The Future of Leap Seconds 429
@10u8 writes "Since 1972 precision clocks around the world have ticked using atomic seconds, but earth rotation is slowing down. Leap seconds have been inserted in order to keep noon happening at noon, but they upset some timekeepers. Recent discussions have considered
discontinuing leap seconds in UTC, and a colloquium in Torino next month will present results. It is a matter of international significance."
precision timekeeping is real interesting stuff (Score:5, Insightful)
Read the article!
It's important for systems programmers, and lots of folks here are at least systems programming fanboys.
It's important for navigation. Yeah, that includes your GPS toys.
It's important for a number of scientific disciplines, including a number of subdisciplines of radio astronomy.
It's also really interesting that the change in the Earth's rotation can't yet be predicted with enough accuracy to set a schedule in advance for adding leap seconds, but must be measured. This is relatively prosaic stuff that's nonetheless at the limits of our current understanding. Doesn't anyone get excited or curious about science anymore?
Accuracy isn't everything... (Score:5, Insightful)
Oh the horror...
Accuracy isn't everything...
Re:Why? (Score:5, Insightful)
The concept of leap years is because the ratio of the length of a year divided by the length of an earth day is not an iteger. No calendar can get around that fact. You either add intercalation days whenever the remainders of your divisions exceed 1, or you keep track of huge numbers and cycles that greatly complicate your timekeeping.
The Julian roman calendar did suck because they didn't get the ratios quite right and it drifted. (The Gregorian calendar fixed this for all practical purposes.) However, prior to Julius Caesar, it sucked even more because there was no mathematical formula. Instead, priests were supposed to observe the sun each year and decide when leap days were needed.
The priests were also involved in politics, so they chose to shorten political terms more often than not by omitting leap days. IIRC, by the time the Julian calendar was instituted, the Romans were off by several months due to these partisan shenanigans.
Time zones (Score:5, Insightful)
The Right Way to solve this problem is for computers to work with TAI internally, and treat the difference introduced by leap seconds as part of the time zone, for human consumption only. Instead of defining PST to be UTC - 08:00, define PST = TAI - 08:00:22.
Computers can keep their straightforward time system, humans can keep our astronomically synchronized system. No need to lose either of those qualities.
Re:precision timekeeping is real interesting stuff (Score:3, Insightful)
So we don't know why the Earths rotation is slowing? I'll bet we do. It's probably the net result of several factors, most if not all of which are understood. The problem is that we have no way to collect enough data to predict the amount of slowing.
The orbit of our Moon is slowing growing larger also. Something to think about; which is more difficult? Speeding up the Earths rotation or stopping the Moon from running off?
Of course, the solution to all this is really big rockets, but we've got plenty of time for that.
Enough Earth-centrism! (Score:4, Insightful)
Re:Leap seconds and leap years, keep em (Score:1, Insightful)
If you hate Bush... (Score:2, Insightful)
Re:Why? (Score:3, Insightful)
Secondly, time needs not be exact for most people most of the time, but perhaps you can recognize that there are certain applications, especially scientific and technological, for which a measure of exactitude is quite necessary.
Thirdly, I would venture to say that the society depicted in 1984 would rather that people be unable to tell what time it was.
Lastly, all these fitful worries are meaningless, because my man Flavor Flav [publicenemy.com] always knows what time it is. Word.
Re:leap seconds are evil (Score:3, Insightful)
-russ
Examine the Purpose of Timekeeping (Score:4, Insightful)
Removing the leap second makes most history recorded with reference to time of day pretty useless. Noon is defined by most people as the time that the sun is in the middle of the sky. Let's keep it that way. If method of keeping time based on exact seconds from one point in time to another (which is actually pretty useless for most things that happen within timeframes longer than a couple of minutes) then let a separate system be designed for it. Start reading off an atomic clock and never account for leap seconds, but don't screw up the rest of the world to please a few.
Re:Enough Earth-centrism! (Score:2, Insightful)
There really isn't a concept of time unless it is relative to something. Think about it.
Re:an attempt at a summary.... (Score:3, Insightful)
I think that the present UTC compromise is quite reasonable. In almost all civilian systems, including non-real-time computers (like the one you are using right now), you really don't need perfectly constant real time and they are probably usually off from the correct time by a few seconds to a few minutes anyway. The leap second is handled seamlessly as just regular clock skew. I've never seen a PC that didn't gain or lose about 30 seconds a day anyway. (That's really pathetic when you consider what a $5 watch can do.)
If you have some kind of real-time system, then just use TAI. It's about 35 seconds off from UTC. I'd like to have a civil time that is closely synchronized to the real world (UT-1).
AFAIK, the loss of time is fairly predictable since a rotation day is about 86400.002 seconds long so a leap second accumulates about every 500 days. They have a leap second about every 1.5 years (on June 30 and December 31).
Old saying (Score:4, Insightful)
A man with a watch always knows what time it is. A man with two watches is never quite sure...