Manhattanhenge 2018

Sevtibidou, CC BY-SA 3.0 , via Wikimedia Commons

The sun will set on Thursday and Friday, July 12 and 13, as usual, if it can be said that a sunset is ever “usual”, with endless variations in moisture, temperature, season, cloud cover, axis of the earth relative to the sun, and even air pollution making every sunset unique. Those of us living in Manhattan will experience a particularly spectacular astronomical phenomenon:  Manhattanhenge.

Manhattanhenge occurs twice a year, in late May and early July, when the setting sun is perfectly aligned with the grid of New York City streets.

It is the continually changing relative axis of the earth to the sun that results in Manhattanhenge. From the first day of winter until the first day of summer, the sun sets increasingly north on the horizon. And, it sets incrementally southward on the horizon from the first day of summer until the first day of winter, rising and setting due east and west only on the spring and fall equinoxes (the first days of spring and fall). With the Manhattan street grid--a design proposed in 1811--tilted at 30 degrees east of due north, rather than exactly aligned north-south/east-west, the alignment of the sunset with our street grid occurs off-calendar from the equinox.

According to the American Museum of Natural History, "For best effect, position yourself as far east in Manhattan as possible. But ensure that when you look west across the avenues you can still see New Jersey. Clear cross streets include 14th, 23rd, 34th. 42nd, 57th, and several streets adjacent to them. The Empire State building and the Chrysler building render 34th street and 42nd streets especially striking vistas."  Full sun on the grid will take place at 8:20 on Thursday, and half sun on the grid will take place at 8:21 on Friday.

Think about observing this local phenomenon, how it can remind us of our relative place in the universe and the continual, awe-inspiring cycles that intersect the chasms of our very human-driven metropolis.

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