Pajala – sundial north of arctic circle

Another contender for the world’s biggest sundial today is in the Torne Valley, north of the Arctic Circle. It is 38.33 m. in diameter and is situated at 23.28

9am May 30th

Shadow indicates brownstone stoops on 45th Ave. between 11th and 21st streets at 9am on May 30th.

Manhattanhenge 2008

Earlier posts about the phenomena of Manhattanhenge: overview and map, and photos.

From the Hayden Planetarium’s “Star Struck” email announcement by astronomer Neal deGrasse Tyson:

It’s that time of year again….MANHATTANHENGE 2008

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 rose 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 on Thursday, May 29h this year, one of only two occasions when the Sun sets in exact alignment with the Manhattan grid, fully illuminating every single cross-street for the last fifteen minutes of daylight. The other day is Saturday, July 12th.

These two days give you a photogenic view with half the Sun above and half the Sun below the horizon — on the grid. The day after May 29th (Friday, May 30th), and the day before July 12 (Friday, July 11) will also give you Manhattanhenge moments, but instead you will see the entire ball of the Sun on the horizon — on the grid. My personal preference is the half-Sun.

As you may know, had Manhattan’s grid been perfectly aligned with the geographic north-south line, then the days of Manhattanhenge would be the spring and autumn equinoxes, the only two days on the calendar when the Sun rises due-east and sets due-west. 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 we have over New Jersey. And tall buildings that line the streets create a kind of brick and steel channel to frame the setting Sun, creating a striking photographic opportunity.

True, some municipalities have streets named after 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 a couple of 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.

IMPORTANT: 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.

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

MAY

Half Sun on grid: Thursday, May 29 — 8:17 p.m. EDT
Full Sun on grid: Friday, May 30 — 8:16 p.m. EDT

JULY

Half Sun on grid: Saturday, July 12 — 8:25 p.m. EDT
Full Sun on grid: Friday, July 11 — 8:24 p.m. EDT
Downloadable Image of the July 2001 “Manhattan Sunset” as it first appeared in 2002 among the photo-essays of “City of Stars,” Natural History magazine:

http://research.amnh.org/users/tyson/ManhattanSunset.php

San Petronio Basilica

The Basilica of San Petronio is the main church of Bologna, the old città d’arte in the Emilia Romagna region of Italy. The church hosts also a sundial in the form of a meridian line inlaid in the paving of the left aisle in 1655; it was calculated and designed by the famous astronomer Giovanni Domenico Cassini, who was teaching astronomy at the University: at 66.8 meters it is the longest sundial in the world, following measurements that were for the time uniquely precise.

The video below shows the passage of the sun on the Cassini’s meridian line inside San Petronio in Bologna on the 30th November 2007. Thanks to matutianu1935 of YouTube-