In message: <[email protected]> Rob Seaman <[email protected]> writes: : So many messages, so little time! : : M. Warner Losh wrote: : : > In general, all systems need to be synchronized to human time : > because at some point they have to interact with humans. : : : Right. And human time is synchronized with mean solar time because : we happen to live on the planet Earth. What we are debating is how : this synchronization should happen and on what schedule.
No. We're synchronized with mean solar time at an arbitrary location on the globe that happens to no longer even be on the prime meridian anymore since GPS' new definition of the geoid. And we're not counting 'natural' seconds anymore either: they are based on oscillations of atoms, not on the rotation of the earth. Who the flip cares of the 'prime' meridian (defined as the places where 0:00:00 corresponds to midnight astronomically) drifts a bit. It just doesn't matter to people. : > Sure, it usually doesn't matter much, and you can usually get away : > with it, but that reason alone is not sufficient to say it is never : > a problem. : : No, but it is a good argument for following a coherent and : transparent decision-making process, and for not rushing into a bad : decision. True, but not relevant to this discussion. You often conflate the decision making process of some committee with the current leap second system. They aren't relevant to discussing the current problems. : > Since we've only been using them for 40 years, there's no real : > posterity to worry about. : : : No. We have been using mean solar time formally since the 19th : century, and informally since we woke each morning to light shining : through the entrance of the cave. Leap seconds are simply the current : mechanism for instituting a civil timescale based on mean solar time. No. We've been using leap seconds for 40 years. We used actual local solar time before the 19th century for a few thousand years before that. The main benefit of using standard time zones is everybody using the same time. It isn't that it is mean solar time, that just happened to be one way to define things that is arbitrary based on some set of aesthetics. It was useful when the second was not realized precisely enough to there to be a difference between the second and 1/86400th of the day. Now that we've defined the second to not be 1/86400th of the day, the aesthetics of the situation has changed. We should really consider if it still matters to have things based on mean solar time at an arbitrary meridian, or if such a coupling really matters at all. This is the crux of the debate: I think it is silly, you think it is so obviously critical that we can't find common ground on this point. : > Since we're going to have to have them with increasing regularity : > over the next 50 years, to the point where 2 a year are unlikely to : > be enough, we need to ask ourselves if there's some better way to : > distribute time than what we're doing. : : The frequency over the next 50 years will be similar to the past 50 : years, and likely for a couple of centuries after that: : : http://six.pairlist.net/pipermail/leapsecs/2008-January/000184.html : : It would be delightful to discuss better ways to define and distribute : civil and professional timescales. It is hard to find time to do this : after 9 years of persistent attempts to rush to judgement. The frequency of the next 50 years is likely to be higher than that of the previous 50 years because the earth's deceleration has been accelerating. Of course, given how hard it is to predict the rotation of the earth, who can say for sure. I'm afraid I don't have a paper reference for this, I learned of it talking with Judah Levine one day about other issues (like why he was seeing issues with the measurement system my company had deployed for him). I've heard others on this list refer to it as well. Warner _______________________________________________ LEAPSECS mailing list [email protected] http://six.pairlist.net/mailman/listinfo/leapsecs
