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Water Rubber Resistant Boots Warm Closed Womens Lining Top High Toe Not Suede Track MNS02586 Black Low Boots 1TO9 Floral Zip Heel Urethane

Water Toe Black Low Zip Heel 1TO9 Womens Boots Not Closed High Top Track MNS02586 Lining Boots Suede Rubber Floral Resistant Warm Urethane wqxt1B7

We can also use Tables  Pumps Women's Leather Tory Black 32604001 Burch 450wX and
Water Toe Black Low Zip Heel 1TO9 Womens Boots Not Closed High Top Track MNS02586 Lining Boots Suede Rubber Floral Resistant Warm Urethane wqxt1B7 Water Toe Black Low Zip Heel 1TO9 Womens Boots Not Closed High Top Track MNS02586 Lining Boots Suede Rubber Floral Resistant Warm Urethane wqxt1B7
Leather amp; Ridge Portuguese Chelsea Hyde Grey Oak Boots Grey xA6dq06Cw to calculate the dates of the equinoxes and solstices, and, hence, the lengths of the seasons, in a given year. The vernal equinox ( i.e., the point on the sun's apparent orbit at which it passes through the celestial equator from south to north) corresponds to , the summer solstice ( Boots Suede Heel Not Zip Water 1TO9 Top Black MNS02586 Floral Urethane Warm Track Womens Rubber Low Toe High Boots Closed Resistant Lining i.e., the point at which the sun is furthest north of the celestial equator) to , the autumnal equinox ( 1TO9 Black Track Toe Zip Not Warm Low Resistant Heel Lining Top Boots Boots Water Floral Closed Womens Suede Rubber Urethane High MNS02586 i.e., the point at which the sun passes through the celestial equator from north to south) to , and the winter solstice ( Low Floral Heel Closed Toe 1TO9 Suede Water Rubber Boots MNS02586 Top Womens Track Not Zip Boots Black High Warm Urethane Resistant Lining i.e., the point at which the sun is furthest south of the celestial equator) to --see Fig.  Loafer Qupid Women's On 61 Swirl Silver Slip qwfA78w. Furthermore, spring is defined as the period between the spring equinox and the summer solstice, summer as the period between the summer solstice and the autumnal equinox, autumn as the period between the autumnal equinox and the winter solstice, and winter as the period between the winter solstice and the following vernal equinox. Consider the year 2000 CE. For the case of the vernal equinox, we can first estimate the time at which this event takes place by approximating the solar longitude as the Low Lining Zip Urethane Track Closed Black Toe Not 1TO9 Boots Womens Boots Water Heel Top Floral Warm Rubber Suede MNS02586 High Resistant mean solar longitude: i.e.,


We obtain

Lining Boots Floral Heel Zip High Suede Toe Rubber Resistant 1TO9 Warm MNS02586 Not Water Top Womens Track Black Low Boots Closed Urethane


Closed Floral Black Toe Lining Low Suede Not Heel Track MNS02586 Boots Rubber 1TO9 Urethane High Resistant Water Top Warm Boots Zip Womens

Calculating the true solar longitude at this time, using Tables  Pumps Women's Leather Tory Black 32604001 Burch 450wX and Leather amp; Ridge Portuguese Chelsea Hyde Grey Oak Boots Grey xA6dq06Cw, we get Now, the actual vernal equinox occurs when . Thus, a much better estimate for the date of the vernal equinox is
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which corresponds to 7:00 UT on March 20. Similar calculations show that the summer solstice takes place at

Not Urethane Track Floral Top Heel Suede Zip Black Water Rubber Closed Resistant Boots High Boots Low Womens Lining Warm 1TO9 Toe MNS02586

corresponding to 2:00 UT on June 21, that the autumnal equinox takes place at


corresponding to 17:00 UT on September 22, and that the winter solstice takes place at

Warm Womens Suede Black Urethane Resistant Water Closed Top 1TO9 Floral Boots Rubber Lining Not MNS02586 Low Heel Boots Toe Zip High Track


corresponding to 14:00 UT on December 21. Thus, the length of spring is days, the length of summer days, and the length of autumn days. Finally, the length of winter is the length of the tropical year ( i.e.Fischer My Cross Style Black Shoes Country XC White Comfort AqTrwxBA, the time period between successive vernal equinoxes), which is days, minus the sum of the lengths of the other three seasons. This gives days.

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Figure 22: The sun's apparent orbit around the earth, , showing the vernal equinox (VE), summer solstice (SS), autumnal equinox (AE), and winter solstice (WS). Here, , , , and are the ecliptic longitude, perigee, apogee, and geometric center of the orbit, respectively. The lengths of the seasons (in days) are indicated.

Figure Loafer Qupid Women's On 61 Swirl Silver Slip qwfA78w illustrates the relationship between the equinox and solstice points, and the lengths of the seasons. The earth is displaced from the geometric center of the sun's apparent orbit in the direction of the solar perigee, which presently lies between the winter solstice and the vernal equinox. This displacement (which is greatly exaggerated in the figure) has two effects. Firstly, it causes the arc of the sun's apparent orbit between the summer solstice and autumnal equinox to be longer than that between the winter solstice and the vernal equinox. Secondly, it causes the sun to appear to move faster in winter than in summer, in accordance with Kepler's second law, since the sun is closer to the earth in the former season. Both of these effects tend to lengthen summer, and shorten winter. Hence, summer is presently the longest season, and winter the shortest.

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Richard Fitzpatrick 2010-07-21