The angular momentum of the Earth-moon system has to be conserved, so if the Earth's rotation slows more, then the moon speeds up in its orbit and moves further away from the Earth. Currently, as a result of the ongoing secular deceleration of the Earth (due to tidal friction), the moon moves about 2 cm further away each year. This was confirmed by lunar laser ranging -- an area I worked in for my postdoctoral studies way back when. Tidal friction is a primary reason for leap seconds, to bring us full circle. This is what I wrote for the previous leap second:
http://www2.unb.ca/gge/Resources/LeapSecond2015.pdf -- Richard Langley ----------------------------------------------------------------------------- | Richard B. Langley E-mail: l...@unb.ca | | Geodetic Research Laboratory Web: http://gge.unb.ca<http://gge.unb.ca/> | | Dept. of Geodesy and Geomatics Engineering Phone: +1 506 453-5142 | | University of New Brunswick Fax: +1 506 453-4943 | | Fredericton, N.B., Canada E3B 5A3 | | Fredericton? Where's that? See: http://www.fredericton.ca/<https://unbmail.unb.ca/owa/redir.aspx?C=tVxi5OaRXE2jUmSNTu0wE7USusV6L9AIh-TKOqhq1DE--EjKeq-SUal8Myg-FGJn53Gm890SFIc.&URL=http%3a%2f%2fwww.fredericton.ca%2f> | ----------------------------------------------------------------------------- ________________________________ From: sundial <sundial-boun...@uni-koeln.de> on behalf of Dave Bell <db...@thebells.net> Sent: Sunday, January 1, 2017 2:24 PM To: 'David'; sundial@uni-koeln.de Subject: RE: Leap Second Quiz Question Logically, tidal power should slow the Earth’s rotation. Mechanical energy, imparted by the combined gravitation of the Sun and Moon is converted to electrical energy, then primarily dissipated as heat. Drag applied to the tidal surge must, to some extent, add drag to the Earth’s rotation. Now, does the extracted energy also slow the Moon’s revolution about the Earth? Dave From: sundial [mailto:sundial-boun...@uni-koeln.de] On Behalf Of David Sent: Sunday, January 1, 2017 7:19 AM To: sundial@uni-koeln.de Subject: Re: Leap Second Quiz Question On 01/01/2017 12:30, Frank King wrote: Dear All, I hope you all enjoyed the extra second in bed this morning and that your alarm clock didn't go off one second early. Here is an easy question to start off the New Year... Every Sunday at 08:00 I check the first stroke of the hour-bell of the University Clock against a radio-controlled UTC clock. If it is slow I add coins to the tray on the pendulum. If it is fast I remove coins. My formula for the required adjustment includes a figure for: Last Week's Gain [LWG] Here are my recent observations: 25 December clock 0.5 seconds fast 1 January clock 2.0 seconds fast Is the appropriate figure for LWG: a) 0.5 seconds b) 1.5 seconds c) 2.5 seconds Frank Frank H. King Keeper of the University Clock Cambridge, U.K. --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial Dear Frank, Happy New Year! I am sorry to hear that it starts with a problem for you albeit one of the horological kind, so that removes the pain. I am somewhat puzzled, too. You say: Every Sunday at 08:00 I check the first stroke of the hour-bell of the University Clock against a radio-controlled UTC clock. If it is slow I add coins to the tray on the pendulum. If it is fast I remove coins. Does the 'it' at the beginning of your second par. refer to the University clock? If so, then if it is slow (i.e. rings after the UTC clock says it should), then its pendulum is too long (C.G. too low), so needs shortening. So coins need to be removed, not added. This assumes that the place where you add/remove the coins is below the current C.G. As to the main question, between 25/12 and 1/1, the clock appears to have gained 1.5 s. But the UTC clock has added a second, so the University clock has gained only 0.5 s so the LWG is 0.5 s. In any case, if the clock has not been tampered with, it is unlikely that the University clock will have changed its previous LWG of 0.5 s to 1.5 or even 2.5 s in the space of a week. So I'll go for 0.5 s as the correct answer. David. ________________________________ [Image removed by sender. Avast logo]<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> This email has been checked for viruses by Avast antivirus software. www.avast.com<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
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