IN a crowded place like Manhattan, there are moments when a certain question flits across people’s minds.
It could happen on a weeknight at the Union Square Trader Joe’s, when the aisles are so packed that shopping for frozen edamame morphs into a full-contact sport. Or perhaps it’s on a Saturday in SoHo when Broadway is transformed into an obstacle course of tourists and jewelry peddlers. Maybe it’s on the No. 2 subway line at rush hour, where personal space — if any — can be measured with a micrometer.