DEAR SUN SPOTS: Does anyone know what the long white lines that airplanes are leaving behind in the sky are? These lines eventually expand into what looks like a hazy white fog that covers the whole sky. I’ve counted nine planes all in the sky together flying the same way, side by side.

I know the difference between a contrail (it’s short, disappears and the plane is at a higher altitude) and a chemtrail (long white exhaust, made of barium, strontium and aluminum and doesn’t disappear, blocking the sunlight).

My question is does anyone else notice this activity and what should we do to stop it? — Wayne via email

ANSWER: Contrails are not always short and fast disappearing. According to several websites, how long they last depends on how humid the air is.

For readers who might not know, contrails are the white streaks you see against the blue sky when a plane passes. They are the result of a very hot jet engine spewing exhaust into very cold air (think 40 below or colder). One of the byproducts of the exhaust is water vapor, so when that hot vapor hits the cold air, a “cloud” of water vapor appears, much like when you breathe outside on a cold winter day.

That water vapor condenses into water droplets and then crystallizes into ice. The ice crystals are the clouds that form behind the engine. This is why the streaks are called contrails, short for “condensation trails.” When the atmosphere is more humid, the contrails linger, but when the atmosphere is dry, the contrails disappear more quickly.

Contrails can form cumulus clouds, which may affect the weather. In the days after 9/11 when all planes were grounded, the average daily temperature was two degrees higher than normal, which some scientists attributed to reduced cloud cover.

There are other byproducts in jet exhaust. According to author and airline pilot Patrick Smith, the contrails consist of not just ice crystals and water vapor but also carbon dioxide, nitrogen oxides, sulfate particles and soot.

Sun Spots did not find anything about barium, strontium and aluminum, other than posts related to conspiracy theories, which say that the government is taking advantage of this scientific phenomenon to secretly release other substances into the atmosphere.

The problem with this theory is that the government officials are breathing the same air full of particulates as the rest of us. They cannot possibly target them just to their enemies.

Sun Spots thinks all exhaust is bad, but she is far more worried about the exhaust on the ground from millions of cars and trucks and coal-fired power plants (which emit many dangerous chemicals including mercury) than she is about airplane exhaust. 

DEAR SUN SPOTS: Thank you so much for printing the information about our pizza-giveaway fundraiser for the Good Shepherd Food-Bank. It was just brought to my attention that the dates were wrong. It should have said Monday and Tuesday, May 6 and 7.

When people donate three or more items on these days, they will get a free pizza. They can bring in the donation and get the pizza on the spot or they can have delivery and they driver will pick up the donation and give them a voucher for a future use.

Thank you for your help. — Cheryl Killian, Papa John’s Pizza

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