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I agree with everything you said, I just don't see why we need both UTC and TAI. That is, I don't understand why we insist on keeping UTC synchronized with Eart

by moefh 2y ago

I agree with everything you said, I just don't see why we need both UTC and TAI. That is, I don't understand why we insist on keeping UTC synchronized with Earth's orientation. On the one hand (like you said before), UTC is what we use for stuff like ordering transactions, which has absolutely nothing to do with the position of the Sun in the Sky. And on the other hand, we already use timezones to reconcile the rough position of the Sun with our universal clock. Timezones only have resolution of 1 hour (or half in very few places), but looking at how fudged a lot them are, people don't really seem to care. I mean, look at Argentina, which fits almost perfectly in UTC-4 but chooses to use UTC-3 instead. China is even crazier, using a single time in its whole territory which could easily have 3 or 4 different timezones.

bloppe 2y ago
At it's core, UTC is about reconciling 2 different clocks; the Earth (basically represented by UT1) and the Cesium atom (represented by TAI). It's a useful basis for Civil time -- which is naturally political -- because everybody seems to intuitively agree that seconds should be defined by the Cesium standard but days should be aligned with the Earth's rotation. It's not guaranteed that all governments would pick the same if forced to pick only one of the two. That would make time zones even harder. Sure, people in Western China may regularly see the sun at midnight, but that's not without controversy. People generally like the sun to be out when they're up. So I think it makes sense to have both UTC and TAI. If the BIPM just turns UTC into TAI plus a constant offset, then I'd wager they would eventually introduce another system to take the place of the former UTC, with leap seconds, so some people can have that system that reconciles the two clocks if they want it. It's hard to predict the future. But the reasoning in the GCPM resolution [1] seems inherently flawed to me. "recalling that the CGPM at its 26th meeting (2018) ... stated that UTC is the only recommended time scale for international reference" is the core of the problem. TAI should be the ultimate basis. UTC is based on TAI (with leap seconds), and civil time based on UTC. [1]: https://www.bipm.org/en/cgpm-2022/resolution-4 https://www.bipm.org/en/cgpm-2022/resolution-4

by moefh 2y ago

bloppe 2y ago

At it's core, UTC is about reconciling 2 different clocks; the Earth (basically represented by UT1) and the Cesium atom (represented by TAI). It's a useful basis for Civil time -- which is naturally political -- because everybody seems to intuitively agree that seconds should be defined by the Cesium standard but days should be aligned with the Earth's rotation. It's not guaranteed that all governments would pick the same if forced to pick only one of the two. That would make time zones even harder. Sure, people in Western China may regularly see the sun at midnight, but that's not without controversy. People generally like the sun to be out when they're up. So I think it makes sense to have both UTC and TAI. If the BIPM just turns UTC into TAI plus a constant offset, then I'd wager they would eventually introduce another system to take the place of the former UTC, with leap seconds, so some people can have that system that reconciles the two clocks if they want it. It's hard to predict the future. But the reasoning in the GCPM resolution [1] seems inherently flawed to me. "recalling that the CGPM at its 26th meeting (2018) ... stated that UTC is the only recommended time scale for international reference" is the core of the problem. TAI should be the ultimate basis. UTC is based on TAI (with leap seconds), and civil time based on UTC. [1]: https://www.bipm.org/en/cgpm-2022/resolution-4 https://www.bipm.org/en/cgpm-2022/resolution-4