Chemtrail conspiracy theory
The chemtrail conspiracy theory is an erroneous belief that the contrails of aircraft are being used for nefarious purposes, ranging from altering the weather to mind control. Chemtrail (a portmanteau of "chemical" and "contrail") sightings are often reported on the r/chemtrails sub-messageboard of reddit.com, a discussion website which claimes to be "the front page of the internet".
On this sub-messageboard, under a section titled "Definitions & such" is the short description of a chemtrail as
Following this is a short text that encourages both believers and skeptics to adopt a tolerant attitude towards each other with a disclaimer:
All viewpoints are allowed here, but please be respectful. This is a subreddit, not a court of law. Please don't badger users into providing concrete evidence. Short of flying us all up into the atmosphere with an evidence bag, you probably won't get it.
Contingency
A contingency plan; a fall-back, a plan B, what to do if all else fails.
Contingencies are incidental to something else, dependent on chance, possible, conditional, but usually unnecessary.
A contingency is what something allows or doesn’t allow one to do, constrained by its form and use. For example, a pen is often used to write with, but also has the contingency of being used for other purposes, such as scratching one’s back.
Contrails
Contrails (a portmanteau of "condensation" and "trail") are the line-shaped clouds left behind by the engines of aircraft flying at low altitude. They are commonly composed of water in the form of ice crystals.
