Comments by "MRA" (@yassassin6425) on "BuzzFeed Unsolved Network" channel.

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  26. A contrail does not "evaporate" - it sublimates. In relation to this their duration is entirely dependent upon the prevailing atmospheric conditions, specifically the interrelationship between temperature, relative humidity and vapour pressure. Contrary to your claim, a contrail may be short lived, persistent, persistent spreading or it may not necessarily form at all. In conditions of supersaturation in respect to ice, the aircraft merely precipitates the trail where 99% of the ice budget is drawn from the available atmospheric moisture. This is why contrails can not only expand and spread, but increase in mass becoming indistinguishable from cirrus clouds which is actually all that they are. Contrails have been observed and measured lasting up to a day. Cloud seeding has absolutely nothing whatsoever to do with the aircraft trails that you are witnessing. Cloud seeding aims to introduce additional nuclei to existing masses (cumulus and stratiform) that are already conducive to precipitation, in an attempt to induce rainfall in a designated area or intensify it. This is precisely why it is conducted at altitudes between 2,000 - 6,500 feet, where the aircraft trails that you are witnessing are formed in the tropopause and stratosphere, six to eight miles above your head. The results are actually erratic and the very science/efficacy behind it questionable. Nonetheless there are private sector organisations that advertise their services online in addition to state sponsored schemes in China and the UAE. In spite of this, it is by no means a widespread practice. It is typically conducted via retrofitted light aircraft using rack mounted flares releasing silver iodide - but may also use pylons, rockets and modified artillery shells. It is highly unlikely that you have ever seen its deployment and it does not produce lasting visible trails. Stratospheric Aerosol Injection has nothing to do with cloud seeding or aircraft contrails. "Admitted process"? SAI is a hypothetical research concept that has never been hidden, secretive or out of the public domain. How do you admit to something that isn't denied? Given that SAI doesn't exist beyond research paper and mathematical modelling, would not form a trail or involve commercial jet aircraft, would take place at double the altitude of the trails that you are seeing; that there is no aircraft on the planet that could currently loft the requisite materials (which have yet to be determined) to the required altitudes (65,000 - 70,000 ft) and has nothing whatsoever to do with cloud seeding or the subject under discussion in this video... may I ask you, what precisely is your point?
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  48. "Correct me if I am wrong" Ok... "Almost all of these long white trails are just below the clouds as you can see almost everyday. Short ones are above clouds." What do you mean below the clouds? Depending on the type, clouds can form on or near the ground or noctilucent or polar mesospheric can be 50 miles above the earth's surface. "airplane should be at least over 30000 - 35000 feet where the temperature is well bellow -30 to 40 degree Celsius. where jet engines can cause or make contrail which they are short lived due to very cold temperature up there not like these white long stretch of widening mists which lasts for a long time" Contrails typically form between 18,000 and 44,000 feet, but can be much higher depending upon the aircraft. If the conditions are conducive they have even been observed at ground level. Contrails are not simply a function of temperature. A contrail may be short lived, persistent, persistent spreading or they may not necessarily form at all. At the altitudes that aircraft cruise the air temperature is very cold. If relative humidity is high and given a sufficiently low vapour pressure a contrail will persist. If the ambient air is supersaturated in respect to ice, then the water in the exhaust will merely precipitate the trails - 99% of the ice budget being drawn from the available atmospheric moisture. What do you mean "very short lived due to the very cold temperature up there" - are you equally confused by cirrus clouds? which is afterall, all that a contrail is. "Next time you ride a plane check to see how long it takes you to go over the clouds where you see no long trails" Cloud decks are multi layered and stratified. What on earth are you talking about? How is it possible to be this confused. A ceiling may be as low as several hundred feet..it may be much higher - again, it depends upon the atmospheric conditions.
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