Tuesday, July 6, 2010

Heat Wave

"If you saw a heat wave, would you wave back?"
~ Stephen Wright

Walking is a muse and a madeleine for me — it stirs up new ideas and old memories. I walk three or four miles almost every day, but some days are easier than others. 

Yesterday, when I set out for a walk at 10 a.m., the temperature was already in the high 80s. As I walked, the heat was set on broil; it burned down from above and smoldered up from the pavement in a fiery feedback loop. The tar on the street was already beginning to turn gummy. It crossed my mind that on relentlessly sunny days like this, every little pool of shade becomes an oasis. 

The thought of an oasis led me to a distant memory of another hot day when I was around three years old. I was in a car, transfixed by highway mirages — the sparkling pools of "water" that appear and disappear on the road ahead. 

When I asked about them, I was told they were a trick of the light or the eye. That answer alerted me to the notion that sight and light are unreliable narrators, but it didn't help me understand what I was seeing — or more accurately, not seeing. The photo above is from NASA's Earth Science Picture of the Day website, which offers the succinct explanation I yearned for as a child. Here it is:
"The effect is caused by a thin layer of hot air just above the ground. The difference in refractive index between the hot air at the road surface and the denser, cooler air above it causes the boundary to act like a mirror: distant objects are reflected...The 'water' is actually a reflection of the blue sky, but a close look at this image also shows reflections of a car, power poles, bushes, a mile marker, and roadside grass. Because the reflection occurs solely at very shallow angles, the mirage appears only in the distance and continually recedes as one moves towards it."
I saw no highway mirages yesterday, but the heat wave isn't done with us yet. I'll keep looking. 

"Our knowledge is a receding mirage in an expanding desert of ignorance."
~ Will Durant


  1. "Fiery feedback loop"—so perfect. And while I may not understand refractive index differences, the mirage photo actually made me nostalgic for hot drives in California. Thank you for this lovely piece.

  2. High 80s in the morning? Oof. I know what you mean about the shade: it's such a relief to have the sun off your back even for a moment. I think this kind of heat is more intense in cities, where it bounces off tarmac, glass, buildings, and so on, not to mention the heat coming from vehicles and other people!

  3. Susan, your comment showed up in my e-mail yesterday but only appeared on the blog now. How odd. But yes, there is something very nostalgic about a drive on a hot day. Perhaps, when we were young, our senses were stirred up by the idea of travel. Come to think of it, travel still does that for me.

  4. Thanks, Stan. And you are so right about buildings, cars and people making the heat worse. On hot days in NYC, it's best to stay close to the river.