Why do some jets show vapour trails and others not-even in the same part of the sky?
448048
Jets fly hi where the air is rare and moisture is....either hi or low.  when the moisture is hi, the airplane cuts through causing a slight change in temperature (afterall the turbines are really hot causing a cycle of condensation, eg.heat then the re-cooling of water molecules) condensing the water molecules around it, leaving a vapour trail behind where it passed through.  when the vapour trail remains in the sky for a long time, it is usually a good indication that rain is on it's way to where you live.  clouds form because of the same idea, when a patch of moisture in the sky hits a colder patch, water molecules condense forming clouds.  When there is little moisture in the sky, jets will not leave a trail behind because there is not enough moisture to condense.
149649
Did they look like this? If so, they were nothing more harmful then Lenticular Clouds. Normally, air moves much more horizontally than it does vertically. Sometimes, however, such as when wind comes off of a mountain or a hill, relatively strong vertical oscillations take place as the air stabilizes. The dry air at the top of an oscillation may be quite stratified in moisture content, and hence forms clouds at each layer where the air saturates with moisture. The result can be a lenticular cloud with a strongly layered appearance.
1053233
the hot pavement creates a layer of hot air just above it.. and the cooler air above that make a difference in density barrier.. which reflects light... as long as it is below a specific angle <so you see the reflection from far off but not right at your feet>\n\nI think.. hehe
588652
They end up becoming the 'seeds' of clouds.  That is, water in the air condenses around them, & once the process starts, those condensation  trails sometimes form into clouds up to 500 miles long.\n\nI read about it in, I believe, Popular Science a couple years ago.  There was also a fascinating article about a study that took place during the 3 days in 9/01 when all planes in the U.S. were grounded:  due apparently to the reduced cloud cover, temps everywhere were a couple degrees higher those days!
706880
Any two lines which are in the same plane and are not parallel will eventually intersect. Two lines which are not in the same plane can be non-parallel without intersecting. Have you ever seen the contrails of two jets in the sky on a clear day...? They may appear to cross, or you may even see one jet appear to fly through the contrail of the other But they do not disturb each others' contrails. The reason is that they are flying at different altitudes-- they are not 'in the same plane'.\n\n8 NOV 06, 2122 hrs, GMT
1156831
Those are called contrails.  They are CONdensation TRAILS.  The hot jet exhaust hitting sub zero temperature air [it's like 40 below at 40.000 feet] condenses the moisture out of the air to form cloud trails.
675159
Actually eclipse is wrong on the static dischargers, too.  All they do is slowly get rid of any excess charge on the plane relative to the surrounding air.\n\nThe answer to the ? is that planes AREN'T grounded electrically.  All the electrical and electronic stuff in them is grounded to the metallic structure of the plane, snd this is the return path for all current using devices.  Planes made of certain non-conductive composites use separate grounding wires and busses to do the job.
66486
Surface maps only show the conditions near the surface (1000 mb), jet streams and upper level pressure systems have more to do with weather than surface conditions.  The winds and pressures at different elevations can vary greatly from those at the surface.
124314
Actually, this happens only under certain atmospheric conditions, when the air is quite clear. It is because the speed of light in the layers of air near the ground is slower than the speed of light in layers of air above that. Therefore, just like a lens, the light is bent by this gradient in the speed of light. \n\nRefraction of light is a wavelength-dependent phenomenon. The longest wavelengths are bent, or refracted the least. and the shortest wavelengths are bent the most. The reds, yellows and oranges are the long wavelengths, and they will bend the least, and will head off into space. The shorter wavelengths, the blues and greens and violets will be bent down by the atmosphere to be visible at the ground. In fact, the sun is actually below the horizon for the last few minutes of the sunset. The light has to bend around the earth, and the color that gets bent the most includes the short wavelengths. \n\nWhy do we see green in the green flash, and not violet or blue? There is also Rayleigh-Tyndall scattering going on, caused by the small nitrogen and oxygen molecules in the air. The shortest wavelengths are most scattered by the air molecules, and are scattered out of the sunlight, leaving longer wavelengths for us to see. The blues and violets have very short wavelengths, and are therefore scattered the most. (This is the same process that creates blue skies and orange and red suns at sunset). However, in this case, the yellows and reds and oranges are not present in the sunlight as the sun sets below the horizon, but have travelled out into space, so only the greens, blues and violets remain. The blues and violets are scattered away, leaving the green for us to see as a green flash. \n\nA more complete explanation complete with pictures is in the references.\n\nIt is also interesting to note that the moon can also exhibit a green flash, or a green edge (and also a red edge, in a kind of red flash). At the poles, when the sun is barely below the horizon for hours, the green flash can last for hours apparently, according to friends that have seen it.
540627
Not an uncommon thing to see. The "sky" is laid out in compass points and most commercial air craft are assigned flight paths that are like "high ways" in the sky. Generally you will find those "trails" are on true points, 00%,45%,90% etc. The reason for the near perfect "X" is due to the vectors the two were heading on.
830457
Hi, I answered this question earlier. I'm going to cut and paste it for you.\n--\nMost sightings happen at night. People see strange lights or shapes in the sky.\nMine happened in broad daylight. Crystal clear blue sky. About noon. No sun in my eyes. An object appeared in the sky directly in front of me. It was traveling parallel to the ground. It wasn't zipping along at lightning fast speed. It was fairly slow. About airplane speed. \nIt wasn't more than a half mile away. Fairly low in the sky.\nI could see every detail. The color. It was a semi-shiny or brushed metallic almost burnt looking. Very hard to explain. All one color. No markings. No lights. I could see the intricate patterns of the body. I wont ever describe them. I'm not planting any seeds. When I hear an identical description then I'll know it was real. You see this was 25 years ago. To this day nobody has matched the description. Not even close. I watched it for a few seconds. I was in amazement. It simply vanished. \n--\nPsst, don't take me wrong. I'm not discounting your sighting at all. Just because it was at night doesn't mean you didn't see it. I totally believe you. Look at my story. People tell me I imagined it. What do they know anyway!\n.
209189
You are referring to "Chem-trails." Supposedly the government or some shadow agency is testing various chemicals on the environment or American citizens (depend on which "investigator" you talk to). Chem-trails are usually distinguished by heavy air traffic in an area, often times forming a criss-cross patterns. Such reports are also often accompanied by unexplained sickness or asthma. On occasion, someone also claims that the chemicals will produce odd substances on the ground the next morning (sometimes described as a crystalline structure, other times spider-webby).\n\nYour pictures, however, only show one trail (which appears to be a con-trail) and some pretty clouds (probably the result of pollution, though other natural explanations are available as well). In all likelihood, your pictures are nothing more than scenic.\n\nAs to if chem-trails are real, I've never seen a reliable source report them, nor have I ever seen any compelling evidence put forth.
922889
Because air at ground level and a significant distanace above is rarely saturated - when it is, fog forms - which is a cloud on the ground. It has to be saturated a significant distance above ground or else you only get shallow areas of ground fog or dew/frost (if it is unsaturated say 50-200 feet above ground).\n\nBases of what we normally consider to be clouds rarely touch the ground because rising air motion is required to saturate the air and form the cloud. If it has to rise to do that, it cannot occur on the ground - though such clouds can be advected to a higher location and perhaps reach ground level there - or as is more common, the rising motion occurs up a slope with a cloud forming at some point along it.
80699
They're called contrails, short for condensation trails. When a jet engine is running it heats up the air traveling through it.  On the ground it's not that noticeable.  Up in the atmosphere where jets fly, the temperature is way below freezing. The warm moist air condenses as it exits the jet engines and you can see the water vapor the same way you can see your breath on a cold day.
861786
Call newschannel 3, I bet they would look into it.  Royal Norman may even already have an answer.  I have not seen them, though I live very close to you.  I'll have to keep my eye on the SE sky.  Do they occur at a certain time, or various times?  Are they low to the horizon?
515706
The atmosphere is made up of several layers,each one with a varying density.Thus,the speed of light differs in different layers of the atmosphere and the light gets refracted(deviated from its path when it travels from one medium to another)when passing from one layer of atmosphere to another.Due to this refraction of light in the different layers of the atrmosphere,stars appear to twinkle
780823
Could be a strange mirage. Sometimes weird mirage can project skyline of cities beyond horizon or just strange shapes in sky when atmosphere refract lights in unusual ways.