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 Post subject: Leap Seconds
PostPosted: April 3rd, 2006 04:27:01 am 
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Leap seconds are more common than you might think. I found out today that in the 34 years that we've been using the current system, 23 leap seconds have been inserted.

That means a year these days is more likely to have an extra second than not.


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PostPosted: April 3rd, 2006 23:16:28 pm 
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Most leap seconds are only artifacts of an imperfect definition of the second. Many Scientists are pushing to change the definition from 9,192,631,770 to 9,192,631,997 cycles of the hyperfine ground state transition of Caesium (133). If this definition were adopted in 1973, this would mean there would only have been 3 leap seconds to account for tidal drag slowing down the orbit of the earth.


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PostPosted: April 3rd, 2006 23:35:25 pm 
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Wouldn't that change what the speed of light is in meters per second? I went to the trouble of memorizing 299,792,458, and I don't want to have to replace that with a new figure.


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PostPosted: April 4th, 2006 00:23:33 am 
Ben: the speed of light is a constant.


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PostPosted: April 4th, 2006 00:29:44 am 
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Yes, but the number of meters per second equal to that constant depends on how "meter" and "second" are defined.

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PostPosted: April 4th, 2006 00:32:09 am 
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Anonymous wrote:
Ben: the speed of light is a constant.

that was me


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PostPosted: April 4th, 2006 00:33:06 am 
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Ben Heaton wrote:
Yes, but the number of meters per second equal to that constant depends on how "meter" and "second" are defined.

I believe it was the great The Notorious L.I.N.C.O.L.N. who once said,

"How many legs does a horse have if you call a tail a leg?"
"4, calling a tail a leg doesn't make it so.

It's a constant, ben, a constant.


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PostPosted: April 4th, 2006 00:36:02 am 
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I think the horse would have one leg, by definition.

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PostPosted: April 4th, 2006 14:46:36 pm 
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I think that the speed of light could remain the same, but the length of a meter would change very slightly.


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PostPosted: April 4th, 2006 15:39:06 pm 
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That sounds fine, then. We could keep the meter defined as the distance light travels in 1/299792458 of a second.

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PostPosted: April 4th, 2006 21:22:33 pm 
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To be precise, the meter would become 0.0000025% (which corresponds to a distance of 25 nm) longer if this definition were adopted. Otherwise, the new speed of light would be 299,792,450.6 m/s, which is no longer a nice round number. It's hard to say which would be more inconvinient to change.


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PostPosted: April 14th, 2006 03:17:36 am 
"The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second."

There is no change to the speed of light. Meters just keep getting longer.


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PostPosted: April 14th, 2006 04:42:18 am 
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No change as measured in meters per second, at least.

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PostPosted: May 22nd, 2006 20:11:21 pm 
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Obviously, the solution is to abandon leap seconds altogether.

If we'd never added any leap seconds, the sun would be directly overhead at 12:00:23 instead of 12:00:00. I doubt many people will notice.

On the other hand, keeping track of GPS sattelites becomes overly complicated, because those extra seconds have to be accounted for.


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PostPosted: May 23rd, 2006 02:58:42 am 
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Ravenswood wrote:
If we'd never added any leap seconds, the sun would be directly overhead at 12:00:23 instead of 12:00:00.


Depending on where in your time zone you are, what time of year it is, and whether you observe daylight saving time or not.

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PostPosted: May 23rd, 2006 03:38:37 am 
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The people who would notice are astronomers and celestial navigators, but both of these groups are so hopelessly backward, that they could not be persuaded to switch to any new system anyway.


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PostPosted: May 23rd, 2006 05:40:59 am 
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The technical term for celestial navigators is "astrogators."

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PostPosted: May 23rd, 2006 21:40:54 pm 
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No, an astrogator is one who navigates a spacheship.


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PostPosted: May 24th, 2006 00:51:30 am 
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Astrogators do not navigate. They astrogate.

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PostPosted: May 31st, 2006 01:26:12 am 
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Ben Heaton wrote:
The technical term for celestial navigators is "astrogators."


No, those are the ones with rounded snouts. Crocodiles have pointy snouts.


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PostPosted: May 31st, 2006 07:29:59 am 
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Please try to stay on-topic.

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PostPosted: May 31st, 2006 20:04:51 pm 
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Ben Heaton wrote:
Astrogators do not navigate. They astrogate.


Obviously. But I find it more usefull to define words in terms of different words. Astrogation and Navigation are very similar, where one occurs in space, the other occurs on the ocean.


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PostPosted: June 2nd, 2006 06:37:39 am 
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Clancy wrote:
Ben Heaton wrote:
Astrogators do not navigate. They astrogate.


Obviously. But I find it more usefull to define words in terms of different words. Astrogation and Navigation are very similar, where one occurs in space, the other occurs on the ocean.


So, they both involve -gating, one inside stars, the other inside the ocean?

So, like Submariners and Solarians are the types of people who can do it?


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PostPosted: May 9th, 2007 20:03:11 pm 
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Justin Time wrote:
So, they both involve -gating, one inside stars, the other inside the ocean?

Well, no, gating inside stars is Stargating, something completely different. "Navigating" comes from the Latin navis meaning ship.

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PostPosted: May 18th, 2007 16:57:56 pm 
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william wrote:
Well, no, gating inside stars is Stargating, something completely different. "Navigating" comes from the Latin navis meaning ship.


Spaceship, in this case, so it still works.

Alternate ending:

The English language is flexible, and constantly being adapted to new linguistic situations which never existed before, such as the need to "navigate" on a space-"ship".

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 Post subject: Re: Leap Seconds
PostPosted: December 4th, 2008 22:04:40 pm 
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I sense a leap second looming in the near future.


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 Post subject: Re: Leap Seconds
PostPosted: December 6th, 2008 13:02:18 pm 
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Indeed, the head of the International Earth Rotation Service (or something like that) has said that there will be one at the end of this year.

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 Post subject: Re: Leap Seconds
PostPosted: December 7th, 2008 02:54:38 am 
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I like that name. It makes it sound like they're the ones responsible for keeping the Earth rotating.

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 Post subject: Re: Leap Seconds
PostPosted: December 7th, 2008 09:06:29 am 
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Ben Heaton wrote:
I like that name. It makes it sound like they're the ones responsible for keeping the Earth rotating.

They are. Anything you hear about "inertia" or "conservation of angular momentum" is a lie.

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