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 layout serves 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. It’s popularly known as Manhattanhenge.
What is Manhattanhenge?
Manhattanhenge is 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 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 at the end of May and mid-July.
A similar phenomenon happens near the winter solstice, usually in December or January, but with the rising sun instead of the setting sun. In 2021, set your alarms early the mornings of January 10, 11, 12 to see it.
Typically, the sun lines up with streets shortly after 7 a.m. The best spots to see the phenomenon are at 41st Street & 5th Avenue. But keep in mind, the time window to see Reverse Manhattanhenge is more narrow than during the summer. Catch the sun just as it reaches the street level.
Reverse Manhattanhenge also doesn’t get as much attention, in part because fewer people are outdoors on cold January mornings (brrrr!), and because fewer people are awake during sunrise than at sunset.
Full Sun Manahttanhenges are generally considered to be the more exciting events and draw more attention.
Sunset Manhattanhenge Dates for 2020:
Friday, May 29th at 8:13 p.m. EDT (half sun).
Saturday, May 30th at 8:14 p.m. EDT (full sun).
Sunday, July 12th at 8:20 p.m. EDT (full sun)
Monday, July 13th at 8:21 p.m. EDT (half sun)
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.”