and also volcanoes everywhere.

This makes no sense. Just because the time Mars takes to orbit the Sun is twice as long as that of Earth, that doesn't mean people of the same species would live twice as long on Earth that they do on Mars. If someone lives on Earth for 60 Earth years, their twin brother on Mars is going to have been alive for the same amount of time, and, ignoring gravity and all the rest of the other stuff, they will be the same physical age. That 30 year old Martian has the body of a 60 year old Earthman.

Unless time in your universe works differently.

 

[Stuart Dren]

You know, it never occurred to me that wormhole-telephoning someone on another planet might be like calling Japan from the West.

I would love it if a story played into this trope, with characters being woken up in the middle of the night, and a good number of the other conversational halves being half asleep or irate.

 

[X Equestris]

Unless your humans are integrating into a wider, established galactic community with their own standards, it makes sense to standardize the year off of Earth. T-years (Terran-years) these are called in the Honor Harrington series. In the first book, the main character references herself as “almost twenty-four years old”, but because Manticoran years are about 630 T-days long, she also notes this makes her “over forty Terran standard years”, and her biological age would likewise be in the forties if she wasn’t the recipient of medical treatments that drastically slow aging.

Hours, minutes, and seconds all make sense to leave untouched. They’d work well enough wherever you apply them. If a planet doesn’t rotate way faster or slower than Earth, you could leave the definition of day as “one full rotation” and recognize the difference between local days and “T-days”. But on somewhere like Venus, where the local day is outrageous, days would probably be set as 24 hours.

 

[Dante Dases]

This makes no sense. Just because the time Mars takes to orbit the Sun is twice as long as that of Earth, that doesn't mean people of the same species would live twice as long on Earth that they do on Mars. If someone lives on Earth for 60 Earth years, their twin brother on Mars is going to have been alive for the same amount of time, and, ignoring gravity and all the rest of the other stuff, they will be the same physical age. That 30 year old Martian has the body of a 60 year old Earthman.

Unless time in your universe works differently.

Yeah, I'm a bit confused about how OP is thinking here, too. Some things change on different planets - bone and muscle density to name two - but not linear time unless there is a gravitational time dilation issue. And if that's the case, it's not telling the story I think it needs to.

I refer all and sundry to Mostly Harmless. A year on the planet Arthur Dent finds himself on is 300 days, which is regarded as good because it means the year doesn't drag by. A day is 25 Earth hours, which Arthur finds good for two reasons: one, an extra hour in bed every morning; two, he could change his watch every day, a pleasant little task.

 

[takadote26]

Unless your humans are integrating into a wider, established galactic community with their own standards, it makes sense to standardize the year off of Earth. T-years (Terran-years) these are called in the Honor Harrington series. In the first book, the main character references herself as “almost twenty-four years old”, but because Manticoran years are about 630 T-days long, she also notes this makes her “over forty Terran standard years”, and her biological age would likewise be in the forties if she wasn’t the recipient of medical treatments that drastically slow aging.

Hours, minutes, and seconds all make sense to leave untouched. They’d work well enough wherever you apply them. If a planet doesn’t rotate way faster or slower than Earth, you could leave the definition of day as “one full rotation” and recognize the difference between local days and “T-days”. But on somewhere like Venus, where the local day is outrageous, days would probably be set as 24 hours.

Well, in my storyline humans co-exist with a more exoplanetary society (Martians, Jovians, Saturnalians and Venusians exist), so there are varying ages amongst the colonists of Mars, Saturn and Jupiter, the Venusians are another factor... But for now I'm focusing on planet Mars as a setting, and so the ages of the colonists on Mars are not syncing well with Earth-time. (I am referring to late 00's tropes, and also I'm trying to be realistic)

 

[Naomasa298]

Well, in my storyline humans co-exist with a more exoplanetary society (Martians, Jovians, Saturnalians and Venusians exist), so there are varying ages amongst the colonists of Mars, Saturn and Jupiter, the Venusians are another factor... But for now I'm focusing on planet Mars as a setting, and so the ages of the colonists on Mars are not syncing well with Earth-time. (I am referring to late 00's tropes)

That's not a late 00s trope, or one from any other era. Just because someone describes themselves as "being 30 (Martian) years old", it doesn't mean that's the same physical state as a 30-year old Earthman. They're going to be physically similar to a 60 year old Earthman. You don't magically get a longer life by moving further away from the Sun.

 

[Stuart Dren]

Long story short, in my storylines which are 'set' on different planets, characters seem much older than they are (for example I just learnt that on planet Mars a 'full year' consists of 687 days, whereas Earth only has 365 days in its rotation)- how to resolve this problem? Not to mention planet Saturn's years are even worse. Tldr; characters' ages are often very wonky because planets rotate differently around the sun- leading to a 56 year old character having the body AND stamina of a 30 year old (because Martian age)

Also, planet Mars is a totally and completely different setting to Earth because no trees and plants and also volcanoes everywhere.

You can also just lean into the wonky age, depending on how much it helps emphasise the interplanetary relationships. I agree with others that using a universal standard time for measuring things like age would be sensible. You can do a bit of both. There might be some Martian pride evident where they refuse to use Earth standard years.

characters' ages are often very wonky because planets rotate differently around the sun- leading to a 56 year old character having the body AND stamina of a 30 year old (because Martian age)

I think the way this is worded is confusing some people. However, I suspect what you're saying is that a 56 Earth-years-old person has the body and stamina of a 30 Mars-years-old person.

 

[Homer Potvin]

I think the way this is worded is confusing some people. However, I suspect what you're saying is that a 56 Earth-years-old person has the body and stamina of a 30 Mars-years-old person.

Yeah, it's like saying somebody who is 183 centimeters is much taller that somebody who is 60 inches, because you're comparing nonstandard units of measure. Can you clarify that, please @takadote26 ? It's veering the discussion unnecessarily unless you actually have people aging at different rates due to some magical/scientific mechanic.

 

[Louanne Learning]

The way an organism would age on any planet is not just due to the time passed (which is really only a measure, not the cause of aging), but environmental factors, like the force of gravity, the level of radiation (related to atmosphere, cloud cover), how toxic the air and soil is, etc.

If all of this is equivalent between two planets, then cells and organisms would age the same way, no matter how one unit of time is measured.

Have you taken into account Circadian rhythms? - Which are set to a 24-hour sleep-wake cycle/clock here on Earth

 

[takadote26]

Yeah, it's like saying somebody who is 183 centimeters is much taller that somebody who is 60 inches, because you're comparing nonstandard units of measure. Can you clarify that, please @takadote26 ? It's veering the discussion unnecessarily unless you actually have people aging at different rates due to some magical/scientific mechanic.

Ah, that's because I have a family set on planet Mars (as a colony) and I had their Earth ages and Martian ages, as shown here:

Family member​	Human years​	Martian age​
Rebecca​	120​	63​
Halycon​	56​	30​

Meanwhile, Laura's from Saturn so she'll be 40 years old in Earth years, but barely 1 year old on her own colony.

 

[Naomasa298]

This is not difficult to handle. Other than using a standardised time unit, we already deal with this in real life. We call a Martian day a "sol", because it is slightly different from an Earth day.

Timekeeping on Mars - Wikipedia

en.wikipedia.org

 

[Stuart Dren]

Ah, that's because I have a family set on planet Mars (as a colony) and I had their Earth ages and Martian ages, as shown here:

Family member​	Human years​	Martian age​
Rebecca​	120​	63​
Halycon​	56​	30​

Meanwhile, Laura's from Saturn so she'll be 40 years old in Earth years, but barely 1 year old on her own colony.

Yes, this is what I thought was going on, since since your math checked out in the first post. Earth being the biological origin, there's an incentive to refer to one's age primarily in Earth years. But again, no harm in leaning into it.