>: So here is my suggestion, and it is an amalgamation of ideas from >: various quarters. Civil time should be based on a quadratic formula >: involving TAI. In other words, civil time should track UT over the long >: term, and be allowed to drift against UT over the short term. > >Well, the varying length of a second is a non-starter, imho.
Why? If you ask "most people", they will tell you that a second is one 86,400-th part of the amount of time that the earth takes to rotate on its axis. Even though they don't know it, such a definition leads to a variable duration of a second. It seems to me that lots of people have timescales to suit their own needs - scientists have TAI, and astronomers have all the rest :). But not everyone has a suitable timescale - UTC is the timescale that's been introduced, it seems, for the benefit of "most people", and it has serious shortcomings. If "most people" are already quite happy with a variable second, then why not codify it? If "most people" want solar time, and solar time is variable, then give 'em what they want! Of course, the serious problem with a variable second is that of determining time intervals - you cannot just subtract the earlier time from the later - you would also have to calculate the appropriate scaling factor. But UTC isn't appropriate for determining time intervals anyway! If you want time intervals, you use TAI - end of story. And, using simple arithmetic with a timescale with a variable second would give an order of magnitude better estimate of the amount of time between 2005 Dec 31 23:59:59.9 and 2006 Jan 01 00:00:00.1 than UTC does! >However, the idea I like most is to preduct the long term drift over >the next 100-500 years. Then, we schedule the leap seconds NOW I suspect that mathematicians and computer programmers alike would prefer to use quadratic equations than look-up tables, even if the latter are well-defined. Quadratic equations are easier to work with than discontinuities. Also, continuing to use leap seconds eventually leads to inserting leap seconds at the end of every month, week, then day, though it may take 1,200 years before a leap second is required at the end of each month. And, which would the general public prefer - a slightly, imperceptibly, varying second that (attempts to) track the earth, or 23:59:60? Finally, over 400 years ago, there was a change made to our calendar that is still in use today, and that looks like it will still be in use 1,000 years from now (an impressive achievement by our forebearers) - I think we should aim for such a long-term solution for the measurement of the time of day. >Perhaps you just want an argument (the arguers, not Chris specifically). Nah - just trying to be helpful! Just to introduce myself - I'm a professional programmer and amateur astronomer, and my interest in precise time started with my involvement in a (professional) experiment years ago to detect a pulsar. Two great memories I have from that time, both of them arising from my confusion as to what a GPS receiver I was using was actually saying to me about the time. One was when I was comparing the output of the GPS to the radio time station RWM in Moscow - I saw that there was an 11ms discrepancy. This, I decided, was because I was about 3,300 km from Moscow! The second great memory was when I saw a one-second discrepancy between my understanding of the GPS output and the national telephone time service (I'm in Ireland). I eventually tracked down the people responsible for that time service, and asked them if they knew if or how there could be a one second error in their clock. I had to explain to them that a one- second error was actually very important to me as I was trying to measure time to millionths of a second. I got as far as them asking me "oh - do you want us to reset the clock?" before I gave up! (Hence my belief that people would rather have the compromise of a varying second than the 23:59:60 compromise). Chris. _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
