By Ben, on March 20th, 2010
Today, at approximately 1:32 p.m. EDT, the Sun will be on the celestial equator, in the constellation Pisces. It will then be at the position known as the first point of Aries. (Makes sense, right? If you’re in Pisces, you pretend to be in Aries. Chalk this one up to the effects of precession.)
Here is an illustration from Wikipedia of the orientation of the Earth relative to the Sun’s rays on the equinox:
This alignment occurs, not because the Earth’s axis is any more or less tilted than it ever is (23.5 degrees from the ecliptic plane), but because the Sun’s [...]
By Ben, on September 22nd, 2009
Today, at 5:18 p.m. EDT, the sun will cross the celestial equator in the constellation Virgo. Often called the autumnal equinox, I prefer to name it by month, since neither South Florida, nor the Southern Hemisphere, experiences autumn in September. (I must admit, though, that the phrase autumnal equinox has a much more mellifluous sound, and is much more satisfying to say, than September equinox. Tennyson, though not an astronomer, would probably agree.)
The celestial equator. Image from NASA
On this day, the sun rises directly in the west, and sets directly in the east. Tomorrow, the sun will rise and [...]
By Ben, on September 22nd, 2008
The September equinox arrives today at one minute before noon, Eastern Daylight Time. One technical definition of the equinox (from the U.S. Naval Observatory) is that day when the geometric center of the Sun’s disk passing through the equator, with that point appearing above the horizon everywhere on Earth for 12 hours. Another definition, one that I like a little bit better, is “the date when the Sun crosses the celestial equator moving southward in the Northern hemisphere.”
One thing many people (including geographers, who really ought to know better) fail to understand is that the astronomical equinox does not mean [...]
