Armillary sphere, Brooklyn Botanic Garden - New York, New York
Posted by: Groundspeak Premium Member blackjack65
N 40° 40.051 W 073° 57.761
18T E 587677 N 4502366
Quick Description: The sphere is made of bronze bands representing the principle celestial circles and constellations. A thin bronze rod, or gnomon, passes through the center of the sphere, pointing north and casting a shadow on the inside of the sphere, to tell time.
Location: New York, United States
Date Posted: 11/18/2018 10:45:39 AM
Waymark Code: WMZJB9
Published By: Groundspeak Premium Member Outspoken1
Views: 1

Long Description:
The armillary sphere is still today a teaching tool to explain the movements of the Sun in the sky depending on the season and latitude. The observer sees, on a horizontal plane, the center of the sphere that rotates around the polar axis. The sky goes around the Earth in a sidereal day (11:56 p.m. minutes), so that the sun makes a turn in 24 hours, which makes it a little late each day. It moves on the ecliptic represented by the circle at an angle between the circles of the tropics. At the equinoxes, the Sun rises due east, rises south (in the northern hemisphere) and sets 12 hours later due west to the intersection of the circle representing the celestial equator and the plane of the horizon. On solstices, the sun rises higher or lower (up to a tropic, on one of the points of the ecliptic farthest from the celestial equator) and the day is longer (in summer) or shorter (in winter).

In general, the top of the sphere represents the sky, moving around the polar axis. The stars are positioned through their equatorial coordinates. The ecliptic is the line on which circulate the planets; it is also the line where the eclipse will pass.

There are the constellations of the zodiac. The instrument also helps explain why some constellations are visible in winter and others in summer.
Scientific Principle(s) being demonstrated:
It is used to show the apparent movement of the stars, the Sun and the ecliptic around the Earth.

Briefly explain if the experiment was effective for you. Could it have been better?:
The tour guide explained the functioning of the sphere.

When is the apparatus/experiment available to the public:
Dawn to dusk, 365.241 days a year.

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