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(visit the link for the full news article)www.dailymail.co.uk...
For just 15 minutes the sun sets in exact alignment with the cross streets of Manhattan's street grid, making the city's towering building look something like a modern-day Stonehenge.
While we have long-marvelled at the beauty of our prehistoric monument in the Salisbury plains of England, Americans have been in awe of the unique urban phenomenon known as Manhattanhenge.
Twice a year the sun aligns to bathe the city in glowing light
The exquisite sight has occurred since buildings north of 14th St. were laid out in a grid pattern back in the 19th century, but it's only recently begun to garner a following. Photographers clamor to get to the best spot to capture the celestial phenomenon.
Looking west along 42nd Street at 8:23 p.m. on July 13, 2006. This photo shows the sun lined up with the center line of 42nd Street. It actually set slightly to the right. It set on the center line on July 12.
The "henge" comes of course from Stonehenge, the prehistoric monument in the Salisbury plains of England. The large structure of stones and earthen mounds is thought to be a burial ground that was oriented to face the midsummer sunrise and midwinter sunset.
Manhattan's street grid doesn't run geographically north to south, but instead aligns itself with the direction of the island. If the grid did run north-south, Manhattanhenge would fall on the spring and autumn equinoxes, the only two days during the year when the Sun rises due-east and sets due-west. (The equinoxes occur when the sun sits directly over the Earth's equator and the length of day and night are roughly equal.)
Because Manhattan's grid is rotated 28.9 degrees east from geographic north, the days of alignment with the cross streets are also shifted.
It's necessary to know this angle to calculate the dates of “Manhattan Solstice,” which the very same section of the Times discussed in the May 21, 2006 edition of the F.Y.I. column. On (or about) May 28 and July 13, the setting sun is oriented with the streets of Manhattan, causing a dramatic casting of long shadows. On (or about) December 5 and January 8, the rising sun has a similar effect. Hayden Planetarium director Neil deGrasse Tyson, who suppled the Times with these dates, obviously knows the 29° figure. (The F.Y.I. column stated that “the Manhattan grid is angled 30 degrees east from geographic north.”)
In “City of Angles,” Sam Roberts says that the 29° offset is “the reason that, looking west on the first day of summer, you couldn't see the sun set down the middle of any crosstown street, but you could have on May 28 and can again on July 13.” Actually, if the Manhattan grid were oriented with the points of the compass, the sun would rise and set parallel to the streets on the two equinoxes, not the solstice. On the vernal and autumnal equinox, the sun rises at due east and sets at due west everywhere in the world. During the summer months, the sun seems to rise north of due east, and set north of due west, and during the winter months, the sun seems to rise south of due east, and set south of due west. The maximum deviation occurs on the summer and winter solstices, but the actual angle of deviation depends on the latitude of the observer. In New York City, this maximum deviation obviously has to be greater than 29° to result in two winter days and two summer days of Manhattan Solstice.
And what is the mystery?
Simply that if you draw a straight line from the obelisk in St Paul’s churchyard to the obelisk in Central Park, it will pass directly through the site of the Worth obelisk at 25th Street -- the three obelisks are directly aligned, pointing roughly 29 degrees east of north, slightly off the central Manhattan axis of Fifth Avenue.