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

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

#21

Post by lutusp »

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…

> Does the Mars Curiousity rover use leap seconds? Does it have Martian time too?

Both the Mars Curiosity rover, and its operators, use the Mars day duration (which is 24h 39m 35.24409s), but with time measured in "normal" seconds. The JPL people directly responsible for this project even switch to a Mars clock in their personal lives.

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

#23

Post by T-hawk »

sonnekki wrote: post #13
freehunter wrote: post #9

I fail to see how this is an attack on science or on Europe. That's just hyperbole. Making time consistent to prevent having to add time or remove time just makes sense. Time is a unit of measurement. We don't redefine the foot just because the new king has 10" feet instead of 12" feet. Time being connected to the sun is a relic of the days before accurate time-keeping methods. One day should always be one day. To re…

> Noon should always be noon In other words, given a point on Earth (or any planet) and it's angle relative to the sun it orbits, when that point aligns exactly with and faces the center of the sun, it is noon. Consider this: The way everyone refers to time is "X Units before noon", much like the 24-hour clock (no am/pm), except 0 is noon. The key is that X must be flexible, it should have no maximum, and no minimum.…

This is not literally true. The period between solar noons oscillates and varies up to tens of seconds away from precisely 12 hours, thanks to the differing orbital speed of the Earth between perihelion and aphelion. What you're referring to is "mean noon", true solar noon averaged over the course of a year. See "mean sun" : http://en.wikipedia.org/wiki/Mean_sun

More complications arise from the position of the Moon. The Earth's rotation is affected by tides (stronger when the Moon is at perigee), and by the Earth's orbit around the Earth-Moon barycenter. Precession of the Earth's rotational axis is also a factor. And many more astromechanical effects also subtly affect the timing of the apparent position of the Sun.

Locking our timekeeping to the actual position of the Sun actually proves to be an intractable problem. At some point, we need abstractions to simplify and assume that that the relation to the Sun is good-enough. Famously, the Julian calendar was good-enough for millennia until the relation to the sun drifted off true by more than 10 days. So arguing over leap seconds could be seen as rather trivial.

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

#24

Post by jmvoodoo »

I'm definitely looking forward to this debate when/if we ever have a permanent mars colony. Will they still use earth/solar time? Use mars/solar time? Some compromise between the two? I imagine someone living on mars could give two shits if the earth/solar time was off by a few seconds, and I definitely don't want to be responsible for handling two entire time systems in my code.

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

#25

Post by lutusp »

sonnekki wrote: post #11

Leap seconds are a work-around to make the 24-hour clock keep time correctly. The reason so many problems occurred was a combination of insufficient programming, but also the affect an inaccurate system. I'm not sure what a correct system should be, but I know that it can't be based on the Earth, the sun, or any one galaxy. In order to have accurate time, it must be external to all of these things, like a meter stick…

> I'm not sure what a correct system should be, but I know that it can't be based on the Earth, the sun, or any one galaxy. In order to have accurate time, it must be external to all of these things, like a meter stick is to an object.

But Einstein's theory of relativity makes that impossible -- there is no absolute time. The larger reason for debates like this is because any timekeeping convention is relative.

As to a "meter stick", that's also relative, and therefore arbitrary, for the same reason -- relativity theory.

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

#26

Post by Codhisattva »

nextstep wrote: post #22

I read through nearly the whole article before I realized this was from 2005. What ever happened to this proposal?

We just had a leap second June 30 so the proposal must have been scrapped.

edit to add link http://en.wikipedia.org/wiki/Leap_second#Proposal_to_abolish...

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

#27

Post by kamjam »

patheman wrote: post #16
sonnekki wrote: post #11

Leap seconds are a work-around to make the 24-hour clock keep time correctly. The reason so many problems occurred was a combination of insufficient programming, but also the affect an inaccurate system. I'm not sure what a correct system should be, but I know that it can't be based on the Earth, the sun, or any one galaxy. In order to have accurate time, it must be external to all of these things, like a meter stick…

"3:00 pm" is in the middle of the night, the time to wake up for work will always "change".. well, one time .. but do you !really! care about how the folks in +600 yrs measure time? I'd guess they invent some kind of "glacial-period-light-saving-time" by then...

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?

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

#28

Post by pixelcort »

> Ending leap seconds would make the sun start rising later and later by the clock -- a few seconds later each decade. To compensate, the U.S. has proposed adding in a "leap hour" every 500 to 600 years...

So it's not abandoning the shifting so much as putting it off into a larger interval, the leap-hour.

Today, that interval is the second. Today, we don't adjust for partial seconds; this proposal just moves the adjustment interval way out.

Perhaps somewhere in the middle like leap-minutes would be better. This would thus occur every 60-90 years.

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

#29

Post by acomjean »

Its all about point of reference. When I worked with radar we liked GPS time, always increasing so its easy to get a difference. But for locating the sun and sun rise, earth time is useful (those griping astronomers have a point).

We figured it out, and it wasn't too bad. Some good time libraries would go a long way...

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

#30

Post by cwe »

jmvoodoo wrote: post #24

I'm definitely looking forward to this debate when/if we ever have a permanent mars colony. Will they still use earth/solar time? Use mars/solar time? Some compromise between the two? I imagine someone living on mars could give two shits if the earth/solar time was off by a few seconds, and I definitely don't want to be responsible for handling two entire time systems in my code.

40 extra minutes in a martian day definitely make things interesting. Going further, how will time work when we're stationed around Saturn's moons? We will probably need some universal units of time that work regardless of how long it takes you to rotate around the sun. (Stardates?)
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