The Curiosity of Contrails

The Curiosity of Contrails             

By Steve Roark

You may not have realized it, but if  you look up on a clear day you will likely see a man-made cloud somewhere in the sky, trailing behind jet aircraft high up in the atmosphere. Contrails, short for condensation trails, are formed from the water vapor found in aircraft exhaust as a byproduct of fuel combustion. Natural clouds form from the same process of water vapor condensing in cool air as it rises, so technically contrails are clouds, just from an unnatural source.

Contrail formation is similar to what your breath does on a cold day, where a body temperature exhale full of water vapor hits cold air upon exiting your mouth and condenses into visible mini-droplets.  Only with contrails the exhale from jet engines is a toasty 1600 degrees Fahrenheit, that hits an air temperature that at cruising altitude is 30 to 60 degrees below zero, resulting in a rapid formation of ice crystals that form a bright linear cloud behind the aircraft.


As you may have observed, there’s a lot of variability in contrail formation. Some days you will see planes with no contrails, while others form contrails that evaporate a short distance behind the aircraft. But on some days the contrails last for hours and form ever expanding crisscross patterns in the sky.   Which it will be depends on what’s going on in the upper atmosphere.  If the air up there is warm enough and dry enough, the ice crystals evaporate shortly after formation. But if the air is cold and moist, then the contrails are long duration. This variability can be a weather indicator. Short or no contrail formation denotes a dry troposphere and may indicate fair weather.  Long lasting contrails indicate that the upper atmosphere is moist and rising, which it normally does with an approaching warm front, which may bring precipitation in a day or so.

In the right conditions, contrails can grow and form a cloud layer called Cirrostratus.  Besides water vapor there are other things in aircraft exhaust, carbon dioxide, hydrocarbons and such, but also a lot of tiny particles of soot and other solids.  These particles act as nuclei on which water vapor can form droplets in the condensation process.  Going from water vapor to visible droplets doesn’t happen just because it’s cold enough.  It can be well below freezing, but if there are no nuclei to form droplets onto there is no condensation.  It’s an oddity, but a critical one when it comes to cloud formation.  So, contrails under the right conditions will grow because the aircraft exhaust particles allow condensation of water vapor in the surrounding air, and so the contrail cloud endures and grows considerably larger.

Clouds of all kinds are pretty cool if you are observant, and it’s something you can do from anywhere. So let the inner child out now and then and be a cloud observer. Lying on the grass is optional, but fun to do with the kids. If you really get into clouds you can join an international organization called The Cloud Appreciation Society. A really good book on clouds is The Cloud Spotter’s Guide, by Gavin Pretor-Pinney.





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The Bad Rap of Snake Oil

The Bad Rap of Snake Oil

By Steve Roark

I have a friend who told a humorous story about being in a meeting where someone was speaking of things that he knew to be untrue, downright bovine excreta.  When he had taken all he could of it, he stood up, got up, slammed a dollar onto the table and cried out “gimme a bottle of that snake oil!” Snake oil is indeed a popular metaphor for anything being touted as true, but in reality is fraud. And those attempting to sell or convince you to accept something fraudulent are referred to as snake oil salesmen.  But snake oil started out as something that was genuinely helpful, so how did it become something derogatory? The answer lies in history.

Back in the mid-1800s over 100,000 Chinese immigrants came to the western U.S. to work on the Transcontinental Railroad.  The labor was hard, and so to relieve body aches they brought with them from China a liniment of sorts made of oil from the Chinese water snake (Enhydris chinensis).  The oil was rich in omega-3 acids which is known to reduce inflammation and joint pain.  As word got out, the desire to make and sell snake oil grew, and so a local substitute for the snake oil ingredient was sought.  Rattlesnake oil was originally used, but it had far less of the beneficial acid in it, and so was not as effective.

Snake oil label.JPG

That didn’t get in the way of making a sale however, and so the inferior American snake oil liniment was put on the market and sold. The late 1800s saw a boom in selling so called patent medicines that were advertised in newspapers and sold by traveling salesmen.  Some took the deception one step further, most notably one Clark Stanley. He made a splash at the World Exposition in Chicago in 1893 by making a show of taking live rattlesnakes, gutting them, then boiling them in water in front of an audience.  When the fat rose to the surface, it was skimmed off, bottled, and sold on the spot. He sold out as fast as he could make it, and afterwards began selling “Stanley’s Snake Oil”, and did quite well.  The problem was that the snake oil product he later sold had no snake oil in it at all.  In 1917 federal investigators revealed that all the product had in it was mineral oil, probably beef fat, red pepper, and turpentine. The connection of snake oil and fraud was pretty much established after that, and western movies emphasized it even more by making the snake oil salesmen a common character.

Snake oil made from Chinese water snakes is still obtainable, and its formulation varies. It is generally a mixture of the extracted snake oil and some sort of carrier oil or salve. It is mainly emphasized as being good for arthritis.


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The Scoop on Sweetgum

The Scoop on Sweetgum

By: Steve RoarkSweetgum2

Sweetgum (Liquidambar styraciflua) is a common tree in our area, normally found growing in low areas where the soil is moist, such as near streams or drains.  The name comes from the taste of its hardened sap that bleeds from wounds on the trunk.

 The tree is easy to identify, with leaves distinctly star-shaped and with a small-toothed edge.  The bark is gray and furrowed with flat ridges that form a diamond pattern.  The twigs are showy in the winter with corky, wing-like protrusions.  The fruit is a spiny ping pong sized ball that hangs on well into winter.

 While not favored as a timber tree here, in the south it is much more prevalent, and millions of board feet are harvested for use in furniture and cabinetry.  With proper staining it can be made to look like walnut, mahogany, or rosewood.  Early pioneers used the sap to treat sores and skin problems, as well as for a chewing gum.   During the war, Confederate army doctors used it to treat dysentery.  The gum is available from pharmacies and is considered to have expectorant, antiseptic, anti-microbial, and anti-inflammatory qualities

 Sweetgum is not used by wildlife to any great extent, but goldfinch and purple finch eat the winged seeds, as do squirrels and chipmunk

 Historically sweetgum goes back a long way.  It is mentioned in a journal kept by one of Hernando Cortez’s soldiers in 1519 which describes Aztec ceremonies that included drinking a liquid amber extracted from sweetgum trees.

 Sweetgum makes for an interesting landscape plant.  In the fall the leaves often go through shades of yellow and orange before culminating in hues of red, crimson, burgundy, and purple. During the winter you can see the pyramidal form and distinct corky twigs.  The fruit, while interesting to look at hanging in the tree, are a nuisance on the ground, where they take several seasons to break down.  If you wish to plant sweetgum, it prefers moist to occasionally wet, slightly acidic, deep soils. It can adapt readily to poor soils that are dry in summer and can grow in full to partial sun.

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Be an Astronomer for One Night

Be an Astronomer for One Night

By: Steve Roark

TN Dept. of Agriculture, Forestry DivisionOrion


The winter night sky gives you the opportunity to see a few things you may not have thought you could see.  In one small part of the sky you can easily identify a constellation, name two stars, see a sun that has a planet orbiting it, and see a Nebula.  This will be the fastest astronomy lesson you’ll ever have, so hang on.

Find yourself a dark place on a clear night and look to the southeast an hour or so after dark.  Look for three stars lined up in a row that point down towards the 7 or 8 o’clock position.  Coming off these three stars is another row of three smaller stars pointing towards the 5 o’clock position.  If you can find these stars you’re officially looking at the constellation Orion, also called “The Hunter”. The first three stars pointing to the left represent Orion’s belt, while the ones pointing to the right represent a knife hanging from his belt.

The big bluish star to the lower right of Orion’s belt is called Rigel, a sun more than 600 light years away.  Rigel is a blue-white super giant, and its name comes from an Arabic term that means “the left leg of the giant”, referring to the figure Orion.

The big reddish star to the upper left of Orion’s belt is the star Betelgeuse (pronounce “Beetle-juice”), and represents Orion’s right shoulder.  When you look at Betelgeuse (a red super-giant star) you’re looking at the largest object you’ll ever see.  It is more than 600 times the diameter of our Sun, which is only around 865,000 miles in diameter.   Betelgeuse made the news a few years ago when astronomers using the Hubble Space Telescope verified that a planet is in orbit around it.

Here’s one more thing to look for in Orion.  Find the three stars going off to the right of Orion’s belt, his knife remember.  The middle one is not really a star, it’s a nebula, specifically the Orion Nebula.  A nebula is a tremendous cloud of gas and dust where stars are being born.  The Orion Nebula is over 1000 light years from Earth, so the faint light you see started out around 1018 AD.  This is about the time the Chinese figured out you could burn coal for fuel. So, astronomy and time travel.  How cool is that?


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Bug Brain Surgery

Bug Brain Surgery

By Steve Roark

TN Dept. Agriculture, Forestry Division

Parasites do not have a positive reputation. I mean let’s face it; they live and feed on other living animals.  They are considered cheaters, degenerates, thieves, evil things.  And yet some of them do amazing amazingly complex things to earn a living, including brain surgery.

Wasp, Emerald.jpg

Let me introduce you to the Emerald cockroach wasp (Ampulex compressa), one of over 200,000 species of parasitic wasps on the planet. As the name implies, the Emerald preys on cockroaches in a very unique way.  The female wasp first finds a victim, a large fat cockroach that is 5 times larger than she is.  She ambushes the roach and they fight, tossing and tumbling about until the wasp is able to reach the cockroaches’ belly and delivers a sting, and the roach eventually goes limp.  He is temporarily paralyzed for a few minutes, giving the wasp time to position herself over the roach’s head, and very precisely (using special sensors) inserts her stinger into just the right part of the brain, and delivers a special cocktail of drugs.  Then she waits. The roach recovers from its initial belly sting, rolls onto its legs, and is perfectly capable of running away, but just stands there. It knows it should run, but all escape instincts are turned off.  The brain sting has turned the roach into a zombie with no will of its own. The female then grabs one of the roaches’ antennae, gives it a tug, and the much larger roach responds like a puppet and follows like a dog on a leash.  She leads him step by step to her burrow and parks him where she wants.  She then lays eggs underneath his belly, seals up the burrow with rocks, and leaves.  In a few days the eggs hatch and hungry larvae emerge and drill their way into the roaches’ belly and begin feeding.  They are careful not to eat vital organs that would kill the roach, feeding instead on body fluids and such.  And still the roach just stands there.  The young wasps finally pupate into adults, and like the gory scene in the movie Alien, burst out of the roaches’ body and fly off.  And only then does the zombie roach die. Gives me the shivers.

We have several parasitic wasps in our area as well, the most famous being the dirt dauber, which uses paralyzed spiders as food for their young. But are they are able to carry them to their nests instead of resorting to the zombie trick. Nature’s resourcefulness is amazing, and at times creepy.





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What Are We Missing?

What Are We Missing?

By: Steve Roark

TN Dept. of Agriculture, Forestry Divisioncreek, forest.jpg


On a cold January morning in 2007 the Washington Post conducted an experiment.  They invited Joshua Bell, one of the most famous classical violinists of our time, to play music at the Washington DC Metro Train Station. No introductions, no fanfare, simply stand on a busy walkway and play.   He did six famous pieces written by J.S. Bach on a violin worth 3.5 million dollars.

During the 45 minutes he played, around 2000 people walked by him on their way to work.   During that time only 6 adults stopped and listened for a short while.  Twenty or so laid down money that totaled $32 (Bell has sold out auditoriums where the tickets were a hundred bucks each). Several children tried to stop and listen, but were always forced to keep moving by their parents.  When he finished playing, the hum of humans bustling about returned.  One of the greatest violinist in the world playing some of the most intricate pieces of music ever written on one of the rarest violins ever made (yeah, it was a Stradivarius), and almost no one took time to notice or applaud.

The Washington Post set this up as a social experiment about perception and people’s priorities.  The question they tried to answer was: In a commonplace and busy environment, do we perceive beauty?  Do we stop to appreciate it?  An unfortunate conclusion one could draw from this is that, if the surge of modern life so engulfs us that we are deaf and blind to something as a great musician playing great music on a great instrument, what else are we missing?

We are so blessed to live in a place where wildflowers bloom along roadsides; fireflies wink a nightly light show;   the moon is still bright and glorious when it’s full; snow totally transforms a landscape; and the mountains surround us with layer upon layer of beautiful scenery.  Did you notice? I’m as guilty as any for not.  And as we become more and more “connected” to our phones and its accompanying technology, we are in danger of becoming more dis-connected to our surroundings.  And the psychology guys have shown through studies that for good mental health we need those snippets of enjoying our surroundings and “being in the moment” that nature can provide. I think that in these modern times the Biblical statement “be still and know…” is even more applicable.


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The Majestic Beech Tree

The Majestic Beech Tree

By: Steve Roark

TN Dept. Agriculture, Division of Forestry

The American Beech (Fagus grandifolia) is very common in our area and is to me one of the nobler trees in the forest.  It has never been in high demand for timber, and so many beech trees have been left to grow large and majestic.  The bark is silvery gray, smooth, and easy to identify even from a distance.

Most beech trees form large flutes where they enter the ground that act as support struts, especially on steep ground.  It gives the base of the tree a dinosaur foot (with toes) appearance.  The leaves of beech are spear shaped and 3-5 inches long.  The leaf edge is uniformly toothed, and a vein runs from the center of the leaf rib to each tooth at the edge. The veins running from the main rib are parallel to each other and form a distinct chevron pattern.

beech trunk and fluted roots.jpg

The smooth gray bark makes beech pretty easy to identify in winter, but there are other clues as well.  The winter buds are dark reddish brown, long, slim, and sharp, reminding one of pointy cigars.  The three-sided nut forms in a small burred husk and appears in the fall.  The nut is an important food source for squirrel and chipmunk, and is also used by grouse, turkey, blue jays, grosbeaks, and the titmouse.  Good beechnut crops occur about every third year.  Back in early American history when more and larger beech forests were present, the beechnut was an important food source for the now extinct passenger pigeon that once flew in such numbers as to darken the sky.  Beech likes to grow in moist rich soil on moderate to level slopes, but these were the areas first cleared for farmland and so beech tree populations aren’t what they once were

Because of its smooth bark, beech is often used for carving initials and dates on its surface, especially by boys in love.   This form of graffiti goes back a long time, for even Shakespeare mentions it in one of his plays:  “O Rosalind!  These trees shall be my books, and in their bark my thoughts I’ll character; that every eye which in this forest looks shall see thy virtue witness’d everywhere.”  Virgil, another famous writer from long ago, wrote:  “Or shall I rather the sad verse repeat which on the beech’s bark I lately writ.”  And then there’s ” D. Boone Cilled A Bar On Tree In Year 1760″.  This one was on a beech tree on Carrol Creek, in Washington County, Tennessee.  The tree fell in 1916, and the Forest Service estimated it was 365 years old.

As mentioned earlier, the wood is not in high demand, but is used for such things as crates, boxes, clothespins, paper pulp, and cross ties. As a medicinal, beech leaves have been boiled and used as a poultice for headaches and other mild pains. The beech nuts are edible, but have also been processed and used as an antioxidant.   The very young leaves have been eaten raw in a salad with other greens.



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