O n July 11, 2016, New York City experienced “Manhattanhenge” — the biannual alignment of the setting sun with the Manhattan street grid, such that the sun’s light shines down all of Manhattan’s east-to-west streets at once, carving a continuous sliver of light through the cracks in the high-rises. Though the phenomenon has been happening as long as there’s been a parallel street grid, the term “Manhattanhenge” was coined and popularized by astronomer Neil deGrasse Tyson.
All the buzz about Manhattanhenge made us wonder, is there a San Franciscohenge too?
Technically, any straight street that runs east to west, in any city, should have its own “henge” at some point during the year, and more likely twice given the motion of the sun in the sky. And it’s not that hard to figure out. (Admittedly I do have a degree in astrophysics, but I swear you don’t need that to calculate it.) Sure, you could go plodding around an astronomy textbook for azimuth equations. Or you could use an online catalog like SunCalc, an interactive map that shows the angle of the sun at sunrise, sunset and at any time during the day, to figure out when San Franciscohenge will happen.
But quickly we run into a problem: our street grids aren’t at the same periodic intervals as Manhattan’s (above the Village) are. Hence, it seems that San Francisco will have multiple henges on different dates, depending on the neighborhood. (Also, we have hills and fog that will block the sun, but more on that later.) So we have to break down SF’s henges by ’hood.
Richmondhenge and theSunsethenge happen on March 11
Since the Earth actually goes around the sun in a non-whole number of days (365.24 precisely), this date will vary from year to year (between the 11th and the 12th of March). In 2017, the most majestic Sunset sunset happens on March 11.
MissionHenge would probably happen on March 9 if Twin Peaks weren’t in the way …
Big hills, like Twin Peaks, eclipse the sun’s path toward the horizon. Still, if you’re at a more northern street, like 16th, you might see a partial Missionhenge.
… but there’s a sunrise MissionHenge on March 28, 2017!
Sunrise is at 7:01 a.m. on March 28, 2017. If there’s no fog, you’ll see a line of light from the east spreading down any non-hilly street. So maybe for five blocks in Potrero?
RussianHillHenge will be on February 27
Downtown SF is on a slightly tilted street grid compared to Richmond and the Sunset. However, because of the occluding quality of the hills, you might have to situate yourself just right. We suggest the side of Russian Hill, where you should gaze west when the sun sets at 6:02 p.m.
SoMa’s too diagonal to have a henge
And thus its corporate monoliths will, appropriately, be wreathed in eternal darkness long before sunset, befitting the sorcery within.
Every other neighborhood has too many hills to the west to have a henge
Also, I tried looking for henges in the East Bay, but the street grid is too irregular to have one. If you want a henge, straighten your streets, Berkeley and Oakland.
Did you find any other interesting street henges in the Bay Area? If so, add them in the comments below.
Note: This data presumes the accuracy of SunCalc within 0.2°, as well as a lack of fog. Future eyewitness data will bear out the accuracy.
Screenshots courtesy of the author.
