No, Manhattan is not an ancient stone monument built by space aliens – although some of the folks you meet in Times Square might make you think twice about that.
But from 14th Street clear on up to Washington Heights, Manhattan’s north-south avenues and east-west crosstown streets form a perfect perpendicular grid. Couple that with the canyons of tall buildings lining those crosstown streets, and the stage is set for a four-times-a-year spectacle – Manhattanhenge.
Neil deGrasse Tyson, noted astrophysicist and engaging science communicator, coined the term “Manhattanhenge” early on in his tenure as director of New York City’s Hayden Planetarium. He observed that every year around May 28 and again around July 13 (in other words, slightly more than three weeks prior to and after summer solstice) the sunset is perfectly aligned with the crosstown streets, lighting them up brilliantly. A similar phenomenon occurs with the sunrise around December 5 and again around January 8 (slightly more than two weeks prior to and after winter solstice).
NYC’s answer to Stonehenge has become a hit with native New Yorkers. When the great moment nears, they gleefully snarl traffic, crowding into the middle of every crosstown street to watch the sun light up blacktop and buildings alike with its bright golden glow (unless of course it is cloudy or raining).
The more astute among you may ask – why does this phenomenon occur twice in summer and twice in winter, instead of precisely on the summer and winter solstices? The reason is that Manhattan’s grid does not point directly north. It is actually 29 degrees off. Accordingly, the sun hits the “sweet spot” as it moves along the horizon toward the solstice, and again as it moves back.
You may also ask – how it is possible that Manhattanhenge occurs on every single crosstown street, not just a well-positioned few? It is because the sun is so far away that any rays which find their way to Manhattan are essentially parallel to one another. It is a sight for all neighborhoods up and down the grid to enjoy, regardless of location.
The phenomenon is not limited to Manhattan. Many other cities with east-west streets also have “henges” on various dates. But as usual, New York gets the glory.