Autumnal Equinox 2010 Northern Hemisphere?

When is the exact date and time of the Autumnal Equinox 2010 in the Northern Hemisphere?
The Autumnal Equinox 2010 is when fall starts in the north, right?
Some said to me the autumnal equinox is September 21 and others mentioned September 23.
Can anyone please let me know the correct date of the Autumnal Equinox 2010?
I know this stuff is grade 3 stuff but I can't remember.

asked by Isabella in Science | 2780 views | 09-20-2010 at 01:54 PM

The Autumnal equinox occurs on September 23rd at at 03:09 (or 3:09am) Coordinated Universal Time (UTC), regardless of where you are on the Earth. It marks the instant that the Sun's apparent position lies directly over the equator (in this case on the Sun's apparent southward trek).

The equinox means 'equal day and night' - from that time on, the days begin rapidly to shorten until we come to the Winter Solstice (measured each year at Stonehenge). On this day all places on earth, except the North and South Poles, get 12 hours of sunlight and 12 hours of night.

Officially, the September equinox is when the sun is in a certain part of the celestial sphere, that is when the apparent ecliptic longitude of the Sun is 180. That is a bit different that when the real sun is directly over the equator; the difference is less than a few minutes. The Autumnal Equinox 2010 is also the first day of fall.

answered by String | 09-20-2010 at 01:55 PM

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