From sla at ucolick.org Mon Sep 1 16:37:49 2008 From: sla at ucolick.org (Steve Allen) Date: Mon, 1 Sep 2008 13:37:49 -0700 Subject: [LEAPSECS] choose the form In-Reply-To: <2173.1218790615@critter.freebsd.dk> References: <20080815060952.GA23990@ucolick.org> <2173.1218790615@critter.freebsd.dk> Message-ID: <20080901203749.GA28893@ucolick.org> On Fri 2008-08-15T08:56:55 +0000, Poul-Henning Kamp hath writ: > In message <20080815060952.GA23990 at ucolick.org>, Steve Allen writes: > >Inspired by Seidelmann and Fukushima's pictorial form, I have been > >working on these > >http://www.ucolick.org/~sla/leapsecs/deltat.html I've been working on them further, mostly on the text. The 1960s deserve a level of explication which defies fitting onto the plots, especially things like the earliest use of the term UTC that I have found by Guinot in Bulletin Horaire, and the conversion of LORAN chains to cesium clocks. > Cool work, do I spot another disciple of the cult of Tufte ? (otherwise > buy his books (www.tufte.com), you will love them :-) As it happens I have photographic evidence http://www.ucolick.org/~sla/leapsecs/cult.jpg I inherited the first three volumes when our principal GUI designer retired. In this context, however, Clive Feather might find it more like the Cult of Skaro. The various national agencies who send reps to ITU-R WP7A and SG7 are preparing their contributions and responses now. The process is far too byzantine for me to follow even in the US, let alone in the national bodies of other countries. -- Steve Allen WGS-84 (GPS) UCO/Lick Observatory Natural Sciences II, Room 165 Lat +36.99855 University of California Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m From sla at ucolick.org Sat Sep 6 12:57:43 2008 From: sla at ucolick.org (Steve Allen) Date: Sat, 6 Sep 2008 09:57:43 -0700 Subject: [LEAPSECS] US DoD and USNO leap second survey Message-ID: <20080906165743.GA18779@ucolick.org> The USNO is conducting a poll for the DoD about leap seconds. http://tycho.usno.navy.mil/leap_second_poll.html I note in the description that they do not recognize the possiblity of having a leap-free broadcast time scale while still allowing leap seconds in UTC. Those really are two separate questions. -- Steve Allen WGS-84 (GPS) UCO/Lick Observatory Natural Sciences II, Room 165 Lat +36.99855 University of California Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m From zefram at fysh.org Sat Sep 13 08:26:07 2008 From: zefram at fysh.org (Zefram) Date: Sat, 13 Sep 2008 13:26:07 +0100 Subject: [LEAPSECS] drift of TAI Message-ID: TAI has reached the grand old age of 1.6 gigaseconds. In honour of the occasion I shall briefly analyse the issue of its secular drift. Like UTC, TAI serves a dual purpose, and those purposes have conflicting requirements. TAI serves civil society by being a global source of regular ticks. Civil society is in the habit of ignoring the labels that TAI attaches to those ticks, instead applying labels derived from Earth rotation. (As I've previously noted, UTC is a calendar: it correlates the cycle of the UT1 day with the cycle of the TAI second, in much the same way that the Gregorian calendar correlates the cycle of the solar day with the cycle of the northward equinoctal year.) TAI also serves astronomers as a realisation of TT, and so indirectly as a way to determine TCG and other coordinate time scales. The standard realisation of TT is defined as TT(TAI) = TAI + 32.184 s Many sources state this equation without the "(TAI)", thus ignoring the deviations of TAI from the true rate of TT. This is acceptable, for work below a certain level of precision, as long as the difference TT-TT(TAI) remains below a corresponding magnitude. But will it? No. TAI is maintained and corrected so as to keep its instantaneous rate as close as possible to that of TAI. This optimises it for use as a frequency standard, including for its use as the minor cycle in the UTC calendar. It comes at the expense of long-term rate accuracy and direct tracking of TT. catalogues the error: over 27 us by the end of 2007, and (more significantly) rising at over 300 ps/day. After a mere four millennia at the current rate of drift, TT(TAI) will not be accurate to the precision implied by its defining equation: once the accumulated drift has exceeded 500 us, TT will be better approximated by TT ~ TAI + 32.185 s. It's only a matter of time before noon TT coincides with midnight TT(TAI)! Unlike the situation with TAI vs UT1, the drift is not accelerating. Indeed, as the rate of drift is inversely proportional to the technological skill of the time laboratories, it is decelerating. But it is non-zero and has a consistent sign: even after years of painstakingly tracking the drift in the TT(BIPMnn) publications, TT(TAI) continues to diverge from TT. Even if the rate of drift is asymptotically approaching zero, the accumulated drift (integral of the rate) may be unbounded. No doubt there are timekeeping systems that rely on TT(TAI) as an accurate source of TT. They will start to go wrong, subtly and progressively, as TT-TT(TAI) exceeds whatever unknown bound was implicitly built into them. Should we be bequeathing this technological timebomb to our grand^200-children? Or should we keep naive expectations unshattered, by ensuring that our broadcast time signals continue to accurately track TT? Happy birthday TAI. (Having been born some 601.266 Ms after TAI's birth, I'll be celebrating my personal gigasecond in two weeks time. If anyone's keeping track, you can put me down as an early eschewer of solar time, for those things where I have the choice.) -zefram From cowan at ccil.org Sat Sep 13 12:56:00 2008 From: cowan at ccil.org (John Cowan) Date: Sat, 13 Sep 2008 12:56:00 -0400 Subject: [LEAPSECS] drift of TAI In-Reply-To: References: Message-ID: <20080913165600.GE32041@mercury.ccil.org> Zefram scripsit: > (Having been born some 601.266 Ms after TAI's birth, I'll be celebrating > my personal gigasecond in two weeks time. If anyone's keeping track, > you can put me down as an early eschewer of solar time, for those things > where I have the choice.) If you enjoy high-end science fiction, check out Joan Vinge's _Heaven Chronicles_, which is set in an asteroid belt. All times are in kilosecs, megasecs, and gigasecs. -- There are three kinds of people in the world: John Cowan those who can count, cowan at ccil.org and those who can't. From zefram at fysh.org Sat Sep 13 14:19:39 2008 From: zefram at fysh.org (Zefram) Date: Sat, 13 Sep 2008 19:19:39 +0100 Subject: [LEAPSECS] drift of TAI In-Reply-To: <20080913165600.GE32041@mercury.ccil.org> References: <20080913165600.GE32041@mercury.ccil.org> Message-ID: <20080913181939.GG11379@fysh.org> John Cowan wrote: >If you enjoy high-end science fiction, check out Joan Vinge's _Heaven >Chronicles_, which is set in an asteroid belt. All times are in kilosecs, >megasecs, and gigasecs. Thanks, I'll look out for that. I'm a fan of Vernor Vinge's "A Deepness In The Sky", where one of the participating civilisations keeps time in that way. -zefram From imp at bsdimp.com Sat Sep 13 15:21:38 2008 From: imp at bsdimp.com (M. Warner Losh) Date: Sat, 13 Sep 2008 13:21:38 -0600 (MDT) Subject: [LEAPSECS] drift of TAI In-Reply-To: <20080913165600.GE32041@mercury.ccil.org> References: <20080913165600.GE32041@mercury.ccil.org> Message-ID: <20080913.132138.-1025553149.imp@bsdimp.com> In message: <20080913165600.GE32041 at mercury.ccil.org> John Cowan writes: : Zefram scripsit: : : > (Having been born some 601.266 Ms after TAI's birth, I'll be celebrating : > my personal gigasecond in two weeks time. If anyone's keeping track, : > you can put me down as an early eschewer of solar time, for those things : > where I have the choice.) : : If you enjoy high-end science fiction, check out Joan Vinge's _Heaven : Chronicles_, which is set in an asteroid belt. All times are in kilosecs, : megasecs, and gigasecs. Cool... A gigasecond is around 31 years, a megasecond is ~11 days and a kilosecond is about 17 minutes. How would you keep such divergent times strait? Let's meet for dinner in about 200 kiloseconds? Warner From phk at phk.freebsd.dk Sat Sep 13 15:31:48 2008 From: phk at phk.freebsd.dk (Poul-Henning Kamp) Date: Sat, 13 Sep 2008 19:31:48 +0000 Subject: [LEAPSECS] drift of TAI In-Reply-To: Your message of "Sat, 13 Sep 2008 13:21:38 CST." <20080913.132138.-1025553149.imp@bsdimp.com> Message-ID: <1567.1221334308@critter.freebsd.dk> In message <20080913.132138.-1025553149.imp at bsdimp.com>, "M. Warner Losh" write s: >Cool... A gigasecond is around 31 years, a megasecond is ~11 days and >a kilosecond is about 17 minutes. How would you keep such divergent >times strait? Let's meet for dinner in about 200 kiloseconds? Actually, gigasecond parties are cool. The local Unix User group (DKUUG) threw a "uptime(1)" party to celebrate when time_t rolled over 1e9 seconds a couple of years back: http://www.uptime1.dk/ I delivered the count-down display using a FreeBSD computer with a Rb+GPS timelock: http://www.superusers.dk/superusers/nyt/images/r0013703.jpg Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk at FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. From zefram at fysh.org Sat Sep 13 15:36:57 2008 From: zefram at fysh.org (Zefram) Date: Sat, 13 Sep 2008 20:36:57 +0100 Subject: [LEAPSECS] drift of TAI In-Reply-To: <20080913.132138.-1025553149.imp@bsdimp.com> References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> Message-ID: <20080913193657.GH11379@fysh.org> M. Warner Losh wrote: >Cool... A gigasecond is around 31 years, a megasecond is ~11 days and >a kilosecond is about 17 minutes. Yes. The kilosecond is a convenient unit of time for intra-day planning. (Metric day folks endorse the centiday, 864 s, for the same purpose.) 100 ks is a reasonable diurnal cycle. I hypothesise that a human civilisation entirely disconnected from natural diurnal cycles would use an artificial 100 ks cycle for this purpose, and a 1 Ms cycle as the analogue of our week. > How would you keep such divergent >times strait? Not sure what you mean here. Relating the SI time units to conventional time of day is messy; determining which calendar day my birthday falls on is non-trivial. In the absence of days and years, though, calculations that involve only metric units are a lot easier than what we presently put up with. >Let's meet for dinner in about 200 kiloseconds? The linear TAI time now, in my preferred notation, is 0m026. (This means 26 ks after a 10 Ms rollover. I'm dropping high- and low-order digits that don't help for the task.) Dinner will therefore be at 0m226. I'll be having some other meals before that, of course, since I don't want to starve. If we're living in an asteroid belt, the 200 ks interval is simply two sleep cycles. -zefram From dwmalone at maths.tcd.ie Sat Sep 13 15:37:36 2008 From: dwmalone at maths.tcd.ie (David Malone) Date: Sat, 13 Sep 2008 20:37:36 +0100 Subject: [LEAPSECS] drift of TAI In-Reply-To: Your message of "Sat, 13 Sep 2008 13:21:38 MDT." <20080913.132138.-1025553149.imp@bsdimp.com> Message-ID: <200809132037.aa70215@walton.maths.tcd.ie> > Cool... A gigasecond is around 31 years, a megasecond is ~11 days and > a kilosecond is about 17 minutes. How would you keep such divergent > times strait? Let's meet for dinner in about 200 kiloseconds? 90ks is probably round enough and close enough to a day that people could use it as a day - it would be 25hrs, which I think people have managed as a daily cycle relatively comfortably? 200ks is then two days and two lots of 10ks, which would be an obvious next unit down? 100ks is almost 28 hours. I don't know for certain, but I suspect a flight accross 4 hours is enough to jetlag some people. That probably means it's a little too long to use as a day. David. From zefram at fysh.org Sat Sep 13 15:45:09 2008 From: zefram at fysh.org (Zefram) Date: Sat, 13 Sep 2008 20:45:09 +0100 Subject: [LEAPSECS] drift of TAI In-Reply-To: <200809132037.aa70215@walton.maths.tcd.ie> References: <20080913.132138.-1025553149.imp@bsdimp.com> <200809132037.aa70215@walton.maths.tcd.ie> Message-ID: <20080913194509.GI11379@fysh.org> David Malone wrote: >100ks is almost 28 hours. I don't know for certain, but I suspect >a flight accross 4 hours is enough to jetlag some people. That >probably means it's a little too long to use as a day. The problem there is in suddenly being 4 hours out of synch with the sun, and having to shift phase. Phase shifting is difficult. I think people are much more flexible about diurnal frequency than you think, especially if the appropriate cues are around to support it. There's some fairly well-known research to the effect that the human biological clock actually has a natural period of 26 hours or so, and its only our exposure to planetary rotation that keeps us on a 24 hour cycle. I've previously mentioned on this list that my personal free-running diurnal cycle is 40 hours, empirically determined when I was an undergrad and had no daily responsibilities. -zefram From dwmalone at maths.tcd.ie Sat Sep 13 16:00:10 2008 From: dwmalone at maths.tcd.ie (David Malone) Date: Sat, 13 Sep 2008 21:00:10 +0100 Subject: [LEAPSECS] drift of TAI In-Reply-To: Your message of "Sat, 13 Sep 2008 20:45:09 BST." <20080913194509.GI11379@fysh.org> Message-ID: <200809132100.aa70468@walton.maths.tcd.ie> > The problem there is in suddenly being 4 hours out of synch with the > sun, and having to shift phase. Phase shifting is difficult. I think > people are much more flexible about diurnal frequency than you think, > especially if the appropriate cues are around to support it. The cueues for this frequency shift look just like a 4 hour phase shift every day. Of course, there could be a long-term adaption I guess. > There's some fairly well-known research to the effect that the human > biological clock actually has a natural period of 26 hours or so, > and its only our exposure to planetary rotation that keeps us on a 24 > hour cycle. AFAIK, that research has been shown to be flawed. > I've previously mentioned on this list that my personal > free-running diurnal cycle is 40 hours, empirically determined when I > was an undergrad and had no daily responsibilities. Unless you were living divorced from daylight, it's unlikely this is your natural period. According to this article (found via wikipedia): http://www.hno.harvard.edu/gazette/1999/07.15/bioclock24.html 95% of people have a natural period of 24h11m +/- 11 minutes, though the range went from 13 to 65 hours. The article also suggests that a 28 hr day is long enough to prevent people's hormones getting in sync with the day. I'm not sure what the practical implications of this are. David. From zefram at fysh.org Sat Sep 13 16:43:56 2008 From: zefram at fysh.org (Zefram) Date: Sat, 13 Sep 2008 21:43:56 +0100 Subject: [LEAPSECS] drift of TAI In-Reply-To: <200809132100.aa70468@walton.maths.tcd.ie> References: <20080913194509.GI11379@fysh.org> <200809132100.aa70468@walton.maths.tcd.ie> Message-ID: <20080913204356.GJ11379@fysh.org> David Malone wrote: >The cueues for this frequency shift look just like a 4 hour phase >shift every day. Except that it's a continuous `shift', rather than an instantaneous four-hour jump. > Of course, there could be a long-term adaption >I guess. That's what I'm expecting. With jetlag you're expected to retain the same frequency and shift phase, so there's no adaptation to a different frequency. >Unless you were living divorced from daylight, it's unlikely this >is your natural period. I had *some* exposure to the outdoors, but this was only a couple of percent of the time, when taking buses between home and campus. Half the time this did not involve sunlight. At both ends of that journey I lived a completely indoor existence, without unobstructed sight of an external window. So desynchronisation seems quite feasible. Probably relevant: before the free-running period I was accustomed to irregular sleep periods that had little synchrony with the planet. Even when I had lectures to go to, I kept completely ad hoc hours. In those years I could shift phase to an arbitrary extent within two days, by simply staying up until the bedtime of the target phase. Nowadays I've become conditioned to working (approximately) office hours, and I seem to be much more tied to the regular cycle: I have difficulty staying up as much as 24 hours. When I need to, though, I still break phase entirely rather than shift gradually. > http://www.hno.harvard.edu/gazette/1999/07.15/bioclock24.html Interesting work. This still, like the discredited earlier work, shows a biological cycle longer than the natural solar day. Evolutionarily you'd expect us to be built for a shorter cycle, since the Earth rotated faster in our evolutionary past. But the day was only a few minutes shorter when our ancestors switched from nocturnal to diurnal behaviour, so there shouldn't be much in it. >a 28 hr day is long enough to prevent people's hormones getting in >sync with the day. They're drawing a strong distinction between the hormone-controlled circadian rhythm and actual sleep/wake rhythm. I hadn't thought about this before. On those occasions when I've stayed awake for lengthy periods of time, occasionally 60 and once over 70 hours, I've certainly had periods of lowered body temperature and lower physical activity, matching what they describe for the hormonally-sleepy phase. I recognised it as such at the time. But the regular 40-hour cycle was different. As I recall, I just didn't feel sleepy at all until I'd been up more than 20 hours. The cycle of 24 hours awake and 16 asleep felt like a normal circadian rhythm, not overriding the natural state at any point. -zefram From magnus at rubidium.dyndns.org Sat Sep 13 16:57:10 2008 From: magnus at rubidium.dyndns.org (Magnus Danielson) Date: Sat, 13 Sep 2008 22:57:10 +0200 Subject: [LEAPSECS] drift of TAI In-Reply-To: <20080913204356.GJ11379@fysh.org> References: <20080913194509.GI11379@fysh.org> <200809132100.aa70468@walton.maths.tcd.ie> <20080913204356.GJ11379@fysh.org> Message-ID: <48CC2926.4090808@rubidium.dyndns.org> Zefram wrote: > David Malone wrote: >> The cueues for this frequency shift look just like a 4 hour phase >> shift every day. > > Except that it's a continuous `shift', rather than an instantaneous > four-hour jump. > >> Of course, there could be a long-term adaption >> I guess. > > That's what I'm expecting. With jetlag you're expected to retain the > same frequency and shift phase, so there's no adaptation to a different > frequency. > >> Unless you were living divorced from daylight, it's unlikely this >> is your natural period. > > I had *some* exposure to the outdoors, but this was only a couple of > percent of the time, when taking buses between home and campus. Half the > time this did not involve sunlight. At both ends of that journey I > lived a completely indoor existence, without unobstructed sight of an > external window. So desynchronisation seems quite feasible. > > Probably relevant: before the free-running period I was accustomed to > irregular sleep periods that had little synchrony with the planet. > Even when I had lectures to go to, I kept completely ad hoc hours. > In those years I could shift phase to an arbitrary extent within > two days, by simply staying up until the bedtime of the target phase. > Nowadays I've become conditioned to working (approximately) office hours, > and I seem to be much more tied to the regular cycle: I have difficulty > staying up as much as 24 hours. When I need to, though, I still break > phase entirely rather than shift gradually. > >> http://www.hno.harvard.edu/gazette/1999/07.15/bioclock24.html > > Interesting work. This still, like the discredited earlier work, shows > a biological cycle longer than the natural solar day. Evolutionarily > you'd expect us to be built for a shorter cycle, since the Earth rotated > faster in our evolutionary past. But the day was only a few minutes > shorter when our ancestors switched from nocturnal to diurnal behaviour, > so there shouldn't be much in it. > >> a 28 hr day is long enough to prevent people's hormones getting in >> sync with the day. > > They're drawing a strong distinction between the hormone-controlled > circadian rhythm and actual sleep/wake rhythm. I hadn't thought about > this before. On those occasions when I've stayed awake for lengthy > periods of time, occasionally 60 and once over 70 hours, I've certainly > had periods of lowered body temperature and lower physical activity, > matching what they describe for the hormonally-sleepy phase. I recognised > it as such at the time. But the regular 40-hour cycle was different. > As I recall, I just didn't feel sleepy at all until I'd been up more > than 20 hours. The cycle of 24 hours awake and 16 asleep felt like a > normal circadian rhythm, not overriding the natural state at any point. No, no, no... with the new SI second based on the observation that a second is 10639620104 and 1/6 oscillation from the hyperfine transition of Cs-133. 100 ks becomes just a day. Let's keep the prespective here! Also, 1 meter is the precission calibrated distance from my fingertip to my noise, assuming of course that I have been given the necessary beers before you are allowed to measure. Instability of measures can't be guaranteed otherwise. Cheers, Magnus From sla at ucolick.org Sat Sep 13 23:39:56 2008 From: sla at ucolick.org (Steve Allen) Date: Sat, 13 Sep 2008 20:39:56 -0700 Subject: [LEAPSECS] drift of TAI In-Reply-To: References: Message-ID: <20080914033956.GA7163@ucolick.org> On Sat 2008-09-13T13:26:07 +0100, Zefram hath writ: > After a mere four millennia at the current > rate of drift, TT(TAI) will not be accurate to the precision implied by > its defining equation: once the accumulated drift has exceeded 500 us, > TT will be better approximated by TT ~ TAI + 32.185 s. It's only a > matter of time before noon TT coincides with midnight TT(TAI)! I noted when preparing my Delta T plots that the 1.e-12 change in the rate of TAI on 1977-01-01 amounts to a difference of 0.1 s at the earliest point on my plots, or less than 0.25 s at the earliest written records of humans. I can't imagine any astronomical observation which, even if described in totally unambiguous language, could make the distinction. I expect that at the time the astronomers who were unconcerned with the rate change of TAI had a similar viewpoint. Looking the other way, I still take a lesson from the agencies which launch payloads intended for rendevous. Their countdowns have always accepted the notion of a discontinuous "hold" in the time scale leading to a future event. -- Steve Allen WGS-84 (GPS) UCO/Lick Observatory Natural Sciences II, Room 165 Lat +36.99858 University of California Voice: +1 831 459 3046 Lng -122.06014 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m From seaman at noao.edu Mon Sep 15 04:29:13 2008 From: seaman at noao.edu (Rob Seaman) Date: Mon, 15 Sep 2008 01:29:13 -0700 Subject: [LEAPSECS] drift of TAI In-Reply-To: <20080913193657.GH11379@fysh.org> References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> <20080913193657.GH11379@fysh.org> Message-ID: Zefram wrote: > I hypothesise that a human civilisation entirely disconnected from > natural diurnal cycles would use an artificial 100 ks cycle for this > purpose, and a 1 Ms cycle as the analogue of our week. A jejune (and rather moot) hypothesis. In such circumstances, why assume the existence of a week in the first place? Or the use of base 10 at all? I'm not sure I want to encourage this thread :-) but the answer is precisely that you are positing a human enterprise. Merely by referring to "civilization", you are conjuring vast webs of connections to natural cycles at all scales. Even in an extreme "Caves of Steel" scenario, the troglodyte trillions are locked to diurnal cycles of solar power stations and the daily cadences of robotic combine harvesters to feed the buried billions, and even commerce with other star systems points to the rhythms of other suns . > In the absence of days and years, though, calculations that involve > only metric units are a lot easier than what we presently put up with. Hence the prevalence of radians in everyday use :-) The only thing natural about the metric system is that humans have ten fingers and the quadrant of the Earth something approximating 10 megameters. That sexagesimal notation emerged from the fertile crescent merely attests to the notation's durability compared to the system debouched by the Reign of Terror. Rob Seaman NOAO From phk at phk.freebsd.dk Mon Sep 15 04:35:55 2008 From: phk at phk.freebsd.dk (Poul-Henning Kamp) Date: Mon, 15 Sep 2008 08:35:55 +0000 Subject: [LEAPSECS] drift of TAI In-Reply-To: Your message of "Mon, 15 Sep 2008 01:29:13 MST." Message-ID: <13289.1221467755@critter.freebsd.dk> In message , Rob Seaman writes: >Hence the prevalence of radians in everyday use :-) The only thing >natural about the metric system is [...] As the T-shirt says: There are 10 kinds of people: Those who understand binary and those who don't. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk at FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. From dot at dotat.at Mon Sep 15 09:45:23 2008 From: dot at dotat.at (Tony Finch) Date: Mon, 15 Sep 2008 14:45:23 +0100 Subject: [LEAPSECS] drift of TAI In-Reply-To: References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> <20080913193657.GH11379@fysh.org> Message-ID: On Mon, 15 Sep 2008, Rob Seaman wrote: > > Hence the prevalence of radians in everyday use :-) The only thing natural > about the metric system is that humans have ten fingers and the quadrant of > the Earth something approximating 10 megameters. The latter was an artificial and deliberate design choice. Nothing natural about it. Tony. -- f.anthony.n.finch http://dotat.at/ TYNE DOGGER FISHER GERMAN BIGHT HUMBER THAMES DOVER WIGHT PORTLAND EASTERLY 3 OR 4, OCCASIONALLY 5. SLIGHT OR MODERATE. MAINLY FAIR. GOOD. From seaman at noao.edu Mon Sep 15 10:08:00 2008 From: seaman at noao.edu (Rob Seaman) Date: Mon, 15 Sep 2008 07:08:00 -0700 Subject: [LEAPSECS] drift of TAI In-Reply-To: References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> <20080913193657.GH11379@fysh.org>

Message-ID: <1F4F94A7-483F-4C89-ABB1-1B468EE441A4@noao.edu> On Sep 15, 2008, at 6:45 AM, Tony Finch wrote: > On Mon, 15 Sep 2008, Rob Seaman wrote: >> > >> The only thing natural about the metric system is that humans have >> ten fingers and the quadrant of the Earth something approximating >> 10 megameters. > > The latter was an artificial and deliberate design choice. Nothing > natural about it. Some would say the same about the former :-) From magnus at rubidium.dyndns.org Mon Sep 15 10:43:02 2008 From: magnus at rubidium.dyndns.org (Magnus Danielson) Date: Mon, 15 Sep 2008 16:43:02 +0200 (CEST) Subject: [LEAPSECS] drift of TAI In-Reply-To: <1F4F94A7-483F-4C89-ABB1-1B468EE441A4@noao.edu> References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> <20080913193657.GH11379@fysh.org>

<1F4F94A7-483F-4C89-ABB1-1B468EE441A4@noao.edu> Message-ID: > On Sep 15, 2008, at 6:45 AM, Tony Finch wrote: > >> On Mon, 15 Sep 2008, Rob Seaman wrote: >>> >> >>> The only thing natural about the metric system is that humans have >>> ten fingers and the quadrant of the Earth something approximating >>> 10 megameters. >> >> The latter was an artificial and deliberate design choice. Nothing >> natural about it. > > Some would say the same about the former :-) You could just as easilly use base 8 (not counting thumbs, a possible alternative use of hands) or base 20 (counting toes also, which some cultures do). Everything is arbitrary as base scale and division. There are some fixed relations in which for instance PI comes up, which seems not to be that arbitrary as a relationship between measures. That the SI second still is indirectly defined out of the 24x60x60 division system is certainly annoyingly non-decadent but practical. Cheers, Magnus From phk at phk.freebsd.dk Mon Sep 15 10:50:32 2008 From: phk at phk.freebsd.dk (Poul-Henning Kamp) Date: Mon, 15 Sep 2008 14:50:32 +0000 Subject: [LEAPSECS] drift of TAI In-Reply-To: Your message of "Mon, 15 Sep 2008 16:43:02 +0200." Message-ID: <2040.1221490232@critter.freebsd.dk> In message , "Ma gnus Danielson" writes: >Everything is arbitrary as base scale and division. Uhm no. All bases larger than 2 are arbitrary and all scalings are arbitrary. But base 2 represents the fundamental counting system, and as such is is unique. This has been acknowledged since Leibnitz. However, following the subsequent mathematical proof that the choice of base makes no difference to any kind of math, apart from expense of ink and paper to write the numbers, base-2 was left alone until somebody much later got the heritical idea to drive thermionic valves way pas their linear behaviour. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk at FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. From dot at dotat.at Mon Sep 15 11:06:00 2008 From: dot at dotat.at (Tony Finch) Date: Mon, 15 Sep 2008 16:06:00 +0100 Subject: [LEAPSECS] drift of TAI In-Reply-To: <2040.1221490232@critter.freebsd.dk> References: <2040.1221490232@critter.freebsd.dk> Message-ID: On Mon, 15 Sep 2008, Poul-Henning Kamp wrote: > > However, following the subsequent mathematical proof that the choice > of base makes no difference to any kind of math, apart from expense > of ink and paper to write the numbers, base-2 was left alone until > somebody much later got the heritical idea to drive thermionic > valves way pas their linear behaviour. "Makes no difference" so long as the base is uniform :-) The civilized world has mostly eliminated non-uniform bases, except for dealing with time. The Americans (and the British to a lesser extent) still cling to the handicap of non-uniform bases for other measurements. Still, could be worse: at least there aren't leap-ounces. Tony. -- f.anthony.n.finch http://dotat.at/ FAIR ISLE: SOUTHERLY 4 OR 5, BECOMING VARIABLE 3 OR 4. MODERATE OR ROUGH. RAIN AT TIMES, FOG PATCHES. MODERATE OR GOOD, OCCASIONALLY VERY POOR. From magnus at rubidium.dyndns.org Mon Sep 15 11:23:29 2008 From: magnus at rubidium.dyndns.org (Magnus Danielson) Date: Mon, 15 Sep 2008 17:23:29 +0200 (CEST) Subject: [LEAPSECS] drift of TAI In-Reply-To: <2040.1221490232@critter.freebsd.dk> References: <2040.1221490232@critter.freebsd.dk> Message-ID: > In message > , "Ma > gnus Danielson" writes: > >>Everything is arbitrary as base scale and division. > > Uhm no. > > All bases larger than 2 are arbitrary and all scalings are arbitrary. > > But base 2 represents the fundamental counting system, and as such is > is unique. You may still choose any base, which was my point. I agree that base 2 is much more convenient, but nothing suggest you must choose base 2 or we would have picked it for general counting much easlier. We have two hands, so it is not too far fetched. > This has been acknowledged since Leibnitz. > > However, following the subsequent mathematical proof that the choice > of base makes no difference to any kind of math, apart from expense > of ink and paper to write the numbers, base-2 was left alone until > somebody much later got the heritical idea to drive thermionic > valves way pas their linear behaviour. The insights of Liebnitz was several thousand years to late for the choice of propper base. We may grumble at this fact and move on. But for a completely normalized world it would be possible choice and probably. However, even if we rescale everything one unit would probably be required to be the master unit which would scale everything else even if every orhter arbitrary unit conversion factor (other than pure mathematical relations) is canceled out. There where plans for converting Sweden to a base 8 country, but I don't have the TAOCP I need at hand to give the details. Cheers, Magnus From cowan at ccil.org Mon Sep 15 11:42:58 2008 From: cowan at ccil.org (John Cowan) Date: Mon, 15 Sep 2008 11:42:58 -0400 Subject: [LEAPSECS] drift of TAI In-Reply-To: References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> <20080913193657.GH11379@fysh.org> Message-ID: <20080915154257.GC4240@mercury.ccil.org> Rob Seaman scripsit: > I'm not sure I want to encourage this thread :-) but the answer is > precisely that you are positing a human enterprise. Merely by > referring to "civilization", you are conjuring vast webs of > connections to natural cycles at all scales. Even in an extreme > "Caves of Steel" scenario, the troglodyte trillions are locked to > diurnal cycles of solar power stations and the daily cadences of > robotic combine harvesters to feed the buried billions, and even > commerce with other star systems points to the rhythms of other suns That's what the author of "The Caves Of Steel" called planetary chauvinism. There weren't any terrestroid planets in the Heaven system, so when it was settled by slower-than-light starships, the colonists occupied the asteroids and the moons of a Saturn-type gas giant. (The book was written thirty years ago, before we fully realized just how nasty the Van Allen radiation around such planets actually is.) With fusion-based interplanetary ships and interstellar communication lasers, the Heavenites grew rich and prosperous. They even went so far as to wrap their capital asteroid, which appears to be Ceres-type, in a transparent bubble and create an atmosphere inside the bubble. But there was war in Heaven, a civil war (no surprise), and when Vinge's book opens, the Main Belt is mostly a wreck of abandoned settlements and desperate survivors. Fusion power has been lost, so Heaven has been cut off from other human colonies. Most of what post-20th-century technology remains is closely held by a government in the trojans of a Jupiter-type giant, but they are starved of hydrogen for reaction mass, fuel, and water -- another government holds the Saturn rings, which are the only remaining accessible source. The two societies have been locked in a mixture of cold war and grudging trade since the fall of the Main Belt, and when a starship from a troubled colony world arrives in the Heaven system, looking for help, all they find is chaos. -- Said Agatha Christie / To E. Philips Oppenheim John Cowan "Who is this Hemingway? / Who is this Proust? cowan at ccil.org Who is this Vladimir / Whatchamacallum, http://www.ccil.org/~cowan This neopostrealist / Rabble?" she groused. --George Starbuck, Pith and Vinegar From seaman at noao.edu Mon Sep 15 12:16:45 2008 From: seaman at noao.edu (Rob Seaman) Date: Mon, 15 Sep 2008 09:16:45 -0700 Subject: [LEAPSECS] drift of TAI In-Reply-To: <20080915154257.GC4240@mercury.ccil.org> References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> <20080913193657.GH11379@fysh.org> <20080915154257.GC4240@mercury.ccil.org> Message-ID: <5A5A8316-C1AC-472B-8FFA-8C080E859E76@noao.edu> On Sep 15, 2008, at 8:42 AM, John Cowan wrote: > Rob Seaman scripsit: > >> I'm not sure I want to encourage this thread :-) but the answer is >> precisely that you are positing a human enterprise. Merely by >> referring to "civilization", you are conjuring vast webs of >> connections to natural cycles at all scales. Even in an extreme >> "Caves of Steel" scenario, the troglodyte trillions are locked to >> diurnal cycles of solar power stations and the daily cadences of >> robotic combine harvesters to feed the buried billions, and even >> commerce with other star systems points to the rhythms of other suns > > That's what the author of "The Caves Of Steel" called planetary > chauvinism. I was referring to the Asimov novel - agoraphobe detective and his positronic partner. Asimov's fiction is firmly located in the so- called hard SF realm of nuts and bolts and the laws of physics. No blood dripping Frazetta princesses on the covers of Isaac's books. It is precisely this common sense world view that was required of the creator of psychohistory. (Although I'm not sure wikipedia will serve to preserve civilization through the coming collapse :-) In both his fiction and nonfiction, Asimov focused on human needs in a technical context. This is heart and soul of issues like timekeeping, systems of units and mathematical notations. Rob From seaman at noao.edu Mon Sep 15 12:20:51 2008 From: seaman at noao.edu (Rob Seaman) Date: Mon, 15 Sep 2008 09:20:51 -0700 Subject: [LEAPSECS] drift of TAI In-Reply-To: References: <2040.1221490232@critter.freebsd.dk> Message-ID: <41EC7887-0BDA-438F-BBC2-4131EBF2806B@noao.edu> On Sep 15, 2008, at 8:23 AM, Magnus Danielson wrote: > There where plans for converting Sweden to a base 8 country, but I > don't > have the TAOCP I need at hand to give the details. This sounds like either an urban legend or some isolated...how do you say "nut job" in Swedish? Another example would be the Indiana legislature voting on pi=3. From seaman at noao.edu Mon Sep 15 12:28:43 2008 From: seaman at noao.edu (Rob Seaman) Date: Mon, 15 Sep 2008 09:28:43 -0700 Subject: [LEAPSECS] drift of TAI In-Reply-To: References: <2040.1221490232@critter.freebsd.dk> Message-ID: <6366A7E1-49AF-45AA-B462-172301CB7777@noao.edu> On Sep 15, 2008, at 8:06 AM, Tony Finch wrote: > The civilized world has mostly eliminated non-uniform bases, except > for dealing with time. And angle. The fundamental confusion here is between TAI - purely a decimal count from some zero epoch - and UTC, an orientation angle. Angles are often expressed using sexagesimal notation. TAI should never be. > The Americans (and the British to a lesser extent) still cling to > the handicap of non-uniform bases for other measurements. Still, > could be worse: at least there aren't leap-ounces. Ever tare a balance in chem lab? Rob From zefram at fysh.org Mon Sep 15 12:31:53 2008 From: zefram at fysh.org (Zefram) Date: Mon, 15 Sep 2008 17:31:53 +0100 Subject: [LEAPSECS] drift of TAI In-Reply-To: References: <2040.1221490232@critter.freebsd.dk> Message-ID: <20080915163153.GM11379@fysh.org> Magnus Danielson wrote: >The insights of Liebnitz was several thousand years to late for the choice >of propper base. We may grumble at this fact and move on. But for a >completely normalized world it would be possible choice and probably. In positing the use of gigaseconds in a future spacefaring society, I'm obviously assuming some continuity with our present civilisation. Specifically, I'm assuming the survival of the SI base units and of the pervasive use of decimal arithmetic. If we switch radix, presumably we'd invent new prefixes to use with the existing units. (Actually we already have, with the binary prefixes such as "Ki".) In a completely normalised system, though, there'd be no reason to use the current SI base units, other than the radian. They're all arbitrary. I'd expect to switch to Planck units, or something similar. How would you fancy road speed limits expressed in nanoplancks? (The nanoplanck (unit of speed) is equal to one nanoplanck (length) per planck (time).) Actually it'd be a pity to lose all dimensional analysis, as one would in the pure Planck system, but we could have dimensionful units that just have the same value as the Planck units. Need some hefty prefixes for everyday quantities, of course. >There where plans for converting Sweden to a base 8 country, but I don't >have the TAOCP I need at hand to give the details. Section 4.1, page 200 in the third edition of volume 2: Charles XII of Sweden, whose talent for mathematics perhaps exceeded that of all other kings in the history of the world, hit on the idea of radix-8 arithmetic about 1717. This was probably his own invention, although he had met Leibniz briefly in 1707. Charles felt that radix 8 or 64 would be more convenient for calculation than the decimal system, and he considered introducing octal arithmetic into Sweden; but he died in battle before decreeing such a change. [See /The Works of Voltaire/ *21* (Paris: E. R. DuMont, 1901), 49; E. Swedenborg, /Gentleman's Magazine/ *24* (1754), 423-424.] Wikipedia has a couple of other details. Octal has the advantage of both being interconvertible with binary and also matching human cognitive capacity (one of those "magic number seven" effects). Strangely there doesn't seem to be much of a movement to adopt it. Unlike dozenal, which has fairly organised groups promoting it. (Unfortunately these groups sometimes get mixed up with the anti-metric crowd, which is a separate issue.) Dozenal seems unwieldy, and only has the factor-3 thing in its favour. -zefram From cowan at ccil.org Mon Sep 15 12:32:37 2008 From: cowan at ccil.org (John Cowan) Date: Mon, 15 Sep 2008 12:32:37 -0400 Subject: [LEAPSECS] drift of TAI In-Reply-To: <5A5A8316-C1AC-472B-8FFA-8C080E859E76@noao.edu> References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> <20080913193657.GH11379@fysh.org> <20080915154257.GC4240@mercury.ccil.org> <5A5A8316-C1AC-472B-8FFA-8C080E859E76@noao.edu> Message-ID: <20080915163236.GF4240@mercury.ccil.org> Rob Seaman scripsit: > I was referring to the Asimov novel - agoraphobe detective and his > positronic partner. Yes, I know. I forget in exactly which of his thousand or so essays Asimov coined the phrase "planetary chauvinism" for the belief that human civilization (in later uses, life) can only exist on or near the surfaces of planets, but the term is definitely out there: 415 Google hits, including a Wikipedia article and a 1971 _Time_ magazine essay called "Is There Life On Mars?" > Asimov's fiction is firmly located in the so-called hard SF realm of > nuts and bolts and the laws of physics. Well, unless you count hyperspace travel and subspace communication, time travel (in _The End Of Eternity_), and a bunch of very clear fantasy stories written near the end of his life, then I don't think so. If anything, the _Heaven Chronicles_ are closer to what is known to be known: slower-than-light starships, for example. -- In my last lifetime, John Cowan I believed in reincarnation; http://www.ccil.org/~cowan in this lifetime, cowan at ccil.org I don't. --Thiagi From cowan at ccil.org Mon Sep 15 12:43:45 2008 From: cowan at ccil.org (John Cowan) Date: Mon, 15 Sep 2008 12:43:45 -0400 Subject: [LEAPSECS] drift of TAI In-Reply-To: <41EC7887-0BDA-438F-BBC2-4131EBF2806B@noao.edu> References: <2040.1221490232@critter.freebsd.dk> <41EC7887-0BDA-438F-BBC2-4131EBF2806B@noao.edu> Message-ID: <20080915164345.GG4240@mercury.ccil.org> Rob Seaman scripsit: > This sounds like either an urban legend or some isolated...how do you > say "nut job" in Swedish? Well, it's neither. The nut-job in question was King Charles XII (1682-1718), and he scribbled down his idea for using base-8 numeration in a meeting with Emanuel Swedenborg in 1716. At the time, Swedenborg was just beginning his successful career as a mining engineer -- it was not until 1744 that he became a theologian -- and was trying (unsuccessfully) to persuade the King to build an astronomical observatory (one of Swedenborg's other interests) in the north. Swedenborg reported that the King thought base 8 more suitable for war purposes (he was a most martial monarch) because the packing boxes used in the Swedish Army for materiel were cubical. -- All Gaul is divided into three parts: the part John Cowan that cooks with lard and goose fat, the part http://ccil.org/~cowan that cooks with olive oil, and the part that cowan at ccil.org cooks with butter. --David Chessler From seaman at noao.edu Mon Sep 15 12:47:12 2008 From: seaman at noao.edu (Rob Seaman) Date: Mon, 15 Sep 2008 09:47:12 -0700 Subject: [LEAPSECS] drift of TAI In-Reply-To: <2040.1221490232@critter.freebsd.dk> References: <2040.1221490232@critter.freebsd.dk> Message-ID: On Sep 15, 2008, at 7:50 AM, Poul-Henning Kamp wrote: > In message >, "Ma > gnus Danielson" writes: > >> Everything is arbitrary as base scale and division. > > Uhm no. > > All bases larger than 2 are arbitrary and all scalings are arbitrary. > > But base 2 represents the fundamental counting system, and as such is > is unique. The place value system itself is a design artifact. Also, calling something "base 2" doesn't denote a unique encoding. 1's complement? 2's complement? Gray code? BCD? The initiation into the secret society of computer scientists includes a requirement for mastery of binary notation. This is similar to ham operators having to master Morse code. (I believe this requirement has been relaxed.) Everyday citizens don't know Morse - and they aren't fluent in binary arithmetic. Decimal and sexagesimal notation persist because over centuries and millennia lay people have demonstrated the ability to reach a minimal level of competency. Which is to say that, for whatever reason, they are better tailored to our purposes. Rob From cowan at ccil.org Mon Sep 15 12:52:08 2008 From: cowan at ccil.org (John Cowan) Date: Mon, 15 Sep 2008 12:52:08 -0400 Subject: [LEAPSECS] drift of TAI In-Reply-To: References: <2040.1221490232@critter.freebsd.dk> Message-ID: <20080915165208.GH4240@mercury.ccil.org> Rob Seaman scripsit: > Decimal and sexagesimal notation persist because over centuries and > millennia lay people have demonstrated the ability to reach a minimal > level of competency. Which is to say that, for whatever reason, they > are better tailored to our purposes. That's vulgar Darwinism. Base 10, like English spelling and the QWERTY keyboard, are good enough, and may even constitute a local minimum. But it's absurd to suppose that they are necessarily a global minimum. Do you suppose that the reason that francophones go on speaking French is because in some sense French is better suited to those particular people than English, or Dogon, or Mandarin Chinese? Hardly. They continue to speak French because children continue to acquire French from their francophone parents and peers. -- "But I am the real Strider, fortunately," John Cowan he said, looking down at them with his face cowan at ccil.org softened by a sudden smile. "I am Aragorn son http://www.ccil.org/~cowan of Arathorn, and if by life or death I can save you, I will." --LotR Book I Chapter 10 From seaman at noao.edu Mon Sep 15 13:04:45 2008 From: seaman at noao.edu (Rob Seaman) Date: Mon, 15 Sep 2008 10:04:45 -0700 Subject: [LEAPSECS] drift of TAI In-Reply-To: <20080915163236.GF4240@mercury.ccil.org> References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> <20080913193657.GH11379@fysh.org> <20080915154257.GC4240@mercury.ccil.org> <5A5A8316-C1AC-472B-8FFA-8C080E859E76@noao.edu> <20080915163236.GF4240@mercury.ccil.org> Message-ID: <9DEF4346-D887-4A11-8ADA-5B6FE4CCBA87@noao.edu> On Sep 15, 2008, at 9:32 AM, John Cowan wrote: > Rob Seaman scripsit: > >> I was referring to the Asimov novel - agoraphobe detective and his >> positronic partner. > > Yes, I know. I forget in exactly which of his thousand or so essays > Asimov coined the phrase "planetary chauvinism" for the belief that > human civilization (in later uses, life) can only exist on or near > the surfaces of planets, but the term is definitely out there: > 415 Google hits, including a Wikipedia article and a 1971 _Time_ > magazine essay called "Is There Life On Mars?" And the missions that actually reached Mars chose clocks based on Solar time. >> Asimov's fiction is firmly located in the so-called hard SF realm of >> nuts and bolts and the laws of physics. > > Well, unless you count hyperspace travel and subspace communication, > time travel (in _The End Of Eternity_), and a bunch of very clear > fantasy stories written near the end of his life, then I don't think > so. > If anything, the _Heaven Chronicles_ are closer to what is known to be > known: slower-than-light starships, for example. Physicists speculate about the laws of physics. Why not authors? The point being that a typical Asimov story was representative of the "Campbellian" mode of positing some delta universe to our own and rigorously deducing logical consequences. One doesn't speculate about technology alone, but rather, its impact on humanity and other intelligent species. Niven's FTL spacecraft make voyages to neutron stars and the center of our Galaxy. But it is the effect of these voyages on Beowulf Shaeffer that makes the story. That is, the stories of even the nerdiest practitioners of this nerdiest profession still hinge on characters and the theatricality of their experience. Not much has changed since the original Beowulf, other than the media used to tell the stories. Rob From cowan at ccil.org Mon Sep 15 13:07:01 2008 From: cowan at ccil.org (John Cowan) Date: Mon, 15 Sep 2008 13:07:01 -0400 Subject: [LEAPSECS] drift of TAI In-Reply-To: <9DEF4346-D887-4A11-8ADA-5B6FE4CCBA87@noao.edu> References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> <20080913193657.GH11379@fysh.org> <20080915154257.GC4240@mercury.ccil.org> <5A5A8316-C1AC-472B-8FFA-8C080E859E76@noao.edu> <20080915163236.GF4240@mercury.ccil.org> <9DEF4346-D887-4A11-8ADA-5B6FE4CCBA87@noao.edu> Message-ID: <20080915170701.GJ4240@mercury.ccil.org> Rob Seaman scripsit: > Niven's FTL spacecraft make voyages to neutron stars and the center of > our Galaxy. But it is the effect of these voyages on Beowulf Shaeffer > that makes the story. That is, the stories of even the nerdiest > practitioners of this nerdiest profession still hinge on characters > and the theatricality of their experience. Not much has changed since > the original Beowulf, other than the media used to tell the stories. I agree absolutely. So pick up a copy of _The Heaven Chronicles_ from your favorite out-of-print bookstore, online or brick and mortar, and enjoy. -- John Cowan cowan at ccil.org http://ccil.org/~cowan No man is an island, entire of itself; every man is a piece of the continent, a part of the main. If a clod be washed away by the sea, Europe is the less, as well as if a promontory were, as well as if a manor of thy friends or of thine own were: any man's death diminishes me, because I am involved in mankind, and therefore never send to know for whom the bell tolls; it tolls for thee. --John Donne From seaman at noao.edu Mon Sep 15 13:12:15 2008 From: seaman at noao.edu (Rob Seaman) Date: Mon, 15 Sep 2008 10:12:15 -0700 Subject: [LEAPSECS] drift of TAI In-Reply-To: <20080915165208.GH4240@mercury.ccil.org> References: <2040.1221490232@critter.freebsd.dk> <20080915165208.GH4240@mercury.ccil.org> Message-ID: <5CD69465-EA4B-473A-871E-D16BA6FAF384@noao.edu> On Sep 15, 2008, at 9:52 AM, John Cowan wrote: > Rob Seaman scripsit: > >> Decimal and sexagesimal notation persist because over centuries and >> millennia lay people have demonstrated the ability to reach a minimal >> level of competency. Which is to say that, for whatever reason, they >> are better tailored to our purposes. > > That's vulgar Darwinism. Base 10, like English spelling and the > QWERTY > keyboard, are good enough, and may even constitute a local minimum. > But it's absurd to suppose that they are necessarily a global minimum. Which was the point of some of my earlier comments. Binary is, however, not good enough for day-to-day human purposes. And to bring this back to the topic of the mailing list, "good enough" civil timekeeping requires a close mimicry of mean solar time. Vulgar or not, Darwin certainly recognized the selective value of mimicry. > Do you suppose that the reason that francophones go on speaking > French is > because in some sense French is better suited to those particular > people > than English, or Dogon, or Mandarin Chinese? Hardly. They continue > to speak French because children continue to acquire French from their > francophone parents and peers. And do we expect society to be show any less inertia in its diurnality? Rob From cowan at ccil.org Mon Sep 15 13:22:15 2008 From: cowan at ccil.org (John Cowan) Date: Mon, 15 Sep 2008 13:22:15 -0400 Subject: [LEAPSECS] drift of TAI In-Reply-To: <5CD69465-EA4B-473A-871E-D16BA6FAF384@noao.edu> References: <2040.1221490232@critter.freebsd.dk> <20080915165208.GH4240@mercury.ccil.org> <5CD69465-EA4B-473A-871E-D16BA6FAF384@noao.edu> Message-ID: <20080915172215.GK4240@mercury.ccil.org> Rob Seaman scripsit: > And do we expect society to be show any less inertia in its diurnality? Not unless we move to somewhere like Heaven, where days are preposterously short, months aren't even a concept, and years depend on what town you live in. Then the kilosecs, megasecs, and gigasecs come into their own. -- Possession is said to be nine points of the law, John Cowan but that's not saying how many points the law might have. cowan at ccil.org --Thomas A. Cowan (law professor and my father) From imp at bsdimp.com Mon Sep 15 15:23:59 2008 From: imp at bsdimp.com (M. Warner Losh) Date: Mon, 15 Sep 2008 13:23:59 -0600 (MDT) Subject: [LEAPSECS] drift of TAI In-Reply-To: References: <2040.1221490232@critter.freebsd.dk> Message-ID: <20080915.132359.-399282205.imp@bsdimp.com> In message: Tony Finch writes: : On Mon, 15 Sep 2008, Poul-Henning Kamp wrote: : > : > However, following the subsequent mathematical proof that the choice : > of base makes no difference to any kind of math, apart from expense : > of ink and paper to write the numbers, base-2 was left alone until : > somebody much later got the heritical idea to drive thermionic : > valves way pas their linear behaviour. : : "Makes no difference" so long as the base is uniform :-) The civilized : world has mostly eliminated non-uniform bases, except for dealing with : time. The Americans (and the British to a lesser extent) still cling to : the handicap of non-uniform bases for other measurements. Still, could : be worse: at least there aren't leap-ounces. UTC is the best example of a variable radix system I can think of. You count 0 to 59, except when you don't :-) Warner From sla at ucolick.org Mon Sep 15 15:39:20 2008 From: sla at ucolick.org (Steve Allen) Date: Mon, 15 Sep 2008 12:39:20 -0700 Subject: [LEAPSECS] drift of TAI In-Reply-To: <5A5A8316-C1AC-472B-8FFA-8C080E859E76@noao.edu> References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> <20080913193657.GH11379@fysh.org> <20080915154257.GC4240@mercury.ccil.org> <5A5A8316-C1AC-472B-8FFA-8C080E859E76@noao.edu> Message-ID: <20080915193920.GA6458@ucolick.org> On Mon 2008-09-15T09:16:45 -0700, Rob Seaman hath writ: > (Although I'm not sure wikipedia will serve > to preserve civilization through the coming collapse :-) Not a chance. Wikipedia is the realization of Bradbury's wall viewers in Fahrenheit 451. The view it gives is always changing. The story it gives about the decisions that spawned this newsgroup are paraphrases of memoirs by folks who wrote down the story the way they wish it had played out at the time. I can't say how much I value the paper in the Lick library for showing what folks were really thinking back then. Along those lines ... The earliest use of the term UTC as such (and TUC in the French) that I have found is in the Jan/Feb 1964 Bulletin Horaire from the BIH. This was the first issue done by Guinot after Anna Stoyko gave it up. Does anyone know of a use of the term UTC/TUC which predates that? -- Steve Allen WGS-84 (GPS) UCO/Lick Observatory Natural Sciences II, Room 165 Lat +36.99858 University of California Voice: +1 831 459 3046 Lng -122.06014 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m From adi at stav.org.il Mon Sep 15 16:23:50 2008 From: adi at stav.org.il (Adi Stav) Date: Mon, 15 Sep 2008 23:23:50 +0300 Subject: [LEAPSECS] drift of TAI In-Reply-To: References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> <20080913193657.GH11379@fysh.org> Message-ID: <20080915202350.GB6802@stav.org.il> (Hi, I'm Adi, long-time lurker, first-time caller) On Mon, Sep 15, 2008 at 01:29:13AM -0700, Rob Seaman wrote: >> In the absence of days and years, though, calculations that involve >> only metric units are a lot easier than what we presently put up with. > > Hence the prevalence of radians in everyday use :-) That's a separate issue. You can base your angle units on perimeter or radius length, and then you can divide them into decimal or sexagesimal subunits as a completely independent decision. Several systems dividing the circle into decimal units have been propsed and used in practice, some still today; on the other hand, it's easy to divide the radian into sexagesimal units. (I'm surprised that I'd never encountered such a system -- dividing the radian into 60 "degrees", each divided into turn into 60 minutes and 3600 seconds, would not only have given "degrees" that are only slighly (5%) smaller than perimetral degrees, but also be more consistent with regards to division by 60.) Actually, our radians don't require any particular radix at all, we use them as whole units. A computer might display a radian in decimal notation, yet stores them in binary floating-point representation, or as nominator-denominator pair, or whatever. Nothing decimal about them. From lang at unb.ca Mon Sep 15 18:55:16 2008 From: lang at unb.ca (Richard B. Langley) Date: Mon, 15 Sep 2008 19:55:16 -0300 (ADT) Subject: [LEAPSECS] drift of TAI In-Reply-To: <20080915193920.GA6458@ucolick.org> References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> <20080913193657.GH11379@fysh.org> <20080915154257.GC4240@mercury.ccil.org> <5A5A8316-C1AC-472B-8FFA-8C080E859E76@noao.edu> <20080915193920.GA6458@ucolick.org> Message-ID: On Mon, 15 Sep 2008, Steve Allen wrote: >Along those lines ... >The earliest use of the term UTC as such (and TUC in the French) that >I have found is in the Jan/Feb 1964 Bulletin Horaire from the BIH. >This was the first issue done by Guinot after Anna Stoyko gave it up. > >Does anyone know of a use of the term UTC/TUC which predates that? At the time I wrote this for lay people (scroll down to "The Origin of UTC"), I knew of nothing earlier. -- Richard >-- >Steve Allen WGS-84 (GPS) >UCO/Lick Observatory Natural Sciences II, Room 165 Lat +36.99858 >University of California Voice: +1 831 459 3046 Lng -122.06014 >Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m >_______________________________________________ >LEAPSECS mailing list >LEAPSECS at leapsecond.com >http://six.pairlist.net/mailman/listinfo/leapsecs > =============================================================================== Richard B. Langley E-mail: lang at unb.ca Geodetic Research Laboratory Web: http://www.unb.ca/GGE/ Dept. of Geodesy and Geomatics Engineering Phone: +1 506 453-5142 University of New Brunswick Fax: +1 506 453-4943 Fredericton, N.B., Canada E3B 5A3 Fredericton? Where's that? See: http://www.city.fredericton.nb.ca/ =============================================================================== From tvb at LeapSecond.com Mon Sep 15 21:47:30 2008 From: tvb at LeapSecond.com (Tom Van Baak) Date: Mon, 15 Sep 2008 18:47:30 -0700 Subject: [LEAPSECS] drift of TAI References: <20080913165600.GE32041@mercury.ccil.org><20080913.132138.-1025553149.imp@bsdimp.com><20080913193657.GH11379@fysh.org><20080915154257.GC4240@mercury.ccil.org><5A5A8316-C1AC-472B-8FFA-8C080E859E76@noao.edu> <20080915193920.GA6458@ucolick.org> Message-ID: <000301c9179e$3171e830$0500a8c0@pc52> > Along those lines ... > The earliest use of the term UTC as such (and TUC in the French) that > I have found is in the Jan/Feb 1964 Bulletin Horaire from the BIH. > This was the first issue done by Guinot after Anna Stoyko gave it up. > > Does anyone know of a use of the term UTC/TUC which predates that? Steve, I don't have one earlier than your 1964. Essen, 1958, no mention of UTC (way too early): http://www.leapsecond.com/history/1958-PhysRev-v1-n3-Markowitz-Hall-Essen-Parry.pdf Essen, 1968, mentions UTC, and proposes what would become leap seconds: http://www.leapsecond.com/history/1968-Metrologia-v4-n4-Essen.pdf /tvb From lang at unb.ca Wed Sep 17 17:57:27 2008 From: lang at unb.ca (Richard B. Langley) Date: Wed, 17 Sep 2008 18:57:27 -0300 (ADT) Subject: [LEAPSECS] Late Pips In-Reply-To: References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> <20080913193657.GH11379@fysh.org> <20080915154257.GC4240@mercury.ccil.org> <5A5A8316-C1AC-472B-8FFA-8C080E859E76@noao.edu> <20080915193920.GA6458@ucolick.org> Message-ID: -- Richard P.S. There was a presentation yesterday at the CGSIC meeting here in Savannah on the work of ITU-R WP7A and the future of UTC (see program: ). The presentation should be on the website within a couple of weeks or so. I didn't hear anything I didn't already know but it was a useful summary of the progress/machinations (choose your word) to date. =============================================================================== Richard B. Langley E-mail: lang at unb.ca Geodetic Research Laboratory Web: http://www.unb.ca/GGE/ Dept. of Geodesy and Geomatics Engineering Phone: +1 506 453-5142 University of New Brunswick Fax: +1 506 453-4943 Fredericton, N.B., Canada E3B 5A3 Fredericton? Where's that? See: http://www.city.fredericton.nb.ca/ =============================================================================== From magnus at rubidium.dyndns.org Sat Sep 27 06:07:02 2008 From: magnus at rubidium.dyndns.org (Magnus Danielson) Date: Sat, 27 Sep 2008 12:07:02 +0200 Subject: [LEAPSECS] drift of TAI In-Reply-To: <41EC7887-0BDA-438F-BBC2-4131EBF2806B@noao.edu> References: <2040.1221490232@critter.freebsd.dk> <41EC7887-0BDA-438F-BBC2-4131EBF2806B@noao.edu> Message-ID: <48DE05C6.4040606@rubidium.dyndns.org> Rob Seaman wrote: > On Sep 15, 2008, at 8:23 AM, Magnus Danielson wrote: > >> There where plans for converting Sweden to a base 8 country, but I don't >> have the TAOCP I need at hand to give the details. > > This sounds like either an urban legend or some isolated... You obviously haven't read Donald Knuths "The Art of Computer Programming; Seminumerical Algorithms" (Vol 2) where chapter 4.1 would be an interesting reading on the topic of number systems. Prof. Knuth is fairly keen on researching his stuff. Charles XII of Sweden (Carl XII in swedish texts) had the idea of radix-8 arithmetic 1717 but was killed in a battle before he could convert this idea into reality. He met Liebniz in 1707, but it is not known if Liebniz work on binary numbers was discussed or known to Carl. I just didn't have that book at hand when I wrote that reference, but it was a quick thing to look up now as I have it at hand. > how do you say "nut job" in Swedish? There are many ways to say it. I am not sure I can properly convey it in the 1717 lingo thougth. I think you are best served in this instance by learning what we call a nutter... "galenpanna". I think you would need to learn some grammar and more words to propperly use it in a meaningfull way thought. > Another example would be the Indiana legislature voting on pi=3. Don't bring US local legislation into this... Cheers, MAgnus From magnus at rubidium.dyndns.org Sat Sep 27 06:21:14 2008 From: magnus at rubidium.dyndns.org (Magnus Danielson) Date: Sat, 27 Sep 2008 12:21:14 +0200 Subject: [LEAPSECS] drift of TAI In-Reply-To: <20080915202350.GB6802@stav.org.il> References: <20080913165600.GE32041@mercury.ccil.org> <20080913.132138.-1025553149.imp@bsdimp.com> <20080913193657.GH11379@fysh.org> <20080915202350.GB6802@stav.org.il> Message-ID: <48DE091A.6050207@rubidium.dyndns.org> Adi Stav wrote: > (Hi, I'm Adi, long-time lurker, first-time caller) > > On Mon, Sep 15, 2008 at 01:29:13AM -0700, Rob Seaman wrote: >>> In the absence of days and years, though, calculations that involve >>> only metric units are a lot easier than what we presently put up with. >> Hence the prevalence of radians in everyday use :-) > > That's a separate issue. You can base your angle units on perimeter or > radius length, and then you can divide them into decimal or sexagesimal > subunits as a completely independent decision. Several systems dividing > the circle into decimal units have been propsed and used in practice, > some still today; on the other hand, it's easy to divide the radian into > sexagesimal units. (I'm surprised that I'd never encountered > such a system -- dividing the radian into 60 "degrees", each divided > into turn into 60 minutes and 3600 seconds, would not only have given > "degrees" that are only slighly (5%) smaller than perimetral degrees, > but also be more consistent with regards to division by 60.) > > Actually, our radians don't require any particular radix at all, we use > them as whole units. A computer might display a radian in decimal > notation, yet stores them in binary floating-point representation, or as > nominator-denominator pair, or whatever. Nothing decimal about them. There are several military systems that approximate radians in this fashion. Used when making precission measurements (of its time in the field) for measuring the destination of ordinance. Cheers, Magnus From seaman at noao.edu Sat Sep 27 10:44:28 2008 From: seaman at noao.edu (Rob Seaman) Date: Sat, 27 Sep 2008 07:44:28 -0700 Subject: [LEAPSECS] drift of TAI In-Reply-To: <48DE05C6.4040606@rubidium.dyndns.org> References: <2040.1221490232@critter.freebsd.dk> <41EC7887-0BDA-438F-BBC2-4131EBF2806B@noao.edu> <48DE05C6.4040606@rubidium.dyndns.org> Message-ID: <4F2FF57B-0C5B-400F-90D5-75C06F0102EC@noao.edu> Knuth has been quite an idiosyncratic seeker after truth, himself :-) Not sure why this thread is reviving now (the continued drift of TAI?) but I see I previously resisted the obvious rejoinder that since it was a monarch who was pursuing this agenda, it proved my assertion about his being a nutjob. One remains skeptical that even a grandee such as Carl XII would have successfully managed to convince the hoi polloi to adopt octal over decimal. Consider the requirements of international trade, for one thing. Does anyone "read" Knuth? If we're moving on to book lists about measurement theory and data representation, I can strongly recommend Widrow and Koll?r's "Quantization Noise", just published. Also "Lavoisier in the Year One", by Madison Smartt Bell, is a good little cautionary tale. Rob -- On Sep 27, 2008, at 3:07 AM, Magnus Danielson wrote: > Rob Seaman wrote: >> On Sep 15, 2008, at 8:23 AM, Magnus Danielson wrote: >>> There where plans for converting Sweden to a base 8 country, but I >>> don't >>> have the TAOCP I need at hand to give the details. >> This sounds like either an urban legend or some isolated... > > You obviously haven't read Donald Knuths "The Art of Computer > Programming; Seminumerical Algorithms" (Vol 2) where chapter 4.1 > would be an interesting reading on the topic of number systems. > Prof. Knuth is fairly keen on researching his stuff. > > Charles XII of Sweden (Carl XII in swedish texts) had the idea of > radix-8 arithmetic 1717 but was killed in a battle before he could > convert this idea into reality. He met Liebniz in 1707, but it is > not known if Liebniz work on binary numbers was discussed or known > to Carl. > > I just didn't have that book at hand when I wrote that reference, > but it was a quick thing to look up now as I have it at hand. > > > how do you say "nut job" in Swedish? > > There are many ways to say it. I am not sure I can properly convey > it in the 1717 lingo thougth. I think you are best served in this > instance by learning what we call a nutter... "galenpanna". I think > you would need to learn some grammar and more words to propperly use > it in a meaningfull way thought. > >> Another example would be the Indiana legislature voting on pi=3. > > Don't bring US local legislation into this... > > Cheers, > MAgnus > _______________________________________________ > LEAPSECS mailing list > LEAPSECS at leapsecond.com > http://six.pairlist.net/mailman/listinfo/leapsecs