[LEAPSECS] Straw men

Ian Batten igb at batten.eu.org
Mon Jan 9 15:14:43 EST 2012

On 9 Jan 2012, at 2004, Gerard Ashton wrote:

> On 1/9/2012 2:40 PM, Ian Batten wrote:

>> So long as those all tick the same thing, its relationship to the rotation of the earth is, +/- several hours, irrelevant. No-one cares what the relationship between their watch/clock/computer and the sun is at anything other than the grossest scale


> The foregoing statement is just not true. The time of sunset and sunrise is important

> in many applications other than astronomy. It is important in all outdoor activities

> where artificial light sources will not be carried.

You mean you time your trips into the mountains to a precision of a few minutes, and don't carry a torch if you know you'll be back at 1843, but will if you're going to be back at 1845? And you do this not by looking up sunset in an almanac, a newspaper, a website, but by performing a calculation that relies on UTC-plus-leapseconds? Could you give me more detail of this? If you use a hundred year old Garmin GPS12 to calculate local sunset in 2100, it's possible the answer might be as much as a minute off from civil time? This matters, because ...?

> It's important for pointing some

> solar arrays, and modeling the output from the same.

And that modelling requires a precision greater than 1min and the code will remain unchanged for a century?

> This would suggest sunset/sunrise

> tables that are to be enforced with a wrist watch should have calculations

> that are accurate to no worse than 20 seconds.

No one has yet provided even the beginnings of the suggestion that sunrise and sunset times are enforced to a precision of better than tens of minutes. And as I've said, if this is a real worry to you, turn your lights on a minute earlier. You're safe for the rest of your life.


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