Reflections 9/22/96
Robert Kern Curtis

The Equinox

Today is the autumnal equinox! The weather channel says that the sun rises at 6:47 and sets at 6:55 today, and that tomorrow the sun will rise at 6:48 and set at 6:53.

So why did the CBS news announcer say this morning that today is the equinox, the day when there are exactly twelve hours of daylight and twelve hours of darkness? He went on to say that the equinox is at two o'clock this afternoon.

At least, no one in my hearing has said anything about standing eggs on their ends on the equinox--this was the one thing most of my physics students seemed to think of when I asked about the equinox in class on Friday.

My 1974 Webster's New Collegiate Dictionary (This is the edition I like because it lists the Ph.L. degree!) says defining "equinox"

1: either of two times each year when the sun crosses the equator and day and night are everywhere of equal length, being about March 21 and September 23
2: either of the two points on the celestial sphere where the celestial equator intersects the ecliptic

This second definition seems to be where the CBS announcer got the two o'clock time for the equinox and how those exact minutes and seconds for the start of Fall are determined.

As for the times given so far, these have all been Eastern Daylight Savings Time since our location is in northern New Jersey. These time zones and standard time seem to have come from the railroads, while daylight savings seems to be a totolitarian invention of government, a subtle way of telling everyone to get up an hour earlier in the morning! The sun actually rises at 5:47 and sets at 5:55 Eastern Standard Time. Galileo did teach us that actually the sun neither rises or sets (and that there are no celestial spheres) but we seem slow to listen to him. This at least puts midnight at about the correct time! We can see that sunrise is thirteen minutes early and sunset is five minutes early according to THE WEATHER CHANNEL. The day of the equinox is about eight minutes longer than it should be, and it will be several more days that day will be longer than night! (Until September 26th)

The consistently early times given by THE WEATHER CHANNEL seem due to standard time and the longtitude for which they are predicting sunrise and sunset; they are not predicting for 75.0000 degrees but rather some place else???? (Hackensack, NJ is at 74.05 long and 40.89 lat) Test this out for yourself UNSO_Sunrise&Sunset

The longer days than nights are caused by the refraction of light as it enters and passes through the atmosphere! The light does not travel in straight lines, but is bent towards the normal to the surface in the more dense medium. This gains about four minutes on the morning of the equinox and another four minutes in the evening! and depends on the angle with with the sun's rays strike the atmosphere.

I wonder what they thought of all this in ancient Greece?


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