Re: [LEAPSECS] new beginning

From: Ed Davies <>
Date: Thu, 04 Aug 2005 15:44:17 +0100

Rob Seaman wrote:
> ...
> 3) Clarify the relationship between the civil second and the SI
> second. It may be too late to define a new unit of duration -
> whether Essen or Fressen - or perhaps it isn't. In any event, there
> are 86400 seconds per solar day, and that usage of the word "second"
> clearly differs from the SI unit which happens to have the same
> name. What are we going to do about it? (Certainly the ITU proposal
> does not address such issues.)
> ...

Perhaps it would be a mistake for the relationship between
civil and SI seconds to be anything other than identity.

There isn't a clear separation between the use of one and
the other. Consider, for example, a TV system. The frame
rate and so on of the TV signal would, presumably, be
defined in SI seconds. On the other hand, the schedule for
the day would be in civil seconds. Of course, the schedule
doesn't need to be held to the exact second (though it's
often done pretty close to that) but somewhere in the chain
there would have to be a switch over. Where, exactly?

In other words, I'm suggesting that any attempt to "fix"
leaps (seconds, minutes, hours or whatever) by use of rate
changes in civil time (relative to atomic time) results in
a cure which is worse than the disease.

Whether or not there are 86400 seconds per solar day is
something which should be up for discussion - not taken as
a matter of definition. Clearly, there's a use for a
"solar second" but perhaps it's even more specialised than
a sidereal second.

Ed Davies.
Received on Thu Aug 04 2005 - 07:46:24 PDT

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