Wednesday, September 22, 2010

Last Day of Summer

Today is the last day of summer. I was curious on what happens on these days... first day of spring, summer, fall and winter. I know we studied this in high school (many, many, many years ago!) My memory it's what it use to be, so I headed to Wikipedia for an explanation.

http://en.wikipedia.org/wiki/Equinox

An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator. The term equinox can also be used in a broader sense, meaning the date when such a passage happens. The name "equinox" is derived from the Latin aequus (equal) and nox (night), because around the equinox, the night and day are approximately equally long. It may be better understood to mean that latitudes +L and -L north and south of the Equator experience nights of equal length.

At an equinox, the Sun is at one of two opposite points on the celestial sphere where the celestial equator (i.e. declination 0) and ecliptic intersect. These points of intersection are called equinoctial points: classically, the vernal point and the autumnal point. By extension, the term equinox may denote an equinoctial point.

An equinox happens each year at two specific moments in time (rather than two whole days), when there is a location on the Earth's equator where the center of the Sun can be observed to be vertically overhead (in astronomical terms, the subsolar point), occurring around March 20/21 and September 22/23 each year.


Goodbye Summer, until next year. We'll miss you.

2 comments:

  1. kristie@makingarrangementsblogSeptember 22, 2010 at 3:08 PM

    sniff, sniff, i miss summer already!!!!

    ReplyDelete