Yesterday afternoon, I was practicing piano when I heard a large bang.  Since we’re not that far from Fort Devens, loud bangs aren’t that unusual.  Devens frequently has training sessions where they’re setting off grenades, mortars, and all sorts of other munitions, and it’s just part of the deal when living in this area.  This sounded different though.  There was a low-frequency component to it that didn’t sound normal to me.  Normally, I’d investigate something like this further, but I was in the middle of practicing and assumed that whatever caused it wasn’t local, so it would be a waste of my time to find the source. Later on in the day, while glancing through Facebook posts, I discovered that …