Contrails (short for “condensation trails”) are formed when hot exhaust gases from aircraft engines mix with cold air at high altitudes, typically above 25000 feet, and in cold and humid atmospheric conditions. The water vapor in the exhaust condenses into tiny ice crystals, forming a visible trail. Contrails usually appear as white lines that quickly dissipate or disappear within a few minutes or seconds, depending on atmospheric conditions.
They are a natural byproduct of jet engines and are essentially artificial clouds.
Chemtrails (short for “chemical contrails”), however, are trails left behind by aircraft are not ordinary contrails but, instead, intentional releases of chemicals or biological agents by governments or other organisations for various purposes, such as weather modification, mind control, or population control. Such trails persist in the sky for much longer than normal contrails and spread out to form a haze or cloud-like appearance.
Weather modification programs are common.
- Project Cirrus (1947) was one of the first large-scale weather modification experiments conducted by the General Electric Research Laboratory and the US Army. Its aim was to investigate the possibility of using cloud seeding to alter hurricanes. In October 1947, they tried to modify a hurricane near the coast of Georgia and, instead of steering the hurricane away, it changed course and hit the coast, causing a lot of damage.
- Operation Popeye (1967-1972) was a covert weather modification program conducted by the US military during the Vietnam War. Its objective was to increase rainfall over specific areas of the Ho Chi Minh trail to impede the movement of enemy troops. Cloud seeding was used to worsen the rainfall, extending the monsoon season and creating muddy and impassable conditions.
Dane’s documentary, The Dimming, explores all of this, particularly chemtrails.