Earth's Slowing Spin

[IceAgeCivilizations]

The Earth spins about half a second slower every year, this is why the atomic-clock timekeepers add leap seconds, so extrapolating that rate back to say "the Carboniferous era," a day then would have been about an hour long, another great indication that the Earth is much younger than commonly advertised.

[mikenostic]

http://i44.photobucket.com/albums/f32/mike240z/nobodycares.jpg

[IceAgeCivilizations]

This fact about the Earth's spin throws a huge monkey wrench in the wheels of Uniformitarian dogma, and nobody cares? I doubt it.

[spuriousmonkey]

The Earth spins about half a second slower every year,

No it doesn't retard. They add leap seconds because the day isn't 24 hours.

The reason for adding a leap second is that the planet does not rotate exactly once every 24 hours (86,400 seconds). The rotation actually takes 86,400.002 seconds so that each day this little difference builds up between the atomic clock and the earth's rotation. When the difference builds up enough (.9 seconds), the time keepers must add another second (leap second) to keep the stars location, relative to the planet's rotation, in exact sync with the superaccurate atomic clocks.


you really don't have a brain.

[IceAgeCivilizations]

No, the Earth's spin rate slows about a half second per year, how else would they compensate for this but by leap seconds?

Do you deny, spur, that the Earth's spin rate is slowing by that amount? Since you appear to be doing so, you in fact are the retard.

[one_raven]

I never did understand why they did not build the "super accurate" atomic clocks to measure a second as 1/86,400 of the earth's rotation.

[spuriousmonkey]

No, the Earth's spin rate slows about a half second per year, how else would they compensate for this but by leap seconds?

Do you deny, spur, that the Earth's spin rate is slowing by that amount? Since you appear to be doing so, you in fact are the retard.

yes, i do deny it.

The atomic clock 24 hours differ from the earth's rotation 24 hours.

Do you understand? they add leap seconds because of the difference between the atomic clock and the actual time it takes for the earth to rotate.

The slowing down of the earth's rotation is much slower than you suggest.

[IceAgeCivilizations]

If not by adding leap seconds, spur, how else would you, in all your wisdom, compensate the atomic clocks because of the Earth's spin rate slowdown?

[IceAgeCivilizations]

And guess what you get when you divide 86,400 by 2?

[spuriousmonkey]

If not by adding leap seconds, spur, how else would you, in all your wisdom, compensate the atomic clocks because of the Earth's spin rate slowdown?

you really are a fucking moron and you should be permabanned.

[IceAgeCivilizations]

It slows by half a second per year, look it up.

[one_raven]

While we know the Earth's rotation is slowing that is not the main reason why the extra "Leap Second" was added by our official time keepers this year. The reason for adding a leap second is that the planet does not rotate exactly once every 24 hours (86,400 seconds). The rotation actually takes 86,400.002 seconds so that each day this little difference builds up between the atomic clock and the earth's rotation. When the difference builds up enough (.9 seconds), the time keepers must add another second (leap second) to keep the stars location, relative to the planet's rotation, in exact sync with the superaccurate atomic clocks.

http://novan.com/earth.htm

It has slowed by .002 seconds in the past 187 years.

[IceAgeCivilizations]

Spur, you should go to permaschool.

[spuriousmonkey]

http://www.gsfc.nasa.gov/scienceques2004/20050318.htm

The length of the day is increasing by 0.0015 seconds every century

[IceAgeCivilizations]

Wrong, it slows by half a second per year, that's why they add a leap second about every two years.

[one_raven]

It slows by half a second per year, look it up.

I just did.

It has slowed by .002 seconds in the past 187 years.

[spuriousmonkey]

Wrong, it slows by half a second per year, that's why they add a leap second about every two years.
post your sources. This is supposed to be a science forum. Who gives a shit what you say?

what NASA says:
http://www.sciforums.com/showpost.php?p=1397307&postcount=13

[one_raven]

Wrong, it slows by half a second per year, that's why they add a leap second about every two years.

Where is YOUR reference.
I assume you looked it up?

[one_raven]

And guess what you get when you divide 86,400 by 2?
Something like this...
http://img.photobucket.com/albums/v203/one_raven/IceAge.jpg

[spuriousmonkey]

Wrong, it slows by half a second per year, that's why they add a leap second about every two years.

I already explained to you what a leap year is. It's to compensate for the difference between the atomic clock and how long it actually takes for the earth to rotate.

Previously the second was based on the earth's day. But once the first accurate atomic clock was installed they used the atomic second to define second.

wiki
The first atomic clock was built in 1949 at the U.S. National Bureau of Standards (NBS). The first accurate atomic clock, a cesium standard based on the transition of the cesium-133 atom, was built by Louis Essen in 1955 at the National Physical Laboratory in the UK. This led to the internationally agreed definition of the second being based on atomic time.

[IceAgeCivilizations]

So why did they calibrate the atomic clock to be off by that amount?

[spuriousmonkey]

So why did they calibrate the atomic clock to be off by that amount?

Because science needs a standard second to do experiments.

[IceAgeCivilizations]

But the atomic clock is much more accurate than that error, so they must have intentionally built the error in if you are correct, does that make sense?

[spuriousmonkey]

But the atomic clock is much more accurate than that error, so they must have intentionally built the error in if you are correct, does that make sense?

No, because it is nonsense.

Since 1967, the International System of Units (SI) has defined the second as the duration of 9 192 631 770 cycles of the radiation which corresponds to the transition between two energy levels of the ground state of the caesium-133 atom.

that's why a second is a second.

[Yorda]

http://novan.com/earth.htm

It has slowed by .002 seconds in the past 187 years.

how do you know that? how could you measure so small differences accurately? and why would the earth slow down?

[IceAgeCivilizations]

Like a gyroscope slows down.

[spuriousmonkey]

and why would the earth slow down?

from a link in this thread you didn't bother to read:
The length of the day is increasing by 0.0015 seconds every century, of which about 0.0007 seconds per century has to do with the tidal breaking of the Moon.

That's half the rotation slowdown explained.

Because the Moon's mass is a considerable fraction of that of the Earth (about 1:81), the two bodies can be regarded as a double planet system, rather than as a planet with a satellite. The plane of the Moon's orbit around the Earth lies close to the plane of the Earth's orbit around the Sun (the ecliptic), rather than in the plane perpendicular to the axis of rotation of the Earth (the equator) as is usually the case with planetary satellites. The mass of the Moon is sufficiently large and it is sufficiently close to raise tides in the Earth: the matter of the Earth, in particular the water of the oceans, bulges out along both ends of an axis passing through the centers of the Earth and Moon. The average tidal bulge closely follows the Moon in its orbit, and the Earth rotates under this tidal bulge in just over a day. However, the rotation drags the position of the tidal bulge ahead of the position directly under the Moon. As a consequence, there exists a substantial amount of mass in the bulge that is offset from the line through the centers of the Earth and Moon. Because of this offset, a portion of the gravitational pull between Earth's tidal bulges and the Moon is perpendicular to the Earth-Moon line, i.e. there exists a torque between the Earth and the Moon. This accelerates the Moon in its orbit, and conversely decelerates the rotation of the Earth.

[IceAgeCivilizations]

So why do they add a leap second about every two years?

[spuriousmonkey]

So why do they add a leap second about every two years?

read the thread and the links moron.

[IceAgeCivilizations]

That's nonsensical, add a leap second every two years because the atomic clock is off by .002 seconds? By that, they would add a leap second every 500 years, go figure.

[Nikelodeon]

Another load of perpetual BS from IAC.

[spidergoat]

But wait, don't your biblical theories depend on the early "days" of the Earth being very long? That's how God could create the world in 6 days. Are you suggesting the creation lasted 6 hours?

[Ophiolite]

Listen you brain dead moron. (Obviously I am speaking to balding, middle aged, slightly effeminate, IAC.) If the Earth were slowing down by a second every two years, then we would have to add one second in year two, two seconds in year four, three seconds in year six. If you really cannot understand this simple concept you need a remedial high school education. You should be ashamed of yourself, publicly parading your gross ignorance with such flamboyance.
And on top of that you lack the common decency of being honest.

Bring back Happeh - at least he was amusing.

[IceAgeCivilizations]

Six days goat, six thousand years ago, as I've told YOU about a million times, you can be so silly.

[IceAgeCivilizations]

Ophi you flaming turd, they've added 22 leap seconds over the last 50 years, so go educate yourself, you're making an ass of yourself, still again.

[one_raven]

Ophi you flaming turd, they've added 22 leap seconds over the last 50 years, so go educate yourself, you're making an ass of yourself, still again.

Think about this for a second...

The atomic second is slightly different than the "earth second", correct?
Noe let's say that the difference adds up to one second per year (just for nice easy numbers).

With me so far?
Now, at the end of the year, teh atomic clock will be one second slow, so they have to add one more second to make it match "earth time".
Right?

Now, in ten years, did they add ten seconds to the day?
Of course they did not, they added one second at the end of each year - because the "earth year" is one second longer than the "atomic year".
The only way that time accumulates is if HOW MUCH they add each year grows.

Do you understand?

Try thinking of it this way....
You have a watch that only counts up to 23 hours.
Each day when you wake uop, you clock will be exactly one hour slow, so you set it forward one hour.
You will have to set it forward one hour EVERY DAY, not just once.
Get it?

[IceAgeCivilizations]

They didn't calibrate the atomic clock to be .002 seconds off, what's the point of having the precision of the atomic clock if you don't use it?

[D H]

So why did they calibrate the atomic clock to be off by that amount?

They didn't. The atomic definition of the second was defined to match one ephemeris second exactly. One ephemeris second was defined based on the Newcomb's "Tables of the Sun". Newcomb's tables covered the time span from 1750 to 1892. The ephemeris second is basically 1/86400 of the average length of a day over that span. One day was exactly 86400 seconds somewhere near the middle of that 142 year span. Now one day takes 86400.002 seconds. In 500 days, that extra 0.002 seconds per day accumulates to one second. So we need to add a leap second once every 500 days or so to keep atomic time (UTC) in sync with time based on the Earth's rotation rate (UT1).

Note well, you blithering idiot. We would still need to add leap seconds if the Earth's rotation rate remained constant at 86,400.002 seconds per day.

[Jeremyhfht]

http://novan.com/earth.htm

It has slowed by .002 seconds in the past 187 years.

Owned the thread.

Ophi you flaming turd, they've added 22 leap seconds over the last 50 years, so go educate yourself, you're making an ass of yourself, still again.

Ophi is correct. During the course of my lifetime, and my parents lifetime, and their lifetime, there has never been any "leap seconds" added. Just simple 0.002 corrections of the atomic clocks, since they run a leetle faster then the earth spins. If there were increasing amounts of "leap seconds", then the time of 0.002 would have increased every year. Especially since .002 is such a sensitive and insignifigant number.

That being said, your point is defeated, since you give no sources anyway.

[IceAgeCivilizations]

How did they measure the length of the day back in the 1800's?

[IceAgeCivilizations]

They've added at least 22 leap seconds over the last 50 years, so you've got this little hurdle.

[Ophiolite]

Stupid.

[Nikelodeon]

A ban would be pointless, I suggest people simply ignore the troll.

[one_raven]

They've added at least 22 leap seconds over the last 50 years, so you've got this little hurdle.

Did you miss this ENTIRELY...
Think about this for a second...

The atomic second is slightly different than the "earth second", correct?
Noe let's say that the difference adds up to one second per year (just for nice easy numbers).

With me so far?
Now, at the end of the year, teh atomic clock will be one second slow, so they have to add one more second to make it match "earth time".
Right?

Now, in ten years, did they add ten seconds to the day?
Of course they did not, they added one second at the end of each year - because the "earth year" is one second longer than the "atomic year".
The only way that time accumulates is if HOW MUCH they add each year grows.

Do you understand?

Try thinking of it this way....
You have a watch that only counts up to 23 hours.
Each day when you wake uop, you clock will be exactly one hour slow, so you set it forward one hour.
You will have to set it forward one hour EVERY DAY, not just once.
Get it?

...or did you simply ignore it in hopes the information would not sink in?

[IceAgeCivilizations]

No answers? Just flaming?

[one_raven]

Please answer my question.
Did you not understand what I said about the 22 leap seconds added?
If not, please tell me what part is confusing you, and I will try and elaborate and clarify.

[IceAgeCivilizations]

The point, one raven, is that the purpose of the atomic clock is so that the atomic second would be the same (within atomic precision) of the Earth second, not "slightly different," you can get slightly different with a wrist watch.

[Jeremyhfht]

Earth slowing does happen. Make sure you all know this. But definitely not to his assumed degree.

http://en.wikipedia.org/wiki/Tidal_acceleration#Historical_evidence


Historical evidence

This mechanism has been working for 4.5 billion years, since oceans first formed on the Earth. There is geological and paleontological evidence that the Earth rotated faster and that the Moon was closer to the Earth in the remote past. Tidal rhythmites are alternating layers of sand and silt laid down offshore from estuaries having great tidal flows. Daily, monthly and seasonal cycles can be found in the deposits. This geological record is consistent with these conditions 620 million years ago: the day was 21.9±0.4 hours, and there were 13.1±0.1 synodic months/year and 400±7 solar days/year. The length of the year has remained virtually unchanged during this period because no evidence exists that the constant of gravitation has changed. The average recession rate of the Moon between then and now has been 2.17±0.31 cm/year, which is about half the present rate.[2]


Happy to educate ^-^. Now kindly just ignore him, it's obvious he's trolling.

Edit: As for the atomic clock, the clock measures time very very precisely due to it's near blinding accuracy precision of the second. It's not set to anything. The problem is even it isn't perfect, and scientists know this. So it's a tad too fast (by a few decimal places) for earth seconds.

[one_raven]

The point, one raven, is that the purpose of the atomic clock is so that the atomic second would be the same (within atomic precision) of the Earth second, not "slightly different," you can get slightly different with a wrist watch.

Firstly...
Wrong.
Dead wrong.
The point was so that everyone, everywhere could be using the same standard measurment of time.

Second...
You still did not answer my question.
If you add a second every year, because your clock counts one second less than a year, that time does not accumulate.
If the rotation of the earth is slowing by one second a year, you will (as was pointed out to you) the number of seconds you will have to add will increase each time.

[IceAgeCivilizations]

Atomic precision is much greater than within .002 seconds, you guys are thinking about sun dials or something.

[Ophiolite]

If you add a second every year, because your clock counts one second less than a year, that time does not accumulate.
If the rotation of the earth is slowing by one second a year, you will (as was pointed out to you) the number of seconds you will have to add will increase each time.I propose adding this statement(which matches my comments in post 33) after each and every nonsensical reply by IAC in this thread.

[IceAgeCivilizations]

Your little statement defies that atomic clocks are much more precise that that, but add away if you must.

[Nikelodeon]

Your little statement defies that atomic clocks are much more precise that that, but add away if you must.

Are you at least trying to use your brain?

[IceAgeCivilizations]

Duh?

[Walter L. Wagner]

Anyone who reads the links posted by the knowledgeable ones (not IAC) will recognize that the atomic second and the current earth second are slightly different, for historical reasons. As I recall, the atomic second is based on what the earth second was about 150 years ago, though I don't recall exactly why that was so,though you can read about it at the links posted, or google it to find out.

In any event, the Earth's slowing of spin is NOT as IAC has posted, but is in fact as posted by the knowledgeable ones. The leap second is added to account for the difference between the atomic second and the current earth second.

This was covered thoroughly in another thread in which IAC and I both posted, quite a few months ago. Evidently, he continues to disregard simple truths, and prefers to believe that everyone else in wrong, particularly the knowledgeable ones who work in their respective fields, and that he alone has the truth.

Apparently, IAC is attempting to make an argument that the slowing of the earth's spin (at the slowing rate he throws out, unsupported by any evidence) means that the earth would have had to have been spinning way too fast in the distant past to allow for life, and therefore the earth was instead created circa 4500 B.C. with everything intact and set in motion almost as we see it today.

Thus, under IAC's theory, the ocean terraces on the mountains surrounding the oceans, and the lake benches on the mountains surrounding dried lake beds, were created as they are circa 4500 B.C. to fool scientists in these latter days into concluding that the earth is ancient, and that the ocean terraces were formed long before the last ice age, when the oceans were much higher than at present hundreds of thousands of years ago, before the last ice age. Google 'marine terraces' for more information on that, if you want to get the details of the dropping ocean levels leaving behind marine terraces. Also see:

http://ceres.ca.gov/ceres/calweb/coastal/terraces.html

Of course, IAC will probably try to claim that as the ocean receded following "the flood" it stablized (for thousands of years, the time it takes to carve such wave-eroded terraces) at various levels (but of course, not at the higher elevations of the mountains, only the lower elevations closest to the ocean level now).

[one_raven]

Your little statement defies that atomic clocks are much more precise that that, but add away if you must.

It has absolutely nothing at all to do with the precision of atomic clocks in any way.

[IceAgeCivilizations]

Why would they not calibrate the atomic clock with the precision with which it is capable, Walter?

[one_raven]

Why would they not calibrate the atomic clock with the precision with which it is capable, Walter?

It is precise.
That is why it is used as a standard of measurment worldwide.

They don't adjust the speed that the clock is running, because that doesn't change (because it is precise).
They adjust the time that is displayed because an atomic second is not exactly 1/86,400 of a day anymore.

The earth is not slowing by half a second a year, the year is about 3/4 of a second longer than it was about 150 years ago, when the second WAS 1/86,400 of a day.

[IceAgeCivilizations]

So what did they use to measure the length of the day which is "not exactly" the length of the atomic clock day?

[Sputnik]

Six days goat, six thousand years ago, as I've told YOU about a million times, you can be so silly.


Heh, heh ........IceAge ..
Man was created october 23 , 4004 BC at 9 o´clock in the morning - Don´t let anybody tell you anything else

http://www.sacred-texts.com/time/timeline.htm

And to the rest of you , don´t waste your time trying to educate IceAge ...... he is actually not capable of understanding logic .....

[Jeremyhfht]

Raven. Shut up. Just ignore the troll. We've already given adequate replies.

[IceAgeCivilizations]

Adequate for what, your daily post count total?

[Jeremyhfht]

Adequate for what, your daily post count total?

*COUGH*sixthousandpostsIAC*COUGH*

[IceAgeCivilizations]

Hey Jeremy, why would you calibrate a clock to be far less precise than it's capable of being?

[Read-Only]

Hey Jeremy, why would you calibrate a clock to be less precise than it's capable of being?

Are you saying it's not precise (in your opinion) because it doesn't match the precise rotation of the sun? If so, what sheer nonsense! What you don't even seem to know yet is that the rotation isn't exactly stable and they also had to REMOVE seconds as well as add them.

Besides, it was once thought that a calendar month matched the phase of the moon - but of course it really doesn't.

I'm not at all sure what you hope to gain by pushing this foolishness but it's VERY obvious that you haven't bothered to read the links that were given to you. Just lazy or what????????? And you've yet to provide ANYTHING to back up the numbers you gave. Why is that??? Can't find any??????

[IceAgeCivilizations]

It's merely logic.

Why would you calibrate a clock to be 10,000 times less precise than its capability, Read-Only?

[Read-Only]

It's merely logic.

Why would you calibrate a clock to be 10,000 times less precise than its capability, Read-Only?

Who says it is???????????????

And where's your response to the rest I asked you??

[IceAgeCivilizations]

The fellas say it was calibrated to be .002 seconds off, go figure.

[Nikelodeon]

IAC is a parrot.

[IceAgeCivilizations]

You're a ferret.

[Nikelodeon]

And that ladies and gentlemen, is that.

[Oniw17]

It's merely logic.

Why would you calibrate a clock to be 10,000 times less precise than its capability, Read-Only?
No...this is logic.
If you add a second every year, because your clock counts one second less than a year, that time does not accumulate.
If the rotation of the earth is slowing by one second a year, you will (as was pointed out to you) the number of seconds you will have to add will increase each time. In case you need it explained again, I'll assume you're an idiot: If the earth's rotation slowed by 1 second every 2 years, and the length of the day stayed the same, you'd have to gradually add more and more seconds to compensate for the time that you didn't add to the year's length.Are you really that stupid?

[Ophiolite]

Why would you calibrate a clock to be 10,000 times less precise than its capability, Read-Only?Why would you use only 1/100th of the logic circuits in your brain that God gave you?

[IceAgeCivilizations]

Glad you agree Oniw.

[Oniw17]

Glad you agree Oniw.

huh?

[spidergoat]

1967 -- The 13th General Conference on Weights and Measures defines the second on the basis of vibrations of the cesium atom; the world’s timekeeping system no longer has an astronomical basis.

A leap second is a second added to Coordinated Universal Time (UTC) to make it agree with astronomical time to within 0.9 second. UTC is an atomic time scale, based on the performance of atomic clocks. Astronomical time is based on the rate of rotation of the earth. Since atomic clocks are more stable than the rate at which the earth rotates, leap seconds are needed to keep the two time scales in agreement.

The first leap second was added on June 30, 1972. Since then, they have occurred at an average rate of less than one per year. Although it is possible to have a negative leap second (a second removed from UTC), so far, all leap seconds have been positive (an extra second has been added to UTC). Based on what we know about the earth's rotation, it seems unlikely that we will ever have a negative leap second.

http://tf.nist.gov/timefreq/general/leaps.htm

[IceAgeCivilizations]

"Since atomic clocks are more stable than the rate at which the Earth rotates .... leap seconds are needed ..... leap seconds added at an average rate of less than one (about .6) per year."

Thanks Spidergoat.

[Nikelodeon]

I think IACs' brain is slowing down.

[IceAgeCivilizations]

But of course.

[Roman]

IAC, if you had a watch that was 5 minutes slow, how many minutes would you have to set it forward each day to keep it on time?

[Walter L. Wagner]

This is for IAC's benefit, though he'll likely ignore it as he's done before:

"LEAP SECONDS
Civil time is occasionally adjusted by one second increments to ensure that the difference between a uniform time scale defined by atomic clocks does not differ from the Earth's rotational time by more than 0.9 seconds. Coordinated Universal Time (UTC), an atomic time, is the basis for civil time.
Historically, the second was defined in terms of the rotation of the Earth as 1/86,400 of a mean solar day. In 1956, the International Committee for Weights and Measures, under the authority given it by the Tenth General Conference on Weights and Measures in 1954, defined the second in terms of the period of revolution of the Earth around the Sun for a particular epoch, because by then it had become recognized that the Earth's rotation was not sufficiently uniform as a standard of time. The Earth's motion was described in Newcomb's Tables of the Sun, which provides a formula for the motion of the Sun at the epoch 1900 based on astronomical observations made during the eighteenth and nineteenth centuries. The ephemeris second thus defined is

the fraction 1/31,556,925.9747 of the tropical year for 1900 January 0 at12 hours ephemeris time.

This definition was ratified by the Eleventh General Conference on Weights and Measures in 1960. Reference to the year 1900 does not mean that this is the epoch of a mean solar day of 86,400 seconds. Rather, it is the epoch of the tropical year of 31,556,925.9747 seconds of ephemeris time. Ephemeris Time (ET) was defined as the measure of time that brings the observed positions of the celestial bodies into accord with the Newtonian dynamical theory of motion.

Following several years of work, two astronomers at the U.S. Naval Observatory (USNO) and two astronomers at the National Physical Laboratory (Teddington, England) determined the relationship between the frequency of the cesium atom (the standard of time) and the ephemeris second. They determined the orbital motion of the Moon about the Earth, from which the apparent motion of the Sun could be inferred, in terms of time as measured by an atomic clock. As a result, in 1967 the Thirteenth General Conference on Weights and Measures defined the second of atomic time in the International System of Units (SI) as

the duration 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.The ground state is defined at zero magnetic field. The second thus defined is equivalent to the ephemeris second.
The Sub-bureau for Rapid Service and Predictions of Earth Orientation Parameters of the International Earth Rotation Service (IERS), located at the USNO, monitors the Earth's rotation. Part of its mission involves the determination of a time scale based on the current rate of the rotation of the Earth. UT1 is the non-uniform time based on the Earth's rotation.

The Earth is constantly undergoing a deceleration caused by the braking action of the tides. Through the use of ancient observations of eclipses, it is possible to determine the average deceleration of the Earth to be roughly 1.4 milliseconds per day per century. This deceleration causes the Earth's rotational time to slow with respect to the atomic clock time. Thus, the definition of the ephemeris second embodied in Newcomb's motion of the Sun was implicitly equal to the average mean solar second over the eighteenth and nineteenth centuries. Modern studies have indicated that the epoch at which the mean solar day was exactly 86,400 SI seconds was approximately 1820. This is also the approximate mean epoch of the observations analyzed by Newcomb, ranging in date from 1750 to 1892, that resulted in the definition of the mean solar day on the scale of Ephemeris Time. Before then, the mean solar day was shorter than 86,400 seconds and since then it has been longer than 86,400 seconds.

The length of the mean solar day has increased by roughly 2 milliseconds since it was exactly 86,400 seconds of atomic time about 1.79 centuries ago (i.e. the 179 year difference between 1999 and 1820). That is, the length of the mean solar day is at present about 86,400.002 seconds instead of exactly 86,400 seconds. Over the course of one year, the difference accumulates to almost one second, which is compensated by the insertion of a leap second into the scale of UTC with a current regularity of a little less than once per year. Other factors also affect the Earth, some in unpredictable ways, so that it is necessary to monitor the Earth's rotation continuously.

In order to keep the cumulative difference in UT1-UTC less than 0.9 seconds, a leap second is added to the atomic time to decrease the difference between the two. This leap second can be either positive or negative depending on the Earth's rotation. Since the first leap second in 1972, all leap seconds have been positive and there were 23 leap seconds in the 34 years to January, 2006. This pattern reflects the general slowing trend of the Earth due to tidal braking.

Confusion sometimes arises over the misconception that the regular insertion of leap seconds every few years indicates that the Earth should stop rotating within a few millennia. The confusion arises because some mistake leap seconds for a measure of the rate at which the Earth is slowing. The 1 second increments are, however, indications of the accumulated difference in time between the two systems. (Also, it is important to note that the current difference in the length of day from 86,400 seconds is the accumulation over nearly two centuries, not just the previous year.) As an example, the situation is similar to what would happen if a person owned a watch that lost 2 seconds per day. If it were set to a perfect clock today, the watch would be found to be slow by 2 seconds tomorrow. At the end of a month, the watch will be roughly a minute in error (30 days of 2 second error accumulated each day). The person would then find it convenient to reset the watch by one minute to have the correct time again.

This scenario is analogous to that encountered with the leap second. The difference is that instead of setting the clock that is running slow, we choose to set the clock that is keeping a uniform, precise time. The reason for this is that we can change the time on an atomic clock, while it is not possible to alter the Earth's rotational speed to match the atomic clocks! Currently the Earth runs slow at roughly 2 milliseconds per day. After 500 days, the difference between the Earth rotation time and the atomic time would be 1 second. Instead of allowing this to happen, a leap second is inserted to bring the two times closer together.
International Atomic Time (TAI) is a statistical atomic time scale based on a large number of clocks operating at standards laboratories around the world that is maintained by the Bureau International des Poids et Mesures; its unit interval is exactly one SI second at sea level. The origin of TAI is such that UT1-TAI is approximately 0 (zero) on January 1, 1958. TAI is not adjusted for leap seconds. It is recommended by the BIPM that systems which cannot handle leapseconds use TAI instead.

Coordinated Universal Time (UTC) is defined by the CCIR Recommendation 460-4 (1986). It differs from TAI by the total number of leap seconds, so that UT1-UTC stays smaller than 0.9s in absolute value. The decision to introduce a leap second in UTC is the responsibility of the International Earth Rotation Service (IERS). According to the CCIR Recommendation, first preference is given to the opportunities at the end of December and June, and second preference to those at the end of March and September. Since the system was introduced in 1972, only dates in June and December have been used. TAI is expressed in terms of UTC by the relation TAI = UTC + dAT, where dAT is the total algebraic sum of leap seconds.

The first leap second was introduced on June 30, 1972. The historical list of leap seconds can be found here.

The Global Positioning System (GPS) epoch is January 6, 1980 and is synchronized to UTC. GPS is NOT adjusted for leap seconds.

As of 1 January 2006,
TAI is ahead of UTC by 33 seconds.
TAI is ahead of GPS by 19 seconds.
GPS is ahead of UTC by 14 seconds.
Until 1960, Universal Time (UT) was taken as the independent variable of astronomical ephemerides. UT was then replaced by Ephemeris Time (ET), based on the motion of the sun. However, ET did not include relativistic effects, such as corrections for the gravitational potential and velocity, as required by advances in the accuracy of time comparisons. Thus ET was superseded in 1981 by Terrestrial Dynamical Time (TDT) and Barycentric Dynamical Time (TDB), which distinguish coordinate systems with origins at the center of the Earth and the center of the solar system, respectively, and are consistent with the general theory of relativity. In the language of general relativity, TDT is a proper time while TDB is a coordinate time. In 1991, TDT was renamed simply Terrestrial Time (TT) and two additional relativistic time scales, Geocentric Coordinate Time (TCG) and Barycentric Coordinate Time (TCB) were adopted. Definitions of these time scales are given in Systems of Time.
Terrestrial Time (TT) is a uniform atomic time scale, whose unit is the SI second, that replaces Ephemeris Time and maintains continuity with it. TT may be regarded as the time that would be kept by an ideal atomic clock on the geoid. To convert a TT value to a prediction of UT1, it is necessary to know the difference dT = TT - UT1. Values of dT are tabulated in the Astronomical Almanac. For example, mathematical predictions of lunar and solar eclipses in the distant past and future depend sensitively on estimates of dT. The computed path of a solar eclipse that occurred 2000 years ago would be in error by about 3 hours, or some 45 degrees in longitude to the west, on the assumption that the rate of rotation of the earth were uniform. Conversely, records of well documented ancient eclipses, together with modern telescopic observations of occultations, Very Long Baseline Interferometry, satellite laser ranging, lunar laser ranging, and other measurements correlated to atomic time scales since 1955, have provided the data on which long term trends and short term fluctuations have been derived. Since dT was approximately 32.184 seconds at the origin of TAI in 1958, a practical realization of TT is TT = TAI + 32.184 seconds. Although this expression gives TT in terms of TAI, in practice TT is obtained from the relation TT = UTC + dAT + 32.184 seconds for a known value of UTC and a given number of leap seconds."

The above is from: http://tycho.usno.navy.mil/leapsec.html

Anyway, I was mistaken, it was not roughly 150 years ago, it was roughly 187 years ago that the Earth had 86,400 seconds in a day. Of course, IAC will probably complain about why we scientists didn't properly measure the exact length of the day back then with an atomic clock.

And now, for the final numerology explanation:

Why was 6 afraid of 7?

Because 7 8 9, of course. (not 4 3 2)

-----------------------------

[IceAgeCivilizations]

Yes, was their measurment of seconds back then as accurate as a .002 error?

[Roman]

IAC, if you had a watch that was 5 minutes slow, how many minutes would you have to set it forward each day to keep it on time?

Hint: It's NOT 432.

[IceAgeCivilizations]

I don't know then, tell me.

[Roman]

You honestly don't know?

[inzomnia]

Hi IAC,

I want to try to explain what these guys fail to explain to you.
I think I know what lead you to false conclusion. It is your
understanding about the definition of an atomic clock. However,
my English is really limited. But let me try as simple as I can.

Let say there is no such things as clock. If I say, lets meet at X Club, 1 hour
from now, how do I make sure that my understanding of 1 hour is equal
to your understanding of 1 hour? We need the SAME 1 HOUR REFERENCE.

If I need 1 hour to walk from Y to Z, and I set the definition "1 hour
is equal to the time required by me to walk from Y to Z", it will be difficult,
isn't it? Because when I feel tired I will walk slower. And if I died, the
reference is gone at all.

So, we need a reference which is continually reproducible to measure.

Now those scientist want to define 1 SECOND; and they define it as the
time needed by a nice Caesium-133 atom to complete a transition
between two energy levels of its ground state. Why? because
everywhere around the world, today or tomorrow, this Caesium-133 atom
needed the same that much time for that transition. So now we could use it
as the SECOND REFERENCE without bias.


Now lets define 60 seconds = 1 minute.

And then define 60 minutes = 1 hour.

We are now agree that 1 hour = 60 x 60 = 3,600 SECONDS.

So now, if I say, lets meet at Club X ONE HOUR from now,
it means we will meet after a time equal to the time needed by
Caesium-133 atom for 3,600 times mentioned transition. Agree with me?

Now we have the same clock. And now we want to measure by that clock,
one day is actually consist of how many seconds? Apparently, the
number is not even.

After 24 hours, which is = 24 x 3,600 = 86,400 seconds, it is not fully one day YET.
Apparently it consist of 86,400.002 seconds.
Which means, 1 day is equal to the time needed by that Caesium-133 atom
to complete 86,400 energy transition, PLUS 0.002 seconds.

But, if we say 1 day is equal to 86,400.002 seconds, it is IMPRACTICAL,
isn't it? So, they "remove" this 0.002 seconds per day.

HOWEVER, after one year, this removal will become 365 x 0.002 = 0.73 seconds.
(Well it is actually 0.9 seconds, because it is not exactly 0.002 seconds).
And this 0.9 second now looks more significant. Therefore, they adjust
the clock, by adding 0.9 second by the end of the year.

And so it does not mean that the earth spins slower half a second every year.

I like colourful text. Hope that helps.

[IceAgeCivilizations]

I just want to see if you know.

[IceAgeCivilizations]

Uh, inzomnia, the length of the second was established by the atomic clock through the measured duration of one Earth spin divided by 86,400.

[IceAgeCivilizations]

And the Earth spin keeps slowing down, so they have to add leap seconds.

[inzomnia]

Uh, inzomnia, the length of the second was established by the atomic clock through the measured duration of one Earth spin divided by 86,400.

No, it is not. I am not trying to be smart here, whatsoever,
trust me. This is the basic of your false conclusion. Please
check here: http://en.wikipedia.org/wiki/Atomic_clock

----- has defined the second as the duration of 9 192 631 770 cycles of the
radiation which corresponds to the transition between two energy levels of
the ground state of the caesium-133 atom.

They make that time period which is needed by that atom for once
energy transition as the reference. So they do not 'create' the
atomic clock. They took from natural phenomena and make that
as a basis. More or less. I over simplify it.

[IceAgeCivilizations]

It is the atomic clock measured second length in 1956, so they've added 23 leap seconds since.

[inzomnia]

It is the atomic clock measured second length in 1956, so they've added 23 leap seconds since.

Yes, if u take it from 1956, it will be around 23 leap (cumulatively).
But for what reason? For the reason which i write in the long post.
Please take time to carefuly read it, really.

[Oli]

Not to the Earth:
The length of the mean solar day has increased by roughly 2 milliseconds since it was exactly 86,400 seconds of atomic time about 1.79 centuries ago (i.e. the 179 year difference between 1999 and 1820). That is, the length of the mean solar day is at present about 86,400.002 seconds instead of exactly 86,400 seconds.

[spidergoat]

The Sub-bureau for Rapid Service and Predictions of Earth Orientation Parameters of the International Earth Rotation Service (IERS), located at the US Naval Observatory, monitors the Earth's rotation. Part of its mission involves the determination of a time scale based on the current rate of the rotation of the Earth. They estimate that the Earth's rotation is slowing at about 1.4 milliseconds per solar day per century which roughly agrees with the rate of rotation of the Earth has actually slowed down since 1820.

Tracing these tiny milliseconds back for 4.5 billion years adds up to a very significant amount of time for a solar day. The author has determined that the day/night rotation was 63,000 seconds shorter than the present 86,400 seconds it is today. This would put the Earth's rotation at about 6.5 hours per day/night cycle, when it was created, 4.5 billion years ago. (This is a much faster rate of rotation than the Cassini-Huygens mission (2003 to 2004) determined Saturn's 10.5 hours rotation period to be.)

That's pretty fast.
http://novan.com/earth.htm

[inzomnia]

But that slowing down has nothing to do with the adjustment
of atomic clock, has that?

http://novan.com/earth.htm

While we know the Earth's rotation is slowing that is not the main reason why the extra "Leap Second" was added by our official time keepers this year. The reason for adding a leap second is that the planet does not rotate exactly once every 24 hours (86,400 seconds). The rotation actually takes 86,400.002 seconds so that each day this little difference builds up between the atomic clock and the earth's rotation. When the difference builds up enough (.9 seconds), the time keepers must add another second (leap second) to keep the stars location, relative to the planet's rotation, in exact sync with the superaccurate atomic clocks.

The Earth's rotation is slowing but at a much slower rate than 1 leap second every so many years. The length of time it takes the Earth, at the present time, to rotate once is 86,400.002 seconds compared to 86,400 seconds back in 1820. The rotation has slowed roughly only by 2 milliseconds since 1820. That seems like an insignificant amount of time BUT over the course of the planet's entire lifetime, it has had very profound effects on the geophysics of the planet.

[Walter L. Wagner]

Inzomnia:

No, the adjustment is exactly as you noted. But please note that IAC doesn't like to read long paragraphs, or he certainly has a hard time understanding them.

Spidergoat:

We covered this before too. Thus, during the dinosaur days, the earth's rotational speed was closer to 22 hours, not 24. Think of how that would affect the climate!

IAC:

Please look at the bold and highlight of my previous post.

Way back in 1956, they decided to base the atomic second on what they believed was the number of seconds on January 1, 1900 A.D., which they defined to be 86,400.00 seconds. Turns out they were somewhat off, and the earth had 86,400.00 seconds way back around 1820 A.D., not 1900 A.D., as we've since determined by better astronomical measurements with satellites, etc., not available in 1956.

They were apparently uncertain as to whether the then-observed very slow slowing of rotation would continue at the same rate, and so they arbitrarily used the year 1900 A.D., as they then calculated it astronomically, to base their atomic second, rather than the then current year (1956). That's not the way I would have done it (I would have used the then current year, or better still 1950, as noted below) but that's the way they did it. Their astronomy was also somewhat off, and we've since learned that their definition of 86,400.00 seconds = one day fits best for the years circa 1820, not 1900. Anyway, that's the system they developed, and that we've used ever since, to define one second, now defined not by astronomical observations, but by the Cesium atom.

Because they started way off on the length of the day (off by about .002 seconds) right at the beginning when they started the atomic clock system, almost immediately they began having to add a 'leap second' every year or two. You can see the dates as to when they were added in the web pages I cited, though they typically add them at New Years. It's about every 500 days or so nowadays. A few thousand years from now, we'll be adding quite a few leap seconds every year due to the rotational slowing; or else we'll go back and re-define the second.

Your misunderstanding is apparently a common mis-perception, engendered by the fact that they STARTED OFF the atomic clock timing system with a day that was off by .002 seconds, i.e 86,400.002 seconds was the length of the day in 1956. If the earth ever speeds up (unlikely, unless we get a huge asteroidal impact in the right direction, or other unlikely event), the length of the day might go back to what it was in 1900 or 1820.

Anyway, I think it would have been preferable if they had used the year 1950 A.D. (my birth-year), rather than 1900 A.D., don't you agree?

[James R]

The issue in this thread has been well and truly resolved.

IAC's initial lie has been exposed, and several people have posted complete and informative exposes of that lie, with correct explanations.

There is no need to keep this thread open for further trolling by IAC, and future trolling of a similar kind may attract a ban.

Thread closed.