Why the autumn equinox isn’t actually when day and night are equal
by Stuart Clark from Science | The Guardian on (#701N4)
Autumnal equinox arrives in northern hemisphere this week, but we must wait a few more days for the equilux
So that's it for the summer. The season comes to a close for us in the northern hemisphere this week on 22 September as we enter the autumn.
The moment is marked by the autumnal equinox, which is the moment when the sun crosses the celestial equator, moving south, and the days become shorter than the nights. The exact moment this happens is 19:19 BST on 22 September and it is caused by the movement of Earth along its orbit, gradually tilting the northern hemisphere away from the sun.
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