March
Armillary Sphere
21
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The first day of spring is the Vernal Equinox. An equinox is a day in which the sun is above the horizon for exactly the same amount of time that it is below the horizon: 12 hours. On this date, the sun will reach its midpoint between the lowest point and the highest point it will reach in the sky, and will continue climbing until the summer solstice. The Spring equinox is also one of the two days of the year that the sun rises exactly in the east and sets exactly in the west everywhere on earth. Most of us think this is always true, but the truth (as you will see as you look at the demonstrations of this exhibit) is that it rises roughly in the east and sets roughly in the west. (At certain latitudes, at certain times of the year, it can actually rise and set closer to north or south than east or west--and it may never "rise" or never "set" at all!) |
Watch the demonstation
Look carefully at the model and you can see that March 21 is one two times where the ecliptic (the imaginary elliptical path followed by the sun, moon, planets, and zodiac constellations) and the celestial equator (the imaginary circle in the sky above and following the earth's equator) cross paths.
Choose another date
How to read an armillary sphere
Watch the sun's path (the ecliptic) move through the year
Back to Armillary Sphere Page
Back to Universe in Your Hands (for sundials & astrolabes)
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Museum.
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