Human beings have always been fascinated by the sky, and for good reason. Until very recently in our history, the sky served countless invaluable functions. The sky was our calendar and our clock, our GPS system, our television, and more.
Some of the world’s most well-known landmarks are either known or believed to have been observatories, helping pre-modern humans to better understand the celestial world, and thereby, their own: Macchu Pichu, Newgrange, Easter Island, Chaco Canyon, Angkor Wat, Stonehenge, Manhattan …
That’s right, the island borough’s famous grid plan layout can serve as a modern-day celestial calendar. A few times each year, the sunrises and sunsets line up perfectly with the city’s east-west oriented streets so that the blazing ball of the sun is framed by skyscrapers and tenements as it dips below or rises above the horizon.
What is Manhattanhenge?
The phenomenon is popularly known as Manhattanhenge, a term that was recently popularized by renowned astrophysicist Neil deGrasse Tyson. The term is a nod to Stonehenge, a prehistoric observatory located in Wiltshire, England. Stonehenge consists of a circle of massive slabs of stacked stone. An outlying stone, known as the Heel Stone, sits so the its tip aligns with the rising sun on the summer solstice.
Ironically, the term “henge” from the name Stonehenge has nothing to do with astronomy. It’s an ancient precursor to our word “hinge,” and refers to a place where two things join together. Stonehenge, then, means something like “the place where all those stones are stacked together.”
The colloquial usage of “henge” to refer to any place where the rising or setting sun lines up with the surrounding architecture has since spread. Although Manhattanhenge is perhaps one of the most dramatic displays of the phenomenon, due to its location on the Atlantic seaboard, other communities built on grid plans boast their own “henges.” There’s Chicagohenge, Torontohenge, Montrealhenge, and even MIThenge at the Massachusetts Institute of Technology (which may actually have preceded Manhattanhenge as the first modern usage of the term).
What Causes the Manhattanhenge Phenomenon?
Most of Manhattan’s east-west streets are aligned at about a 29° angle clockwise from true east-west. So, twice each year, a couple of weeks before and a couple of weeks after the summer solstice, when the azimuth for sunset is 29° northward of due west, the setting sun aligns with the east-west streets at the moment it sits on the horizon. This is known as Half Sun Manhattanhenge, because half of the sun is below the horizon.
The exact date of the Manhattanhenges varies each year, depending on the date of the summer solstice, but they usually fall around May 28th and July 12th.
A similar phenomenon happens near the winter solstice, usually around December 5th and January 8th, but with the rising sun instead of the setting sun. The summer Manhattanhenge events get more attention, in part because more people are outdoors in the summertime, and in part because more people are awake during sunset than sunrise.
Also of note is the Full Sun Manhattanhenge, during which the full ball of the sun, sitting low above the horizon, is framed by the city’s structures. Full Sun Manhattanhenges usually take place a day or two after the May Half Sun Manhattanhenge, and a day or two before the July Half Sun Manhattanhenge.
Full Sun Manahttanhenges are generally seen to be the more exciting events, and draw more attention.
Manhattanhenge Dates for 2018:
Tuesday, May 29th at 8:13 p.m. EDT, you will see a “half sun” — that is, half above and half below the landscape.
Wednesday, May 30th at 8:12 p.m. EDT, you will see a “full sun,” with the entire solar disk resting above the horizon.
If you miss out in May, you’ll get a second chance in July, on the 12th and 13th. On the first July date, a “full sun” will appear at 8:20 p.m. EDT, while on the second date, we get the “half sun” effect at 8:21 p.m. EDT.
The best streets to capture the event are the larger cross streets that ensure the best views of the west-northwest horizon (toward New Jersey), including 14th, 23rd, 34th, 42nd, and 57th. Neil DeGrasse Tyson notes, “The Empire State Building and the Chrysler Building render 34th Street and 42nd Street especially striking vistas.”
If you plan on visiting Manhattan and capture a Manhattanhenge photo, share it with us on our Facebook page or tag us on Instagram @FarmersAlmanac!
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