[LEAPSECS] leap in june

[Richard B. Langley]

The secular change in the rotation of the Earth as related to the motion of the Moon had been detected by 1695 by Edmond Halley. Suggested explanation given by Emanuel Kant in 1754. Will send the Harold Spencer Jones paper on this later today. The smaller, atmosphere-related fluctuations were discovered in the 1930s (I think) using pendulum clocks.
-- Richard Langley

On Friday, January 9, 2015, 9, at 3:23 PM, Pierpaolo Bernardi wrote:

> Markus Kuhn writes: "The varying length of the day has been known for
> centuries but only became a practical concern (outside astronomy) with
> the invention of atomic clocks in the 1950s."
> 
> Is this true?  I though it was discovered only in the 20th century?
> From the context he refers to mean solar day, I understand.
> 
> 
> On Fri, Jan 9, 2015 at 2:24 PM, Tom Van Baak <tvb at leapsecond.com> wrote:
>> They were wise enough to ask Markus to write it; a nice balance between
>> popular and technical. They were kind enough to ask permission to use a
>> cesium clock leap second photo from my web site. "Not something you see
>> every day" indeed!
>> 
>> https://theconversation.com/an-extra-second-on-the-clock-why-moving-from-astronomic-to-atomic-time-is-a-tricky-business-35970
>> 
>> Markus -- your LOD plot ends in 2011?
>> 
>> /tvb
>> 
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| Richard B. Langley                            E-mail: lang at unb.ca         |
| Geodetic Research Laboratory                  Web: http://gge.unb.ca/     |
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