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Comment by remram | Hacker News Reader

You mean that from a remote place or fast-moving ship, the time on Earth would appear to go at a different speed? So local time would not just have a constant offset?

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If time is moving at a different speed, it wouldn't just be a constant offset. You'd also need a multiplier. Think of two cars moving at different speeds on a road. They don't stay the same distance apart.

Yea, but if we're going to use a "number of seconds since ..." Type system like Unix time, SOMEONE has to be the origin point, so I don't think this is a knock against Unix time.

Its unfortunate to use an accelerating reference (earth rotating sun, sun rotating galaxy, galaxy intermixing with andromeda) because it requires you to awkwardly keep track of the astronomy of earth for timekeeping. Instead, you would want a standardized reference time frame, say, "unix time assuming earth in 1970 never experienced any acceleratiom or dilation" and then everyone, including earth people, would track their acceleration and dilation offsets to be able to compare time when meeting or convert signal timestamps from any source back to their local time.

Quasar time plus position, motion vector, and acceleration vector should be a good enough reference for anybody.

You can't do math on that directly though. You'd still need to convert them to a common reference frame for comparison.

You would want some global reference time, and that could be a number of seconds passing on Earth. However locally you can't work with a clock that doesn't tick at a constant rate (if seconds on your spaceship go twice as fast, the crew can work with that; if the rate changes day-to-day as you accelerate, that's a problem).

In addition, you will probably want clocks that run at a given perceived speed, to time physical processes that take the same time everywhere (e.g. so your cookie recipe saying "bake for 600 seconds" work without translation).

Well we already have to keep track of the size and shape of Earth. Go and read the SI Brochure from the BIPM. Local measurements by atomic clocks on Earth have to be weighted according to how far they are from a reference surface of equal gravitational potential. There's a publication named Circular T that comes out every 5 days.

You don't need science fiction for this.

* https://www.bipm.org/en/bipm-services/timescales/time-ftp/Ci...

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