Re: Leap Second Quiz Question

[Tony Finch]

Frank King  wrote:

> The U.K. telephone-service speaking clock gets it right too but only by
> a fudge.  You hear:
>
>   At the thiiird stroke...
>
> with a bit of noise in "third"!

The recording I have heard has the usual three pips, but with two seconds
between the second and third pips:

https://twitter.com/womump/status/815976395906174976

(i.e. the pips at the end of the minute were :58, :59, :00 as usual!)

> Ordinary domestic radio-controlled clocks adjust themselves at some
> convenient time later.  None of mine had changed at 00:30 but all had by
> changed by 07:00.

My radio clock resets at 01:00 which seems inconveniently early to me -
I haven't checked exactly how it handles the summer time changes.

I also have a cheap little bare MSF receiver, but it's essentially useless
during the day. It works OK in the night (better atmospheric conditions)
which is good for watching June leap seconds.

Tony.
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Re: Leap Second Quiz Question

[Geoff Thurston]

Happy New Year to one and all,

The University Clock has gained 0.5 seconds against UTC in the past week
but is now 2.0 seconds ahead of UTC because of the leap second. If Frank
removed coins in accordance with the LWG for 0.5 seconds, then the clock's
rate would be rectified but the clock would still be 2 seconds fast next
week. Therefore, Frank should apply a LWG of 2.5 seconds and adjust again
when the clock is showing the correct time.

Geoff



On 1 January 2017 at 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 Januaryclock 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.
>
>
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>
>
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RE: Leap Second Quiz Question

[Frank King]

Dear All,

Many interesting comments...

David Brown wrote:

> ...the place where you add/remove the coins
> is below the current C.G.

This is a theoretical possibility but all
the large pendulum clocks I have looked
at have an annular tray round the shaft
ABOVE the pendulum bob...

There are good reasons for this.  A long
pendulum (mine is 4m long) swings in a
pit which is not a convenient place to
scrabble about in.  More important is
the safety element.  Clock makers long
ago discovered what devastation can be
wrought if the line to a clock weight
breaks.  Second only to one of these
lines breaking is the pendulum snapping
off at the swinging point.  My pendulum
weighs 150kg and I wouldn't like that
falling on my fingers.

> ...if the clock has not been tampered
> with, it is unlikely that the...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.

While "unlikely", this kind of jump in
rate happens several times a year.  I
have a temperature compensated pendulum
but this seems to be defeated if there
is a sudden spell of hot sun shining
on the face of the clock tower.

Fritz wrote:

> It seems that you would need to be
> able to make two separate adjustments
> (and probably more); one would be for
> the clock's rate and a separate for
> the reading.

This is the most astute comment so far.
Users of chronometers for navigation,
never adjusted either the rate or the
reading while at sea.  They made
corrections based on astronomical
observations made in port.

My clock is not as good as a chronometer
and the rate changes with temperature
and humidity [high humidity makes the
bob more buoyant and effectively changes
the value of g].  I have to change the
rate BUT...

I never change the reading except when
the clocks change by an hour.

Fritz suggests:

> ... you would rather approach the
> correction slowly over 5 weeks ...
> .5  .4  .3  .2  .1 

This is almost exactly my approach
except that my goal each Sunday is
to change the rate so that the
clock is right next Sunday.  This
rarely happens.  Sometimes I
over-correct and sometimes I
under-correct.  I try to predict
temperature and humidity but my
predictions are not perfect!

The formula I use is:

  Coins to add =  (DG - LWG)/1.3

  DG  = Desired Gain
  LWG = Last Week's Gain
  Coins = U.K. pence

This a linear relationship which
I established by experiment.

The factor 1.3 is a long-term
average.  Each week I determine
what the correct factor should
have been last week.  In 2016
the value I should have used
ranged from -4 to +6 which is
disappointing.

Roger Bailey wrote:

> I expect the impoundment of
> water in hydro power reservoirs
> adds mass to northern hemisphere. 

Is this right?  Where would the
water goif it weren't impounded?
Probably into a river which
discharges into a northern
hemisphere ocean.

Most stored water is in the oceans
and in ice.  The north-south ice
balance varies with the time of
year but attempts to discern an
associated effect on the Earth's
rotation show a negligible change.

You are probably safe to store
water in reservoirs but be very
careful about interfereing with
the moon!

Meantime, Mike Shaw and Dave Bell
asked about the effect of tidal
energy on the moon.  Richard
Langley's reply explains all.

Frank


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Re: Leap Second Quiz Question

[Richard Langley]

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. LangleyE-mail: l...@unb.ca |
| Geodetic Research Laboratory  Web: 
http://gge.unb.ca<http://gge.unb.ca/>  |
| Dept. of Geodesy and Geomatics EngineeringPhone:+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.=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 Januaryclock 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.





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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.







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RE: Leap Second Quiz Question

[Dave Bell]

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 Januaryclock 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.
 
 
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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.



 

 

 

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Re: Leap Second Quiz Question

[David]

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 Januaryclock 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.


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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.




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Re: Leap Second Quiz Question

[Frank King]

Dear All,

The voting pattern has swung away from
1.5s to 0.5s and we shall see whether
this trend continues!

There is an embellishment to Mike Shaw's
comment:

  The radio clock stopped for 1 second
  at midnight

This isn't quite what happens.  Indeed,
there seems not to be a general pattern.

The Definitive UTC Clock is more a
mathematical construct than a physical
object that ticks along with high
precision.  It (the construct) certainly
never stops and, during the night, it
ticked up:

  23:59:59   23:59:60   00:00:00

The formal representation of UTC midnight
is 00:00:00 and one second before that
(in this special case) is 23:59:60.  There
is a continuum of times in between, like
23:59:60.875

There are real clocks which can and do
display 23:59:60 but I don't own one.

The U.K. six-pip time signal extends
to seven pips and I have heard that.

The U.K. telephone-service speaking
clock gets it right too but only by
a fudge.  You hear:

  At the thiiird stroke...

with a bit of noise in "third"!

Ordinary domestic radio-controlled
clocks adjust themselves at some
convenient time later.  None of
mine had changed at 00:30 but all
had by changed by 07:00.

Given my special requirement, I
checked a radio-controlled clock
against the speaking clock before
I set out.  You can't trust radios
these days.  Most are digital and
give the six (or seven) pip signal
about 2.5s late.

The speaking clock is really two
clocks which normally run in
sync.  One is live and the other
is back-up.

When the clocks go forward or back
an hour, the two are set exactly an
hour apart and someone throws a
switch at the critical moment.
You don't hear any stutter in the
spoken words.

When the clocks go back one second
the same thing happens.  Someone
switches from one clock to the
other but in the middle of the
word "third".

Remember, the speaking clock
announces times which are
multiples of 5 seconds.  It
announces 23:59:55 and then
lets the next announcement
start running before the
switch is thrown.  The speaking
clock never announces 23:59:60.

I am a huge fan of leap seconds
and see no reason to change this
scheme until the earth starts
slowing down more than 2 seconds
a year.  All this wind power and
tidal power could accelerate that
happening!

Frank

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Re: Leap Second Quiz Question

[jmikeshaw]

Well I think I'll go for 0.5 seconds.

Frank's clock has apparently gained 1.5 seconds in the week.
The radio clock stopped for 1 second at midnight, but Frank's didn't and 
so gained 1 second.


Mike Shaw



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