A question that comes up with some consistency is based on the observation that some planes in the sky leave trails that persist and spread, and other planes, in the same sky, leave short-lived trails, or no trails at all.

This difference is often used as evidence of the “chemtrail” theory, which states that the longer lasting trails (or some of them) are being deliberately manipulated for some reason.  So you see helpful images like this.

These trails are called contrails.  They are not smoke from the engines, they are formed when the water in jet exhaust (and there’s a lot of it, like car exhaust on a cold day) mixes with wet cold air, and condenses out as ice crystals.  Contrails are actually a type of cirrus cloud.  When the air is wet and cold enough the trails can stay around for a long time, and sometimes spread out.

Now there are two main reasons why some planes leave trails and some do not.  One, the less common reason, is that different planes have different engines.  Some engines need different conditions to leave contrails.  Here, for example are an Airbus A340 (maiden flight: 1991) on the left, leaving contrails, and a Boeing 707 (maiden flight: 1957) not leaving contrails. Both are flying at 33,000 feet (part of a German test to study contrail formation), but the newer engines of the A340 produce more water vapor at a different temperature, and so make contrails.

So, on to the main reason why you see trails on some planes but not on others, and I’ll emphasize it, because although it’s simple, it’s also easy to miss.

The planes are at different altitudes.

Yes, it’s really that simple.  The reason that one plane makes contrails, or makes contrails that persist, and the other plane does not, is that they are in different regions of air.   For simplicity, let’s refer to these regions of air as wet air and dry air, although the differences are a bit more complex.

When the plane is in wet air, it makes a contrail.  In dry air it does not.

Surely, you might object, they would have to be miles apart?  Well, no, and that brings me to another point I fear I must emphasise:

Wet and dry air can exist within a few feet of each other.

Consider, for example, clouds:

Inside the cloud it’s wet.  Outside it’s dry.  What’s the difference between inside and outside?  It’s a few feet.

Look at the bottom of those clouds, see them extend off into the distance.  They form a layer at a specific altitude. Above that altitude there are clouds.  Below it there are no clouds.  The difference between clouds and no clouds is just a few feet.

Now those are low altitude cumulus couds.  Let’s look at high altitude clouds.

Again they are in a flat layer.  The different between being in the layer and not in the layer is just a few feet.

This layering of the air into wet and dry layers is not limited to clouds.  Seemingly clear air also contains exactly the same kind of variation in layers.  This was very neatly illustrated by the recent launch of the Solar Dynamics Observatory.  As it ascended it did not leave a contrail, until it hit a layer of wet air, when it left a contrail that lasted quite a while, and then it went into dry air again, and no more contrail

So, if a plane were flying in that middle region then it would probably  leave a persisting contrail.  If it were above or below it then it would not.

But, you may cry, the planes are at the same altitude.   Now you might even disagree with a “few feet”, and say the planes were too close for them to be in different layers.  I’d respond with:

You can’t tell how high a plane is

And you certainly can’t tell if one plane is at the same altitude as another.   These planes fly at 30,000 to 40,000 feet.   Let’s see what the visual difference is at around that altitude:

I took one image of a jet nominally at 35,000 feet. Then scaled it for 34,000 (97.1%) and 32,000 feet (91.4%). I think you’ll agree they all look pretty much the same. Especially as this is more zoomed in than you’d see with the naked eye, which would be more like:

Or, considering you generally can hardly see the wings of a plane with the naked eye, a fully realistic representation would be:

If the planes are flying lower, then it’s still similar. If the top plane was flying at 20,000 feet, then the bottom would be at 18,285 feet, still nearly 2,000 feet apart, and looking pretty much the same to the naked eye.

And that is with THE SAME PLANE, if the planes are different, it is IMPOSSIBLE for you tell the relative altitudes when they are high in the sky.  Just look at this:

Or from the ground, with the planes at 30,000 feet.

They look about the same height, right?  In fact if they were not overlapping, you’d think the JAL plane was lower, as it seems bigger, hence closer.  But actually the JAL plane (a B777) is at least 1000 feet above the DHL plane (an A300).

So, a simple question gets a simple answer:

The planes leave different trails because the planes are at different altitudes.

Popular Science, March 1943. Page 55.

The Chemtrail theory proposes that some of the persistent white trails we see in the sky behind airplanes are not actually normal contrails, but are either modified contrails, or some kind of different trail entirely. The theory states that the trails contain chemicals that do something, and that there is a huge secret operation to create these trails that has been going on since at least 1999.

I personally don’t believe in this theory. I’m an avid cloud watcher, and a private pilot (only single engine VFR), and the photos and videos of supposed “chemtrails” all look like contrails to me. So I’ve been discussing this on this site, and quite often proponents of the theory come on to join the discussion.

Unfortunately this frequently devolved into me (or other commenters) saying “show me the evidence”, and the chemtrail theorists saying “there’s lots of evidence”. Then no evidence gets presented, or if it does it’s something I addressed months ago.

The problem here for the theorists is that there seems to be no one place that simply lists all this evidence that they claim is out there. Without this central evidence repository, they just bring up the random bits of supposed evidence in a haphazard and counterproductive manner.

So I’ve decided to help, and on this page to arrange as well presented, organized and honest a representation of the best evidence for “chemtrails” that I can muster.

What I’ll do is take each claim, such as “the government has admitted it”, or “persistent trails have been observed in conditions that should not support them”, and I’ll find the five (or so) best examples of evidence for that particular claim. I’ll leave it up as a work in progress – anyone can challenge a particular piece of evidence, and anyone can suggest a new piece in the comments section.

If the evidence is something I’ve looked at before, then I’ll just add a link to the relevant article. If not, then I might add a comment, or maybe write a new article.

I’ll start out will less than five pieces of evidence, to allow suggestions to be quickly added. Also feel free to suggest new categories. My hope is that eventually this will grow to be a definitive collection of the best evidence for the chemtrail theory.

I apologize for the incomplete nature of this list. I hope to refine it as time goes by. Please feel very free to speak up with any suggestions, which should make it into the list within a few hours.

Persistent Trails were not observed before 1998 (date varies)
(Note:  not all theorists agree with this, some simply state things are different)

1. California Skywatch / Rosaline Peterson – Notes on Discovery Show Transcript, page 8, claims a review of outdoor photos says contrails changed in the late 1980s.

2. Many individual accounts of recollecting contrails not persisting.  Details vary.

3. Ideally I’d like a science book or pre 1990 book that says how long contrails last.  Lots of books say they last for hours.  Any counter evidence?

4.

5.

Persistent trails have been observed in conditions that would not support persistent contrails (Specifically RH <70% and/or temperature >-40F)

1. Chemtrail Central’s Trail Research Report

2. WatchTheSky.org Chemtrails captured on NWS Doppler Weather Data

3. Holmestead – How to detect unusual trails

4.

5.

Trails appear in grid patterns

1. William Thomas

2. Educate-Yourself

3.

4.

5.

Unidentified Spray Planes have been photographed

1. I await candidates. First check here and here.

2.

3.

4.

5.

People Get sick after Chemtrail Spraying

1. William Thomas “Emergency Rooms Jammed”

2. I think there’s a KTLA video about this, some mountain community?

3.

4.

5.

Chemical Analysis has shown the presence of unexpected chemicals in rain water.

1. KSLA Barium contrails.

2. Arizona Skywatch – Phoenix Air Particulates.

3. Clifford Carnicom – Barium, etc. Confirmed in rainwater.

4.

5.

The government has admitted spraying/bioweapon testing/geoengineering/weather modification.

1. Welsbach patent

2. British bioweapon tests

3. Owning the Weather in 2025

4. AP: Obama looks at climate engineering (Alex Jones likes this story)

5. Kucinich and HR 2977.

People don’t remember persistent contrails

1. There’s several individual claims of this, but also several claims to the contrary. Awaiting some kind of study, or even a poll. But I’ll post pretty much any link you think is good evidence of this.

2.

3.

4.

5.

The sky is a different color now

1. See above.

2.

3.

4.

5.

There are open plans to spray aerosols into the atmosphere to mitigate global warming.

1.

2.

3.

4.

5.

The government are doing similar things, and have done before, so why not this?

1. HAARP

2. I’m a little reluctant to include this category, but since it’s brought up, I might as well.

3. Fake Moon Landings (yeah yeah, it belittles your cause, I’ll remove it if you think so, speak up, either way).

4.

5.

I am very willing to add, remove, reorder, or edit the above, based on any suggestions in the comments section below.

An interesting contrail cropped up off the coast of San Clemente, Orange County, California on December 31st 2009. The curious shape led some people to think it’s a missile launch, which it does kind of look like (all taken from San Clemente)

http://sciencedude.freedomblogging.com/2009/12/31/mystery-launch-visible-off-oc/75161/

Click these for larger images:

The idea that it’s a missile launch comes from three misconceptions. Firstly that the trail is vertical – it’s not, it’s a horizontal trail, at around 32,000 feet (about six miles). It’s the same as this:

This contrail is no more vertical than the road is, and nor are the power lines at 45 degrees. Everything is horizontal – it’s the just the angle you are look at it from. All of these show horizontal contrails.

Secondly there’s the misconception of direction, that it’s flying away from the viewer, when it’s actually flying towards the viewer. This is because the “base” of the contrail seems wider than the tip. Perspective tells the brain that this mean the base is closer. But actually you can see the base has been greatly spread by the wind. Since it’s still so far away the effects of perspective are greatly diminished, meaning the actual width of the contrail is what is creating the illusion. Imagine is a plane with a 100 mile long spreading contrail were coming towards you; what would it look like? It would look exactly like this.

Thirdly there’s the idea that it goes all the way down to the ground. Now that might be true if the Earth was flat, but the Earth is round, and things go beneath the horizon eventually, no matter how high they are. A plane 200 miles away but five miles up is always below the horizon. If the horizon is raised (as it is here, with Catalina Island), then the distance is less. Here’s some math:

This diagram is not to scale, but the math is the same regardless. The solid curved line is the surface of the earth. The dot at the top is San Clemente. The little triangle is Catalina. “d” is the distance to Catalina (d=35 miles). “c” the amount of Catalina that is visible above the horizon (c=0.05 miles, really a bit more, but let’s be conservative). “a” is the altitude of the plane, (a = 6 miles). “r” is the radius of the earth (r=3963 miles).

The green wavy line is the contrail. Notice it’s at a fixed height above the surface of the earth, and is going directly towards the OC.

The point labeled (0,0) is the center of the earth. (0,0) means X=0, Y=0, where X is horizontal and Y is vertical. What we want to know is how far away the plane is, the value x. We do this with cartesian geometry, noting that the lowest visible point of the trail is at the intersection of the dotted line, which is a circle of radius (r+a), hence the equation x^2 + y^2 = (r+a)^2 and the line labeled “sight line”, which is has the equation y=x*c/d. Combining these equations to solve for x yields a quadratic equation, which we can solve with Wolfram Alpha:

intersection of (y=r+x*c/d) and (x^2+y^2 = (r+a)^2)

and with the real numbers:

intersection of (y=r+x*c/d) and (x^2+y^2 = (r+a)^2) where a=6 and d=35 and c=0.05 and r=3963

Which gives x = 212, meaning that the bottom of the contrail is around 200 miles away. So if the front of the contrail (the actual aircraft) is somewhere above and behind catalina, then that means the contrail is over 100 miles long. At 500 mph, that means it could have formed in 12-15 minutes, which seems consistent with the descriptions in the discussion above. (feel free to play around with the numbers there to see the affect of various assumptions)

Looking at the satellite image for noon on that day (12/31/2009) and the next day (1/1/2010), we see contrails in approximately the same position, and around 100 miles long, showing it’s quite possible, given the right weather.

Really what makes this odd looking is the position of the people taking the photo. Obviously the same contrail would be visible all the way up the coast, however the only people who though it was really odd were those who were lined up with it, in OC. People in LA would see a dramatic looking contrail, but more obviously just a contrail, so less worthy of writing to the newspaper about. I actually saw it myself, but was in a car, and could only get a poor cell-phone snapshot:

That was from somewhere around San Diamas, on the 210 freeway, so I’m looking South West, probably around 45 degree the the contrail, which you can only see a bit of behind the Home Depot sign. It looked quite impressive at the time. I’m sure there are other photos of it from various other angles which show it’s contrail-ness more clearly, and I’d appreciate it if someone could send me some.

[UPDATE] I found this photo of the same contrail, taken from Santa Monica:

You can see from this angle (and taken a bit earlier) it looks far less interesting, as it’s very apparent it’s just a contrail.

In the meantime, here’s a similar photo, but with the contrails going in the other direction (away from the camera):

[Update 1] Here’s another image of the New Year from another angle, from Corona del Mar, about 20 miles Northeast of San Clemente:

A photo from the Oxnard/Ventura region should put the matter to rest. Anyone?

Here’s a similar photo (of a different contrail, obviously) on the same day at the other side of the country:

Here’s some more contrails at sunset (From a very nice set of contrail photos), note how they look exactly the same as sections of the New Year contrail:

Here’s a very similar photo from Michigan:

I took this photo this morning:

It’s an interesting contrail as most trails you see are straight lines, planes generally fly directly from one place to another. This plane was flying in a south east direction. After making this left turn it made a right turn to continue roughly in the same direction as before.

I realised this would make a quite distinctive track on FlightAware, so I went inside to have a look and found this:

You can see it’s an Air Mexico 737, flight AMX665, from San Francisco (KSFO) to Mexico City (MMMX), flying at 37,000 feet and 437 knots.

I then checked the temperature aloft, San Diego is the closest:

http://www.usairnet.com/cgi-bin/Winds/Aloft.cgi?location=SAN&Submit=Get+Forecast&hour=06&course=azimuth

Looks like about -75F forcast at 37,000 feet (11,277 meters).

What about relative humidity with respect to ice? That needs to be above 100% for contrails to last, that means, approximately, a relative humidity of above 70%. Unfortunately there’s no way of knowing what the humidity is at that level and at that time, as it’s only measured twice a day at stations hundreds of miles apart: these stations:

The two closest to here (the West Side of of Los Angeles) are VBG (Vandenburg AFB, 130 Miles North West) and NKX (San Diego, 110 miles South East). Both stations send up a sounding balloon at 00Z (4PM the previous day for us) and 12Z (4AM). We have today’s 4AM sounding here for VBG and NKX

Here’s the results for around 11,000m:

72393 VBG Vandenberg Afb Observations at 12Z 03 Jan 2010

 —————————————————————————–

   PRES   HGHT   TEMP   DWPT   RELH   MIXR   DRCT   SKNT   THTA   THTE   THTV

    hPa     m      C      C      %    g/kg    deg   knot     K      K      K

—————————————————————————–

  361.0   8153  -34.9  -37.3     79   0.43    271     26  318.8  320.4  318.8

  341.4   8534  -38.2  -40.4     80   0.33    280     27  319.4  320.6  319.4

  326.6   8839  -40.9  -43.0     80   0.27    260     32  319.8  320.8  319.8

  320.0   8978  -42.1  -44.1     81   0.24    262     32  320.0  320.9  320.0

  312.2   9144  -43.4  -45.7     78   0.21    265     32  320.4  321.2  320.4

  300.0   9410  -45.5  -48.3     73   0.16    265     27  321.1  321.8  321.1

  298.2   9449  -45.8  -48.6     73   0.16    270     27  321.2  321.8  321.2

  271.0  10080  -51.1  -53.5     75   0.10    267     35  322.4  322.9  322.5

  250.0  10600  -55.3  -59.5     59   0.05    265     42  323.7  323.9  323.7

  235.7  10973  -58.1  -62.9     55   0.03    260     46  324.9  325.1  324.9

  231.0  11100  -59.1  -64.0     53   0.03    264     43  325.3  325.5  325.4

  213.7  11582  -62.9  -67.2     55   0.02    280     29  326.8  326.9  326.8

  203.4  11887  -65.3  -69.3     57   0.02    290     33  327.6  327.7  327.6

  200.0  11990  -66.1  -70.0     58   0.02    290     32  327.9  328.0  327.9

  194.0  12175  -67.3  -70.3     66   0.02    280     31  328.9  328.9  328.9

  193.4  12192  -67.3  -70.3     65   0.02    280     31  329.2  329.2  329.2

So for contrails we need below -40C and 70% relative humidity. This seems quite reasonable based on these figures, very good contrail conditions from 8839 to 10080 meters (29,000 to 33,000 feet), marginal up to 12,192 meters (40,000 feet).

It’s interesting that between 10080 and 10600 meters (33,000 and 34,776 feet) the humidity changes from 75 to 59, all within 2000 feet. That quite clearly demonstrates why you can can sometimes see two planes at apparently the same height, and they leave very different contrails.

Note that this set of readings was taken four hours before the photo, and 130 miles away, but it’s the best info we have available. Obviously the local reading will differ somewhat.

For a contrail enthusiast, I picked the wrong place to live. We hardly ever get persistent contrails here in the summer, but things have been picking up a bit as we go into fall, and today we had this:

A very nice triple set of contrails of three planes that, within about 10-15 minutes of each other flew north along the same flight path.  This was taken today, October 26th, 2009, at around 11:20AM in Santa Monica, California, looking east.

It’s actually a 180 degree panoramic shot, the trails are NOT curved, they were straight, and are just distorted because of the nature of the photo (it’s stitched together from about 10 individual images).  It looks a lot stranger in this photo than it did in real-life.

There’s a couple of interesting things about this photo.  Firstly the middle trail peters out on the right of the photo (the south).  This is probably to do with the jet changing altitude.

Secondly there’s a trail in the bottom right corner that crosses the other two at right angles.  This was from a jet that was flying in a westerly direction, probably towards Hawaii.

Note the large amount of Cirrus clouds,  that usually indicates a change in the weather due to a new weather system bringing in a moisture laden front at high altitude.  It’s often a precursor to rain.   Indeed the weather is set to change.  Today in Santa Monica, the high was 83F, tomorrow it drops suddenly to 63F.  Quite a dramatic change

Contrail season in Los Angeles is also the start of the local “Chemtrail” season, where people see these trails, and figure it’s part of some secret government spraying program – not realizing it’s only the weather.

(The following was written as a comment by “boenoid”, but I thought it was interesting enough to deserve its own post. I (Uncinus) have added the assembly line image)

For what it is worth, I am a Boeing engineer with 20 years of experience in the aerospace industry.

* There are no special tanks anywhere on our airplanes to hold chemicals to be sprayed out.
* There are no spray nozzles on the airplanes either, unless you count the emergency fuel dump nozzles on the widebody jets.
* This can be readily ascertained by simply looking through an airplane before the interior wall panels are installed. Here is a list of all the tanks which are on a jetliner:
** Fuel, potable water, waste water, engine fire suppressant (Halon + other stuff), cargo fire suppressant (just Halon), hydraulic reservoirs. On the new airplanes you will also see tank-like devices which generate nitrogen to inert the fuel tanks.
* Further, there is no room for such stuff to get installed. You would have to carry TONS of liquid to make spray trails independent of the exhaust condensation, and the only liquid we carry tons of is Jet-A fuel.
* In Everett Washington, the Seattle flight museum has a restoration center where you can go see dismantled airplanes being readied for display in the museum. The work is done almost entirely by volunteers. I assume other flight museums have similar workshops. If you can find one where you live, go to the restoration center and see the planes up close. There’s no where to hide a sprayer system where it wouldn’t be seen by maintenance crews.

* The Boeing final assembly plant is open for tours by the public, and VIPs from all over the world can get close-up tours. The airplanes are built in a staggered sequence, so that two airplanes side-by-side are usually being made for two different airlines.

* The majority of Boeing’s production is sold overseas. In fact, the company is the nation’s largest exporter.
* Thus, if a domestic airplane was modified for “chemtrail production” in the factory, it would be as easy as pie for a foreign VIP to walk over and say, “What are these fancy tanks and sprayers on the American plane which aren’t on my airplane?”
* If any airplane WAS modified for chemtrail to add chemtrail sprayers, the thousands of Boeing employees would have to know. I don’t work in Fuels, and I can identify every tank and tube in the wing area.
* If thousands of Boeing employees knew, then so would thousands of supplier employees who go through our factories, thousands of airlines employees who go through our factories, and all the FAA and NTSB and DOT people as well. Also, our airplanes and factories are inspected by the Aviation Authorities of foreign countries (like EASA from Europe) and they would also need to be in on the conspiracy.
* There would simply be too many people involved to prevent this from leaking out. If the chem trail sprayers were being added in the factory, the secret would be out.

* So what if the chemtrail sprayers were being added by an aftermarket shop?
* You’re back to the same problem. It takes hundreds of people to design, build, and install a major modification on a jetliner, and the mod shops are just as open as Boeing is. You wouldn’t be able to keep the secret.
* Further, most airlines have their planes maintained by outside suppliers, who would have to be in on the conspiracy. Those who do their own maintenance do the work in open bays that again would make it easy to view the modification.
* And you have the same problem that you need to get thousands of maintenance people, suppliers, and certification authorities in on the conspiracy. It would have leaked by now. All it takes is one guy with a cell phone camera, and the world would know.

* So what if they somehow managed to do all this stuff anyway? Now you have to realize that somebody, somewhere, has to be pumping TONS of chemtrail chemicals into these mysterious hidden tanks on the airplanes. You would need a fill valve, and a distribution system, and special trucks carrying the chemicals disguised as fuel trucks. That would take thousands more people to be in on the conspiracy.
* One giveaway would be two fuel trucks pulling up to the same jetliner – one with the fuel and one with the chemicals. Remember, we’re talking about tons of liquid here.
* It just doesn’t work – you would need independent chemical fill ports, and somebody, somewhere, would notice.
* And while we’re talking about it, remember that every jetliner pilot has to check the weight of the plane and calculate a talk off runway length and other factors. The charts are the same for every jetliner of a given type, but if there really were chemtrail sprayers, then the charts for those airplanes would have to be different to account for the tons of chemicals that might be on the airplane.

* So, I really don’t think there is any way to hide the sprayers on jetliners. Too many people would have to know, and it would be too easy to detect by passerby.

* So, what if the chemtrail chemicals are in the jet fuel? This wouldn’t require ANY visible modifications to the airplanes, and far fewer people would have to know about the conspiracy.
* This would be harder to refute, BUT, you would have to discard the “on and off” contrails as being caused by pilots turning sprayers on and off. All the fuel on the plane came from the same fuel trucks and the same fuel tanks, so the supposed chemtrail would have to be continuous from takeoff until landing. I think that would have been noticed by now.

* So to my mind, that pretty much eliminates the possibility of using jetliners to create chemtrails.
* Which means you have to be using military jets, and thousands of them, flying unnoticed back and forth on normal commercial routes. So now you have to have all the air traffic controllers in on the conspiracy as well.
* And the planes will again need special tanks for the chemicals, and special fill ports, and special sprayers, and special tanker trucks filling the chemical tanks on the planes, special non-military suppliers delivering the stuff, and you’re right back to the same issue of needing to keep thousands of people from talking.

Bottom line:
You would need a special delivery system on the airplanes.
You would need a special fill system.
You would need independent tanker trucks.
You would need a separate supply chain.
You would need thousands and thousands of people to hold their tongues, and never have even ONE person leave any incriminating evidence in a safe deposit box to be discovered after their deaths.

It ain’t happening.

Well, it looks like the cat is out the bag. The secret government has slipped up and allowed the release of a History Channel special that spills the beans on the whole Chemtrail program!

Several clips from this show are available on youtube:

The unfortunate thing about the show is that, regarding “chemtrails” it’s all theory and zero facts. Far from “validating” any chemtrail theory, the show simply repeats the theory.   What’s more it’s basically just a platform for William Thomas to repeat the same nonsense he’s been spouting for the last ten years, totally ignoring both science and common sense. For Example:

Thomas: I think most of us in North America have been wondering about these plumes criss-crossing the sky in grid patterns, rows, and the now-familiar X’s, and many of us have wondered what these trails are.

Well, actually no – most people don’t wonder what these plumes are. And for those that do, we know EXACTLY what they are. They are contrails. This has been explained time and time again, with vast amounts of scientific and historical evidence behind the explanation. What evidence does Thomas give? None. Zero. Zip. Nada.

In fact, Thomas’s entire theory is based on a simple misconception that he continues to repeat over and over, totally ignoring all evidence to the contrary. He claims that “normal” contrails vanish in a few seconds, and that “chemtrails” last for hours. This is demonstrably untrue. Contrails last for a varying amount of time based on the weather at the altitude they form. They can last for hours, and spread out to cover the sky. Any book on clouds will tell you this, and spreading contrails have been observed since 1921.

Yet Thomas manages to get his nonsense into the show:

VO: They first appear to be simply contrails, coming from high flying jet airplanes. But these trails linger in the sky for many hours, some for even an entire day, forming an artificial cloud

It seems that, like Thomas, the writers of the show chose to ignore the fact that THIS IS WHAT CONTRAILS SOMETIMES DO!!

You simply need to read the Encyclopædia Britannica article on vapour trails (contrails):

Contrail, streamer of cloud sometimes observed behind an airplane flying in clear, cold, humid air. It forms upon condensation of the water vapour produced by the combustion of fuel in the airplane engines. When the ambient relative humidity is high, the resulting ice-crystal plume may last for several hours. The trail may be distorted by the winds, and sometimes it spreads outwards to form a layer of cirrus cloud.
vapour trail. (2007). In Encyclopædia Britannica.Retrieved May 4, 2007,from Encyclopædia Britannica Online: http://www.britannica.com/eb/article-9074829

Or read “A Field Guide to the Atmosphere“, by Schaefer and Day, 1981:

“Sometimes [contrails] are ephemeral and dissipate as quickly as they form; other times they persist and grow wide enough to cover a substantial portion of the sky with a sheet of cirrostratus“ (Page 137)

Or read, all these articles on contrails. In particular the one titled “Airborne Observations of Contrail Effects on the Thermal Radiation Budget“, from 1970:

The spreading of jet contrails into extensive cirrus sheets is a familiar sight. Often, when persistent contrails exist from 25,000 to 40,000 ft, several long contrails increase in number and gradually merge into an almost solid interlaced sheet.
[....]
Contrail development and spreading begins in the morning hours with the start of heavy jet traffic and may extend from horizon to horizon as the air traffic peaks. Fig. 1 is a typical example of midmorning contrails that occured on 17 December 1969 northwest of Boulder. By midafternoon, sky conditions had developed into those shown in Fig. 2 an almost solid contrail sheet reported to average 500 m in depth.

Airborne Observations of Contrail Effects on the Thermal Radiation Budget
Peter M. Kuhn
Journal of the Atmospheric Sciences
Volume 27, Issue 6 (September 1970) pp. 937–942

The History Channel is an entertainment channel, pure and simple.    They do shows on UFOs, Psychics, Ancient Astronauts, etc, all without any real pretense of being scientifically objective.    They want an entertaining story, and if that means ignoring the facts, and interviewing on the people with the most entertaining theory.

I’m sorry that “It’s just Contrails” is a boring theory.  But it’s the only theory that actually has ANY science behind it.

Not a contrail, but a nice image:

A U.S. Air Force AC-130 Gunship aircraft executes an evasive maneuver and drops chaff and flares during a firepower demonstration at the Nevada Test and Training Range in Nevada on Sept. 14, 2007.

http://www.defenselink.mil/photos/newsphoto.aspx?newsphotoid=9540

I don’t know if you can actually see the chaff. I suspect that’s all just smoke from the flares. I suspect that when they are released simultaneously then it’s as a countermeasure for incoming missiles, and so will be very short-lived, a few seconds at most.

I’ve never actually seen a photo of modern chaff being dispensed. Is such at thing even possible to photograph? I’d be grateful if someone could point me at a photo of chaff.

Okay, it’s not actually a contrail.   But it’s a related phenomenon – a plume of hot humid air is rising from a volcano, and where it hits the cold upper air, the water vapor it contains condenses out.  Possibly into ice, but it’s hard to tell.

The brown clouds are volcanic ash.   The white round cloud is condensed water.

Here’s a wider shot:

You can see the plume must be very high.  See it has cast a shadow on the cloud layer, which has been pushed away from the volcano by the rising air.

Here’s the original image from NASA

http://eol.jsc.nasa.gov/scripts/sseop/photo.pl?mission=ISS020&roll=E&frame=9048

Continue Reading »