This is not only a modern sculputure but the Sun Triangle, created by Athelstan Spilhaus.

You can see the sun at the end of each point through this special triangle 4 times a year.
The sides of the sun triangle point to four seasonal positions of the sun at solar noon in NYC.

When the Sun reaches an altitude of 73°in the sky on the summer solstice at noon about June 21 and its rays align exactly with the short, steep side of the triangle.

Shortest bottom side points to the sun's lowest position on the winter solstice at noon about December 21.

Longest side points to the sun on the Spring and Fall Equinox at noon about March 20 and September 20.

Location: McGraw-Hill Building Plaza in NYC (49th Street and 6th Avenue)

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The Sun Triangle はただのモダーン・スカルプチャなのではなくて、年に四回、太陽が特別の位置に達するときに三角形の各頂点と太陽が一致して見えるというもの。

すなわち、太陽が一番高くなる夏至の時は短く傾斜度の急な三角の点に光線が照らされる。
いちばん短い底辺のポイントは太陽の位置が一番低くなる冬至の時の太陽光線と一致。
長い辺のポイントは春分の日と秋分の日の太陽光線と一致。

時間は13:00。
場所：McGraw-Hill Building Plaza in NYC (49th Street and 6th Avenue)