I remember, as a kid, being endlessly fascinated by vertical cutaway maps of the miles beneath New York City. Layer after subterranean layer, the parking garages piled atop subways atop water mains atop the electrical grid. I loved that each layer seemed to exist in silent parallel to the ones above and below. That each was its own little world.

I thought of those maps again this afternoon, climbing down the stairs to the C/E subway line. While the day’s suddenly wintry air whipped along the sidewalks above, thirty feet below, the stop was still, luke-warm, stale. And, as I passed into a waiting subway car, I hit yet another little weather system. Though, during the summer, the subways are brisk, ventilated by strong air conditioning, now, as the heaters are just put back into use, each car bakes slowly in its own languid cloud.

Nine years after coming East from Northern California, I’m still a bit unused to these manufactured ecosystems. Growing up, we had no air conditioning, only ran the house’s radiant heat during wintry nights. The difference between temperature indoors and out was usually, quite literally, a matter of degree.

But here, on the East Coast, the little worlds we create seem to operate in complete divorce from/ the larger one surrounding them. In the midst of summer, as humidity threatens to turn spontaneously into midair raindrops and the mercury clears 100, we push air-conditioners to full throttle, toting sweaters to the office to wear over short sleeves. In winter, we bundle layer upon layer to brave snow-bound treks, only to enter homes and stores so blisteringly heated we strip to near our skivvies the moment we clear the door.

Which, for years, always struck me as rather strange. But, today, as I rode the subway and thought of those cutaway maps, started to make a bit more sense. New York, after all, is nothing but a collection of separate little worlds, of sewers and cables and subways below, of streets and buildings and even taller buildings above. And while each might be intimately intertwined with the others, with so many all wedged in to such little space, we’ve no choice but to pretend they’re all separate, parallel, self-sustaining. No choice but, as the wind howls outside our windows, to crank the heat to full high in our little apartments, tied so tightly to the millions surrounding us, yet desperately, willfully, setting ourselves apart.