[LEAPSECS] BBC article

Rob Seaman seaman at noao.edu
Mon Nov 14 23:34:02 EST 2011

On Nov 14, 2011, at 8:43 PM, Doug Calvert wrote:

> On 11/04/2011 02:10 PM, Steve Allen wrote:


>> I think this is because GPS is one of the systems which was designed robustly with the notion that configuration changes are a routine part of the operation, so a leap second is just another routine change.


> Why is redefinition of UTC / end of leap seconds not just another routine change?

Read the discussions from the past 12 years. To summarize: because time-of-day is - well - time-of-day, that is, mean solar time. And if civil timekeeping approximates time-of-day then many problems don't arise in the first place. Astronomy is the canary in the coal mine. If clocks start lying about time-of-day, astronomers will notice very quickly what others will perceive later.

Leap seconds are the price to pay (under the current system) for civil time to remain stationary with respect to mean solar time, that is, time-of-day. Just like leap days are the price to pay for the civil calendar to remain stationary with respect to the seasons.

Gedanken: if omitting leap seconds is deemed acceptable, why shouldn't pretending that the length of day is 100,000 SI-seconds be acceptable? Where is the dividing line? What does the line divide?

Rob Seaman
National Optical Astronomy Observatory

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