Vernal Equinox

Welcome to boreal Spring! With the Vernal Equinox, the Sun entered the sign Aries earlier today at 0100 UTC, which is another way of saying that the Sun’s geocentric longitude along the ecliptic is starting back at zero degrees again. Or, from the point of view of the Sun, we on the Earth are beginning another cycle around the Sun. But don’t worry, we’ll be back here in another (tropical) year.

Also, the Sun’s geographic position (GP), or the point on the Earth’s surface where the Sun is directly overhead, crossed the equator from south to north at the mighty speed of 1.8 km/h! Now if the Earth did not rotate about its axis, the west-to-east speed of the GP would be about 4.2 km/h at the equator. But when you take into account the rotation, the speed is much faster at about 1671 km/h (and in the opposite direction).

But at least now Spring can begin in the Northern Hemisphere. (Oh, and welcome to Fall if you are in the Southern Hemisphere.)

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