Notes on clocks and daily rotation

"Craig" wrote in message
...
On Jan 19, 12:51 pm, BDK wrote:
In article 1f3b5169-9176-486d-83aa-
,
says...

Which universe is that? In the universe that I'm aware of, the
earth's rotation rate has both positive and negative changes, mostly
seasonally dependent.

It's always been slowing down, days used to be shorter, much shorter,
if
you go back 100's of millions of years.
...
Example: http://tycho.usno.navy.mil/leapsec.html

Apparently you were having difficulty viewing the "length of day" plot
referenced. The plot shows that the earth's rotation rate both speeds
up and slows down, depending on the timescale being examined.

CM

Have someone smack you upside the head and maybe you'll understand. The
earth has been slowing down since it was formed. Days used to be much
shorter. Damn, this isn't rocket science!!!

Having somebody smack me upside my head won't change the data on the
referenced plot, which you apparently ignored, that shows real
observational data. (and, for example, shows the earth's rotation
rate has sped up in the past three decades, thus invalidating your
assertion that "it's always been slowing down.") It's not "rocket
science" to look at actual data either.

CM

Ahem...
Excuse me if I'm puzzled by your assertion, but does that page not say
"The aged Earth is slowing down in its daily rotation, at
least in the current epoch." immediately below the graph?
In the extreme case where the Earth slowed so much as to
make a day the same as a year (same face toward the Sun)
the number of caesium133 seconds would be much greater;
in other words adding a second implies the Earth has slowed.
Where do you get this notion that "Earth's rotation rate
has sped up in the past three decades"?

On Jan 19, 9:08*pm, "Androcles" wrote:
"Craig" wrote in message

...
On Jan 19, 12:51 pm, BDK wrote:



In article 1f3b5169-9176-486d-83aa-
,
says...

Which universe is that? In the universe that I'm aware of, the
earth's rotation rate has both positive and negative changes, mostly
seasonally dependent.

It's always been slowing down, days used to be shorter, much shorter,
if
you go back 100's of millions of years.
...
Example:http://tycho.usno.navy.mil/leapsec.html

Apparently you were having difficulty viewing the "length of day" plot
referenced. The plot shows that the earth's rotation rate both speeds
up and slows down, depending on the timescale being examined.

CM

Have someone smack you upside the head and maybe you'll understand. The
earth has been slowing down since it was formed. Days used to be much
shorter. Damn, this isn't rocket science!!!

Having somebody smack me upside my head won't change the data on the
referenced plot, which you apparently ignored, that shows real
observational data. * (and, for example, shows the earth's rotation
rate has sped up in the past three decades, thus invalidating your
assertion that "it's always been slowing down.") *It's not "rocket
science" to look at actual data either.

CM

Ahem...
Excuse me if I'm puzzled by your assertion, but does that page not say
"The aged Earth is slowing down in its daily rotation, at
least in the current epoch." immediately below the graph?
In the extreme case where the Earth slowed so much as to
make a day the same as a year (same face toward the Sun)

A person at either geographical poles is not rotating but will
experience,to all intents and purposes ,a year long cycle of daylight
and darkness.This means that any given location on the planet,aside
from daily rotation, does not keep the same face to the Sun but
changes it through an entire 360 degrees over the course of an annual
orbit.It is not an opinion but actually observed in great detail using
the equatorial rings and unique orientation of Uranus as a guide.

You are from the same group who believes that a star returning to a
meridian every 23 hours 56 minutes 04 seconds represents the daily
rotation of the Earth and then judge whether the rotation is speeding
up and slowing down,it is nothing but childish junk by people who do
not know what they are doing astronomically and if any other
scientific discipline acted the way you and your colleagues do,there
would be one serious global investigation.

There is a point to getting this right rather than showing where the
guys in the late 17th century jumped the tracks,a planet has two 360
degree motions,intrinsic to the planet itself,with respect to the
central Sun,people can actually see these motions in action via modern
time lapse footage -

http://hubblesite.org/newscenter/arc...999/11/video/b

It takes two intrinsic 360 degree motions to explain the seasons -
daily rotation which generates rotational orientation (tilt) and a
separate 360 degree motion which turns a location through 360 degrees
to the central Sun over the course of a year,this latter motion does
not follow daily rotation or its tilt but turns at right angles to the
circle of illumination.











the number of caesium133 seconds would be much greater;
in other words adding a second implies the Earth has slowed.
Where do you get this notion that "Earth's rotation rate
has sped up in the past three decades"?

On Jan 19, 3:08*pm, "Androcles" wrote:
"Craig" wrote in message

...
On Jan 19, 12:51 pm, BDK wrote:



In article 1f3b5169-9176-486d-83aa-
,
says...

Which universe is that? In the universe that I'm aware of, the
earth's rotation rate has both positive and negative changes, mostly
seasonally dependent.

It's always been slowing down, days used to be shorter, much shorter,
if
you go back 100's of millions of years.
...
Example:http://tycho.usno.navy.mil/leapsec.html

Apparently you were having difficulty viewing the "length of day" plot
referenced. The plot shows that the earth's rotation rate both speeds
up and slows down, depending on the timescale being examined.

CM

Have someone smack you upside the head and maybe you'll understand. The
earth has been slowing down since it was formed. Days used to be much
shorter. Damn, this isn't rocket science!!!

Having somebody smack me upside my head won't change the data on the
referenced plot, which you apparently ignored, that shows real
observational data. * (and, for example, shows the earth's rotation
rate has sped up in the past three decades, thus invalidating your
assertion that "it's always been slowing down.") *It's not "rocket
science" to look at actual data either.

CM

Ahem...
Excuse me if I'm puzzled by your assertion, but does that page not say
"The aged Earth is slowing down in its daily rotation, at
least in the current epoch." immediately below the graph?

Yes, and I believe the text's statement is true... IF one averages
over centuries and millenia. This is not actually shown on the plot.
The *plot* shows that on shorter time scales -- decades -- the earth
has epochs of both spin-up and spin-down. I linked to the particular
page I linked to, for the figure and not the text.

In the extreme case where the Earth slowed so much as to
make a day the same as a year (same face toward the Sun)
the number of caesium133 seconds would be much greater;
in other words adding a second implies the Earth has slowed.
Where do you get this notion that "Earth's rotation rate
has sped up in the past three decades"?

Well, because the figure shows that the length of day has shortened by
about 3 msec in the past three decades. Shortening of the length of
day implies an *increase* in rotation rate.

While I concur that the major, millenial trend appears to be gradual
spin-down, on shorter time-scales the situation is not so simple.

CM

"Craig" wrote in message
...
On Jan 19, 3:08 pm, "Androcles" wrote:
"Craig" wrote in message

...
On Jan 19, 12:51 pm, BDK wrote:



In article 1f3b5169-9176-486d-83aa-
,
says...

Which universe is that? In the universe that I'm aware of, the
earth's rotation rate has both positive and negative changes,
mostly
seasonally dependent.

It's always been slowing down, days used to be shorter, much
shorter,
if
you go back 100's of millions of years.
...
Example:http://tycho.usno.navy.mil/leapsec.html

Apparently you were having difficulty viewing the "length of day" plot
referenced. The plot shows that the earth's rotation rate both speeds
up and slows down, depending on the timescale being examined.

CM

Have someone smack you upside the head and maybe you'll understand. The
earth has been slowing down since it was formed. Days used to be much
shorter. Damn, this isn't rocket science!!!

Having somebody smack me upside my head won't change the data on the
referenced plot, which you apparently ignored, that shows real
observational data. (and, for example, shows the earth's rotation
rate has sped up in the past three decades, thus invalidating your
assertion that "it's always been slowing down.") It's not "rocket
science" to look at actual data either.

CM

Ahem...
Excuse me if I'm puzzled by your assertion, but does that page not say
"The aged Earth is slowing down in its daily rotation, at
least in the current epoch." immediately below the graph?

Yes, and I believe the text's statement is true... IF one averages
over centuries and millenia. This is not actually shown on the plot.
The *plot* shows that on shorter time scales -- decades -- the earth
has epochs of both spin-up and spin-down. I linked to the particular
page I linked to, for the figure and not the text.

In the extreme case where the Earth slowed so much as to
make a day the same as a year (same face toward the Sun)
the number of caesium133 seconds would be much greater;
in other words adding a second implies the Earth has slowed.
Where do you get this notion that "Earth's rotation rate
has sped up in the past three decades"?

Well, because the figure shows that the length of day has shortened by
about 3 msec in the past three decades. Shortening of the length of
day implies an *increase* in rotation rate.

While I concur that the major, millenial trend appears to be gradual
spin-down, on shorter time-scales the situation is not so simple.

CM
=============================================

1)
"The last leap second was introduced in UTC at the end of December 2005.
There WILL be (now was, this is Jan 2008)
a another positive leap second introduced in UTC on 31 December 2008. "

2)
"The ephemeris second thus defined is the fraction
1/31,556,925.9747 of the tropical year for 1900
January 0 at 12 hours ephemeris time."

So by 2) this degree of precision did not occur before 1900
and by 1) there was a decrease in rotation rate in just 3 years.

Looking at the graph, the mean slope is upward between 2004
and 2007, and has falling since.

Because leap seconds are only added on Dec 31, the shortest time
scale the layman can reasonably consider is the year. To reinforce
this view, there are 36 PEAKS on the graph between 1973 and 2009,
so there is clearly a yearly cycle embedded in the data and any variation
within a year should be considered as noise or we'll be having 86,399.999
seconds one day and 86,400.001 seconds another, or even worse
3600 +/- delta seconds per hour, throwing all time-keeping into
hopeless confusion. Would it make sense if we added or subtracted
leap-nanoseconds to the hour? Is anyone going to modify their clock
driven telescopes to compensate for daily variations in the rotation
of the Earth? No, of course not.
The standard we choose has to be one that is readily available to the
majority.

It would therefore appear that the arbitrary choice of 9 192 631 770
periods of the radiation corresponding to the transition between the
two hyperfine levels of the ground state of the cesium 133 atom
(which is not available to the majority) was inappropriately based
on the year 1900 and not 2000; we are having to add leap-seconds
frequently and need to redefine the second. The year has to remain
the absolute standard to make any sense of time-keeping at all.
Indeed, the retention of the arbitrary Julian date only makes sense
to astronomers for locating planetary positions, nobody else uses
it but everyone uses the year.

Perhaps it is rocket science to look at actual data after all,
because where you can arbitrarily choose 3 consecutive decades to
make your claim I can arbitrarily choose 3 consecutive years to
show the opposite, leaving poor old BDK wondering what the hell
we two idiots are rattling on about.

On Jan 20, 2:26*am, "Androcles" wrote:
"Craig" wrote in message

...
On Jan 19, 3:08 pm, "Androcles" wrote:



"Craig" wrote in message

...
On Jan 19, 12:51 pm, BDK wrote:

In article 1f3b5169-9176-486d-83aa-
,
says...

Which universe is that? In the universe that I'm aware of, the
earth's rotation rate has both positive and negative changes,
mostly
seasonally dependent.

It's always been slowing down, days used to be shorter, much
shorter,
if
you go back 100's of millions of years.
...
Example:http://tycho.usno.navy.mil/leapsec.html

Apparently you were having difficulty viewing the "length of day" plot
referenced. The plot shows that the earth's rotation rate both speeds
up and slows down, depending on the timescale being examined.

CM

Have someone smack you upside the head and maybe you'll understand. The
earth has been slowing down since it was formed. Days used to be much
shorter. Damn, this isn't rocket science!!!

Having somebody smack me upside my head won't change the data on the
referenced plot, which you apparently ignored, that shows real
observational data. (and, for example, shows the earth's rotation
rate has sped up in the past three decades, thus invalidating your
assertion that "it's always been slowing down.") It's not "rocket
science" to look at actual data either.

CM

Ahem...
Excuse me if I'm puzzled by your assertion, but does that page not say
"The aged Earth is slowing down in its daily rotation, at
least in the current epoch." immediately below the graph?

Yes, and I believe the text's statement is true... IF one averages
over centuries and millenia. *This is not actually shown on the plot.
The *plot* shows that on shorter time scales -- decades -- the earth
has epochs of both *spin-up and spin-down. *I linked to the particular
page I linked to, for the figure and not the text.

In the extreme case where the Earth slowed so much as to
make a day the same as a year (same face toward the Sun)
the number of caesium133 seconds would be much greater;
in other words adding a second implies the Earth has slowed.
Where do you get this notion that "Earth's rotation rate
has sped up in the past three decades"?

Well, because the figure shows that the length of day has shortened by
about 3 msec in the past three decades. *Shortening of the length of
day implies an *increase* in rotation rate.

While I concur that the major, millenial trend appears to be gradual
spin-down, on shorter time-scales the situation is not so simple.

CM
=============================================

1)
"The last leap second was introduced in UTC at the end of December 2005.
There WILL be (now was, this is Jan 2008)
a another positive leap second introduced in UTC on 31 December 2008. "

2)
"The ephemeris second thus defined is the fraction
1/31,556,925.9747 of the tropical year for 1900
January 0 at 12 hours ephemeris time."

So by 2) this degree of precision did not occur before 1900
and by 1) there was a decrease in rotation rate in just 3 years.

Leap seconds are implemented only as a modification to *civil* time,
in order to track the gross accumulated rotational changes of the
earth. The measurements of length of day stand by themselves,
independent of leap seconds, hence leap seconds are irrelevant to the
question of whether the earth rotation rate is increasing or
decreasing. I only referenced that particular web page for the plot.

Looking at the graph, the mean slope is upward between 2004
and 2007, and has falling since.

Because leap seconds are only added on Dec 31, the shortest time
scale the layman can reasonably consider is the year. To reinforce
this view, there are 36 PEAKS on the graph between 1973 and 2009,
*so there is clearly a yearly cycle embedded in the data and any variation
within a year should be considered as noise or we'll be having 86,399.999
seconds one day and 86,400.001 seconds another, or even worse
3600 +/- delta seconds per hour, throwing all time-keeping into
hopeless confusion. Would it make sense if we added or subtracted
leap-nanoseconds to the hour? Is anyone going to modify their clock
driven telescopes to compensate for daily variations in the rotation
of the Earth? No, of course not.

You are incorrect. Of course, modern telescopes *do* use fractional
"leap seconds" for pointing, although it's really termed "UT1-UTC".

The standard we choose has to be one that is readily available to the
majority.

Again you are confusing civil timekeeping with terrestrial physics.

It would therefore appear that the arbitrary choice of 9 192 631 770
periods of the radiation corresponding to the transition between the
two hyperfine levels of the ground state of the cesium 133 atom
(which is not available to the majority) was inappropriately based
on the year 1900 and not 2000; we are having to add leap-seconds

Actually if you read the article, it was based on the year 1820. The
date is not arbitrary; rather, it was based on the observations
available to Newcomb, who reduced all of the data.

frequently and need to redefine the second. The year has to remain
the absolute standard to make any sense of time-keeping at all.
....

The actual length of year varies as well, so it cannot be an "absolute
standard."

Perhaps it is rocket science to look at actual data after all,
because where you can arbitrarily choose 3 consecutive decades to
make your claim I can arbitrarily choose 3 consecutive years to
show the opposite,

Since my point was that the earth rotation history is quite complex,
with me noting explicitly that there are recent trends of both spin-up
and spin-down, you have apparently just affirmed my point.

CM

"Craig" wrote in message
...
On Jan 20, 2:26 am, "Androcles" wrote:
"Craig" wrote in message

...
On Jan 19, 3:08 pm, "Androcles" wrote:



"Craig" wrote in message

...
On Jan 19, 12:51 pm, BDK wrote:

In article 1f3b5169-9176-486d-83aa-
,
says...

Which universe is that? In the universe that I'm aware of, the
earth's rotation rate has both positive and negative changes,
mostly
seasonally dependent.

It's always been slowing down, days used to be shorter, much
shorter,
if
you go back 100's of millions of years.
...
Example:http://tycho.usno.navy.mil/leapsec.html

Apparently you were having difficulty viewing the "length of day"
plot
referenced. The plot shows that the earth's rotation rate both
speeds
up and slows down, depending on the timescale being examined.

CM

Have someone smack you upside the head and maybe you'll understand.
The
earth has been slowing down since it was formed. Days used to be much
shorter. Damn, this isn't rocket science!!!

Having somebody smack me upside my head won't change the data on the
referenced plot, which you apparently ignored, that shows real
observational data. (and, for example, shows the earth's rotation
rate has sped up in the past three decades, thus invalidating your
assertion that "it's always been slowing down.") It's not "rocket
science" to look at actual data either.

CM

Ahem...
Excuse me if I'm puzzled by your assertion, but does that page not say
"The aged Earth is slowing down in its daily rotation, at
least in the current epoch." immediately below the graph?

Yes, and I believe the text's statement is true... IF one averages
over centuries and millenia. This is not actually shown on the plot.
The *plot* shows that on shorter time scales -- decades -- the earth
has epochs of both spin-up and spin-down. I linked to the particular
page I linked to, for the figure and not the text.

In the extreme case where the Earth slowed so much as to
make a day the same as a year (same face toward the Sun)
the number of caesium133 seconds would be much greater;
in other words adding a second implies the Earth has slowed.
Where do you get this notion that "Earth's rotation rate
has sped up in the past three decades"?

Well, because the figure shows that the length of day has shortened by
about 3 msec in the past three decades. Shortening of the length of
day implies an *increase* in rotation rate.

While I concur that the major, millenial trend appears to be gradual
spin-down, on shorter time-scales the situation is not so simple.

CM
=============================================

1)
"The last leap second was introduced in UTC at the end of December 2005.
There WILL be (now was, this is Jan 2008)
a another positive leap second introduced in UTC on 31 December 2008. "

2)
"The ephemeris second thus defined is the fraction
1/31,556,925.9747 of the tropical year for 1900
January 0 at 12 hours ephemeris time."

So by 2) this degree of precision did not occur before 1900
and by 1) there was a decrease in rotation rate in just 3 years.

Leap seconds are implemented only as a modification to *civil* time,
in order to track the gross accumulated rotational changes of the
earth. The measurements of length of day stand by themselves,

================================================
You are incorrect, civil time and the unit of time called the "day"
are unrelated to the dual standards of the year and the atomic clock.
=================================================



independent of leap seconds, hence leap seconds are irrelevant to the
question of whether the earth rotation rate is increasing or
decreasing.
=================================================
You are incorrect, all rates are measured against some standard second.
=================================================


I only referenced that particular web page for the plot.

Looking at the graph, the mean slope is upward between 2004
and 2007, and has falling since.

Because leap seconds are only added on Dec 31, the shortest time
scale the layman can reasonably consider is the year. To reinforce
this view, there are 36 PEAKS on the graph between 1973 and 2009,
so there is clearly a yearly cycle embedded in the data and any variation
within a year should be considered as noise or we'll be having 86,399.999
seconds one day and 86,400.001 seconds another, or even worse
3600 +/- delta seconds per hour, throwing all time-keeping into
hopeless confusion. Would it make sense if we added or subtracted
leap-nanoseconds to the hour? Is anyone going to modify their clock
driven telescopes to compensate for daily variations in the rotation
of the Earth? No, of course not.

You are incorrect.
=================================================
That accusation is a good way to end a discussion and start an
escalating flame war.
=================================================

Of course, modern telescopes *do* use fractional
"leap seconds" for pointing, although it's really termed "UT1-UTC".
=================================================
So you add leap-nanoseconds to the day, do you?
=================================================

The standard we choose has to be one that is readily available to the
majority.

Again you are confusing civil timekeeping with terrestrial physics.
=================================================
You are incorrect.
=================================================


It would therefore appear that the arbitrary choice of 9 192 631 770
periods of the radiation corresponding to the transition between the
two hyperfine levels of the ground state of the cesium 133 atom
(which is not available to the majority) was inappropriately based
on the year 1900 and not 2000; we are having to add leap-seconds

Actually if you read the article, it was based on the year 1820. The
date is not arbitrary; rather, it was based on the observations
available to Newcomb, who reduced all of the data.

=================================================
You are incorrect.
"The ephemeris second thus defined is
the fraction 1/31,556,925.9747 of the tropical year for 1900 "

=================================================

frequently and need to redefine the second. The year has to remain
the absolute standard to make any sense of time-keeping at all.
....


=================================================
The actual length of year varies as well, so it cannot be an "absolute
standard."
=================================================

It does indeed, which is why leap seconds are added. So we have an

exact number of years and an inexact number of seconds in a year,

making the year the absolute standard. Oh, and I almost forgot to add: you
are

incorrect.

=================================================

Perhaps it is rocket science to look at actual data after all,
because where you can arbitrarily choose 3 consecutive decades to
make your claim I can arbitrarily choose 3 consecutive years to
show the opposite,

Since my point was that the earth rotation history is quite complex,
with me noting explicitly that there are recent trends of both spin-up
and spin-down, you have apparently just affirmed my point.
CM

=================================================

Your point, "shows the earth's rotation rate has sped up in the

past three decades" is false. It has done both.

You are incorrect. You have apparently just affirmed my point.

On Jan 20, 7:47*pm, Craig wrote:
On Jan 20, 2:26*am, "Androcles" wrote:



"Craig" wrote in message

....
On Jan 19, 3:08 pm, "Androcles" wrote:

"Craig" wrote in message

....
On Jan 19, 12:51 pm, BDK wrote:

In article 1f3b5169-9176-486d-83aa-
,
says...

Which universe is that? In the universe that I'm aware of, the
earth's rotation rate has both positive and negative changes,
mostly
seasonally dependent.

It's always been slowing down, days used to be shorter, much
shorter,
if
you go back 100's of millions of years.
...
Example:http://tycho.usno.navy.mil/leapsec.html

Apparently you were having difficulty viewing the "length of day" plot
referenced. The plot shows that the earth's rotation rate both speeds
up and slows down, depending on the timescale being examined.

CM

Have someone smack you upside the head and maybe you'll understand. The
earth has been slowing down since it was formed. Days used to be much
shorter. Damn, this isn't rocket science!!!

Having somebody smack me upside my head won't change the data on the
referenced plot, which you apparently ignored, that shows real
observational data. (and, for example, shows the earth's rotation
rate has sped up in the past three decades, thus invalidating your
assertion that "it's always been slowing down.") It's not "rocket
science" to look at actual data either.

CM

Ahem...
Excuse me if I'm puzzled by your assertion, but does that page not say
"The aged Earth is slowing down in its daily rotation, at
least in the current epoch." immediately below the graph?

Yes, and I believe the text's statement is true... IF one averages
over centuries and millenia. *This is not actually shown on the plot.
The *plot* shows that on shorter time scales -- decades -- the earth
has epochs of both *spin-up and spin-down. *I linked to the particular
page I linked to, for the figure and not the text.

In the extreme case where the Earth slowed so much as to
make a day the same as a year (same face toward the Sun)
the number of caesium133 seconds would be much greater;
in other words adding a second implies the Earth has slowed.
Where do you get this notion that "Earth's rotation rate
has sped up in the past three decades"?

Well, because the figure shows that the length of day has shortened by
about 3 msec in the past three decades. *Shortening of the length of
day implies an *increase* in rotation rate.

While I concur that the major, millenial trend appears to be gradual
spin-down, on shorter time-scales the situation is not so simple.

CM
=============================================

1)
"The last leap second was introduced in UTC at the end of December 2005..
There WILL be (now was, this is Jan 2008)
a another positive leap second introduced in UTC on 31 December 2008. "

2)
"The ephemeris second thus defined is the fraction
1/31,556,925.9747 of the tropical year for 1900
January 0 at 12 hours ephemeris time."

So by 2) this degree of precision did not occur before 1900
and by 1) there was a decrease in rotation rate in just 3 years.

Leap seconds are implemented only as a modification to *civil* time,
in order to track the gross accumulated rotational changes of the
earth. *The measurements of length of day stand by themselves,
independent of leap seconds, hence leap seconds are irrelevant to the
question of whether the earth rotation rate is increasing or
decreasing. *

Sane people reading that would try and make sense of two opposite
statements within the same paragraph but then again,they probably
don't mind as there is so much contrived rubbish out there and who has
the time to consider these things.There is so much pseudo-authority
around that even the very simple proposal that scientists do not know
the basic astronomical fact which links the 24 hour clock to the daily
cycle through 360 degrees due to very specific reasons arising from a
specific error made by a known individual turns into a blizzard of
'time' terms other than the basic relationship between the 24 hour day
and the annual orbital cycle of 365 days 5 hours 49 minutes -

"hang two plummets, each by a small thred or wire, directly over the
said Meridian, at the distance of some 2. feet or more one from the
other, as the smalness of the thred will admit. When the middle of the
Sun (the Eye being placed so, as to bring both the threds into one
line) appears to be in the same line exactly...you are then
immediately to set the Watch, not precisely to the hour of 12. but by
so much less, as is the Aequation of the day by the Table."

http://www.xs4all.nl/~adcs/Huygens/06/kort-E.html

The 24 hour day is created out of natural noon and that is where the
daily cycle stays and how clocks keep sync with daily rotation through
360 degrees.Western society owes much of its advancement to this
simple operation which furnishes the benchmark for the creation of
accurate watches for all sorts of purposes such as determination of
location on the planet.

How it came to be that a group arose and decided that there can be an
alternative value to the 24 hour/360 degree correlation probably
belongs in a section of the sci.med newsgroup but the point of the
original post is to draw attention to what is correct rather than how
others vandalised the precepts.Those who formally believed in the
23h56m04s value as a fact are welcome to promote the 24 hour/360
degree value in accordance with the correct astronomical and
historical version ,especially in this International Year of
Astronomy.







I only referenced that particular web page for the plot.

Looking at the graph, the mean slope is upward between 2004
and 2007, and has falling since.

Because leap seconds are only added on Dec 31, the shortest time
scale the layman can reasonably consider is the year. To reinforce
this view, there are 36 PEAKS on the graph between 1973 and 2009,
*so there is clearly a yearly cycle embedded in the data and any variation
within a year should be considered as noise or we'll be having 86,399.999
seconds one day and 86,400.001 seconds another, or even worse
3600 +/- delta seconds per hour, throwing all time-keeping into
hopeless confusion. Would it make sense if we added or subtracted
leap-nanoseconds to the hour? Is anyone going to modify their clock
driven telescopes to compensate for daily variations in the rotation
of the Earth? No, of course not.

You are incorrect. *Of course, modern telescopes *do* use fractional
"leap seconds" for pointing, although it's really termed "UT1-UTC".

The standard we choose has to be one that is readily available to the
majority.

Again you are confusing civil timekeeping with terrestrial physics.

It would therefore appear that the arbitrary choice of 9 192 631 770
periods of the radiation corresponding to the transition between the
two hyperfine levels of the ground state of the cesium 133 atom
(which is not available to the majority) was inappropriately based
on the year 1900 and not 2000; we are having to add leap-seconds

Actually if you read the article, it was based on the year 1820. *The
date is not arbitrary; rather, it was based on the observations
available to Newcomb, who reduced all of the data.

frequently and need to redefine the second. The year has to remain
the absolute standard to make any sense of time-keeping at all.

...

The actual length of year varies as well, so it cannot be an "absolute
standard."

Perhaps it is rocket science to look at actual data after all,
because where you can arbitrarily choose 3 consecutive decades to
make your claim I can arbitrarily choose 3 consecutive years to
show the opposite,

Since my point was that the earth rotation history is quite complex,
with me noting explicitly that there are recent trends of both spin-up
and spin-down, you have apparently just affirmed my point.

CM

On Jan 20, 2:25*pm, "Androcles" wrote:
"Craig" wrote in message
[ ... snip ... ]
While I concur that the major, millenial trend appears to be gradual
spin-down, on shorter time-scales the situation is not so simple.

CM
=============================================

[ "Androcles:" ]
1)
"The last leap second was introduced in UTC at the end of December 2005..
There WILL be (now was, this is Jan 2008)
a another positive leap second introduced in UTC on 31 December 2008. "

2)
"The ephemeris second thus defined is the fraction
1/31,556,925.9747 of the tropical year for 1900
January 0 at 12 hours ephemeris time."

So by 2) this degree of precision did not occur before 1900
and by 1) there was a decrease in rotation rate in just 3 years.

[ Markwardt: ]
Leap seconds are implemented only as a modification to *civil* time,
in order to track the gross accumulated rotational changes of the
earth. *The measurements of length of day stand by themselves,

[ "Androcles:" ]
You are incorrect, civil time and the unit of time called the "day"
are unrelated to the dual standards of the year and the atomic clock.

Uh, since civil time (i.e. UTC) is defined by an atomic clock
standard, your statement is already unsubstantiated. Furthermore,
your claim is also vague since there are many definitions of
"day" (mean solar, sidereal, 86400 sec, etc). And finally, if you had
bothered to read the article, the leap second is a modification to the
civil time, but not terrestrial time.


[ Markwardt: ]
independent of leap seconds, hence leap seconds are irrelevant to the
question of whether the earth rotation rate is increasing or
decreasing.
[ "Androcles:" ]
You are incorrect, all rates are measured against some standard second.


If the unit of 1 second were redefined today, it would only shift the
entire "LOD" plot I referred to up or down by a *constant* amount.
It would not change the peceived rate of increase or decrease of the
earth's rotational rate, which would still appear as a sloped trend.


[ Markwardt: ]
*I only referenced that particular web page for the plot.

Looking at the graph, the mean slope is upward between 2004
and 2007, and has falling since.

[ "Androcles:" ]
Because leap seconds are only added on Dec 31, the shortest time
scale the layman can reasonably consider is the year. To reinforce
this view, there are 36 PEAKS on the graph between 1973 and 2009,
so there is clearly a yearly cycle embedded in the data and any variation
within a year should be considered as noise or we'll be having 86,399.999
seconds one day and 86,400.001 seconds another, or even worse
3600 +/- delta seconds per hour, throwing all time-keeping into
hopeless confusion. Would it make sense if we added or subtracted
leap-nanoseconds to the hour? Is anyone going to modify their clock
driven telescopes to compensate for daily variations in the rotation
of the Earth? No, of course not.

[ Markwardt: ]
You are incorrect. ...
*Of course, modern telescopes *do* use fractional
"leap seconds" for pointing, although it's really termed "UT1-UTC".
[ "Androcles:" ]
So you add leap-nanoseconds to the day, do you?

What I "do" is irrelevant. What ground-based telescope observers do,
might be considered equivalent to that, but in reality, they just keep
track of the accumulated fractional "leap second," known as "UT1-UTC,"
which is adjusted by ~milliseconds each day.

....
[ "Androcles:" ]
It would therefore appear that the arbitrary choice of 9 192 631 770
periods of the radiation corresponding to the transition between the
two hyperfine levels of the ground state of the cesium 133 atom
(which is not available to the majority) was inappropriately based
on the year 1900 and not 2000; we are having to add leap-seconds
[ Markwardt: ]
Actually if you read the article, it was based on the year 1820. *The
date is not arbitrary; rather, it was based on the observations
available to Newcomb, who reduced all of the data.

[ "Androcles:" ]
You are incorrect.
"The ephemeris second thus defined is
* * * * the fraction 1/31,556,925.9747 of the tropical year for 1900 "

You stopped reading too soon.
(a) the 1960 resolution of ephemeris time was superceded some years
later by an atomic standard, on which the graph is based. (ref. next
few paragraphs of same page)
(b) if you had bothered to read the rest of the page, the 1960
resolution is based on Newcomb's data, which was approximately
centered on the year 1820, and thus is weighted to that epoch. 86400
seconds as defined by Newcomb would approximately equal one mean solar
day in 1820. The reference to the year 1900 in the above (obsolete)
definition, refers to the *duration* of the year 1900. The duration
of year 1900 was the (obsolete) standard of measure, and has little to
do with how many units of that measure compose one second of time.

[ "Androcles:" ]
frequently and need to redefine the second. The year has to remain
the absolute standard to make any sense of time-keeping at all.
[ Markwardt: ]
The actual length of year varies as well, so it cannot be an "absolute
standard."

[ "Androcles:" ]
It does indeed, which is why leap seconds are added. So we have an
exact number of years and an inexact number of seconds in a year,
making the year the absolute standard. ...

Huh? Leap seconds are designed to keep the civil time system
synchronized with the physical rotation of the earth. Leap seconds
have nothing to do with the orbital period of the earth, other than
chosing when to insert leap seconds. Case in point: leap *days* are
added in some years and not others. If the goal were to maintain
annual synchronization, one would need to add slightly less than 6
hours each year to the civil time, which is obviously ludicrous to
maintain, from a civil timekeeping standpoint.

[ "Androcles:" ]
Perhaps it is rocket science to look at actual data after all,
because where you can arbitrarily choose 3 consecutive decades to
make your claim I can arbitrarily choose 3 consecutive years to
show the opposite,
[ Markwardt: ]
Since my point was that the earth rotation history is quite complex,
with me noting explicitly that there are recent trends of both spin-up
and spin-down, you have apparently just affirmed my point.

[ "Androcles:" ]
Your point, "shows the earth's rotation rate has sped up in the
past three decades" is false. It has done both.

Congratulations on selective reading. I also wrote, "It depends on
when you look, and over what timescale (days, years, decades)." The
trend -- *averaged over three decades* -- is indeed a spin-up. The
cited plot certainly shows other trends when averaged over other time-
scales.

CM

"Craig" wrote in message
...
On Jan 20, 2:25 pm, "Androcles" wrote:
"Craig" wrote in message
[ ... snip ... ]
While I concur that the major, millenial trend appears to be gradual
spin-down, on shorter time-scales the situation is not so simple.

CM
=============================================

[ Androcles: ]
1)
"The last leap second was introduced in UTC at the end of December 2005.
There WILL be (now was, this is Jan 2008)
a another positive leap second introduced in UTC on 31 December 2008. "

2)
"The ephemeris second thus defined is the fraction
1/31,556,925.9747 of the tropical year for 1900
January 0 at 12 hours ephemeris time."

So by 2) this degree of precision did not occur before 1900
and by 1) there was a decrease in rotation rate in just 3 years.

[ "Markwardt": ]
Leap seconds are implemented only as a modification to *civil* time,
in order to track the gross accumulated rotational changes of the
earth. The measurements of length of day stand by themselves,

[ Androcles: ]
You are incorrect, civil time and the unit of time called the "day"
are unrelated to the dual standards of the year and the atomic clock.

["Markwardt": ]
Uh,

[ Androcles: ]
[...snip...]

That grunt should be "ugh", "Markwardt", and I have corrected
your quotation marks. I am Androcles, you are "Markwardt".

On Jan 21, 9:43*am, Craig wrote:

Huh? *Leap seconds are designed to keep the civil time system
synchronized with the physical rotation of the earth. *Leap seconds
have nothing to do with the orbital period of the earth, other than
chosing when to insert leap seconds. *Case in point: leap *days* are
added in some years and not others. *If the goal were to maintain
annual synchronization, one would need to add slightly less than 6
hours each year to the civil time, which is obviously ludicrous to
maintain, from a civil timekeeping standpoint.


These are wonderful fairytales that you make up as you go along.

I am sure Julius Caeser pondered adding the leap day every 4th year
because of daily rotation but for any other intelligent
person,rotation was not discovered until Copernicus.Leap second
corrections,and there are 86 400 seconds added every 4th year
represent an orbital component which allows the annual cycle
calculated via the human devised 24 hour day to be transfered to a
seamless transition of years with equable days in them -
2007,2008,2009..

Thank God there were once brilliant minds who worked out the
timekeeping systems as an extension of astronomical observations,today
all that exists are people who think they are building concepts on
'time' when all they are doing is building ideas based on the humble
clock.

So,has everyone got it straight,the human devised 24 hour day is
referenced off natural noon and the calendar extension is an orbitally
based outrigger which allows the progression of years to be reset to a
cyclical framework .It is so easy to understand with a bit of effort
and so magnificent that were it not for the pretension of some
people,it would truly be enjoyed as the great human achievement that
it actually is.