We're all familiar with the white trails that follow in the wake of high-flying jet airplanes. These temporary clouds are known as contrails and were first reported by high-altitude planes in the 1920s. That's nearly 100 years ago. I emphasize their age because some people make a lot of hay with conspiracy theories that contrails are chemicals sprayed into the atmosphere meant to hurt us in some way. Other than deliberate attempts to attempt to create precipitation under certain circumstances, contrails are harmless and a natural consequence of high-flying aircraft.

Each engine of a passing jet aircraft leaves a trail of condensing water vapor as it flies through the cold air near the top of of the troposphere, the lowest layer of the atmosphere. 
Contributed / Bob King
Each engine of a passing jet aircraft leaves a trail of condensing water vapor as it flies through the cold air near the top of of the troposphere, the lowest layer of the atmosphere. Contributed / Bob King

The trails are made of water vapor and soot that are produced by burning jet fuel and exactly mimic the "contrails" of vapor pouring out of your automobile tailpipe on a frigid morning. Or for that matter when you exhale after breathing cold air. Most jets fly at an altitude of around 35,000 feet (11.9 km), where the air temperature hovers at 70 degrees below zero (-55 C). Warm vapor quickly condenses into a cloud drawn into a line in the sky as the plane moves forward.

Depending upon atmospheric turbulence and humidity, trails can linger and spread into sheets of cloud or quickly evaporate, often breaking up into short whorls or arcs visible from the ground. Binoculars reveal marvelous detail in these tiny cloudlets.

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Two days ago, flying to Dallas, Texas, our plane closed in on a distant contrail and before I knew it, we slammed right into it. The smooth flight suddenly turned turbulent for about one second before flattening back to calm. For an instant, I looked directly down the contrail and saw whorls of dark smoke that looked like dissipating smoke rings from a pipe. I'd never experienced this before and couldn't believe our luck.

Scouting the view, I looked for more contrails in the distance, hoping for a repeat performance. Unbelievably, it happened three more times, but the pilots, perhaps deliberately, guided the plane under the disturbances to avoid potential turbulence. Similar to a wake behind a speeding boat, a plane leaves a wake in the atmosphere that other flying objects experience as a temporary obstacle.

Clouds shroud the rising sun as seen from 40,000 feet. The sense of a horizon, caused by the sharp edge of the cloud deck, created the false but wonderful impression of the sun appearing "below" the horizon. 
Contributed / Bob King
Clouds shroud the rising sun as seen from 40,000 feet. The sense of a horizon, caused by the sharp edge of the cloud deck, created the false but wonderful impression of the sun appearing "below" the horizon. Contributed / Bob King

On a later, overnight flight, at an altitude of 40,000 feet, we flew above a layer of ice-crystal cirrus clouds (the feathery ones) and watched the sun rise. But impossibly, it first appeared below the horizon. Of course, that can't happen. Yet the impression was strong and disorienting. The sharp edge of the cloud layer convinced my brain that I was looking at the horizon.

I encourage you to be on the lookout for similar encounters and sights from the window seat during your plane travels. Keep that mobile phone handy!

"Astro" Bob King is a freelance writer for the Duluth News Tribune. Read more of his work at duluthnewstribune.com/astrobob.