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Old June 30th, 2012, 08:34 PM
Doug Kerr Doug Kerr is offline
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Default Leap second caught in the act

At 2012.06.30 23:59:59, a positive leap second was inserted in the UTC time scale. In effect, all UTC clocks paused for one second.

The manifestation of this in official time notation is that one second after the epoch 2012.06.30 23:59:59, the time became 2012.06.30 23:59:60 (an ordinarily-anomalous value), and one second later the time became 2012.07.01 00:00:00.

This maneuver is done from time to time in order to keep consistent, within one second, the UTC time scale (based on an "atomic clock") and the UT1 time scale (based on the mean rotation of the earth).

These get out of sync since the earth's rotation is slower than it was when the SI second, the unit of the UTC scale, was defined in terms of the "atomic clock". The deviation accelerates owing to the ongoing further slowing of the earth's rotation.

By custom, leap seconds are only inserted at the end of June 30 or December 31. In recent years, a positive leap second has been inserted about every 3 or 4 years.

Carla and I "watched" the leap second being inserted by observing UTC on an online "widget" provided by the National Institute of Standards and Technology (NIST), the primary standard time distribution authority for the United States.

These screen shots show the sequence at one-second intervals:






Note that there is afloat a proposal to eliminate the use of leap seconds. The ramifications of this are beyond the scope of this note.

At he present time, no decision is planned by the scientific community on this prospect prior to the meeting of the World Radio Council in 2015, where it is now thought that the matter will be decided.

It is likely that, even if it is then decided to forgo the use of leap seconds, at least one more insertion will take place. Still, we were glad to not miss this one.

Best regards,

Doug
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Old July 1st, 2012, 12:52 AM
Asher Kelman Asher Kelman is offline
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That's a leap of faith, Doug, but I believe you! Noe do all parts of the globe need the same full leap second? Folk in the poles need less time to do a circle, LOL!

These pictures are classic! good catch!

Asher
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  #3  
Old July 1st, 2012, 08:40 AM
Doug Kerr Doug Kerr is offline
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Quote:
Originally Posted by Asher Kelman View Post
That's a leap of faith, Doug, but I believe you! Noe do all parts of the globe need the same full leap second? Folk in the poles need less time to do a circle, LOL!
Only if they are walking! If riding on the earth, it is all the same.

Indeed, unlike the "leap day", leap seconds are inserted at the same instant for everybody.

Quote:
These pictures are classic! good catch!
Thank you. That work had to be interleaved with shooting, through the window of our room at the Paris Hotel in Las Vegas, Nev, the elaborate setup process for an upcoming band concert to be held on the giant pool deck (which our room overlooks perfectly). I'll post some of that as time allows (right now we are packing out).

The concert - by KC and the Sunshine Band - a freebie for members of the Bally empire rewards program, was dreadful. The music was all from the 70's and could have been rendered to evoke nostalgia, but it just had every earmark of a has-been at work.

Best regards,

Doug
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Old July 1st, 2012, 09:03 AM
Mark Hampton Mark Hampton is offline
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Posts: 1,330
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Quote:
Originally Posted by Doug Kerr View Post
At 2012.06.30 23:59:59, a positive leap second was inserted in the UTC time scale. In effect, all UTC clocks paused for one second.

The manifestation of this in official time notation is that one second after the epoch 2012.06.30 23:59:59, the time became 2012.06.30 23:59:60 (an ordinarily-anomalous value), and one second later the time became 2012.07.01 00:00:00.

This maneuver is done from time to time in order to keep consistent, within one second, the UTC time scale (based on an "atomic clock") and the UT1 time scale (based on the mean rotation of the earth).

These get out of sync since the earth's rotation is slower than it was when the SI second, the unit of the UTC scale, was defined in terms of the "atomic clock". The deviation accelerates owing to the ongoing further slowing of the earth's rotation.

By custom, leap seconds are only inserted at the end of June 30 or December 31. In recent years, a positive leap second has been inserted about every 3 or 4 years.

Carla and I "watched" the leap second being inserted by observing UTC on an online "widget" provided by the National Institute of Standards and Technology (NIST), the primary standard time distribution authority for the United States.

These screen shots show the sequence at one-second intervals:






Note that there is afloat a proposal to eliminate the use of leap seconds. The ramifications of this are beyond the scope of this note.

At he present time, no decision is planned by the scientific community on this prospect prior to the meeting of the World Radio Council in 2015, where it is now thought that the matter will be decided.

It is likely that, even if it is then decided to forgo the use of leap seconds, at least one more insertion will take place. Still, we were glad to not miss this one.

Best regards,

Doug
Doug,

the exposure is only smeared for 1/50th on each - should have made it a second mate !

i was thinking of this when I listened to 7 pips on the radio last night !
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