***The Contrail Question & Answers Post*** -What causes a contrail? Similar to a cloud, contrails form when water vapor from a planes exhaust condenses into a cloud. -Why do contrails persist, I thought they were supposed to evaporate? Same reason some (not all) clouds persist. The water vapor will freeze into ice crystals. These ice crystals will not melt into a liquid, but you may be wondering why this occurs. Sublimation is a process where a solid transforms directly into a gas. If the humidity is below 70%, then (this is the general threshold from what Ive been reading) this process will allow a contrail to evaporate. However, if the humidity is above 70%, then the air will remain full of moisture. The ice crystals wont be able to evaporate due to the air not having enough room for extra water vapor. When this occurs, you get the long-lasting contrail. -Why do contrails spread? For a contrail to spread out we need a couple of things. Firstly we need a supersaturated environment. And we also need the high winds that are found at the altitudes at which planes fly. One such type of wind is known as the jetstream, which has recorded winds in excess of 200mph. So the prevailing winds in a dry eair environment would normally disspate a contrail quite quickly. In a supersaturated environment. The winds push moisture into other areas already moist, causing more ice crystals to form and a layer of cloud to from over the sky. As long as there are high winds and mositure, the clouds will continue to spread (abovetopsecret/forum/thread412301/pg1) -If theyre contrails, then why do they make me sick? In scientific experiments, they usually call this confirmation bias. Think about the best meal you can remember, imagine the taste, the smell, and the atmosphere around you. Your mind can make whatever you imaging start to feel real. If you start imagining a sickness, I can almost guarantee youll start feeling it. -Does the government pay you to spread this information? No. -How can I be sure youre not lying and the atmosphere really works by a process I call insert unknown process here? Experiment. Read scientific papers. Research and come to your own conclusions. Never blindly accept what youre told. This is why science is open for anyone who wants to learn. -How can I quickly confirm what youre telling me is true? While you may not be able to get 100% certainty, you can perform these experiments if you seek scientific validity... •Next time its humid outside (if you live in a humid area) note how your sweat tends to stick instead of evaporating. •Boil some water and hold a lid up to it. Youll see the water vapor condense back into a liquid You can also watch these these videos: npr.org/blogs/thetwo-way/2014/01/06/260188337/dont-just-shiver-here-are-3-cold-weather-experiments-to-try Further reading... Sublimnation: en.wikipedia.org/wiki/Sublimation_(phase_transition) Humidity: en.wikipedia.org/wiki/Humidity Cloud formation: en.wikipedia.org/wiki/Cloud Cirrus clouds: en.wikipedia.org/wiki/Cirrus_cloud Clouds, fog, rain, snow, drizzle: usatoday30.usatoday/weather/resources/askjack/archives-clouds-precip.htm ==== Question not listen here? If so, then ask in the comments! Note: Anyone who responds with ad hominem attacks against me (or anyone else) in this thread will be simply ignored. (y)
Posted on: Mon, 05 Jan 2015 20:05:07 +0000