New Yorkers are about to experience the second "Manhattanhenge" of the year. Friday, July 12, and Saturday, July 13, are the evenings to be outside at sunset to capture a magical moment. On those dates, only the sun will set on the grid, between skyscrapers, as seen from any east-west street in Manhattan.
The bi-annual event's nickname comes, of course, from England's Stonehenge, where the rising sun on June's summer solstice aligns with the neolithic monument's Heel Stone.
In New York, things are different. Unlike any European city, its streets are aligned east-west and north-south, though the resulting grid layout isn't perfectly aligned. It's aligned 29 degrees east of true north. The result is that the sun sets on the grid at sunset exactly 22 and 23 days before the June solstice (which already occurred on May 28 and 29, with only the latter visible in a clear sky) and 22 and 23 days after.
"What will future civilizations think of Manhattan Island when they dig it up and find a carefully laid out network of streets and avenues?" said Neil deGrasse Tyson, head of the Hayden Planetarium at New York's American Museum of Natural History who coined the term Manhattanhenge. "Surely the grid would be presumed to have astronomical significance."
There are two dates for Manhattanhenge this weekend. On both evenings, you'll see the sun set between the skyscrapers as long as you stand on one of Manhattan's main east-west thoroughfares at sunset, but the spectacle is subtly different on each evening. Here's what you'll see, and when, on Friday and Saturday:
Friday, July 12: 'Full Sun on the Grid'
On this date, at precisely 8:20 p.m. EDT, the sun will set on Manhattan's grid. Its entire disk will appear above the grids and be visible between skyscrapers from Manhattan's east-west streets.
Saturday, July 13: 'Half Sun on the Grid'
New Yorkers looking west at 8:21 p.m. EDT tonight will see a half-sun about to disappear beneath the Manhattan grid, a moment known as the "kiss the grid" moment.
"These two days happen to correspond with Memorial Day and Baseball's All Star break," says deGrasse Tyson. "Future anthropologists might conclude that, via the sun, the people who called themselves Americans worshipped War and Baseball." He advises that the best places to witness Manhattanhenge from are on 14th Street, 23rd Street, 34th Street, 42nd Street and 57th Street.
There are two occurrences of Manhattanhenge on either side of the solstice because the sunset point varies throughout the year. As seen from the northern hemisphere, the sun rises due east only at the equinoxes in March and September. The sun rises at its most northeast point on the horizon on June's solstice. Since the grid is oriented 29 degrees east of true north, the sunrise points 22 and 23 days before and after the solstice align with it.
It's the opposite in winter when the sun sets at its most southeasterly point on the horizon on December's solstice. So why aren't there Manhattanhenges 22 and 23 days before and after that date? There are, but since they occur at sunrise during a bitterly cold and cloudy winter, they're rarely seen — or sought.
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