* * * IT'S JUST FROZEN WATER * * *   
CONTRAILS, NOT CHEMTRAILS
A PUSU Fact Sheet for Young People · draft for schools
THE CLAIM
The white trails left behind aeroplanes are secret chemicals ('chemtrails') sprayed to poison people or to control the weather.
▶ THE FACTS ◀

» What the trail actually is
A jet engine burns kerosene and, like any burning, gives off water vapour and carbon dioxide. High up where airliners fly it is bitterly cold -- around minus 40 to minus 60 degrees -- so that water vapour freezes at once into millions of tiny ice crystals. The white line is a man-made cloud of ice, exactly like the cloud you make when you breathe out on a frosty morning.

» Why some trails last and some vanish
It depends on the air, not the plane. When the air up there is dry, the ice crystals turn straight back into invisible vapour and the trail disappears in seconds. When the air is already damp, the crystals linger and spread into wispy cloud, just like natural cirrus. A long, spreading trail simply means the air was humid that day.

» Why there is no secret spraying
The make-up of jet exhaust has been measured thousands of times and holds no surprises. Spraying a whole country would need huge tanks on every aircraft and would be noticed at once by the pilots, engineers and refuellers who work on planes every day. A secret shared by that many people would not stay secret for long.

★ TRY IT YOURSELF ★
Breathe out hard on a cold day and watch your own 'chemtrail' appear and then fade. You have just done what a jet engine does -- only smaller, and with no chemicals at all.

PUBLIC UNDERSTANDING OF SCIENCE UNIT (PUSU) · Schools & Media-Literacy Programme
DRAFT for distribution to schools · staged copy only.
Every statement in this sheet is scientifically accurate and may be relied upon.
Not to be attributed to the Partner. © Crown Copyright 2013.