9 ms·

The U in UTC stands for Universal. If we can't use UTC for whole universe, or even for the nearby solar system, should we rename it Coordinated Global or Earth

The U in UTC stands for Universal. If we can't use UTC for whole universe, or even for the nearby solar system, should we rename it Coordinated Global or Earth Time (GTC or ETC) instead?

greggsy 3y ago
GTC is easily confused with Galactic Time, which will likely cause mass havoc a rewrites in dead languages like Imperial C and Scala sometime after the year 48,000AD.
- kijin 3y ago
  A true visionary must plan for job security for millennia to come. Next on the todo list: code up a Kwisatz Haderach to do your all your data modeling work while you slack off. On a more serious note, Galactic Time probably won't be useful because relativity introduces too much irreconcilable error at that scale. We'll be back in the early days of the railroad when every station had their own clock, adjusted to local noon.
- randomdata 3y ago
  Not to mention that universal, by definition, refers to earth already. Universal does not relate to universe any more than carpet relates to car.
zokier 3y ago
Terrestrial Time is a thing: https://en.wikipedia.org/wiki/Terrestrial_Time https://en.wikipedia.org/wiki/Terrestrial_Time > TT is indirectly the basis of UTC, via International Atomic Time (TAI). Nobody is going to bother renaming UTC at this point, misnomer or not. Besides, if they stop adding leap seconds to UTC (as is planned) the whole point of UTC goes away anyways.
belter 3y ago
You should not because on Earth, where gravity is relatively strong compared to the Moon, time runs slightly slower due to the gravitational time dilation effect. This means that clocks on Earth tick slightly slower compared to identical clocks in a region of weaker gravity, such as on the Moon's surface. So the UTC is from Earth perspective. From rough calculations, the time experienced on the surface of the Moon is 0.99999999999848 times the experienced on Earth
- nerdjon 3y ago
  I have seen references to this but I am constantly confused by how this is actually a thing. There was a video I watched that stated that in some situations 2 identical clocks that are in perfect working order, that if one of them was on a ship and doing certain things (that is purposefully vague since I don't remember) that if that ship came back to earth it would have a different time. It is one of those things that really boggles my mind, even though it fascinates the hell out of me. If you have any resources to read or watch on this (the video I watched was space time I think) I would love it.
  - akdev1l 3y ago
    this phenomenon is called “time dilation” you can search for it. Not trying to be a dick, just not qualified to explain this myself
    - nerdjon 3y ago
      Honestly that helps, just having a name to look for instead of somehow making a google search out of this will help.
      - 7thaccount 3y ago
        There is also time dilation from motion through space (motion through space + motion through time is equal to the speed of light, so as you speed up, your motion through time slows down) as well as time dilation due to gravity (like when near a black hole I think). I'm also not a physicist, but read some popsci books in my youth like "A brief history of time" from Stephen Hawking (it's written for normal people). That's probably the best book you'd want. He later wrote a more modernized version called "a briefer history of time" as well. They both cover time dilation from a high level iirc. Of course, to truly understand you'd need to learn the math. I'm looking forward to doing that during retirement in a few decades.
  - belter 3y ago
    Maybe this one: "Does the Past Still Exist?" - https://youtu.be/GwzN5YwMzv0 https://youtu.be/GwzN5YwMzv0
ta1243 3y ago
You can't use any time for observers in different reference frames as the length of a second will be different. UTC is generally fine as far as normal time goes as we're all in roughly the same reference frame on Earth, and indeed anywhere in the Solar System. It would still drift by noticeable milliseconds per year, but we can cope with leap seconds just fine with UTC and that's a larger drift. You'd probably want to avoid leap seconds and use TAI though, but we should avoid leap seconds anyway IMO.
belter 3y ago
"Falsehoods Programmers believe about Time" - https://hn.algolia.com/?q=Falsehoods+Programmers+believe+about+Time https://hn.algolia.com/?q=Falsehoods+Programmers+believe+abo...
hbrav 3y ago
I'm afraid it becomes even worse when you learn that the concept of 'simultaneous' is ambiguous.
gadders 3y ago
Go back to GMT. Embrace tradition.
shawncampbell 3y ago
ETC. Time, etcetera. I like that. There's something poetic about it.
andrewla 3y ago
What you are describing is not just impractical, it is actually impossible. Someone linked to "falsehoods programmers believe about time" but I think maybe "falsehoods non-physicists believe about time" might be more apt. There is no such thing as a universal frame of reference is the somewhat depressing outcome of Einstein's theories.
- Retric 3y ago
  You can select a rest frame based on the velocity of all observable galaxies adjusted for the expansion of the universe and the impact of local sources of gravity. As far as we can tell any observer would come to similar conclusions about that reference frame would be. It’s just not a particularly useful reference.
  - nyrikki 3y ago
    There is no objective concept of 'now' even at distance scales of Alpha Centauri with reasonable curvature and speeds. If you want to stick to special relativity, the Andromeda paradox will show the problem with simultaneity with distance, and Einstein's train thought experiment about trains will show the problem of simultaneity with high speed. The order of events, timing of events, and even causal structure of events are not fixed. Even the Conventional Celestial Reference System is only quasi-inertial, only inertial like over small periods of time. The incredible smoothness of the earth approximating a co-rotating frame with a high error tolerance is the only reason we can treat time as absolute on the surface of the Earth. But to derive the new definition of the Kilogram requires lots of corrections as do modern atomic clocks. Don't confuse the ability to choose a reference frame with the Newtonian concept of universal reference frames. When making measurements SR is a framework that allows you to pick any reference frame that is convenient, but the speed of causality(light) prevents the existence of a universal reference frame.
    - numpad0 3y ago
      I don’t get it, can’t you just set off neutron bomb every second on Earth and use it as a monotonic counter signal? Isn’t that like, speed of light or wavefront of event propagation in the universe isn’t consistent but unavoidably potato shaped - but if so, wouldn’t it be at least difficult to have multiple potatoes intersecting, or potato being shaped like Klein bottle? Self intersecting potato shaped space-time would be cool, though.
GuB-42 3y ago
We can use (Earth based) UTC on the moon, or on the whole universe for that matter. The problem is that on the moon, due to relativistic effects, a UTC second is not really a second, it is slightly longer, and that makes it inconvenient for conducting experiments on the moon. So for moon-based operations, moon time will be used, it can then be converted to UTC for "universal" operations. It is not the first time we use different clocks. In fact, we already have plenty: UT0, UT1, TAI, etc... That's because the Earth rotation is not that great at timekeeping, atomic clocks do better, but we still want our days to be aligned with the sun, so depending on whether you are more interested in the Earth rotation or in precisely counting seconds, you will use different clocks, with UTC being a compromise you can always convert to. GPS time is one such example, it is a few seconds off UTC because it doesn't account for leap seconds. All that is not even accounting for local (earth) time zones.
- ant6n 3y ago
  Aren’t seconds different based on latitude, as well as elevation? Should we perhaps have many more time zones than the 30 or so we have now, all requiring occasional leap-ms to sync up to UTC?
foxyv 3y ago
Time dilation is a bit of a PITA. https://en.wikipedia.org/wiki/Gravitational_time_dilation#:~:text=For%20example%2C%20considered%20over%20the,clock%20set%20at%20sea%20level https://en.wikipedia.org/wiki/Gravitational_time_dilation#:~....
deleted 3y ago
[deleted]
randomdata 3y ago
> should we rename it Coordinated Global or Earth Time (GTC or ETC) instead? No, why? Universal is already defined as referring to earth (the world). From the Oxford Languages dictionary: u·ni·ver·sal – of, affecting, or done by all people or things in the world

The U in UTC stands for Universal. If we can't use UTC for whole universe, or even for the nearby solar system, should we rename it Coordinated Global or Earth Time (GTC or ETC) instead?

greggsy 3y ago

GTC is easily confused with Galactic Time, which will likely cause mass havoc a rewrites in dead languages like Imperial C and Scala sometime after the year 48,000AD.

kijin 3y ago
A true visionary must plan for job security for millennia to come. Next on the todo list: code up a Kwisatz Haderach to do your all your data modeling work while you slack off. On a more serious note, Galactic Time probably won't be useful because relativity introduces too much irreconcilable error at that scale. We'll be back in the early days of the railroad when every station had their own clock, adjusted to local noon.
randomdata 3y ago
Not to mention that universal, by definition, refers to earth already. Universal does not relate to universe any more than carpet relates to car.

zokier 3y ago

Terrestrial Time is a thing: https://en.wikipedia.org/wiki/Terrestrial_Time https://en.wikipedia.org/wiki/Terrestrial_Time > TT is indirectly the basis of UTC, via International Atomic Time (TAI). Nobody is going to bother renaming UTC at this point, misnomer or not. Besides, if they stop adding leap seconds to UTC (as is planned) the whole point of UTC goes away anyways.

belter 3y ago

You should not because on Earth, where gravity is relatively strong compared to the Moon, time runs slightly slower due to the gravitational time dilation effect. This means that clocks on Earth tick slightly slower compared to identical clocks in a region of weaker gravity, such as on the Moon's surface. So the UTC is from Earth perspective. From rough calculations, the time experienced on the surface of the Moon is 0.99999999999848 times the experienced on Earth

nerdjon 3y ago
I have seen references to this but I am constantly confused by how this is actually a thing. There was a video I watched that stated that in some situations 2 identical clocks that are in perfect working order, that if one of them was on a ship and doing certain things (that is purposefully vague since I don't remember) that if that ship came back to earth it would have a different time. It is one of those things that really boggles my mind, even though it fascinates the hell out of me. If you have any resources to read or watch on this (the video I watched was space time I think) I would love it.
- akdev1l 3y ago
  this phenomenon is called “time dilation” you can search for it. Not trying to be a dick, just not qualified to explain this myself
  - nerdjon 3y ago
    Honestly that helps, just having a name to look for instead of somehow making a google search out of this will help.
    - 7thaccount 3y ago
      There is also time dilation from motion through space (motion through space + motion through time is equal to the speed of light, so as you speed up, your motion through time slows down) as well as time dilation due to gravity (like when near a black hole I think). I'm also not a physicist, but read some popsci books in my youth like "A brief history of time" from Stephen Hawking (it's written for normal people). That's probably the best book you'd want. He later wrote a more modernized version called "a briefer history of time" as well. They both cover time dilation from a high level iirc. Of course, to truly understand you'd need to learn the math. I'm looking forward to doing that during retirement in a few decades.
- belter 3y ago
  Maybe this one: "Does the Past Still Exist?" - https://youtu.be/GwzN5YwMzv0 https://youtu.be/GwzN5YwMzv0

ta1243 3y ago

You can't use any time for observers in different reference frames as the length of a second will be different. UTC is generally fine as far as normal time goes as we're all in roughly the same reference frame on Earth, and indeed anywhere in the Solar System. It would still drift by noticeable milliseconds per year, but we can cope with leap seconds just fine with UTC and that's a larger drift. You'd probably want to avoid leap seconds and use TAI though, but we should avoid leap seconds anyway IMO.

belter 3y ago

"Falsehoods Programmers believe about Time" - https://hn.algolia.com/?q=Falsehoods+Programmers+believe+about+Time https://hn.algolia.com/?q=Falsehoods+Programmers+believe+abo...

hbrav 3y ago

I'm afraid it becomes even worse when you learn that the concept of 'simultaneous' is ambiguous.

gadders 3y ago

Go back to GMT. Embrace tradition.

shawncampbell 3y ago

ETC. Time, etcetera. I like that. There's something poetic about it.

andrewla 3y ago

What you are describing is not just impractical, it is actually impossible. Someone linked to "falsehoods programmers believe about time" but I think maybe "falsehoods non-physicists believe about time" might be more apt. There is no such thing as a universal frame of reference is the somewhat depressing outcome of Einstein's theories.

Retric 3y ago
You can select a rest frame based on the velocity of all observable galaxies adjusted for the expansion of the universe and the impact of local sources of gravity. As far as we can tell any observer would come to similar conclusions about that reference frame would be. It’s just not a particularly useful reference.
- nyrikki 3y ago
  There is no objective concept of 'now' even at distance scales of Alpha Centauri with reasonable curvature and speeds. If you want to stick to special relativity, the Andromeda paradox will show the problem with simultaneity with distance, and Einstein's train thought experiment about trains will show the problem of simultaneity with high speed. The order of events, timing of events, and even causal structure of events are not fixed. Even the Conventional Celestial Reference System is only quasi-inertial, only inertial like over small periods of time. The incredible smoothness of the earth approximating a co-rotating frame with a high error tolerance is the only reason we can treat time as absolute on the surface of the Earth. But to derive the new definition of the Kilogram requires lots of corrections as do modern atomic clocks. Don't confuse the ability to choose a reference frame with the Newtonian concept of universal reference frames. When making measurements SR is a framework that allows you to pick any reference frame that is convenient, but the speed of causality(light) prevents the existence of a universal reference frame.
  - numpad0 3y ago
    I don’t get it, can’t you just set off neutron bomb every second on Earth and use it as a monotonic counter signal? Isn’t that like, speed of light or wavefront of event propagation in the universe isn’t consistent but unavoidably potato shaped - but if so, wouldn’t it be at least difficult to have multiple potatoes intersecting, or potato being shaped like Klein bottle? Self intersecting potato shaped space-time would be cool, though.

GuB-42 3y ago

We can use (Earth based) UTC on the moon, or on the whole universe for that matter. The problem is that on the moon, due to relativistic effects, a UTC second is not really a second, it is slightly longer, and that makes it inconvenient for conducting experiments on the moon. So for moon-based operations, moon time will be used, it can then be converted to UTC for "universal" operations. It is not the first time we use different clocks. In fact, we already have plenty: UT0, UT1, TAI, etc... That's because the Earth rotation is not that great at timekeeping, atomic clocks do better, but we still want our days to be aligned with the sun, so depending on whether you are more interested in the Earth rotation or in precisely counting seconds, you will use different clocks, with UTC being a compromise you can always convert to. GPS time is one such example, it is a few seconds off UTC because it doesn't account for leap seconds. All that is not even accounting for local (earth) time zones.

ant6n 3y ago
Aren’t seconds different based on latitude, as well as elevation? Should we perhaps have many more time zones than the 30 or so we have now, all requiring occasional leap-ms to sync up to UTC?

foxyv 3y ago

Time dilation is a bit of a PITA. https://en.wikipedia.org/wiki/Gravitational_time_dilation#:~:text=For%20example%2C%20considered%20over%20the,clock%20set%20at%20sea%20level https://en.wikipedia.org/wiki/Gravitational_time_dilation#:~....

deleted 3y ago

[deleted]

randomdata 3y ago

> should we rename it Coordinated Global or Earth Time (GTC or ETC) instead? No, why? Universal is already defined as referring to earth (the world). From the Oxford Languages dictionary: u·ni·ver·sal – of, affecting, or done by all people or things in the world