Sukkot

[cellio]

Tonight begins the week-long festival of Sukkot. (That's "booths", for those who were wondering what all the little huts springing up on lawns in Squirrel Hill are about.) Chag sameach to those who celebrate, and happy fall to everyone else.

Naturally, in a week when we're supposed to take our meals outdoors under the fragile roofs of these booths, it's slated to rain more than a little. :-)

(Oddly, according to my favorite weather site, the equinox is today. Isn't that rather late? Or should I automatically view with suspicion a site that tells me that there are "11:60" hours of daylight today?)

Comments

[dr-zrfq.livejournal.com]

Well, the US Naval Observatory (http://aa.usno.navy.mil/cgi-bin/aa_pap.pl) and the Weather Underground (http://www.wunderground.com/history/airport/KAGC/2007/9/26/DailyHistory.html) also say that the day of 12-hour sunlight was yesterday. But the local weather folks were saying that the official time of the sun being directly over the equator was in the 5 a.m. hour of *Sunday* morning! I don't know how to explain the discrepancy. I wouldn't be surprised if the equinox was a few hours later than average this year, since it's been 3.5 years since the last Leap Year Day -- but that shouldn't affect it by a whole day, much less two...

And I concur with the wishes that you have a blessed Sukkot.

[cellio]

That's really odd.

I would expect the leap-year cycle to affect these events by up to, oh, 21 or 22 hours, not multiple days.

[dr-zrfq.livejournal.com]

So we agree there -- I just wish I had some idea what *does* explain the difference.

12 hours sunlight

[rob-of-unspace.livejournal.com]

There are several things that come into play.

One, the sun is bigger than the Earth. The sun "sees" past the halfway mark on the Earth, while we see less than 50% of the sun. Put a big circle next to a little circle: draw the line through the centers and the perpendicular lines to that line through the centers of the circles. Those two lines mark the "halfway." Now draw tangents to both circles -- there should be two of them. The smaller circle's tangents are beyond the halfway, while the larger circles tangents are before the halfway.

Two, the atmosphere refracts sunlight, so we get more than 50% daylight on the day when the sun is at it's highest point overhead.

Does that make sense to anyone but me?

Rob

Re: 12 hours sunlight

[cellio]

I'm not following the diagram, but atmospheric reflection sure makes sense, and I can grok the "the sun is big" idea even without the diagram. Thanks.