For a few select evenings in the late spring and early summer, sunlight aligns with Manhattan’s grid. The city’s bustling streets are washed with golden light as the sun sets, while tourists and locals alike flood the streets to snap that perfect picture. This event is nicknamed Manhattanhenge and it will begin on May 28 and continue through July 12.
However, you don’t need to live in the Big Apple to see a “henge” like Manhattanhenge. They actually pop up in a few places and a website called Hengefinder can help you find the closest henge.
Meet Hedgefinder
Data scientist and engineer Victoria Ritvo created the website, while software engineer John Pribyl built the accompanying app. Ritvo wrote about creating Hedgefinder in her blog, and details the three basic steps that scientists can use to find a henge. First, find the angle of the road, or its bearing relative to true north. Second, find the angle of the sun at sunset, or its azimuth. Third, find the dates when those two angles match.
While you don’t have to do any of that high-level math, you can read about how Rivoto and Pribyl made their calculations. You simply put in an address or city and can get a calculation for the closet henge near you.
“Having Hengefinder active means henges are now explorable outside of Manhattan, and I’ve been searching for them using the app,” Ritvo writes. “My favorite one so far, I haven’t actually seen. I’m intrigued by the Haarlemmertrekvaart, a canal which traces the southern edge of Westerpark in Amsterdam.”
Interestingly, much of Europe is left out of henge mania due to medieval street design. Amsterdam’s famed canals do offer an option, where sunlight can reflect off of the water. Henges may have been occurring twice a year for the past 400 years on the Haarlemmertrekvaart.
How henges work
The sun does not set in the same place every day. Its position changes along the horizon with the seasons. While the angle does not usually match the directions of a street, it will on a few days each year if the street is angled correctly.
In 1997, the term Manhattanhenge was first coined by Neil deGrasse Tyson, an astrophysicist and director of the Hayden Planetarium at New York’s American Museum of Natural History. Tyson noted that the setting sun framed by Manhattan’s building was comparable to how the sun’s rays strike the center of England’s Stonehenge on the solstice. The Neolithic humans who built the stone circle in stages between 3100 BCE and 1600 BCE intended for the light to shine that way on the solstice. But the builders of Manhattan? Not so much.
Manhattanhenge with Neil deGrasse Tyson and Jackie Faherty
Chicagohenge in Illinois and Baltimorehenge in Maryland both occur when the sunset lines up with the grid systems in those cities around the spring and fall equinoxes in March and September. In Canada, Torontohenge occurs in February and October.
