In case you missed the first instance of this phenomenon this year on 30 May, be sure to look for the sun to set directly down the E-W axis of Manhattan's street grid on 11 July Wednesday at 8:24 PM this week.


Description: Description: Description: The sun shines down 42nd Street in New York City at sunset during "Manhattanhenge," May 30, 2011. Photographer: Xinhua News Agency/eyevine/Redux


Twice a year the sunset in Manhattan lines up with the east-west axis of its street grid, creating a beautiful visual effect. (The photo above from the Xinhua News Agency [here lifted from BloombergBusinessweek of 30 May 2012] was taken looking west on 42 Street the first time it happened last year, on 30 May 2011. The photo below by Julio Cortez of the Associated Press [here lifted from The Washington Post of 30 May 2012, but also published in The New York Times of 6 July Friday] was taken looking west on 42 Street the second time it happened last year, on 13 July 2011.)


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This phenomenon was given the name "Manhattanhenge" by Neil deGrasse Tyson (the wonderful astrophysicist who heads the American Museum of Natural History's Hayden Planetarium) by analogy to the famous axial alignment with the summer and winter solstices at Stonehenge.


Manhattanhenge occurs twice each summer, on either side of the actual summer solstice. Earth's maximum axial tilt to the Sun during a solstices is 23° 26'; and that occurred this year on 20 June at 2309 UT. Manhattanhenge happens twice because the street grid is not actually aligned north-south, but rather is aligned with the major lengthwise geographic axis of the island itself, 29° offset from N-S. This means that on the sun's apparent annual journey northward (in reality, of course, the progressive change in the sun's position relative to the tilt of the earth on its annual orbit around the sun), sunset aligns with the E-W axis of Manhattan once on the way to the solstice, and once on the way back from it. (Which is more often correct: a watch that runs 2 seconds slow/day, or one that is broken?)


The first 2012 Manhattanhenge was on 30 May. The second will occur on 11 July Wednesday at 8:24 PM this week. (The 11th is the day one sees the full orb of the sun lined up with the grid at sunset. There is a second version the following day, when one sees the hemisphere of the half-set sun lined up with the grid, 12 July Thursday, at 8:25 PM.)


The article from The Washington Post is reproduced in its entirety at the end of this piece.


The Hayden Planetarium is having an event on 11 July Wednesday at 7 PM. It will be led by astrophysicist Jackie Faherty, and it will explain the history and simple astronomy behind this unique event in a special presentation at the Hayden Planetarium. The program will be followed by a live viewing of Manhattanhenge outside the Museum. Tickets can be obtained online (click here).

Neil deGrasse Tyson did one of his typically wonderful presentations in a recent interview on NPR with Margo Adler, which quoted one of his essays in which he wrote (the full text of the essay is included below):


What will future civilizations think of Manhattan Island when they dig it up and find a carefully laid out network of streets and avenues? Surely the grid would be presumed to have astronomical significance, just as we have found for the pre-historic circle of large vertical rocks known as Stonehenge, in the Salisbury Plain of England.


He also said in the interview:


This evening and July 12th are the days for Manhattanhenge for 2012. On these evenings the setting sun will illuminate both sides of every cross street in Manhattan, the wide ones, like 57th and 14th are considered the best views. On the following day says Tyson you can see the entire ball of the sun as it sets looking east on these cross streets. Tyson, tongue in cheek, says since they happen to coincide this year with Memorial Day and the All Star game, future anthropologists may come believe we worship baseball and battle."


Here is Neil's own essay about Manhattanhenge from the Museum's website:


Sunset on the Manhattan Grid

by Neil deGrasse Tyson, © 2001-2012

Description: Description: Description: Manhattan-henge: Sunset down 34th Street

Sunset looking down 34th Street. One of two days when the sunset is exactly aligned with the grid of streets in Manhattan. Photo © Neil deGrasse Tyson, 2001.


What will future civilizations think of Manhattan Island when they dig it up and find a carefully laid out network of streets and avenues? Surely the grid would be presumed to have astronomical significance, just as we have found for the pre-historic circle of large vertical rocks known as Stonehenge, in the Salisbury Plain of England. For Stonehenge, the special day is the summer solstice, when the Sun rises in perfect alignment with several of the stones, signaling the change of season.


For Manhattan, a place where evening matters more than morning, that special day comes twice a year. For 2012 they fall on May 29th, and July 12th, when the setting Sun aligns precisely with the Manhattan street grid, creating a radiant glow of light across Manhattan's brick and steel canyons, simultaneously illuminating both the north and south sides of every cross street of the borough's grid. A rare and beautiful sight. These two days happen to correspond with Memorial Day and Baseball's All Star break. Future anthropologists might conclude that, via the Sun, the people who called themselves Americans worshiped War and Baseball.


For these two days, as the Sun sets on the grid, half the disk sits above and half below the horizon. My personal preference for photographs. But the day after, May 30th, and the day before, July 11, also offer Manhattanhenge moments, but at sunset, you instead will find the entire ball of the Sun on the horizon.

Manhattanhenge times for 2012.

Arrive a half-hour earlier than the times given below.

Description: Description: Description: Manhattanhenge: half sun on the grid

Mock-up of the half sun on the grid during Manhattanhenge.

Half Sun on the grid:

Tuesday, May 29 — 8:17 P.M. EDT

Thursday, July 12 — 8:25 P.M. EDT

Description: Description: Description: Manhattanhenge: full sun on the grid

Mock-up of the full sun on the grid during Manhattanhenge.

Full Sun on the grid:

Wednesday, May 30 — 8:16 P.M. EDT

Wednesday, July 11 — 8:24 P.M. EDT

For best effect, position yourself as far east in Manhattan as possible. But ensure that when you look west across the avenues you can still see New Jersey. Clear cross streets include 14th, 23rd, 34th. 42nd, 57th, and several streets adjacent to them. The Empire State building and the Chrysler building render 34th street and 42nd streets especially striking vistas


Unnoticed by many, the sunset point actually creeps day to day along the horizon: northward until the first day of summer, then returning southward until the first day of winter. In spite of what pop-culture tells you, the Sun rises due east and sets due west only twice per year. On the equinoxes: the first day of spring and of autumn. Every other day, the Sun rises and sets elsewhere on the horizon. Had Manhattan's grid been perfectly aligned with the geographic north-south line, then the days of Manhattanhenge would coincide with the equinoxes. But Manhattan's street grid is rotated 30 degrees east from geographic north, shifting the days of alignment elsewhere into the calendar.


Note that any city crossed by a rectangular grid can identify days where the setting Sun aligns with their streets. But a closer look at such cities around the world shows them to be less than ideal for this purpose. Beyond the grid you need a clear view to the horizon, as Manhattan has across the Hudson River to New Jersey. And tall buildings that line the streets create a vertical channel to frame the setting Sun, creating a striking photographic opportunity.


True, some municipalities have streets named for the Sun, like Sunrise Highway on Long Island and the Sunset Strip in Los Angeles. But these roads are not perfectly straight. And the few times a year when the Sun aligns with one of their stretches of road, all you get is stalled traffic solar glare temporarily blinds drivers.


So Manhattanhenge may just be a unique urban phenomenon in the world, if not the universe.


Note that several years ago, an article in the New York Times identified this annual event as the Manhattan Solstice. But of course, the word solstice translates from the Latin solstitium, meaning stopped sun, in reference to the winter and summer solstices where the Sun's daily arc across the sky reaches its extreme southerly and northerly limits. Manhattanhenge comes about because the Sun's arc has not yet reached these limits, and is on route to them, as we catch a brief glimpse of the setting Sun along the canyons of our narrow streets.


While we are on the subject, when viewed from all latitudes north of the Tropic of Cancer (23.5 degrees north latitude), the Sun always rises at an angle up and to the right, and sets and an angle down and to the right. That's how you can spot a faked sunrise in a movie: it moves up and to the left. Filmmakers are not typically awake in the morning hours to film an actual sunrise, so they film a sunset instead, and then time-reverse it, thinking nobody will notice.


Here's the article from The Washington Post:


The Washington Post

Posted at 03:19 PM ET, 05/30/2012TheWashingtonPost

Manhattanhenge: Sunset and streets aligned in unique spectacle; a D.C. equivalent?

By Justin Grieser


The summer solstice is still three weeks away, but this evening might offer New York City residents an enchanting sunset experience on the streets of Manhattan. Sun-observing enthusiasts call it “Manhattanhenge” – one of only two days of the year when the setting sun aligns perfectly with the city’s east-west street grid.


The name “Manhattanhenge” was coined by Neil deGrasse Tyson, a respected astrophysicist at the American Museum of Natural History. Tyson found this sun alignment on New York’s streets similar to the dramatic sun alignment that occurs at Stonehenge, England on the summer and winter solstices.


On May 30 – about five minutes before sunset at 8:20 p.m. – observers looking down any westward-facing street in Manhattan have the chance to catch a dramatic glimpse of the setting sun.


The big wild card for eager photographers is whether lingering clouds and shower chances will dampen the sun’s dazzling show. If that happens, tomorrow (May 31) will still offer a golden, but less perfectly aligned, sunset in Manhattan. The next opportunity for the setting sun’s alignment with Manhattan’s westward facing streets will occur on July 12, a few minutes before 8:27 p.m.


Why are May 30 and July 12 unique to New York City? On these two dates, the sun sets far enough to the northwest (300º from due north to be exact) to line up with the city’s street grid. A map of downtown Manhattan illustrates that east-west streets are actually tilted on a northwest-to-southeast angle. Moreover, New York’s low elevation allows observers to see the setting sun very low in the sky as it descends over the Hudson River.


Optimal sun orientations in other locations


If you don’t live in New York, other areas experience a similar sunrise and/or sunset phenomenon, albeit on different dates.


A similar glowing phenomenon occurs at California’s Yosemite National Park in February: on two days each year, the southwest-facing Horsetail Fall is so exactly aligned with the setting sun that the sun’s light gives the cascading water a lava-like appearance.

In Washington, D.C. the due east-west orientation of the National Mall and major cross streets allows residents to see the rising and setting sun coincide with the spring and autumn equinoxes.


Capital Weather Gang photographer Kevin Ambrose, who frequently photographs landmarks around D.C., recommends the following times of year for capturing them with ideal sun alignment:


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In his blog post “Ducks at Sunrise”, Ambrose writes: During the spring and autumnal equinox, the sunrise aligns in the eastern sky with D.C.’s monuments and the Reflecting Pool. Within a week or so on either side of the equinox is the optimal time for photographing a Washington sunrise.


Additional reading:


Manhattanhenge proves the sun orbits New York (Bloomberg Businessweek)

Manhattanhenge: the sun, the city and a special rendezvous (NPR)

Every February, Yosemite waterfall turns to lava (Yahoo News)


(Kevin Ambrose and Jason Samenow contributed to this post)

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