Avoiding the Leap Second

In the beginning, there was Ephemeris Time.

Then, it got replaced by TAI.

Both were made up of seconds the length of which was based on the
length of the second in 1900. But the Earth's rotation has been
slowing down, due to tidal forces.

Because TAI started off from civil time at the time of its adoption,
while Ephemeris time presumably started on noon, December 31st, 1899,
GMT, a clock showing Ephemeris Time would be 32.184 seconds ahead of
one showing TAI.

And a clock showing TAI would be 19 seconds ahead of one showing the
time used in the GPS system.

Civil time switched over to atomic time with inserted leap seconds
when TAI was already 10 seconds ahead of civil time.

Anyways: a while back, there was a message in these newsgroups about
how a group, shrouding its activities in mystery, came forwards with a
proposal to just forget about leap seconds. We could always adjust our
clocks an hour at a time, if we really felt strongly about wanting
local 12 noon to happen around lunchtime.

I don't think the mass of humanity really considers it so important to
be "modern" and "scientific" that they would willingly allow the clock
to be independent of the real time of day.

But it is true that leap seconds are awkward and confusing. I would
like to suggest an alternative for those whose concerns are precise
ones.

There are 86,400 seconds in a day, and about 365 days in a year. If we
add one second to a year, then, that lengthens the year by one part in
365 times 86,400.

If we instead increased the length of every *second* in that year by
the same proportion, we would be making the civil second equal to 1 SI
second and 31.70979198... SI nanoseconds.

This would be an approximation to UT1, or mean solar time, the way
civil time was kept *before* we had leap seconds.

Adding 30, 32, or 33 1/3 nanoseconds... or going from 9,192,631,770
cesium atom oscillations to 9,192,632,061.5 cesium atom oscillations
(adding 291.5)... or whichever approximation might be most convenient,
for the forthcoming year to the length of the second; or subtracting,
or adding twice that, as necessary, would allow us to have a civil
time without leap seconds.

The length of the civil second would vary, but there would only be a
limited number of possible variations, separated by uniform steps.

I presume this would be good enough for those applications where leap
seconds are disruptive; those where a second absolutely fixed in
length is required would have to cope with the difference between TAI
and civil time and its changes.

Since I'm proposing changing the length of a second, though, by an
approximation, rather than the *exact* proportion that adding an extra
second would make, this would not lead to TAI minus civil time being
an integer number of seconds at least at the start of each new year.
There are two possible cures: use the exact proportion instead
(adjusted in leap years!), or switch from a longer second to a regular
one before the end of the year (for example, splitting the leap second
up among all the seconds of the first 360 days of the year would lead
to an "even" lengthening of the second in some senses).

John Savard

On May 30, 5:51 pm, Quadibloc wrote:
[...]
Since I'm proposing changing the length of a second, though, by an
approximation, rather than the *exact* proportion that adding an extra
second would make, this would not lead to TAI minus civil time being
an integer number of seconds at least at the start of each new year.
There are two possible cures: use the exact proportion instead
(adjusted in leap years!), or switch from a longer second to a regular
one before the end of the year (for example, splitting the leap second
up among all the seconds of the first 360 days of the year would lead
to an "even" lengthening of the second in some senses).

John Savard

Why not simultaneously go decimal for time?

For example: 100 new seconds to a new minute, 100 new minutes to a
new hour, and, say, 10 new hours in a standard day. The present use
of 60/60/24 is archaic.

Gawd only knows what that'd do to RA and Dec. :-)

thad:

Why not simultaneously go decimal for time?

For example: 100 new seconds to a new minute, 100 new minutes to a
new hour, and, say, 10 new hours in a standard day. The present use
of 60/60/24 is archaic.

A bit of quibbling over a leap second notwithstanding, our method of
measuring and reporting time is not broken. It is understood by more
people by far than any other international standard.

Gawd only knows what that'd do to RA and Dec. :-)

Can you imagine the $cost of such a change!? The veritable mind boggles.

Davoud

--
usenet *at* davidillig dawt com

In article .com,
wrote:
On May 30, 5:51 pm, Quadibloc wrote:
[...]
Since I'm proposing changing the length of a second, though, by an
approximation, rather than the *exact* proportion that adding an extra
second would make, this would not lead to TAI minus civil time being
an integer number of seconds at least at the start of each new year.
There are two possible cures: use the exact proportion instead
(adjusted in leap years!), or switch from a longer second to a regular
one before the end of the year (for example, splitting the leap second
up among all the seconds of the first 360 days of the year would lead
to an "even" lengthening of the second in some senses).

John Savard

Changing the length of the second is out of the question!!! Why?
Because a change in the length of the second would affect so many
other units which all depend on the second.

One can look at the history of the meter as an example: one meter was
originally supposed to be one ten-millionth of the length of a
meridian on the Earth, from equator to pole. Realizing that each time
a meter prototype was needed would be too awkward though, so instead a
meter prototype was manufactured and used as the primary standard. A
few decades later it turned out that the meter prototype had been
manufactured erroneously, so that it was some fraction of a millimeter
too short. But instead of "correcting the error", one let the meter
prototype become the new standard, and the length of the Earth's
meridians, from equator to pole, became slightly longer than ten
million meters. Since then the meter has been redefined twice and
we're no longer dependent on some particular physical object for the
definition of the meter. But in each of these redefinitions of the
meter, great care was taken to not change the length of the meter,
i.e. the length of the "new meter" should be equal to the length of
the "old meter", to the accuracy of the old definition. The only time
the meter changed length significantly was when that first meter
prototype was manufactured.

You just don't change the size of a fundamental unit!


Why not simultaneously go decimal for time?

For example: 100 new seconds to a new minute, 100 new minutes to a
new hour, and, say, 10 new hours in a standard day.

Sorry, but it's too late! The French succeeded in getting its metric
system (which originated from the time around the French revolution)
accepted by the world. But they failed to get its revolutionary
calendar accepted - it was used only in France and even there it was
abandoned after only a few decades. The French revolutionary calendar
did have the properties you're asking for: 100 new seconds to a new
minute, 100 new minutes to a new hour, and, say, 10 new hours in a
standard day. But it went further than that: one week was 10 days,
one month was 3 weeks of 10 days each i.e. 30 days, and one year was
12 months of 30 days each, i.e. 360 days -- plus 5 or 6 "revolutionary
days" at the end of the year, which were outside all weeks and months.

The present use of 60/60/24 is archaic.

....but it does have some advantages: you can quite easily split up
an hour in 2, 3, 4, 5 or 6 equal parts - they'll become 30, 20, 15,
12, and 10 minutes each. If an hour was 100 minutes, the parts
would become 50, 33+1/3, 25, 20, and 16+2/3 minutes each.

Personally I think (although I of course know this won't happen) that
we really should switch from the decimal (base 10) to a duodecimal
(base 12) system for representing numbers - that would bring the
advantage of easy divisibility by 2, 3 and 4. The sexagesimal
(base 60) system brings easy divisibility by 5 and 6 as well.

Btw, in the duodecimal system one hour will be equal to 50 minutes,
since 50-base12 equals 60-base10. And one day would be equal to 20
hours, since 20-base12 equals 24-base10. Wouldn't that be something?


Gawd only knows what that'd do to RA and Dec. :-)

You could always switch to degrees and fractions of degrees... :-)

But hey! You wanted to go decimal, right? Why should one quadrant be
90 degrees? Why not, say, 100 degrees instead? There is actually
such a measure for angles - it's called gons, or (sometimes) "new
degrees": one quadrant is 100 degrees and one revolution is 400
degrees. Sometimes this has been used for surveying, and there it
fits neatly: while one degree of latitude on the Earth's surface is
some 111 km, one "new degree" is very close to 100 km and one "new
minute" (equal to 1/100 "new degree" of course) is very close to 1 km.

So the decimal angular units are already there - you just have to start
using them! :-)

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

Paul Schlyter wrote:
Changing the length of the second is out of the question!!! Why?
Because a change in the length of the second would affect so many
other units which all depend on the second.

I'm not proposing that we change the length of a second for purposes
of measuring speed and acceleration, so as to change the value of the
newton relative to the meter, or to change the volt, the ohm, the
joule, or so on.

I am merely proposing that we change the second of *civil time* so
that it is longer than the 1900 second of Ephemeris Time, also the SI
second. That is simply *going back* to the situation we had before
atomic time, with leap seconds, was adopted in 1972.

The difference is simply that to compromise with our world in which
things are measured with greater precision, I propose that instead of
having a second that gradually increases in length in a somewhat messy
and indeterminate way, let us have a time scale that is still tied
closely to TAI, but by changing the length of the civil second in a
controlled manner, so as to produce an effect essentially equivalent
to having leap seconds.

Since I am proposing lengthening the second *only in those years with
leap seconds*, obviously I would not seriously propose that the ohm,
volt, et cetera be different in those years too. That would be
insanity, and rest assured I suggest no such thing.

John Savard

On 31 mei, 09:04, Quadibloc wrote:
Paul Schlyter wrote:

Since I am proposing lengthening the second *only in those years with
leap seconds*, obviously I would not seriously propose that the ohm,
volt, et cetera be different in those years too. That would be
insanity, and rest assured I suggest no such thing.

John Savard

But you'd have no choice, what does a frequency counter (piece of
electronic
equipment show? Pulses per second (Hertz).
And these may wel be calibrated against NIST, and some measure in pico
seconds, quite a bit of error would show!
Now endless arguments would be created if it was your new second or
the real
second or whatever,
The wavelength scale on your radio, basically all other physics
constants,
you car's km/hour or miles/hour... what not!
I say: Forget it:-)

In article .com,
Quadibloc wrote:

Paul Schlyter wrote:
Changing the length of the second is out of the question!!! Why?
Because a change in the length of the second would affect so many
other units which all depend on the second.

I'm not proposing that we change the length of a second for purposes
of measuring speed and acceleration, so as to change the value of the
newton relative to the meter, or to change the volt, the ohm, the
joule, or so on.

I am merely proposing that we change the second of *civil time* so
that it is longer than the 1900 second of Ephemeris Time, also the SI
second. That is simply *going back* to the situation we had before
atomic time, with leap seconds, was adopted in 1972.

Before 1972, UTC time was adjusted in steps of fractions of a second,
much more frequently than the frequency of leap seconds. It was to
get rid of that mess that leap seconds were introduced.

The difference is simply that to compromise with our world in which
things are measured with greater precision, I propose that instead of
having a second that gradually increases in length in a somewhat messy
and indeterminate way, let us have a time scale that is still tied
closely to TAI, but by changing the length of the civil second in a
controlled manner, so as to produce an effect essentially equivalent
to having leap seconds.

Since I am proposing lengthening the second *only in those years with
leap seconds*, obviously I would not seriously propose that the ohm,
volt, et cetera be different in those years too. That would be
insanity, and rest assured I suggest no such thing.

And how would you determine which years are "those years with a leap second"?
Yep, that process too is as unpredictable as the leap seconds. So there
would be a need to transform the information about how long a second will
last this year ..... it would be just as awkward as the leap seconds
themselves.

I think applications which really need a time accuracy better than
a few seconds over long time interval should use TT, TAI, GPS time, or
some other suitable *uniform* time scale *without* *leap* *seconds*!
All other applications, where it doesn't matter whether the time is
off by a few seconds, should adjust for leap seconds whenever they
occur, but ignore leap seconds when computing the time interval
between two instants - much like the UNIX time() family of funtions do
today.

John Savard
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

In article .com,
Quadibloc wrote:
I am merely proposing that we change the second of *civil time*

Paul Schlyter wrote:
Before 1972, UTC time was adjusted in steps of fractions of a second,
much more frequently than the frequency of leap seconds. It was to
get rid of that mess that leap seconds were introduced.

Let's consider a new time scale... call it UTx. On days with no leap
second, UTx = UTC. On days having a leap second, UTx uses a second
86401/86400 times longer than the SI second with no leap second added.
There is, of course, no redefinition of the SI second itself.

What would be the advantages and disadvantages of using UTx instead of
UTC for civil time?

In sci.astro.amateur message , Thu, 31 May
2007 17:42:23, Paul Schlyter posted:

I think applications which really need a time accuracy better than
a few seconds over long time interval should use TT, TAI, GPS time, or
some other suitable *uniform* time scale *without* *leap* *seconds*!
All other applications, where it doesn't matter whether the time is
off by a few seconds, should adjust for leap seconds whenever they
occur, but ignore leap seconds when computing the time interval
between two instants - much like the UNIX time() family of funtions do
today.

I use "broadcast" in the widest possible sense here.

The time for civil chronometrical purposes should be substantially the
traditional GMT, a mean solar time, with adjustments for longitude and
season in the present manner. Time-and-date signals for this should be
broadcast. The human race can adapt its activities to short- and long-
term variations in the terrestrial motions causing corresponding
variations in the length of the civil year month day hour minute and
second.

The unit of time for all measurement processes should be the SI second,
as presently fixed and possibly in future redefined. There should be
broadcast signals for these too, quite independently of civil time, and
in a fully-decimal system.

In some fields, it seems possible to use either system, and hence
necessary to make a choice - aero-navigation might be one, using SI time
in the cockpit while on the runway and in the air, and civil time in the
cabin and on the ground.

Astronomers should use SI time for recording observation, terrestrial
time for pointing telescopes, and civil time for ordinary life - they
should be smart enough to manage.

Under such a scheme, NASA might have been guided into using SI time for
controlling the Shuttle (retaining GMT for the crew's activity) and so
would not have fallen into the rather obvious Year Rollover Difficulty.
Since the Shuttle is supposed to be up for of the order of a fortnight
at most, 32 bits of SI seconds should give an ample margin.


To avoid confusion, the SI second should have a new name and symbol.
Since ms is so widely written mS, and there's rarely any possible
ambiguity between second and Siemens, and the latter is somewhat
specialist, ISTM that the Siemens should revert to the Mho (thus
removing the trap of writing One Siemen) and the symbol S be used for
the SI Second, with a suitable new name. I think the Schlyter is
available, though it might be necessary to choose something easier to
spell ...

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Web URL:http://www.merlyn.demon.co.uk/ - FAQish topics, acronyms, & links.
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Paul Schlyter wrote:
But hey! You wanted to go decimal, right? Why should one quadrant be
90 degrees? Why not, say, 100 degrees instead? There is actually
such a measure for angles - it's called gons, or (sometimes) "new
degrees": one quadrant is 100 degrees and one revolution is 400
degrees. Sometimes this has been used for surveying, and there it
fits neatly: while one degree of latitude on the Earth's surface is
some 111 km, one "new degree" is very close to 100 km and one "new
minute" (equal to 1/100 "new degree" of course) is very close to 1 km.
..
So the decimal angular units are already there - you just have to start
using them! :-)
..
I thought they were called "grads". But, in any case, since you are
apparently a stickler for SI units, you should of course know that the
official unit for angular measure, the one that fits with everything
else in the metric system, is the *radian*.

Of course, it is a little awkward that the number of radians in a
right angle, or indeed any aliquot part of the circle, is an
irrational, even transcendental, number. One could include pi
explicitly in descriptions of angles to get out of this; then, an
angle would be called "N pi radians". Since the circle contains 2 pi
radians, a protractor with 100 big marks on it to cover 180 degrees,
instead of 200 marks, would make sense, covering the expanse from 0 to
1 pi radians.

John Savard