Every year on March 13, I wake up with the nagging feeling that I’ve forgotten something important. And I have: Baltimorehenge. That’s the name for one of the two days each year where the sun’s alignment matches up perfectly with the city’s street grids, resulting in an urban “canyon sunset” precisely between the city’s east-west street canyons.
If Baltimore were a Druid city, our streets would fall on a precise north/south/east/west axis, and Baltimorehenge would take place at the Equinox. But we’re not. Back in 2007, the Sun‘s Frank Roylance cited “streetcorner astronomer” Herman Heyn‘s precise calculations (they rely in part on the city’s original surveying plan from 1730!) to determine that Baltimore’s north-south streets are about 3 degrees west of true north. Using some weather/math/time magic, Heyn calculated that Baltimorehenge would fall on September 29 and March 12.
So we missed it once again. The good news: because the sunset’s angle changes so slowly, you can probably get a Baltimorehenge-like effect if you go downtown this evening. And if you don’t mind waking up early, the sunrise version of the effect is still to come — it takes place on September 18 and March 25. Mark your calendars!