NavList:

   

Reply

Frank,

I can offer no opinion on the navigational aspects of this, but I wonder what 
will happen 200 years from now.  Will noon be 11:30 am?  That would be 
unacceptable to me.  Is it really that difficult to keep the leap seconds 
convention going?

Fred Hebard

On Sep 8, 2011, at 10:00 PM, Frank Reed wrote:

> I have committed to do a presentation at the colloquium next month in 
Pennsylvania (Oct. 5/6) regarding the proposal to drop leap seconds from the 
definition of UTC. One of the things that I want to do is get opinions from 
NavList members. Suppose leap seconds are dropped from time-keeping. Since 
the Earth's rotation does not quite match the definition of the second, the 
Earth's rotation will slowly fall out of line with the mean times kept on the 
vast majority of the world's clocks. If this proposal takes effect, then, in 
the year 2025 for example, if you calculate when the star Sirius crosses the 
meridian at your location naively using UTC, you might find that it is seven 
or eight seconds late. Similarly "local noon" would not occur at twelve 
o'clock, even on average, even at the center of a time zone. This is easily 
observable, and this sort of discrepancy could easily put a vessel's position 
out by a couple of miles. Of course this would only happen if we were to 
BLINDLY apply the rules without correction. The simple solution is to include 
a table in the annual Nautical Almanac and other "nautical almanac" 
equivalents giving the "watch error" of UTC relative to navigators' time 
(whatever that might be). There might be other ways to handle this, too. In 
principle, this should be no problem. In practice, there may be serious 
education issues. Since celestial navigation is primarily a backup method of 
navigation, and many people who would use it in an emergency could be fairly 
described as "rusty" on the details, would a navigator so be confused in an 
actual case where the methods were needed that navigation would be 
compromised?
> 
> I would like to get as much input on this as possible. All opinions welcome! 
I need to finalize my presentation within the next couple of weeks, so start 
thinking and get back to me as soon as possible. Naturally, I will give 
individual credit where credit is due (for any non-obvious ideas!) and 
general credit to the NavList membership for your help.
> 
> -FER
> 
> ----------------------------------------------------------------
> NavList message boards and member settings: www.fer3.com/NavList
> Members may optionally receive posts by email.
> To cancel email delivery, send a message to NoMail[at]fer3.com
> ----------------------------------------------------------------
> 

   

Reply