Equinox

From a (SEPTEMBER 1991) message by a Curious Questioner--
>CQ> Subject: Moonstruck?

>>RC> At our latitude the equal day/night occurs about 3 days later (today) for the autumnal equinox and about 3 days earlier for the spring (vernal) equinox. (Due to latitude and tilt of earth.)

>CQ> The reason that the equinox is not the time of exactly 12 hours of light is not because of latitude but rather because of the way in which we calculate "daylight".

Not correct. Quote: "Taking into account the proper definitions, the periods of daylight and dark are equal on some date prior to the vernal equinox and after the autumnal equinox, depending on the observer's latitude." (--World Almanac, p.235, "Rising and Setting of Sun and Moon; Twilight")

>CQ> Sunrise is when the disk of the sun first appears and sunset is when none of the sun is visible any longer.

OK. The basic calculation is begun by figuring from the center of the earth to the center of the sun's disc. Then correction is added for the "apparent" radius of the sun (which appears larger when the earth is closer to the sun in its orbit.) Then correction is figured for the location on the earth (latitude and longitude) and about a half of a degree allowance is made for refraction through the atmosphere.

Sunrise and sunset are officially defined as: "Visible rising and setting of the sun's upper limb across the unobstructed horizon of an observer whose eyes are 15 feet above ground level." (Mighty tall observer! "There were giants in the earth in those days..." :)

>CQ> Therefore, the time when the sun is partially present is counted as light. This would naturally add a few days to the summer half of the year.

The "summer half" is about 7 days longer than the other half, due to the earth's orbit around the sun not being exactly circular. (The sun was not created until "the fourth day", or exactly in the middle of the 7 days of Genesis 1,2. :)

>CQ> I haven't looked it up in any almanac, but I do not remember the autumnal equinox ever before occurring as late as it did this year. [1991]

Early, not late. Don't you remember the equinox on September 24th in 1903? (grin) The time of the equinox occurs about 11 minutes and 14 seconds EARLIER each year due to the seasonal year being a little LESS than a quarter-day longer than 365 days, but leap year every fourth year sets the time back a whole day. Currently, the equinox occurs on September 22nd in leap year and the year after leap; and then on September 23rd in the other two years of the 4-year cycle.

BTW: It's now NIGHT-TIME on the North Pole until "the spring of the day".[1Sam.9:26p] A year-long "day" is interesting in the light of prophecies in the Bible like Numbers 14:34 ("each day for a year") and remember that the Lord dwells in Zion in "the sides of the north." The grace of the Lord Jesus Christ be with your understanding. Amen. --Richard