The house I grew up in faced an open field. About five miles in front of it was the Edmonton Municipal Airport, a further 10 beyond that was the Edmonton International Airport, and just a few miles behind it was Namao Air Force Base.
A lot of airports.
On summer days I used to sit on the porch, mostly waiting for the girls to go by, but in their absence, watching the planes in the sky.
I was especially interested in the high-flying jets, barely visible but for the thin white vapor trail they left behind them.
With my younger and much sharper eyes, I used to try to see the exact moment that the vapor disappeared. Usually it would be gone within a second or two, but sometimes on a cold day, it would last five or six seconds.
One day, I asked my dad, “Why does the smoke disappear?”
This was his reply, “It’s not smoke. It’s just hot air coming out of the jet engines condensing when it mixes with the cold air up high. When it cools down it disappears. It’s a lot like the steam coming from a teapot.”
As usual, when my father explained something, it made perfect sense.
As anyone who has ever watched jet planes on a runway can attest, jet engines do not emit visible ‘smoke.’ Otherwise, airports would be perpetually smoggy places. What you do see are the wavy lines in the air showing the great heat.
If this seems ridiculously obvious, be warned, I am just getting warmed up.
In all those years of watching planes from my front porch, I saw hundreds, maybe thousands of high flying jets go by, and not one of them, never, ever, ever turned its engines off for a split second and then turned them on again.
Never.
How do I know that?
Because the little vapor trail, also known as a contrail, always came out in a continuous uniform stream until the jet was beyond my ability to see.
Naturally this is just what one would expect to see. Ask any commercial pilot, “Do you ever flick the engines off for a sec, just to freak everyone out?”
They are likely to look at you like you’re a crazy person. Do it in an airport and they’ll probably call security.
Why do I mention these rather obvious things?
I would like you to agree to a couple of things before I proceed much further.
1. Jet engines do not emit ‘smoke.’
2. The vapor trails
Oakland
On my way for a jog around Oakland’s Lake Merritt, I noticed a plane doing something odd. It was leaving a contrail behind it, but instead of dissolving as the hot air cooled, it remained in the sky.
While I was reaching for my phone, And a gap…
In scientific terms, my fathers explanation was the ‘theory,’ and my gazing from the porch was the ‘experiment,’ or observation.
