[LEAPSECS] Leap smear and Big Ben

[mike cook]

Le 02/10/2011 00:38, Tom Van Baak a écrit :

> To implement a leap second they add coin (yes, time is money).

> Each penny changes rate by about "2/5 second per day", which

> is about 5 ppm.

There is nice animated description of the clock mechanism at
http://www.parliament.uk/about/living-heritage/building/palace/big-ben/inside-clock-tower/how-great-clock-works


> Now, I've glanced at:

> http://en.wikipedia.org/wiki/Penny_(British_pre-decimal_coin 

> <http://en.wikipedia.org/wiki/Penny_%28British_pre-decimal_coin>)

> but perhaps one of our UK members can tell us the exact mass

> of a pre-decimal penny and so tell us the rate change of Big

> Ben per £ or per kg. Which will tell us how many kg-seconds

> or £-hours is takes to implement one leap second in Big Ben.

  The clock was made in 1854, though not installed and started in the 
tower until 1859. In those days the penny was 18,8 grams, twice that of 
the 1860 and latter pennies.
So I wonder which ones are currently in use? If the penny story is true 
I would have thought that pennys available at the time of testing and 
installation would still be there. The halfpenny of the 1825-1860 period 
was 9,3 grammes, so maybe the original weights were halfpenny's and 
later swapped with 9.4g penny's.


> /tvb

>


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