http://chemtrails.cc/2009/01/25/what-are-chembows/
by qbit on Jan.25, 2009, under Optical Phenomena, What are they?
If you’ve been paying attention to chemtrails, you may have observed rainbow smearing (diffraction) of light reflected off them. Dark sunglasses can bring the subtle rainbows into the dynamic range of the human eye. Chembows are often visible when the sunlight reflects at approximately 45• angle to the chemtrail. Wikipedia entry on diffraction
A popular chembow image. Notice how only the wispy remnants of the chemtrail diffract the sunlight, not the clouds.
Diffraction is a quantum interaction between photons of light and edges of atoms. When metallic surfaces have features smaller than a wavelength of visible light (nanometer scale), different wavelengths will be reflected at different angles. When features are ordered in a linear pattern (such as on a DVD optical disc), a rainbow will appear.
Illustration of white light diffracting off a metallic diffraction grating
In the rain, or other atmospheric conditions where water droplets are large enough, rainbows appear due to refraction. Atmospheric refraction (such as from a rainbow in a rainstorm) is a similar phenomenon to chemtrail diffraction. Its important to note, however, that rainbows can be seen in light reflected off chemtrails, not only refracted from behind, which may occur under other atmospheric conditions, such as the presence of large ice crystals or droplets.
Refraction thru a prism (or water droplet of sufficient size). Refraction occurs when light passes thru a surface into a material with different index of refraction
More examples of chembows:
Dark sky indicates reduced exposure, necessary to bring rainbow into dynamic range of the sensor.
Filamentous wisps may indicate presence of heavier-than-water particulate aerosol. Pink and green dominate the rainbow, matching emission spectra of barium.
Mock me if you will she-el......but I am only posting fact, not fiction. Scientific facts. Real photographs, real evryday phenomenon that is going on above our heads.....suggest you LOOK UP ! occasionally....
yes, get off your computers everyone and go outside and start looking up at your sky everyday.
It's not rocket science to observe you know.
............................
.............................as for suggesting 'aliens' well, this is typically the rubbish thrown by those who don't understand fact and science
My brain is nearing burn out 
So is it Mother Nature or a result of man's intervention with the atmosphere?
paints, I often look at the sky and surroundings, doesn't mean I know why or what causes some of the pecularities of my interest.
I've just thought it was Nature putting on a show for us. You know, just to divert our attention from yukky other stuff that can fill our lives with confusion and animosity.
Or is Mother Nature using Man's Makings and bringing some beauty to it?
DEB
@the_great_she_elephant wrote:http://www.sciencealert.com.au/news/20140511-26457.html
OMG! What are THEY hiding from us this time? In here, quick, with your favourite conspiracy theory.
amazing isn't it?
and nope, no conspiracy theories -
sorry to disappoint 
perfectly logical, scientific explanation
Fallstreak holes are a cloud formation that occurs as gaps in mid or high level cloud layers. Below them, trails of ice crystals dangle. In order for a fallstreak hole to form, the cloud layer must be composed of supercooled droplets (liquid water), despite the temperatures at cloud level being well below 0°C. When one region of the cloud begins to freeze, the fallstreak hole forms. This begins a chain reaction whereby all the moisture from the supercooled droplets in the nearby area is drawn in and joins the ice crystals. These then grow big enough to fall beneath the hole; fallstreak holes have been known to reach 50 kilometres across just an hour after the hole began to form.
Though these cloud formations have been known about for some time, scientists were unclear as to why the freezing began in one area of a cloud layer and how it grew in size. Research published in Science in July 2011 sought to answer these questions.
The research was performed by Andy Heymsfield and his colleagues at the NationalCenter for Atmospheric Research in Boulder, Colorado. The team used a satellite called GOES to track 92 cloud holes over Texas over 4 hours in January 2007. The holes grew a considerable amount within an hour and then slowly began to shrink. Most of the holes had a diameter between 10 and 50 kilometres. Heymsfield theorised that a side effect was at play, creating the ice that caused the holes to grow.
To test this theory, Heymsfield ran a detailed computer model of the internal workings of a cloud, introducing a line of ice crystals like those produced by an aircraft. The simulation showed a hole that grew to a diameter of 4.4 kilometres in 90 minutes. If the heating effect of creating ice in the simulation was turned off, the hole grew slowly; if the effects of evaporation were also removed, the hole didn't grow at all.
The research confirmed that aircraft flying through the cloud could be what is setting off the freezing process. The air expands as it passes over the aircraft wings and over the blades of its propellers. This causes the air to cool; this cooling can be long enough to decrease the temperature enough for the droplets to start to freeze. When these droplets change into solid particles, they emit a small amount of heat, which causes the air around them to expand and rise somewhat. This rising current causes the surrounding air to sink slightly.
When the air around the frozen fallstreak sinks and begins to warm up, the droplets within begin to evaporate. This appears to be why the fallstreak of ice crystals produced by the plane flying through the cloud layer forms a circular hole that looks like it has been ‘punched’ out of the cloud layer. It does not seem to matter whether the plane is ascending or descending through the cloud layer.
@j*oono wrote:Apparently there was one recently over Perth too She_el. I wish I had seen it.
Several PerthNow readers have woken to a sight described as “out of this world” after spotting a puzzling UFO-shaped cloud in the sky.
The unusual cloud formation even had experts baffled, with the Bureau of Meteorology taking some time to investigate what the strange phenomenon may be.
Anyone fearing an alien invasion can now have their minds put at rest as experts at the Bureau of Meteorology have confirmed their original suspicions are true – the strange phenomenon sighted in Perth skies this morning was in fact a Fallstreak Cloud.
According to the bureau’s Neil Bennett, the cloud – which was sitting high above Perth Airport – contained extremely cold water particles.
As air crafts flew through the cloud, the particles in their jet exhaust caused this extremely cold water to instantly freeze.
The newly frozen ice crystals inside the cloud became a lot heavier then the cloud itself.
As a result, the heavier ice crystals fell through the cloud, leaving an usual hole – just like the one Perth locals reported seeing this morning.
A fallstreak hole is a cloud formation that gives the appearance of strange holes in the sky’s cloud layer.
The unusual sight is causing quite a storm on Twitter with many locals continuing to speculate that the cloud may be evidence of something a lot more sinister.
Mr Bennett said: “It doesn’t occur often so it’s no surprise that it’s causing quite a stir”.
would have been great to see it
