Friday, September 23, 2011

Happy Equinox!

Happy autumnal equinox: here’s a year of sunrises | Bad Astronomy | Discover Magazine: "At 09:05 UTC (05:05 Eastern US time) this morning, the position of the center of the Sun’s disk, moving south, crossed the celestial equator on the sky. For normal people, this means it was the moment of the autumnal equinox. ...  On Earth, it means that the length of time of day and night are almost exactly equal (they’re off by a bit due to the elliptical shape of Earth’s orbit, plus the presence of our atmosphere throwing off the time of sunrise and sunset). It also means the line marking day and night — technically called the terminator — is perpendicular to the Earth’s equator. That sounds funny, but maybe an animation is worth a thousand words:"

'via Blog this'

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