I'd only vaguely heard of the 'chemtrail' nonsense. Every time I hear another so-called conspiracy I wonder for some time if my leg is being pulled. Are people really that ignorant of science? Apparently so. But we can at least try.
Advancedboy, are you aware of the following facts?
1. Modern airplanes fly at a wide range of altitudes up to and beyond 40,000 feet or 12 km.
2. Up through this range of altitudes, the temperature of the earth's atmosphere drops sharply at first, reaching a minimum of about -55C.
3. Except at fairly low altitudes, atmospheric temperatures are below the freezing point of water, even in the tropics.
4. Modern aircraft burn petroleum-based fuels, mixtures of liquid hydrocarbons. When burned with air, the primary reaction products are water and carbon dioxide.
5. Sometimes, when the conditions are right, the water condenses into droplets and/or freezes to fine ice crystals visible as a white cloud. We call these contrails.
Please tell me, do you know these facts? I have learned never to assume even the most basic levels of knowledge in discussions like this.