Every year around May 29 and 30 – and again for a day or two around July 12 – people in New York City look forward to Manhattanhenge. EarthSky community member Gowrishankar Lakshminarayanan wrote:
Manhattanhenge is a phenomenon where the sunset aligns perfectly with the streets of Manhattan, more importantly along 42nd, 34th and 14th Streets. It happens twice every year – around the end of May and early July. May 29th and 30th are the most talked-about dates in media.
As Gowri says, note that you don’t have to look on the precise dates of May 29 and 30. In fact, he captured the image above on June 1, 2017.
The phenomenon of Manhattanhenge isn’t mysterious, of course. Similar alignments occur around the world, on various dates. Think Stonehenge. The point of sunset along the horizon varies throughout the year. At this time of year – between the March equinox and June solstice – the sunset point is shifting northward each day on the horizon, as seen from around the globe. It’s the northward-shifting path of the sun that gives us summer in the Northern Hemisphere and winter in the Southern Hemisphere.
The June solstice on June 21 will bring the sun’s northernmost point in our sky – and northernmost sunset – and afterwards the sun’s path in our sky, and the sunset point, will both start shifting southward again. As for the sun’s alignment with the city of New York, and the streets of Manhattan Island … well, thank the original planners of this city. Scientific American explained:
The phenomenon is based on a design for Manhattan outlined in The Commissioners’ Plan of 1811 for a rectilinear grid, or “gridiron” of straight streets and avenues that intersect one another at right angles. This design runs from north of Houston Street in Lower Manhattan to just south of 155th Street in Upper Manhattan. Most cross streets in between were arranged in a regular right-angled grid that was tilted 29 degrees east of true north to roughly replicate the angle of the island of Manhattan.
And because of this 29-degree tilt in the grid, the magic moment of the setting sun aligning with Manhattan’s cross streets does not coincide with the June solstice but rather with specific dates in late May and early July.
Bottom line: Each year on May 29 and 30, New Yorkers watch for Manhattanhenge. Here’s what causes it.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.