March 03, 2004 :: Ribbon in the sky

I had an argument with my stepmother the other day. She's normally a fairly intelligent person, often paranoid and occasionally very country. I was driving her around in my car on a beautiful sunny day, with hardly a cloud in the sky. She was visiting the Washington metro area from her normal home in southern California. We were having a nice conversation about various family topics (with my sister dozing in the back seat), until she started talking to me about comets.

She was expressing mystic wonder to me at how she sees these comets every day, in the same positions in the sky, and how she is 3,000 miles from her home yet she still sees them. I was highly confused. Comets? I didn't see anything in the sky resembling a comet. She insisted they were there, and I was beginning to wonder if she would be needing psychotropic medication as she transitioned into senior citizenship. Besides, I told her, I needed to keep my eyes on the road.

After some effort, she was finally able to point one out that was in the forward direction from the car. I looked up in the sky, and saw.... a contrail. For those of you who aren't familiar, witness the picture:

A contrail from a jumbo jet

A bit of etymology and science: Contrail is a coined word for "condensation trail", in reference to the trail of condensed water that jet engines leave behind in the air. One of the byproducts of jet fuel combustion is water vapor. The air at high altitudes is generally a lot colder than the air on the surface, so that hot water vapor quickly cools into liquid (and sometimes frozen) micro-droplets, which are then visible as white clouds. They form lines because the planes move in lines.

So when I explained to her that what she was seeing were contrails, she told me I was flat-out wrong. They couldn't be caused by airplanes, because she couldn't see the planes, and they weren't moving, and anyway, why would they be in the same positions at the same times in the sky every day? It did not matter that it would make more sense for planes to fly the same routes at the same times every day than for "comets" to appear in the sky in the same position every day. She knew she was right, and she didn't understand why I wouldn't believe her.

I quickly gave in on that argument.