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Sun over the yardarm?
February 2, 2011 10:33 PM   Subscribe

Is the sun over the yardarm earlier when one is closer to the equator?
posted by pompomtom to Science & Nature (14 answers total) 1 user marked this as a favorite
This is a nautical expression, from the days of rum, sodomy, and the lash. My understanding is that this is approximately equivalent to noon, when the sun could appear above most yard-arms of naval vessels in the Northern Hemisphere, where the British navy was based. This is the end of the forenoon watch, the first tot of grog for the day was typically issued then. However, yardarms on different masts would be at different heights, and the perspective of the observer can affect this as well. It is believed that the expression is pretty inexact, therefore.

As with other British Navy drinking rituals, such as order to splice the main-brace, the exact circumstances were variable. Since the forenoon watch does not depend on latitude, the answer would seem to be no. But, given that the sun is higher in the sky as one approaches the equator, the answer could also appear to be yes. It depends why you are asking, then.
posted by PareidoliaticBoy at 11:03 PM on February 2, 2011 [1 favorite]

That would depend on the time of year, wouldn't it?
posted by nomis at 11:03 PM on February 2, 2011

I'd think it would occur slightly earlier in the day (and stay above until slightly later in the day) the closer you were to the latitude where the sun passes directly overhead, which varies over the year. Close to either equinox, that would be at the equator. During the solstice, it would be at the Tropic of Cancer or Tropic of Capricorn (depending on which hemisphere you were in.)
posted by ctmf at 11:08 PM on February 2, 2011

which hemisphere you were in which solstice.
posted by ctmf at 11:09 PM on February 2, 2011

Of course, that's speaking literally. "Sun over the yardarm" is a figure of speech, kind of in the same way as "noon" is. Depending on your exact position in the time zone, status of daylight savings time, etc., local apparent noon (the sun at it's highest point) might not occur exactly at 12:00pm, but we still call 12pm "noon". Similarly, the sun is over the yardarm at around 11 am (even if it's really not.)
posted by ctmf at 11:15 PM on February 2, 2011

It's certainly been my experience that the metaphorical sun is over the metaphorical yardarm earlier in the day, in that I'm inclined to turn to drink earlier in tropic climes. Are you asking about a literal yardarm?
posted by mumkin at 11:23 PM on February 2, 2011 [2 favorites]

Isn't it basically just like sunrise? I mean, aren't you essentially comparing the time that the sun rises over a local horizon?
posted by gingerest at 12:15 AM on February 3, 2011

I mean really "is the sun quicker to reach an arbitrary angle above the horizon as one approaches the equator, ceteris paribus?"

Sorry all, I didn't know I was being so vague.

I am presently far closer to the equator than usual, so the sun is much higher in the sky at noon. I'm wondering how the subjective angle (sorry, I'm sure there's a technical term for it.... Possibly 'azimuth'?) compares at, well, elevenish.
posted by pompomtom at 4:29 AM on February 3, 2011

Here is a solar position calculator that shows elevation and azimuth of the sun as a function of your position and the time of day. The sun travels along the ecliptic, shown as the red line in the calculator, and you'll see that the closer you get to the equator the greater the maximum solar elevation. In the tropics the sun is directly overhead (its elevation is 90 degrees) at least once a year.
posted by jet_silver at 6:53 AM on February 3, 2011 [1 favorite]

If the "sun is over the yardarm" at noon, then it doesn't matter what latitude you're at. The sun always reaches its peak at noon (barring Daylight Savings Time fooleries).

If "the sun is over the yardarm" depends on the sun rising to a certain height in the sky relative to the yardarm -- i.e. if you're not looking straight up -- then the question is meaningless as it depends on how far away you are from the yardarm.
posted by musofire at 9:50 AM on February 3, 2011

Anyway, Mine's a Mojito thanks
posted by DrtyBlvd at 11:43 AM on February 3, 2011

I would just drink if I were you.
posted by wilful at 4:11 PM on February 3, 2011

But we know you're a total soak, wilful...
posted by pompomtom at 5:14 PM on February 3, 2011

musofire: even taken literally, there's only so far away from the mast you can get on the deck of the ship. Presumably you would be eagerly awaiting the sun to be over the yardarm, and so be standing in the most advantageous place for that to be observed, but still have to wait.

The deck of a ship not being round with the mast in the center, it would, of course still depend on the ship's heading. Which is why this is a colorful figure of speech and not really a dependable time reference in the same way apparent noon is. Still, all other things being equal, it would happen earlier in the day closer to the latitude of the sun's current position on the ecliptic. It might not occur at all in the higher latitudes.
posted by ctmf at 6:31 PM on February 3, 2011

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