2004_05_manhattanhenge.jpg

Besides it being the start of the summer, today is very special: The sun will set in the centerline of every NYC street (photobloggers, get ready!). American Museum of Natural History astrophysicist Neil DeGrasse Tyson desrcribes this phenomenon beautifully in the Natural History Magazine, explaining that like Stonehenge where the sun sets in alignment with stones during the summer solstice, Manhattan has two "special" days where the sun sets between buildings - May 28 and July 12:

On these days, the Sun fully illuminates every single cross street during the last fifteen minutes of daylight and sets exactly on the street's centerline. Upon studying American culture and what is important to it, future anthropologists might take the Manhattan alignments to be cosmic signs of Memorial Day and, of course, baseball's All-Star break.
If the Manhattan grid matched the geographic north-south line, then our special days would be the equinoxes, the two days on the calendar when the Sun rises due east and sets due west. But Manhattan is rotated 30 degrees east from geographic north, shifting the special days elsewhere in the calendar.

The weather looks iffy today, so we're not sure of visibility. Just mark your calendars to catch it on July 12.

Many thanks to Michael, Roy, and Jason for telling us about this.