Galactic Timekeeping

[fenderzilla]

Imagine that, in the future, the human race achieves interstellar travel and comes into contact with many other interstellar civilizations, and that communication is achievable between these civilizations and ourselves. How would dates work? If a document said, for example, "this event happened on the eighteenth of november, 2022," how would he aliens know what the heck we were talking about? Days, and years are subjective to the planet on which they are recorded. I suppose that yes, the aliens could come to earth and say "Oh, so that's how fast it spins, and that's how fst it orbits. So that would mean that... this is exactly what they mean by 'day', and this is what they mean by 'year'." But it would be very complicated for each and every civilization to have its own way of writing down dates.

My idea is that we would choose a star (preferrably the largest star in the galaxy for clarity) let's say UY Scuti, and track how long it takes to make a full revolution around the galactic center. This length of time would be known as a "Galactic Cycle" or a "Scuti Revolution" or something, and fractions of it would be used instead of years. So we could say, for example, that Spacejam came out 1/24586956.304406th of a Galactic cycle ago.

I would love to hear your opinions on this. (by the way, how far is UY Scuti from the galactic core and how long does it actually take to go around once?)

[baggers]

Nah, stars don't really "orbit" in a galaxy. Yes, they make a revolution in about 230 millions years (for the sun), but this is pretty random and subject to big variations from one rotation to another.

This is how our star make a revolution in milky galaxy:

Please note another thing: in less than 16 sun milky way revolutions, a big, big thing will make a ....ing mess:

https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_collision

[Shpaget]

Once (if) we encounter another space faring civilization and after (if) we establish diplomatic relations (read: not get wiped out) we will certainly need to agree on some system.

That system will probably be imposed by the more advanced/populous side. If at the time of encounter we have a single space ship wandering around the nearby stars while the other side has dozens or thousands of colonies, or even already established relations with other civilizations, we are going to accept whatever system they already have in place and vice versa.

Also, remember that even here on Earth we still haven't synchronized the time keeping standards across the globe.

[Thomassino]

We will probably agree on mutual time, which would be used in interactions between us and aliens, probably based on atom nucleus oscillations (like our own, it's exact, better than orbit of a star). On the other hand, I think Earth will keep its time for "Earthy stuff". It has been here for centuries and it's almost perfect, so will probably do aliens.

EDIT: imagine we are trying to agree on a mutual time on a meeting. How are we gonna agree when the meeting will be? And if one side wouldn't miss it by, let's say, 20 hours?

Edited August 10, 2015 by Thomassino

[ChrisSpace]

Demand everyone else uses our absurd Geocentric timekeeping system, or else.

[K^2]

Pulsars. Enough said.

[Shpaget]

Pulsars. Enough said.

Not quite. Pulsars are good enough at timekeeping for our Earthly standards, however, on astronomical time scales, they are not stable, meaning that distant observers will observe different frequencies.

[SargeRho]

Half Life of Tritium? It's undoubtedly going to be an important element even for very advanced species.

[Shpaget]

Honestly it doesn't need to be important, as long as it's known.

Also, at almost 12 and a half years, it's quite imprecise.

Furthermore, it (and pulsar) only provides a base unit. What about the rest of the "calendar"? We base our time system on the second, but don't use it in calendars, do we?

Let me go back to my first post here. Why do you assume there will be any discussion about it? Whoever establishes a wide system dictates what it looks like, unless a very convincing argument arises. If a newcomer doesn't like it, he can use conversions to adjust it to his needs.

Just like we now on Earth have multiple calendar systems, and if you happen to live in a country that doesn't use Gregorian calendar you are pretty much forced to convert to it if you want to do business with any western country that does use it, because a large US or European company will probably just return any document using something else.

[YNM]

Multiples of hydrogen spin-flip transition is pretty much eternal and mutual (how can we tell that they know caesium ? Better to bet on hydrogen). More of a problem will be distance and relativity. For date system, guess it's going to be better if we use a decimal year system, where it'll contain the month, days, hours, minutes, and second already. Long live french revolution xD

[RainDreamer]

I think by that point we possibly also have technology that is capable of using quantum entanglement to sync time across great distance.

[andrewas]

You can't communicate by quantum entanglement.

But we dont need to. Everyone agrees on a time signal, and uses that to translate between their own systems. No one has to live on universal time, it's just an intermediate, so unless someone is already broadcasting a suitable signal, we can just use a convinient pulsar.

[RainDreamer]

You can't communicate by quantum entanglement.

Well, yeah, but if we have quantum clocks that are entangled, then we don't need to communicate, we just need to know that the result from observing them will always be the same no matter where they are. Or is there something wrong with that?

[Shpaget]

That is still transfer of information.

[PB666]

Nah, stars don't really "orbit" in a galaxy. Yes, they make a revolution in about 230 millions years (for the sun), but this is pretty random and subject to big variations from one rotation to another.

This is how our star make a revolution in milky galaxy:

http://www.slate.com/content/dam/slate/blogs/bad_astronomy/2013/03/04/sunpath_milkyway.jpg.CROP.original-original.jpg

Please note another thing: in less than 16 sun milky way revolutions, a big, big thing will make a ....ing mess:

https://en.wikipedia.org/wiki/Andromeda%E2%80%93Milky_Way_collision

The sun as you know it won't be around then to view the spectacle, by then it will have thrown off its gas into space and become a smouldering soft-glowing chunk of coal with no interior planets.

The only plausible universal time would be a static point at the center of inflation that we can neither proves exists or ever hope to see. Every object move away faster than the speed of light during inflation and subsequently expanded close to the speed of light with expansion, so that now everything is can only reference its own space-time. You can select any clock for any space and use it, but referencing other parts of the universe is virtually useless.

Edited August 10, 2015 by PB666

[K^2]

Not quite. Pulsars are good enough at timekeeping for our Earthly standards, however, on astronomical time scales, they are not stable, meaning that distant observers will observe different frequencies.

Doesn't matter. Everyone is going to get their pulse at whatever delay they get it at, and that's the local time. And while the clock rate is going to be different in different parts of the galaxy due to the more distant areas getting older signal, the change is easily predicted. It might not be the most convenient time unit for actual day-to-day activities, but it gives us a simple way to synchronize clocks across the galaxy. What we actually decide to be the length of "one second", or whatever, is totally arbitrary, as you've pointed out. Computers will do actual time-keeping and conversions, anyhow. And pulsar pulse count can be the equivalent of the Epoch.

[o Atomsk]

Is it wrong that I found it funny that there would possibly two records of timekeeping, similar to the metric and US measuring systems? A lot of parts of the world handle measurements of everything differently than the US. There are parts of the country that have different methods of record keeping according to their own belief system, and possibly mathematical perspective. And we're all on the same planet.

As much as a galatic timekeeping would be fun, realistically I would have to agree with YNM that relativity would play a big part. Something closer to a black hole would generate a higher relativity, leaving the measure of a year possibly being 7 years somewhere else. Logically deriving, I would say any kind of travel among any solar systems would be like visiting any country on Earth - where you change timezones depending on your location and the placement of the sun, how you accept how they track their own record keeping but you can translate it to your own timekeeping of choice. Yet instead of following the sun we would be following distance, lightyears, and relativity and use a method of translation.

I'm not a physicist though, so I might not have the best scientific background to provide the more scientifically accurate perspective.

[livefree75]

Use atomic clocks, and set up a universal "stardate" similar to that in Star Trek.

Pros:

-Very precise

-Position doesn't matter

Cons:

It might be difficult agreeing on a standard unit of time. (e.g. does one unit equal 3,000,000,000,000 oscillations of the cesium-3 atom or 4,000,000,000,000?)

[baggers]

Use atomic clocks, and set up a universal "stardate" similar to that in Star Trek.

Pros:

-Very precise

-Position doesn't matter

Cons:

It might be difficult agreeing on a standard unit of time. (e.g. does one unit equal 3,000,000,000,000 oscillations of the cesium-3 atom or 4,000,000,000,000?)

And what about time distortion when approaching ligth-speeds? counting 3x10^12 cesium-3 oscillations in a spacecraft watch may not take the same "time" on another target planet?

[Cydonian Monk]

Timekeeping? Well, the second is a somewhat well defined measure of time, though getting an exact value of it can be tough. Coordinating the second with whatever other power we're talking to would be a first step. Probably one of the first-year Computer Science projects would be writing a routine to convert between SquishyHumanTime and BlargTime, much like we now write Roman Julian to Gregorian programs.

Telling what "year" it is would be more difficult. Even in the western world we have many common timescales, one measured from 1AD (AD/BC or ACE/BCE), one measured in time "Before Present" in which present is defined as January 1st, 1950 (BP). And then there's the only timescale that matters - the Unix Epoch - seconds ellapsed since 00:00:00 January 1st, 1970. You could throw in Macintosh Time too, but that's largely irrelevant now that Mac is Unix. And that's only dealing with Western European calendars.

"Years" and days and whatnot in the far future would probably be replaced by some multiple of seconds, perhaps in powers of 2 or 10s. That's assuming we don't kill each other while squabbling over our different calendars first.

[heng]

this is exactly what they mean by 'day', and this is what they mean by 'year'."

Mwhahahahha:

The hypothetical aliens would be very confused by our timekeeping...

[magnemoe]

Mwhahahahha:

The hypothetical aliens would be very confused by our timekeeping...

How do you get around timezones on an planet? that is unless you are tidal locked or day is stupidly long.

One option is to use an global time and just move working hours and night around the clock, it would keep one time but might even be more problematic, clock it the same but its dark outside and the shops open two hours later.

For online stuff from meeting to webcasts and MMO its just as smart to use Zulu time/ GMT like nato does as they regularly has to do operations over multiple time zones.

- - - Updated - - -

We don't really need aliens for this, teraforming mars is enough. Now length of day on Mars is so close to earths they might keep seconds and just use either shorter hours or an short hour to even out.

Keeping minutes and seconds the same help for an lots of issues from cooking books to computer games.

Year is another issue, you are likely to use Mars year for farming and summer holidays birthdays and religious holidays will use the earth calendar.

Easiest just to use an conversion like we do between various measurements today. Even with faster than light travel the physiological effects of different lengths of day will be more off an issue than various clocks and calendars.

Without faster than light it would be no reason to use an unified time at all outside of perhaps an agreed reference.

[ChrisSpace]

mwhahahahha: The trouble with timezones (youtube, 10min)

aaahhh my braiiinnn!!!

[Cydonian Monk]

Mwhahahahha:

And then you discover somebody included all these timezones into your OS, but inverted half of them because the original programmer intended for them to be offsets from local while every subsequent programmer thought they were offsets from UTC, and that EEST is suddenly somewhere in the mid Atlantic. And then you wonder why people think it's odd that you're drinking from a flask at one in the afternoon......

[o Atomsk]

Mwhahahahha:

The hypothetical aliens would be very confused by our timekeeping...

ogod.