Why the U.S. Wants To End the Link Between Time and Sun • Hacker News Board

Re: Why the U.S. Wants To End the Link Between Time and Sun

#51

Post by sageikosa » Wed, Aug 29, 2012, 6:01 PM UTC

But whose clock do we trust? No clock on this planet is in an inertial frame of reference. Over time, clocks at different latitudes and altitudes will diverge because they are moving at different speeds, even if they have the same atomic decay "tick" process. Which do we pick as the standard?

Even if one clock were picked, observations of when the clock ticked would vary over the planet as well.

Astronomical distant fixed points are more stable over long time spans than Earthbound clocks or the Earth's rotational and orbital characteristics, and the relative displacement with regard to Earthbound distance is negligible.

Re: Why the U.S. Wants To End the Link Between Time and Sun

#52

Post by ta12121 » Wed, Aug 29, 2012, 6:50 PM UTC

mdonahoe wrote: post #17

I was expecting something more like Swatch Internet time. http://en.m.wikipedia.org/wiki/Swatch_Internet_Time Why must time be be earth centric? Imagine how hard it must have been for Copernicus to convince everyone to use his model. Lazy programmers isn't as compelling argument, but it has similarities. http://en.m.wikipedia.org/wiki/Copernican_Revolution Non-rhetorical questions: Does the Mars Curiousity rover use…

    Why must time be earth centric?

Because time is ultimately for human end users, and humans live on Earth.

Re: Why the U.S. Wants To End the Link Between Time and Sun

#53

Post by wmf » Wed, Aug 29, 2012, 6:58 PM UTC

agwa wrote: post #47

> leap seconds present a "risk to air travel in the future" because a glitch might shut down traffic-control systems. This downright scary if true - a system that's not robust and fault tolerant enough to withstand a leap second bug without putting lives in danger is going to suffer from other bugs which will put lives in danger. Since software development practices actually tend to be very paranoid when it comes to…

A "leap hour" would presumably require changing the UTC-equivalent itself.

Earlier I proposed exactly the opposite. Never change UTC, just redefine your timezone to create an apparent leap hour. Since we already do this twice a year in many countries, it should be less of a problem.

Re: Why the U.S. Wants To End the Link Between Time and Sun

#54

Post by adjwilli » Wed, Aug 29, 2012, 8:45 PM UTC

pixie_ wrote: post #32

adjwilli wrote: post #15

I was hoping this was a more radical proposal like http://en.wikipedia.org/wiki/Swatch_Internet_Time was. Our current way of measuring time is absurd. It starts as base 1000 with milliseconds, then base 60 with seconds and minutes, then 24 for hours, 7 for days, 4.3whatever for months or 28-31 however you want to track it. I like that China only has one time zone for the entire country. We should all go by UTC times…

Swatch Internet Time sounds awful. Your idea to go from intuitive measurements of time to abstract measurements sounds awful. A single timezone for a 3,000 mile wide country sounds awful.

Admittedly, a single timezone for the world might be a bit far fetched. But there's nothing intuitive about 60 seconds in a minute, 60 minutes in a hour, then all of a sudden 24 hours in a day, and roughly 4.3 weeks in a month or somewhere between 28 and 31 days in a month. The only numbers in our calendar that are vaguely intuitive is 3 months in a season and 265 days in a year, and even those have problems.

Re: Why the U.S. Wants To End the Link Between Time and Sun

#55

Post by agwa » Wed, Aug 29, 2012, 10:48 PM UTC

wmf wrote: post #53

agwa wrote: post #47

> leap seconds present a "risk to air travel in the future" because a glitch might shut down traffic-control systems. This downright scary if true - a system that's not robust and fault tolerant enough to withstand a leap second bug without putting lives in danger is going to suffer from other bugs which will put lives in danger. Since software development practices actually tend to be very paranoid when it comes to…

A "leap hour" would presumably require changing the UTC-equivalent itself. Earlier I proposed exactly the opposite. Never change UTC, just redefine your timezone to create an apparent leap hour. Since we already do this twice a year in many countries, it should be less of a problem.

Interesting idea! So basically every several hundred years we would shift the center of time farther and farther away from Greenwich. That explains why the British are opposed. I was thinking timezones would stay relative to Greenwich and the "leap hour" would be thousands of accumulated leap seconds applied at once. Your proposal sounds better.

Re: Why the U.S. Wants To End the Link Between Time and Sun

#56

Post by wmf » Wed, Aug 29, 2012, 11:43 PM UTC

weavejester wrote: post #49

Alternatively, just store times using system that's already divorced from the rotation of the Earth, such as Unix Time.

Isn't Unix time UTC, which includes leap seconds which is what is causing all these glitches?

Re: Why the U.S. Wants To End the Link Between Time and Sun

#57

Post by bloat » Thu, Aug 30, 2012, 7:41 AM UTC

agwa wrote: post #47

> leap seconds present a "risk to air travel in the future" because a glitch might shut down traffic-control systems. This downright scary if true - a system that's not robust and fault tolerant enough to withstand a leap second bug without putting lives in danger is going to suffer from other bugs which will put lives in danger. Since software development practices actually tend to be very paranoid when it comes to…

> The only thing appealing about this is that we'll all be long dead by then.

I'm going to use this line a lot in all my future planning meetings.

Re: Why the U.S. Wants To End the Link Between Time and Sun

#58

Post by kamjam » Thu, Aug 30, 2012, 8:15 AM UTC

freehunter wrote: post #46

kamjam wrote: post #27

Earlier quoted context omitted.

I know it's a joke, but it's lazy programming/lazy thoughts like this that caused the issues with the systems in the first place :) Although I still don't fully understand why leap seconds caused such a problem - we can handle leap years and we can handle daylight savings, surely this is just another clock correction action such as these?

The problem with programming for a leap second is you don't know when a leap second will occur. Compare this to a leap year, which happen every 4 years, always. Leap seconds are sporadic [1]. Programming a clock to accept the time of 11:59:60 only on occasion is trivial in a web app, but slightly more complex in a firmware or high-reliability system like flight controls. [1] https://en.wikipedia.org/wiki/Leap_second#…

Thanks for the explanation, makes sense. I see what you mean about the sporadic nature of the insertions!

Re: Why the U.S. Wants To End the Link Between Time and Sun

#59

Post by weavejester » Thu, Aug 30, 2012, 9:18 AM UTC

wmf wrote: post #56

weavejester wrote: post #49

Alternatively, just store times using system that's already divorced from the rotation of the Earth, such as Unix Time.

Isn't Unix time UTC, which includes leap seconds which is what is causing all these glitches?

No, Unix Time is the number of seconds since a fixed origin. In human time the origin is usually expressed in terms of UTC time, but Unix Time itself is divorced from Earth's rotation. Leap seconds only have to be taken into account when converting into human dates and times.