What would a suitable measurement for time be that can be used universally? [duplicate]

I have recently been trying to come up with a measurement of time, such as years, seconds, etc, that can be used irrespectively of galactic location and universe location.

Star-treks stardate was quite an elegent, albeit fictional solution. Reading articles such as How Stardates work, a stardate still fundamentally has the roots in Earth's perception of a century, related to the birth of Jesus, this obviously is not transferable to other worlds.

Because relativistic properties are almost minute for speeds less than $$\frac{c}{10}$$ Formulation of speeds that start to require relativistic properties, and that speeds of bodies within a galaxy such as our sun are around $$\frac{c}{1300}$$, got from a galatic year, my original thought was that:

1. The datetime format could be prepended with a galaxy identifier
2. Then add maybe some rotational number of the galaxy since its birth

But then I am not sure how to progress into measuring the rotational number, and that it also needs a time measurement since the big bang and the birth of the galaxy, which then begs the question of at what stage can a galaxy be considered to be birthed?

Another perspective is that our current definiton of a second, and I then got led onto an optical lattice clock, but I am still unsure of how to apply these universally.

Any help or suggestions would be great.

You want a system that everyone across the galaxy can observe together and has a regular periodicity. The solution is Pulsars

Pulsars are highly regular rotating neutron stars that emit beams of electromagnetic radiation from their poles. While not all pulsars are good enough for the most precise time keeping, the regularity of millisecond pulsars is even more precise than the most precise atomic clock.

For example, the brightest one in our sky is PSR J0437−4715 rotating every 5.75 milliseconds at a distance of around 510 lightyears. Civilizations wanting to synchronize their clocks could refer to the number of rotations of this pulsar since record keeping began.

• I quite like this idea, but need to read up more. A system of universal datetimes contain galactic identifiers, and a system of active pulsars relative to each other in order to keep track of time for the deaths of pulsars. What would you suggest as a good event for the start of record keeping to be that all galaxies observe? Oct 18 '19 at 6:14
• @jupiar Pulsars are formed when a supernova collapses into a neutron star (which spins as a pulsar). So the creation date of the observed pulsar would mark the beginning of its time keeping. Oct 19 '19 at 0:29
• Yeah thats a pretty good point. Although the process of becoming a neutron star would introduce datetime conversion errors of well over a second.. from all the answers so far I think I am finding the best way is for civilizations across the universe to syncronize their times with a common fixed time keeping event, and then using Planck time with some mathematical equation to then convert between the two. Oct 19 '19 at 6:20
• Are pulsars detectable everywhere, or only on the cone swept by the beam? Nov 22 '19 at 18:24
• @AntonSherwood I don't know. This would be a good question for Astronomy SE. Nov 22 '19 at 22:01

Why do you need a universal time measurement?

You can treat time intervals (such as years) as we treat currencies between countries. You have to pay tax to Empire Capital at Earth per one earth-year? Just convert that time measurement to your planet's years and collect local taxes on basis of that.

I would argue that one a multi-starsystems empire you cannot have many things universal as we can have on earth. For example, currency. You just have to trade on basis of what a particular planet want AND what do you want. Same would have to work for taxations. As in Foundation Series by asimov Earth may be more interested in some agricultural crop that you have plenty of, so trade in that, and give taxes in that, not in any currency.

When you are travelling you primarily focus on spaceship time, when you land at some planet you take into account time there but only as long as you stay there. Once you are in space again you dont worry about length of their days and durations of their years and number of crops they can have per their-year and so on. Empire Center should also not worry about such locality-specific matters, especially when it has a multi-star empire to manage. It need to worry only about what it can get from each of its province-planets in taxes and in trade etc; and what it has to give back to them, basically in security, and let locals administer themselves. Just control some key resources and you are ok.

• That actually makes a lot of sense, and most likely combined with the response from Gython and Planck time, would provide the basis for being able to convert time measurements from one civilization to another. Oct 18 '19 at 9:52

Time is nothing but events. If you have any idea how much time passed between two events it's only because other events happened between those events.

Since your time measurement is meant to be universal let's make it about the universe. It started with the big bang and it'll end with the heat death. So why not just measure every moment in time as some value between 0 and 1 between those events? This sets the bounds of our system.

Or between 1 and 0 so we can have a good countdown. Well crap, so much for universal. Now people will have an endian war over which to use.

As for the events between 0 and 1, I recommend something everyone can observe, which excludes pulsars that have to be pointing at you to work. I recommend an atomic clock and an accelerometer so you can predict what an atomic clock at rest would have measured. That lets you standardize the precision of the system.

As for synchronizing the more macro "when we are" event I'd look for a unique event such as the gravity wave created when black holes collide. Periodic events risk arbitrary choices of when to start counting.

• Interesting idea, what would you think would be a good system to divide up the time intervals between the two events 0 and 1? Oct 18 '19 at 6:12
• @jupiar better now? Oct 18 '19 at 13:00