Autumnal Equinox arrives at 5:18 p.m.

The fall, or autumnal equinox arrives this afternoon just as the rush hour begins – at 5:18 p.m. That’s the moment when the the sun, as seen from Earth, crosses the planet’s equatorial plane and heads for the southern hemisphere. And, the sun rises due east today.

Or, you could say the Earth’s northern hemisphere is no longer tilted toward the sun, or the length of the night is equal in both the northern and southern hemispheres. You can also note the place on your western horizon where the sun sets, and watch in the coming days and weeks how quickly that spot moves to the south.

It is the official end of summer and the beginning of autumn for the northern hemisphere, and the first day of spring for those south of the equator. So we’re off to work today in summer, and return home tonight in the fall.

You can read more about the equinox here.

(NASA illustration)