r/skeptic • u/Arkkhitekkton • 13h ago
A quick refresher on thermodynamics: Why high-altitude aircraft trails are physics, not chemistry.
Ugh. It is baffling that in an age of accessible information, the "chemtrail" conspiracy theory still persists. Anyone who has ever stepped outside on a freezing winter morning and watched their own breath condense into a visible cloud has already witnessed the exact same physics that occur at 35,000 feet.
Here is what is actually happening:
The Chemistry of Combustion: Commercial jet engines burn hydrocarbon fuel (kerosene). The chemical reaction of burning hydrocarbons combines fuel with oxygen, producing carbon dioxide, thermal energy, and water vapor as primary exhaust byproducts.
The Environment at Altitude: At cruising altitude (typically 30,000 to 40,000 feet), ambient air temperatures are brutally cold often around -40°C or lower.
Condensation and Freezing: When hot, moisture-laden engine exhaust hits that freezing, low-pressure external air, the water vapor instantly condenses and freezes into microscopic ice crystals. This creates a contrail (short for condensation trail), which is functionally identical to the cloud of vapor you see when you exhale on a cold day.
Why Do Some Contrails Linger? People often point to trails that spread out and persist as "proof" of chemical spraying. In reality, this depends entirely on the atmospheric humidity and wind shear at that specific altitude. If the upper atmosphere is already humid, the ice crystals can not evaporate quickly, causing them to spread out and form cirrus-like clouds. If the air is dry, they dissipate rapidly.
It all comes down to basic eighth-grade physics and meteorology—no secret spraying required. Maybe it's time to brush up on thermodynamics before inventing a global conspiracy. I'm so tired of people saying commercial passenger jets are spraying chemicals into the air. Ugh.