Technically known as “paresthesia”, this syndrome is caused by the compression of specific nerves. When you sit cross-legged, sleep with your arm above your head, or position any limb in such a way to put excess pressure on a nerve, that nerve will stop sending impulses normally. Should the pressure be great, or the duration be long, the nerve will eventually stop sending impulses altogether.  Any area the nerve services will essentially then “fall asleep”.  Think of a person standing on a garden hose. It’s hard for the water to get to the nozzle when the person’s feet get in the way. If the person’s heavy enough, or she stands on the hose for too long and the hose fully compresses, water will eventually stop flowing entirely. Once this pressure is relieved, your nerve will start to function normally again (hopefully) and you can now move your hand/legs/arms/feet. Nerves, like a well worn hose, may take some time to work properly (expand) and you may feel some tingling, “pins and needles”, during the process.

Nerve cells, for the most part, have their main bodies located in the spinal cord itself. They have what are known as “axons” that branch out to your limbs (and other parts of the body, but we will focus on the limbs) and carry nerve impulses out from the spinal cord. Together with another cellular protrusion known as a dendrite, these projections allow us to feel the world around us.

Nerve impulses require a healthy energy supply, known as the axonal transport system.  This well developed micro-vascular distribution method provides the blood flow needed to maintain the cells in good working order. If pressure is put on the correct spot, though, all the tiny arteries, veins and capillaries that supply the nerves’ nutrients become pinched off and the nerve cells begin to function abnormally. If you doubt me, hit the Ulnar nerve (the funny bone) on something and see how sudden, extreme pressure makes you scream!

Studies have shown that it doesn’t take much to cause the axonal transport system go haywire. External pressures of as little as 20 mmHg (about ½ pound per square inch) caused intermittent paresthesia due to the veins supplying the nerve having their blood flow reduced.  When you get to around 1 pound per square inch for around 2 minutes, this can cause numbness, impaired dexterity, and result in muscle weakness.

Compression isn’t the only thing that can cause limbs to fall asleep. Excessive vibration will also lead to paresthesia. Operating hand-held vibrating tools is an extremely common cause of this.  For example, dirt bike racers who need to grip handlebars tightly, while jumping frequently, experience this and commonly refer to these symptoms as “arm pump”. The process that causes these symptoms in the presence of vibration hasn’t yet been fully clarified, but these pulsations have been shown to injure the entire neuron.

Any discussion of what causes limbs to fall asleep would be remiss without talking about the common misconception that a limb falling asleep is caused by a lack of blood flow to the entire limb involved. While blood flow is blocked to the nerve specifically, if the entire limb were to be cut off from blood, severe life threatening problems would arise every time we sat “crisscross applesauce” in grade-school (see the problems with tourniquet use in the bonus Factoids below).

In medical terms, this is referred to as compartment syndrome. When blood flow is halted or reduced, life sustaining PH balance is in jeopardy. The area affected begins to become extremely acidic and cells begin to break down. Waste products and lethal levels of electrolytes, like potassium, begin to build up. Once the pressure on the limb is released, this “acid blood” is then sent back to the heart with potentially lethal consequences. Ask all those people on death row if excessive potassium is a good thing.  They might want to reconsider investing in a portfolio that backs the production of potassium chloride.  Cardiac arrest anyone!

Bonus Factoids:

• The three most common drugs used in execution by lethal injection are: Sodium Thiopental (causing anesthesia); Pancuronium Bromide (a paralyzer that causes you to stop breathing); and Potassium Chloride (causing cardiac arrest).
• The total cost for the drugs involved in lethal injection is about $86.08.
• In 2009, the only US supplier of Sodium Thiopental stopped production of the drug forcing several states to postpone some executions because they had to adjust their protocol for putting to death the accused.
• One of the most common diagnosis of chronic paresthesia is carpal tunnel syndrome.
• The use of tourniquets to stop blood loss in trauma patients was once thought to be a staple life-saving treatment. The resulting induced compartment syndrome, created by their use, has shown the risks of using them far exceed the benefits, in most cases. Once applied, a strict protocol of reperfusion (restoring blood flow) must be followed to ensure fatal metabolites will not be introduced into the bloodstream. After only 60 minutes of use of the tourniquet, the metabolites can cause damage to vital organs; after 2 hours, permanent injury to the limb affected will result; and after 6 hours of tourniquet application, amputation of the limb is the preferred treatment. So next time Timmy the neighbor skins his knee in a bicycle accident, make sure that you instill the nick-name “stubby” before you take off your belt and cinch it around his bloody leg.
• The use of tourniquets does have a place in certain situations, though.  For instance, the most common use of tourniquets today is in the military. The need for the rapid control of blood loss in a hostile environment has been shown to reduce battlefield deaths, despite the potential risk factor in using a tourniquet. Once the fight has ended, the need for such a method of bleeding control is then reconsidered.
• Carpal Tunnel Syndrome occurs more often in women than men and is most common between the ages of 30-60. It usually pops up in people who perform repetitive motion activities like typing, sewing, or playing musical instruments and gets its named from the “tunnel” that provides the pathway for the median nerve being narrowed. This creates a problem when repetitive activities cause minor swelling in the area surrounding the nerve. Pressure is then placed on the nerve and symptoms like numbness tingling and pain are the result.
• Prolonged numbness, tingling or loss of motor control, to any limb, should be evaluated by a medical professional. It could be a sign of a more serious problem like a tumor, peripheral neuropathy, or stroke.

References:

• Pathophysiology Of Nerve Compression Syndromes
• Fluid Pressure Measurements
• Paresthesia
• Death Penalty Drug Shortage
• Paresthesia Causes
• Carpel Tunnel Syndrome
• Tourniquet Use In The Civilian Setting
• Image Source

One of the main components of skin is a protein called collagen.  Skin collagen is primarily made from specialized cells called fibroblasts. After scab formation, fibroblasts that are hanging out under the surface of the skin will begin leaking into the clot just under the scab. Once the clot is sufficiently soaked with fibroblasts, these cells begin to secrete collagen and release a growth factor. The growth factor allows the fibroblasts to begin expressing their contractile proteins. This changes them from migratory cells into a cell that can contract and pull a wound tightly together.

Even though scar tissue is made from the same type of proteins as normal skin, the difference in appearance stems from the composition of the proteins. Specifically, instead of lying in a “basket weave” type structure, the proteins are pulled into alignment in one direction. Scars also do not contain sweat glands, hair follicles, or skin protecting sebaceous glands. Because of this, their texture is usually smoother and can become very itchy.

There are a few different types of scars. Their classification is usually appearance based and is a result of differing amounts of collagen over-expression, or the degranulation of certain types of cells. Specifically, the three types of scars are: Hypertrophic (a subset of which is Keloid, which is sometimes distinguished from Hypertrophic), Atrophic, and the common Stretch mark.

Hypertrophic and Keloid are the most common forms of scars.  These types of scars have a raised appearance that extends over a formerly injured area.  Keloid Scars differ from other hypertrophic scars in that they can continue to grow and become a type of benign tumor. What exactly causes this overproduction of collagen is still up for debate. What is known is that a decrease in cross-linked (basket weave) collagen and an increase in soluble collagen is present in this type of scarring. It is also known that genetic factors play a role in who is more likely to get these types of scars.

Atrophic scars, on the other hand, are scars that have a sunken appearance. They are most commonly the result of acne, chicken pocks, or infections of the skin.  They can also be caused by muscle and fat tissue below the scar area being destroyed, possibly during an inflammation process resulting from an injury, which results in the loss of the support structure under the scar, hence the sunken appearance.

Finally, there are the beauty lines attained by mothers everywhere: stretch marks, also known as “Striae Distensae”. Stretch marks form when skin gets forced to stretch faster than its capacity to expand. When this happens, a type of cell called a “mast cell” begins to degranulate, releasing molecules that help in destroying unwanted microorganisms. When too much degranulation happens, the result is the appearance of the scar that we see. This type of scarring is very common during pregnancy, teenage growth spurts, and during certain types of surgery.

Bonus Factoids:

• Wounds on early mammalian embryos will heal perfectly with no scarring or evidence of injury. Once grown, the same skin that would have once healed with no sign of injury will produce a scar if injured. The difference in embryonic growth factors, secreted by fibroblasts, are thought to be the reason for this phenomenon. The same researchers who discovered this were able to manipulate the growth factors in adults to mimic those of embryos.  Once they did this, they found that the wounds healed scar free. Using this rationale, drugs have been created that help modify growth factors and some are currently in FDA trials. Time will tell if we will soon see a scar-free world.
• Stretch marks are more common than most think. In the United States, about 90% of pregnant women, 70% of teen-age girls, and 40% of teen-age boys attain these marks of the stretched!
• Animals like star-fish regenerate limbs when they are cut off. The mechanisms involved in scaring have long been thought to be very similar to those of regeneration. Animals that regenerate can also scar in the same tissue.
• Regeneration of limbs in humans is also possible. In 1931 in Montreal Canada, a Dr. at Montreal General Hospital had the tip of his finger amputated due to infection. Within one month, his finger had regrown. Amazingly enough, this is not too uncommon. Studies in the 1970′s showed that children before the age of 10 can regrow their fingertips as long as a flap of skin isn’t surgically applied over the injury.
• Keloids are more common in pigmented ethnic groups like Hispanics, Asians and black skinned people. Approximately 16% of these population groups have them. This is about 15 times higher than in Caucasian populations.

References:

• Scar Tissue Formation
• Mechanical Insights Into Scar Tissue Formation
• Stretch Marks
• Hypertrophic And Keloid Scarring
• Atrophic Scarring
• Scar-Free Healing
• Human Regeneration
• Image Source
• Fibrolast

In 1820, a mutation occurred in a group of sweet orange trees growing on the grounds of a monastery in Bahia, Brazil. The mutation created a seedless orange that was much sweeter than the original citrus fruit. In addition, the new species had an underdeveloped twin orange growing within the same skin of each fully developed orange. From the outside, this growth looked like a human belly button, which resulted in the naming of the newly grown citrus variety: navel oranges.

Since navel oranges are seedless, farmers couldn’t simply grow another tree from the seeds to get more of the fruit. The only way to grow more navel oranges is to amputate a blossoming bud from an existing navel orange tree and unite it with another compatible fruit tree’s trunk or root. This process is called grafting and is only successful if the grafted fruit trees are compatible with one another. Since navel oranges belong to the same species as grapefruits, lemons, and limes, they can be grafted with any of these.

Two years after the discovery of the navel orange tree, Brazil sent a dozen navel orange seedlings to the United States Department of Agriculture (USDA) in Washington DC. Five years later, a woman named Eliza Tibbets planted one of these seedlings at her home in Riverside, California and it started producing fruit. Mrs. Tibbets success growing this fruit spread, and other California orange growers decided to take buds from her tree to grow as well, since the California climate proved perfect for navel oranges. This variety of navel orange became known as the Riverside Orange, but its name was later changed to the Washington Navel Orange and is the most popular type of navel orange in the world.

Bonus Factoids:

• The color orange was actually named after the orange fruit, not the other way around, as one might expect.  To read more on this, go here: The Color Orange was Named After the Fruit
• Orange is the world’s third favorite flavor (number one and two belong to chocolate and vanilla).
• An navel orange tree can grow 30 feet tall and live for well over 100 years (the exact number isn’t known yet because the variety is relatively young and, for instance, one of Eliza Tibbets’ original navel orange trees is still growing and producing fruit today).
• There is an orange tree in Europe called “Constable” that is estimated to be almost 500 years old.
• Orange trees will not bear quality fruit until the third growing season.
• The majority of people peel an orange to get at the juicy fruit on the inside. However, even though the peel of an orange lacks the sweet juiciness of the actual orange, it is edible and nutritious. The peel is primarily eaten in environments with limited resources and that require minimal waste to be generated, like on submarines. The peel is also a source of nutritional value, particularly containing vitamin C and fiber. Word to the wise: if you’re planning to eat the peel of an orange, stick to the organically grown or processed oranges that haven’t been treated with chemical pesticides and herbicides.
• If you choose not to eat the peel of an orange, there are a variety of other ways to use it including repelling the annoying slug and garden pests, producing orange oil for the purpose of adding flavor to food and drinks and adding fragrance to perfumes and aromatherapy.
• When choosing an orange of ample ripeness to eat, skin color is not a good indicator.  Make sure the orange is heavy for its size and has a good fresh odor and isn’t too squishy, nor too firm.
• In 1848, thousands of people rushed to California after gold was found. This time is known as the California Gold Rush.  The “other” California Gold Rush occurred in 1882 when California was home for over 500,000 growing citrus trees.  It was during this time that California helped establish the citrus industry.
• The sweet orange is the most commonly grown fruit tree in the world and accounts for approximately 70% of the world’s citrus production.
• Brazil leads the world in orange growth and production. Due to their ideal climates, Florida and California are the leading growers of oranges in the United States and both states sell the majority of their oranges in the U.S.
• Eighty-five percent of the world’s orange juice is produced between Brazil and Florida. Although the entire world benefits from Brazil’s production since they export 99% of their product, Florida mostly fulfills the domestic demand in the United States. To reduce storage and transportation costs and to reduce the volume used, orange juice is traded internationally in the form of frozen concentrate.
• During re-greening, ripe oranges might change from orange back to green. Even though it may look strange, re-greening does not affect nutritional quality or taste. It only affects the outer color of the orange.
• More orange trees are killed per year by lightening than any disease.
• There is no single English word that rhymes with orange.  There are however half rhymes such as “hing”, “syringe”, “sporange”, etc.  There are also proper nouns that come very close to being a perfect rhyme with it, such as “Blorenge”, which is a mountain in Wales, and “Gorringe”, which is the last name of the US Naval Commander who discovered and named Gorringe Ridge in 1875.
• Each year, the United States grows over 25 billion oranges. With that many oranges, every American can eat approximately 83 oranges every year.
• Oranges must ripen while they are on the trees. No man-made process to date can artificially ripen oranges, so they must be ripe at the time of harvesting.
• Everyone knows oranges are, well, orange. When a consumer sees a green orange, their first, and perhaps their only, thought is that the orange is not ripe. However, some oranges, even after they ripen, maintain some yellow or green spots. These colored spots are not indications of an unripe fruit, but they are still unattractive to consumers looking for their ideal orange. As a result, oranges exhibiting colors of yellow or green after they mature, go through a process called degreening, which turns the outer skin of the orange its ideal orange color so consumers will purchase them.
• Like navel oranges, Cavendish bananas (the kind you find in most grocery stores today) are also all perfect clones of one another.  You can read more on this here: Commercial Banana Plants are All Perfect Clones of One Another  
• Interestingly, the Cavendish banana was not the world’s most popular banana until the 1960s.  In fact, it was relatively unknown among the masses and even after the 1960s the former world’s most popular banana, the Gros Michel or “Big Mike”, was generally preferred by businesses and consumers alike.  The Gros Michel was preferred by businesses due to being easier to ship and they stored longer before spoiling than the Cavendish.  Consumers also liked them better for the increase in storage time as well as the fact that they are larger and sweeter and generally considered to taste better. The latter being one of the reasons it was the world’s most popular banana in the first place.  Unfortunately, the world was forced to switch bananas in the middle of the 20th century.  So what happened to force this switch?  What happened was a banana apocalypse on a global scale.  You see, the drawback of the fact that within each variety of banana nearly all the bananas are clones of one another is what will kill or harm one banana plant will do the same to all other banana plants of the same variety.  Enter the Panama disease which caused the near extinction of the Gros Michel Banana within a few year span.   Panama disease is a type of fungus that lives in the soil and to which fungicides do not work against, which is why it is such a threat.  There are a variety of strains of this fungus out there, one of which wiped out the Gros Michel Banana as a commercial product.
• Because all Navel Oranges are clones of one another, they are highly susceptible to all being wiped out on a global scale by various diseases, similar to what happened to the Gross Michael banana.
• Unfortunately, a new strain of the Panama disease, that the Cavendish banana is not resistant to, sprung up in 1992 and threatens the world’s most popular banana once again.  This time however, there has not yet been found a similar substitute banana among the other 1000 or so varieties out there.  Most varieties of banana contain giant hard seeds throughout the soft fleshy inside and generally taste nothing like the bananas we are used to eating.  A second banana apocalypse, if it happens soon before a new variety can either be genetically engineered or carefully bred, will likely see the end of the fruit as a popular commercial product.  Since this new strain of Panama disease has showed up, it has already wiped out plantations in Indonesia, Malaysia, Australia, and Taiwan and is currently spreading through Southeast Asia.  It is also thought that it is only a matter of time before it spreads through Africa and Latin America, which would be the death knell for the Cavendish as a commercial product.
• Bananas are naturally radioactive, read more on this here: The Radioactive Banana
• Bananas do not grow on trees.  Rather, they grow from a root structure that produces an above ground stem.  The plant is specifically classified as an arborescent (tree-like) perennial herb; in fact, it is the largest herbaceous flowering plant.
• Just as interesting as the banana plant being an herb is that the banana itself is a berry.
• The round dark center on the one end of Cavendish bananas is not a seed, but rather the vestige of what would be the fruit’s reproductive core, if it had one.
• Although no longer viable for mass cultivation, the Gros Michel still grows in certain areas of the world that has not been touched by the particular strain of Panama disease that wiped it out as a commercial product.  For similar reasons, the Cavendish is not likely to ever be completely wiped out, though it is thought it will eventually go the way of the Gros Michel and eventually no longer be commercially available.

Sources:

• What makes the navel on a navel orange?
• Designer Fruit
• Orange
• Navel Oranges
• Growing Texas Oranges
• Florida Oranges
• Orange
• A Delightfully Sweet Experience
• Facts About Oranges
• Fun Facts About Oranges
• Orange Fun Facts
• The Color Orange was Named After the Fruit
• Bergamot Orange
• Commercial Banana Plants are Perfect Clones of One Another
• Bananas are Naturally Radioactive
• Image Source

There are approximately 200 different types of headaches, classified in two main groups: primary and secondary. There are in the neighborhood of 42 types of primary headaches and 157 secondary headaches (unless I lost count, but should you want to verify those numbers, or just need a sleep-aid, feel free to review the 233 page article that outlines them; it’s in the references!)  ”Primary” simply means that the cause of the headache is the problem itself, an example would be a migraine. “Secondary” means the problem is something other than a headache and the headache is just a symptom of that problem. One example of this being a hemorrhagic stroke (a bleed in your brain, see What Causes Strokes). This may cause a headache, but the problem is the stroke, not the headache.

The most common types of headaches are primary ones. The various causes for most primary headaches are still being debated on the whole. What little is known about the causes is changing the way some are treated. These treatments are outlined as guidelines given to physicians by The International Headache Society (IHS, who in my opinion doesn’t spend nearly enough time studying the link between Bieber and headaches). Secondary headaches are usually the result of things like, trauma, infection, stroke, vascular problems or psychiatric causes. The treatment for these revolves around finding the problem and fixing it, at which point the headache will take care of itself.  Or, in the case of a severe stroke or the like, you might die, in which case: headache gone. There’s probably no better cure for a headache than dying.  You’re welcome IHS.

Primary headaches are subdivided by the IHS into 4 classes: migraines, tension-type, Cluster or other trigeminal autonomic celalalgias, and other types.  Tension headaches, also known as a muscle contraction headache, are the most common primary headache. Depending on which study you read, 30-90% of all adults will experience them. Despite the fact that it has the most societal impact, it’s surprisingly the least studied of all the types. The pain is usually on both sides of the head, and described as “pressing or tightening”. Rated at between mild to moderate in intensity, it doesn’t seem to increase with any type of physical activity. There is no known causal factor and, as such, treatment revolves around symptom control. Taking over the counter medications like Aspirin, Tylenol, or Ibuprofen, will usually help.

Migraines are the second most common type of primary headache, and are further subdivided into two categories: with an aura (a premonition or sensation that precedes the migraine) or without. While seemingly a mild annoyance to those who don’t experience them, migraines are actually the 19^th most debilitating disease world wide, according to the World Health Organization. About 12% of the U.S. Population will experience them. Before puberty, they affect men and women equally; however, after puberty, women are most likely to experience them at about 18% compared to 6% for men. A typical attack lasts about 4-72 hours, usually are rated as moderate to severe, and are aggravated by most any physical activity and sometimes by even small amounts of light.

Migraines with aura involve a focal neurological symptom that precedes the attack. These occur hours to days before the attack and can include a combination of symptoms including nausea, fatigue, difficulty concentrating, stiff neck, and repetitive yawning. The most common aura is a visual one that can involve sensitivity to light or blurred vision. There is no known link between a person’s aura and their migraine; however, it has been shown that blood flow is decreased to the area of pain, at or near the time of the aura. The decrease usually starts near the back and moves to the front of the head and can reach ischemic levels, which is basically the level that there is not adequate blood flow to the cells involved. In extremely rare cases, this can even damage the brain cells.

Migraines without an aura are a syndrome class that involves a headache with specific associated symptoms. It isn’t known exactly what causes this type of headache either. These were once thought to be due to a decrease in blood flow to specific areas of the brain; however, recent studies have shown that the only possible decrease in flow is to the brain-stem and that may be due to pain and not a cause itself. As vascular problems are slowly being weeded out as a cause of this type of headache, several aspects of migraine pain and how it’s transmitted throughout the brain have been recognized. Molecules like nitric oxide and calcitonin-gene-related peptide have shown to be clearly involved. Drug advances, like the use of a class of drugs known as “triptans”, are also helping doctors narrow down the possible causes of this type of headache.

Cluster headaches are a type of primary headache that is rare compared to their counterparts. Affecting only about one in a thousand people, they usually begin presenting between 20-40 years of age. Men are 3-4 times more likely to be affected by them then women. They tend to be severe in nature and cause pain around the orbits and temporal regions. These types of headaches can cause other physical symptoms as well, like infection of your conjunctiva, lacrimation, nasal congestion, sweating, and eyelid edema. Most people experiencing a cluster headache become restless and agitated during the attack, and some people are not able to even lie down, but instead pace around the house. The acute cluster attacks seem to activate the back portion of your hypothalmic grey matter. They can last for weeks to months and then go into a remission for months or years. It has been shown that about 5% of cluster headaches are inherited, and for an unlucky 10-15% of sufferers, they’ll have chronic symptoms with no remission periods.

There are a range of treatment options for cluster headaches. If the attack is not well established, the use of high concentrations of oxygen has been shown to help. Migraine medications like Imitrex, Zomig, and Maxalt can be used, along with others like lidocaine, Migranal or even caffeine. To prevent a cluster headache from returning, there are also several medications being used, for instance, calcium channel blockers like verapamil, cardizem and dilacor, as well as steroids like prednisone or solu-medrol. Some antidepressants such as lithium and seizure medications like Depakote are also used.

In the “other primary headache” category given by the IHS, there are several types of headaches with similar characteristics of the other three, but are categorized as separate. They are mostly poorly understood and the treatment for them seems to be based on trials that are not well controlled, or on individual accounts of what helps the person’s symptoms. They include a stabbing headache, cough headache, exertional headache, Pre-orgasmic and Orgasmic headache (the Pavlovian response to this affliction would be most unfortunate), hypnic headache, thunderclap headache, hemicrania continua, and a daily-persistent headache.

The other main class of headaches are Secondary headaches.  These are treated very differently than primary headaches, because the cause is usually another affliction where a headache is a symptom. Doctors commonly spend quite a bit of time in examining whether a headache falls into a secondary or primary class. It would be very unfortunate if a doctor were to diagnose someone as simply having a migraine, and it turned out the patient actually was bleeding into their brain. Whatever the cause of the pain, a definitive treatment is to solve the problem that is the source of the headache. Should the affliction take some time to solve, a doctor can choose to treat the pain with medication until a solution is found. Some common causes of a secondary headaches include; head and neck trauma, cranial or cervical vascular disorders, intracranial disorders, substance abuse or withdrawals, infections, disturbances of the bodies homeostasis, any disorder of the neck, eyes, ears, nose, sinuses, or teeth, and psychiatric disorders.

So the next time you have a headache, try not to worry about the cause of the headache, it might just make it worse. Instead, try common treatments like over the counter pain medications. Should the pain persist, go see a doctor; nobody wants to have an undiagnosed brain-bleed… or really, a diagnosed brain-bleed, but the latter is certainly superior to the former. If none of these fixes help, just be happy in the knowledge that at least you don’t have sexually mediated headaches!  Or, if you do, I’m sorry for pouring lemon juice on your paper-cut there.  It could be worse, there’s always cancer… or, you know, Fibrodysplasia ossificans progressiva, where your body’s tissues (including muscle) slowly turns to bone.  There’s no cure and doctors operating to try to help tends to make the problem worse. Further, because it’s so rare, nobody’s spending much of any money trying to find a cure.  Your sexually mediated headaches aren’t looking so bad now are they?

Bonus Factoids:

• The average cup of coffee in America has between 125-250 mg of caffeine. A can of Coke has about 34 mg of caffeine. 30% of the population can feel the effects of caffeine after only 18mg. After approximately 7 days of exposure, one can become dependent on caffeine and experience withdrawals if it’s not consumed. 100mg a day is enough to maintain this dependency and withdrawal symptoms can be avoided with as little as 25mg.
• Two migraine genes have been identified in rare migraines known as “Familial hemiplegic migraine”. They only account for about half of the patients with this disorder, so continued gene research will most likely have an impact in the future.
• Caffeine has been shown to reduce pain in migraine sufferers. Caffeine is known to be the most popular drug world-wide. Coffee is commonly thought of as the second most valuable product in the world, and up to 90% of people will consume it. 50% of people use it and the drug in it, caffeine, daily.
• Decaffeinated coffee only has to be 97.5% caffeine free according to the US Department of Agriculture. It has been shown that an 8 oz cup of Starbucks decaf has about 6.9mg of caffeine and 15.8mg in one shot of decaf espresso.
• There is what is known as “The Migraineur’s Bill of Rights” written by the American Headache Society. This 10 right document mostly focuses on receiving treatment and consideration by those who have misconceptions about the severity, or lack thereof, surrounding headaches.  These misconceptions often stem from so many people falsely claiming they have migraines when they really are just experiencing normal headaches.  Bottom line, if you see someone more or less functioning normally and they claim they are experiencing a migraine, they’re probably wrong.  If you see someone barely able to stand and possibly acting like every light source, no matter how small, is stabbing them in the brain and has the power of 10,000 suns, then you might just have a migraineur.
• Alcohol is a known cause of migraines with about 1/3 of patients reporting it as a trigger. Red wine is the most likely drink to cause a migraine. Cluster headache sufferers have a higher alcohol sensitivity at about 50-80%, and there appears to be no difference in incidence between men and women.

References:

• Headaches
• Guidelines For Headaches
• Caffiene And Migraines
• Migraineurs Bill Of Rights
• Alcohol And Migraines
• Image Source

An intracerebral bleed

Today I found out what causes a stroke.

A stroke, known in the medical field as a cerebral vascular accident (CVA) or brain attack, is more or less a “heart attack” for the brain.  Like any organ in the body, the brain needs blood to supply it with oxygen and nutrients. Should this blood flow become blocked by a clot or emboli, or the rupture of a blood vessel, the cells that occupy that area of the brain begin to die. Although every person has a different presentation, some of the most common symptoms of a stroke include trouble speaking, slurred speech, weakness or paralysis of one or both sides of the body, altered mental status, vision problems, or headache.

There are two types of strokes: Ischemic and Hemorrhagic. Ischemic strokes are the most common type, accounting for nearly 80% of all strokes. This type of stroke is caused by a blockage of an artery that leads to the brain, or smaller specific area of the brain. “Ischemia” simply means a deficiency of blood supply produced by vaso-constriction or local obstacles to the arterial flow, thus, the term “Ischemic stroke”. Blood-clots are the leading cause of these blockages; however, anything that can block the blood vessel like an air bubble, a tumor, constriction of the blood vessel, or (rarely) a foreign object, can result in an Ischemic stroke.

Treatment for ischemic strokes involves removing or reducing the blockage. If this is not done quick enough and the cells in that area of the brain die, the only option left is physical therapy to try and increase the function of the body area affected.  If doctors have the opportunity to treat the stroke in a timely manner, there are two therapies they can try. The first is to use thrombolitics (clot dissolving drugs) like Activase (Alteplase). Using a protein called “tissue plasminogen activator” (tPA) this type of drug breaks down clots allowing blood to begin flowing again.

Using this drug has its own problems. The first is that they require administration within 3 hours of the onset of symptoms. Although some studies have suggested that doctors can give the drug, under certain circumstances, within 6 hours. The second complication is that this drug will break down all the clots in your body, not just the ones in your brain. So as you would expect, the chance of unwanted bleeding is very good.

The second treatment attempts to get around the unwanted bleeding problem. It uses a type of interventional radiology (basically an image guided surgery) called Local Intra-Arterial Thrombolysis. This is basically taking a tPA and, using a wire guided delivery system, putting the drug directly on the unwanted clot. This treatment also comes with a short window of effectiveness and is best used within 4 hours of the onset of symptoms.

Hemmorhagic strokes account for the other 20% of strokes. This type also results in blood flow to an area of the brain to be interrupted. Instead of the artery being blocked, though, it bursts open and the blood leaks out and does not get transported to the cells of the brain.

Hemorhagic strokes come in two varieties: intracerebral and subarachnoid. Intracerebral simply means that an artery within the brain itself ruptures. Not only do the cells downstream of the break begin to die, but blood gets introduced into the brain and causes the area around the bleed to compress the brain tissue resulting in further damage. Subarachnoid hemorhage is also a rupture of an artery within the skull. The difference is where the bleed occurs. Instead of happening within the brain itself, it happens in the area surrounding it. The skull does not allow for the blood to escape so it puts pressure on the brain causing damage.

Doctors have two choices when it comes to treating a hemorrhagic stroke: fix it with surgery, or let it resolve on its own. In an effort to keep this article less than the short lifetime a neurosurgeon goes to school, I will not go in to all the factors that lead a doctor to decide between surgery or the “wait and see” approach. I will simply say that if surgery can be avoided, it will be. If it can’t, then hope your surgeon has steady hands or is using remote hands via a robotic aid device. No one wants shaky shakerson going at their brain with a scalpel!

Bonus Factoids:

• Medical documentation of strokes can be traced all the way back to Hippocrates. He referred to the problem as “apoplexy”, meaning “struck down by violence”. It was thought he chose this term because the victims would often suddenly become paralyzed on one side of the body or have a sudden change in their mental status. For centuries it wasn’t known what the cause of apoplexy was. Not until the 17th century was it known that an apoplexy could be caused by either a brain bleed or a blockage of the arteries supplying the brain. The classification of the two different types wasn’t categorized until 1928.
• In the United States, strokes are the third leading cause of death at approximately 140,000 per year. 795,000 people will have a stroke each year, approximately one every 40 seconds. World-wide approximately 15 million people have a stroke annually. Five million of them die and another five million are permanently disabled.
• After the age of 55, the risk of having a stroke doubles every 10 years.
• Smoking doubles your chance of having a stroke. A heart condition known as atrial fibrillation increases your chance 500%.
• High blood pressure is the most important risk factor. It is thought that it contributes to 12.7 million strokes per year world wide.
• A “transient ischemic attack” (TIA), also known as a mini-stroke, is when blood flow to the brain is interrupted for only a brief time period. The victim will have stroke-like symptoms that usually resolve within 24 hours. This affliction is usually a warning sign that a stroke will happen in the near future.
• A study done by the American Heart Association showed that if you are a woman and had heart disease, you were more likely to have a mother who had a stroke, then a father who did. The point being that there could be a gender link between the heritability of vascular disease.
• The Strokes are a band from New York, led by singer Julian Casablancas and guitarist Albert Hammond. They seem to be more popular in Britain then the United States. After hearing one of their songs, I believe it is similar to the way David Hasselhoff was big in Europe.

If you liked this article, you might also like: How a Heart Attack Works

References:

• The Brain Of An Over-Caffeinated Paramedic (the author of this article)
• Activase
• History Of Stroke
• LIT In Acute Ischemic Stroke
• What Is A Stroke
• Stroke Statistics
• Stroke Study
• Image Source

The problem with the forces generated from the gyroscopic effect on a typical bicycle is that they simply aren’t very powerful when considering the physics involved in having the majority of the center of mass of the bike at the top (with you on it). You are basically forming an inverted pendulum, which is much harder to balance than the other way around.

To illustrate how much force is needed here, have a person get on a bike that is completely still. Now try and hold the bike and person centered by simply holding on around the axle of one of the tires. To compare this force with the amount generated from gyroscopic effects, take a detached bike tire with pegs on the sides and hang on to them. Now have someone spin the tire really fast; once it’s spinning, try to lean the tire one way or the other. You’ll feel the gyroscopic effects, but you should be able to do it somewhat easily as the force you’ll feel here is likely only a few kilograms or 5-10 pounds (though it might feel like more with your arms outstretched and straight in front of you). In the previous case, with the person sitting on the bike, unless they were extremely light or you are Hercules, I’m guessing you couldn’t even come close to keeping them balanced, particularly if your arms are outstretched fully.

If that didn’t convince you, let’s look at the math (an example done by Dr. Hugh Hunt of Cambridge University):

So the gyroscopic effect on a bicycle, even at 12 mph, is practically nothing in terms of what would be required to keep you upright. So how are you not falling over every two seconds on your bicycle?

Partially this is due simply to your ability to balance.  However, you’ve probably noticed it’s hard to stay balanced on a bike when at a stand still.  When you start to go really slowly, you’ll notice you naturally make large steering corrections to keep yourself balanced.  This, in fact, is the primary thing that is actually keeping you upright on a bicycle at any speed, namely corrective steering. As you feel an imbalance in one direction, it will cause you to steer the bike in that direction to compensate, the resulting centripetal force ends up balancing you back out, assuming your adjustment was the proper amount of turn given your speed and other such factors. If you over turned, then you’ll have to make another correction to compensate for the imbalance created from your over correcting.  The faster you go, the smaller the correction that is needed to keep you balanced.

In the beginning, these corrective motions tend to be relatively large and often with you overcompensating, because your body is still learning to ride a bike. This is why you tend to be a bit wobbly and wreck a lot when you are first learning. Over time, these corrections will get smaller and smaller and more accurate until you don’t really notice you are doing them at all while you ride a bike above super slow speeds (obviously you’ll still notice them when barely moving on your bike and the like, as pointed out above).

Bonus Factoids:

• Many people think that if you took two tires and spun them in opposite directions, that you’d have the same gyroscopic effect as if they were spinning in the same direction. In fact, what will happen is that, if the wheels were spun in opposite directions, the two would cancel each other out, in terms of gyroscopic effect. This fact has been used to demonstrate to people that they can ride a bike with no problems without the gyroscopic effect by mounting extra wheels raised slightly off the ground which counter rotate the actual tires.
• The farther forward the center of mass for the bike + person riding the bike, the less front wheel movement that will be needed to maintain balance. This is probably most noticeable on certain custom motor cycles where the front wheel sticks well out from the bike.
• Another less known factor in a bike’s ride-ability is something called “trail”. Simply put, this is a measure of how much the distance from the front wheel’s point touches the ground trails the steering axis’ contact point, which is where the entire steering mechanism (fork, handlebars, front wheel, etc) pivots. A longer trail will make a bike feel much more stable than a shorter one. However, if the trail is too long, the bike will feel difficult to steer. Bikes with too little trail, or even negative trail, will feel inherently unstable; though, due to corrective steering, you can still ride them. Due to the steering issue with the increased trail, mountain bikes and touring bikes typically have much less trail than street bikes. In the case of mountain bikes, this allows for more “agility” on the bike to help compensate for rough terrain. In the case of touring bikes, this helps compensate for the fact that you’ll probably be packing along quite a bit of baggage with you and thus, extra weight low to the ground. This is why touring bikes will often feel unstable if you don’t have that baggage added on and low to the ground.
• While gyroscopic and trail forces aren’t nearly sufficient to keep you balanced on a bike, they are typically sufficient to keep a riderless bike going straight until it slows to a certain point, which varies from bike to bike based on wheel size and trail.
• Something called a “gyrobike” is currently in development to help people learn to ride bikes. This bike has an internal flywheel that provides a significant increase in gyroscopic effect. The inventors of this bike then hope that one could be developed where the gyroscopic effect would be sufficient to keep the bike mostly balanced even with a rider, while still not being too cumbersome a bike in terms of weight and the like.
• Another place you’ll see this somewhat subconscious “auto-correcting” phenomenon pop up is when you are trying to stand in one place on one foot. When doing so, you have to carefully balance yourself to keep from falling over. As soon as you start hopping though, most people have little difficulty keeping themselves balanced. This is because, when you hop, you not only somewhat naturally generate corrective movements, but you will also have your foot land around where it needs to be to keep yourself balanced.

Sources:

• A Bike With Reverse Spinning Wheel
• Gyroscopic Forces
• Bicycle Wheel
• Bicycle and Motorcycle Dynamics

The reality is that the asteroids in asteroid fields are incredibly far apart and most of the objects in these fields are very tiny. There are generally hundreds of thousands of miles between these objects and most of them are no bigger than a tennis ball (called meteoroids, with the cutoff for being called an asteroid at around 164 feet or 50 meters on a side).

In fact, if you added up the mass of all the asteroids in our solar system’s asteroid belt, it’s a mere 4% of the mass of our moon with about 1/3 of that total mass coming from one asteroid, Ceres, and about 1/2 of the total mass from just four asteroids, Ceres, Vesta, Pallas, and Hygiea.

So that’s our asteroid belt. What about others? Could there be an asteroid belt out there that would be dangerous to fly through? It’s a big universe, so it’s entirely possible that there exists such fields at any given moment in time somewhere in the universe, but it would be very unlikely that you’d encounter it, even if you could travel anywhere you wanted in the universe. The reason being that even if the asteroid belt is initially packed with debris that are colliding everywhere and basically is like what is depicted by Hollywood, this would quickly (on a galactic time scale) sort itself out with most of the mass being ejected from the belt, due to these collisions. Eventually, the system would stabilize itself to something like what our asteroid belt is. So you’d need to find a system that was just forming and even then you’d likely see vast distances between the objects in the fields in such a system.

It’s estimated that our asteroid belt once contained about 1000 times the mass it currently contains. However, within about one million years of its formation, it was down to somewhere in the vicinity of the stabilized amount we see today. Once this system was stabilized with almost no collisions, the asteroids simply travel in their respective orbits with the field itself neither increasing nor decreasing in mass significantly since that initial stabilization period.

So how many collisions actually occur in our solar system’s asteroid belt? Of the asteroids above about 6 miles wide, it’s expected they’ll encounter about one collision of some sort every 10 million years. While that’s certainly a lot of collisions on a galactic time scale, it would have made Han Solo’s daring flight through the Hoth system’s asteroid field a bit less dramatic if depicted accurately…

In case you’re wondering, the odds of successfully navigating an asteroid field isn’t “approximately 3,720 to 1!” The actual odds would entirely depend on what asteroid field you were talking about and a variety of other factors. But for reference, NASA estimates the odds of one of their probes traveling through our asteroid field actually hitting an asteroid to be about one in a billion.

Bonus Factoids:

• To date, 12 probes have traveled through the asteroid field: Pioneer 10; Pioneer 11; Voyagers 1 and 2; Ulysses; Galileo; NEAR, Hayabusa, Cassini; Stardust; New Horizons; and Roesseta. None has encountered a problem due to asteroids or debris and several of them didn’t spot any asteroids whatsoever while they passed through. It should also be noted that of some of those that did spot asteroids did so because they were specifically aimed such as part of their mission.
• NASA recently launched a new probe aimed at being the first to encounter two asteroids in our asteroid field. This Dawn spacecraft is set to look at Vesta and Ceres and study them in detail. If it happens to still be functional afterward, they plan on pointing it at other asteroids to study them as well.
• The largest known asteroid in our solar system’s asteroid field is Ceres, which is around 650 miles in diameter and is now sometimes classified as a dwarf planet. The runner up is Pallas, which is about 360 miles in diameter.
• Ceres was discovered by Giuseppe Piazzi in 1801. Once it was realized that it was neither a comet nor a planet, Sir William Herschel named it an asteroid, a word he made up. The word itself means “star-rock” or “star-planet” (aster-oid). Sir William Herschel was also the astronomer who discovered Uranus.
• To date about 280,000+ asteroids have been found in our solar system with that number continuing to rise rapidly. Of those 280,000 only about 200 are bigger than about 60 miles in diameter (about 100km). It’s estimated that there are around 1-2 million asteroids in our solar system.
• The vast majority of asteroids seem to be made of mostly carbon (3/4, called C-type); the vast majority of the rest seem to be made of iron and nickel (M-type) with some are composed of silicates (S-type).

Sources:

• Asteroid Belt
• Kuiper Belt and Oort Cloud
• Hoth Asteroid Feild
• Asteroids In Fiction
• The Asteroid Belt
• Image Source

Known as Hansen’s Disease, leprosy is caused by a type of bacteria (mycobacterium leprae) that multiplies very slowly. Its incubation period can last up to 20 years and it mainly affects the skin and peripheral nerves. Contrary to the social stigma, leprosy is not highly contagious, and does not cause body parts to fall off. In fact, 95% of the world’s population is naturally immune to the disease and, once diagnosed, a person is easily cured.

Transmission from human to human is through respiratory droplets. It’s also possible get the bacteria from armadillo and other non-human primates. Leprosy, left untreated, causes damage to the nerves, limbs, skin and eyes. This damage gives the patient decreased feeling in the areas affected. The decreased feeling can leave the patient unaware that they have injured themselves and they can get secondary infections. These infections result in the loss of body tissues. Further, the fingers and toes can become shortened and deformed due to cartilage being absorbed back into the body.

Named after Gerhard Henrik Amrmaur Hansen, who was the physician that discovered the bacterium that was the cause of leprosy, Hansen’s disease presents itself differently depending on how a person’s immune system responds. This presentation has made it necessary to classify patients so they can be better treated, based on the progression of their disease. There are two different classification systems in use globally.

The first is the Ridley-Jopling system. This system has 5 categories that describe the patient’s presentation. A person will usually progress through each category as their disease evolves and is treated. This system is used mainly as the basis for clinical studies of leprosy and is the preferred method when assessing treatment needs and risk of complications. The least serious (as evidenced by a person’s resistance to the bacteria) is Tuberculoid leprosy, followed by: Borderline Tuberculoid Leprosy, then Mid-borderline Leprosy, and Borderline Lepromatous Leprosy. The most serious form is the latter Lepromatous leprosy.

The second classification system is easier understood and is used by the World Health Organization (WHO). It classifies leprosy into two different categories defined by the number of skin lesions and the presence of visible bacilli on a skin smear. They are Paucibacillary Leprosy and Multibacillary Leprosy. Paucibacillary simply meaning very few bacilli. Mutlibacillary means more than 6 bacilli present on a skin smear. The most serious of the three classifications of leprosy, in the Ridley-Jopling system, usually fall under the Multibacillary classification. Because this WHO endorsed system is easier and requires no special laboratory equipment, it makes it much more useful to those underdeveloped countries that do not have access to more advanced medical care.

The symptoms of someone with leprosy can be wide ranging. They can start out as mild and progress into presentations that are the subject of misconceptions and folklore. The hallmark signs of leprosy are hypesthesia (an abnormally weak sense of pain, cold, heat, or touch), skin lesions, and peripheral neuropathy.

The first indications someone has leprosy are usually have to do with the skin. Things like painless skin patches (lesions) that are not itchy begin popping up. They tend to be circular with a dry scaly center. These usually first present themselves on the buttocks, face, and the surfaces of limbs. This is because the bacteria prefer cooler zones of the body. In fact, the organisms involved grow best at 80-86 degrees Fahrenheit.

As the disease progresses, the skin’s features like sweat glands and hair follicles are destroyed. Further, the nerves become enlarged and can become quite painful. The patient loses their ability to “feel” and they can injure themselves easily. These injuries lead to muscle atrophy, weakness, and infections. This can cause “foot drop” or clawed hands. Ulcers can also form on the hands and feet.

As the face becomes involved, a person can begin to sound hoarse, loose their eyebrows, and eyelashes. Their nasal cavities may collapse because of the breakdown in the septum. When the eyes become involved in the process, the person can get glaucoma or keratitis. The facial skin can also become thickened and corrugated. Basically, all the horror stories you’ve heard about in the Bible!

“Worry not!”… said the organ donor to the leper! Most people are naturally immune to the disease. Those that are not are easily cured once the disease is diagnosed. In 1991, WHO passed a resolution that would eliminate leprosy as a problem by the year 2000 (the definition of a problem meaning less than 1 case per 10,000 people). Because of the advances in drug treatments and the use of multi-drug therapies, WHO did accomplish their goal. In 1995, they began offering free therapies to any patient in the world who contracted the disease.

Unfortunately, approximately 249,000 people are newly diagnosed with the disease each year mainly in Africa and Asia.  Approximately 150 new cases are reported in the US every year, but don’t go to pieces over it (pun intended)! There have been no known resistant strains of the bacteria to anti-leprosy treatments when a multi-drug therapy is used. A person is also not contagious after a few weeks of the treatment. This, combined with many surgical options that decrease a person’s deterioration and increase their nerve function, give leper colonies everywhere something to party over.

Bonus Factoids:

• The word leprosy comes from the ancient Greek word Λέπρα [léprā], meaning “a disease that makes the skin scaly”.
• The first known written mention of leprosy is dated at 600 BC. Throughout history, those infected with this disease have typically become outcasts of their families and communities. Even though there is a cure for leprosy and the misconceptions about its transmission have been shown to be false, the stigma is still very strong. In India, for instance, there are currently over 1,000 leper colonies.
• The first proven case of a human having suffered from leprosy was dated at between 1-50 C.E.  DNA from the remains of a man discovered in a burial cave were tested by Prof. Mark Spigelman and Prof. Charles Greenblatt of the Sanford F. Kuvin Center for the Study of Infectious and Tropical Diseases at the Hebrew University of Jerusalem. The remains showed that the man had DNA consistent with both Leprosy and Tuberculosis.
• Located in the Hinnom Valley, the burial cave in which the unfortunate person was found, was a part of what is known as the “Field of Blood” mentioned in the Bible: Matthew 27:3-8 and Acts 1:19.
• To date, the relapse rate following completion of multidrug therapy has been only 1% for both types of leprosy.
• Globally, the number of registered people with leprosy at the beginning of 2011 was 192,246. 228,474 new cases were detected during 2010 .
• Quick leper joke; What’s the difference between a leper and a tree? A tree has limbs!!
• Second quick leper joke; What do you do when a female leper bats her eyes at you? Catch them and yell “you’re out!!”

References:

• Leprosy
• Hansens Disease
• CDC Infectious Diseases
• Leprosy In India
• Facts About Leprosy
• Medscape
• Oldest Leper
• Image Source

During the period when the Earth is furthest from the sun (aphelion), the average temperature of the entire planet is about 4°F (2.3°C) higher than when it is closest to the sun (perihelion). On average, the intensity of sunlight falling on Earth during aphelion is about 7% less than during perihelion. Despite this, the Earth ends up being warmer during the period in which it is furthest away from the sun.

So what’s going on here? During the winter months, for the Northern Hemisphere, the overall temperature of the Southern Hemisphere, where it is summer, doesn’t change as much as the other way around. This is because a much larger portion of the Southern Hemisphere, compared to the Northern Hemisphere, is made up of water and water has a significantly greater heat capacity than land. On a similar vein then, during the summer for the Southern Hemisphere, the overall average temperature of the Southern Hemisphere doesn’t increase as much as the Northern Hemisphere does during its summer, for this same reason.

So the “tl;dr” version is: there is a lot more land in the Northern Hemisphere than the Southern Hemisphere; this land heats up much faster than water and water cools down much slower than land. So even though there is less intensity of sunlight during the summer in the Northern Hemisphere, the Earth’s average temperature is higher at this time when it’s furthest from the sun.

As you might have guessed then or already known, the seasons are not caused by the distance the Earth is from the sun, but rather are caused completely by the fact that the Earth is tilted on its axis 23.5°. This is why when it’s summer in the Northern Hemisphere, it’s winter in the Southern Hemisphere, and vice-verse. Without this tilt, there would be no seasons and the weather from day to day across the globe would be relatively uniform. In this case, there would only be a very slight variation in temperature as the Earth got closer or further away from the Sun, but for the most part, everything weather-wise would stay the same year round.

Bonus Factoids:

• The Earth orbits the sun at a speed of about 18.4 miles per second or about 66,600 mph.
• The energy required to stop the Earth orbiting the sun then is about 2.6478 × 10³³ joules or 7.3551 × 10²⁹ watt hours or 6.3285*10¹⁷ megatons of TNT. For reference, the largest nuclear explosion ever detonated (the Tsar Bomba by the Soviet Union) “only” produced 50 megatons of TNT worth of energy. So it would take about 12,657,000,000,000,000 of those nuclear bombs detonated at the correct location to stop the Earth from orbiting the sun.
• Along with orbiting around the sun at 66,600 mph, the Earth is also rotating at its axis at about 1,070 miles per hour. So you are simultaneously hurtling around the sun at 66,600 mph while sitting on a rock that is spinning at 1,070 mph. On top of that, our whole solar system is rocketing through space around the center of the Milky Way at around 559,234 mph. On top of that, our galaxy is hurtling through space at around 671,080 mph, with respect to our local group of galaxies. On top of that, for all we know, our entire Universe is hurtling through some unknown medium at some other ridiculous speed.
• It takes approximately 225 million Earth years for our solar system to make one trip around the Milky Way.
• The Earth is about 28,000 light years from the center of the Milky Way, on the outer rim. Most all the mass in the Milky Way is much closer in than we are; this is good because, if the density was the same out here as it is closer to the center, the increase in cosmic radiation would kill us all.
• All planets in our solar system travel around the sun in elliptical orbits. The distance to the sun for the Earth varies by about 1.7%. We are closest to the sun in January (perihelion) at about 91.1 million miles (146.6 million km). We are furthest from the sun in July (aphelion) at around 94.8 million miles (152.6 million kilometers). The average distance from the sun to the Earth is known as 1 Astronomical Unit, (1 AU or about 93 million miles).
• Summers in the Northern Hemisphere last 2 to 3 days longer than summers in the Southern Hemisphere. The reason why is that the Earth moves more slowly at aphelion than at perihelion.
• The date of the period where the Earth is furthest away from the sun is called Summer Solstice. The date at which the Earth is closest to the sun, is called Winter Solstice. Summer Solstice happens on June 21/22. Winter Solstice happens on December 21/22.
• In between these two points, there is a point in time where the Sun will appear to rise and set along the equator, so that the length of night and day is almost exactly equal everywhere on the planet. These two points are called the vernal equinox (March 20/21) and autumnal equinox (September 22/23).
• The average temperature of the Earth year round is around 61°F (16.1°C). The average coldest temperature on the Earth, in Antarctica, is around -60°F or -51.1°C and the average of the hottest part of the Earth, in the Sahara Desert, is around 130°F (54.4°C).
• The hottest temperature ever recorded on Earth was 136°F (57.77 °C) in El Azizia, Libya on the edge of the Sahara Desert. The second hottest, 134°F (56.6°C), was recorded in Death Valley, California in the Mojave Desert way back in 1913.
• The coldest temperature on the Earth was recorded at Vostok, Antarctica on July 31, 1983 at -128.6°F (-89.22°C).
• Unlike the Earth, which is only shifted about 23.5° on its axis, Uranus’ spins almost perpendicular to the sun. Interestingly, despite this fact, Uranus is hotter at its equator than at the poles. The reason why this is the case is not currently known.

Sources:

• The Distant Sun
• Earth
• Seasons
• The Tilting of the Earth: Shaping Our Seasons and Climates
• Earth Speeds
• Tsar Bomba
• Image Source

It has been observed since the 4^th century BC that geckos have the ability to climb walls, hang upside down, and apparently “stick” to anything. Aristotle was the first known to have commented on the phenomenon, stating gecko’s have the ability to “run up and down a tree in any way, even with the head downwards” It wasn’t until recently that it was discovered what gave them this spider-man-like ability.

Gecko’s have millions of tiny hairs on their toes called setae (“setae” being Latin for “bristle”). All combined, these hair-like tissues give a washboard type appearance to a gecko’s toes. Each one of these seta have thousands of thinner hair-like structures that have flat caps at the ends called spatulae (yes the same meaning as the thing that flips our pancakes).  These caps called “spatulae”  use what is called “van der Waals” force to allow the gecko’s feet to adhere to objects.

More specifically, all of these seta and spatulae combined give the gecko’s feet an extremely large surface area, compared to its size. This surface area allows the gecko to take advantage of attraction caused by van der Waals force. Van der Waals force, simply stated, is the combined attractive forces between molecules (for more detail, see the Bonus Factoids below).  Normally, the force between molecules is too minute to matter; however, given the light weight nature of a gecko (approximately 2.5 ounces) and the extreme number of spatulae (which are about the size of a bacterium), the combined force allows the gecko to “stick” to almost anything.  This surface area is so great that it has been shown if a mature gecko were to have all of their setea in contact with a surface at one time, it could potentially support up to 290 lbs.

Interestingly, a study published in the Journal of the Royal Society Interface in the summer of 2011 has shown that geckos leave footprints. Specifically, they leave a Phospolipid residue. Phospolipids are a type of lipid (molecule that forms fats and waxes) that can form with 2 layers. These layers allow it to both attract water on one side and repel it on the other. This is why they are able to form things like cell membranes. This study suggests that there might be more going on with a gecko’s ability then we currently realize and it is thought by its publishers that these phospholipids might also play a role in a gecko’s sticky talent.

While the discovery of phospholipids in the gecko’s footprint brings a new factor to the equation, the ancillary evidence that a gecko cannot “stick” to Teflon is a strong indication that van der Waals force is the main mediator in their abilities.  Teflon (Polytetrafluoroethylene) is mainly carbon and fluorine. Fluorine itself is highly electronegative, meaning it really really likes to attract electrons to itself. Because of this, it tends to mitigate what is known as the “London dispersion force”. This force is thought to usually be the dominate player in the van der Waals force. A gecko, who is dependent on the sum total of all of the factors of van der Waals force, would find it extremely difficult to stick to anything that eliminates its ability to utilize the force. As such, geckos cannot “stick” to Teflon.

Bonus Factoids:

• Named after Hohannes Diderik van der Waals, the van der Waals force is the combined force of atoms, molecules, and other intermolecular forces that are caused by correlations in the fluctuating polarizations of nearby particles. In English, that means when particles of a positive or negative charge are in close proximity, they can have an effect on the polarization (whether something is positive or negative) of nearby particles. These intermolecular forces have several different characteristics like orientation, induction, and dispersion.
• There are currently over 1000 known species of gecko. They range in size from ¾ of an inch to 14 inches long. The largest by mass is The New Caledonian giant gecko, the largest by length is the Tokay at approximately 14 inches.
• Geckos are able to detach their tail leaving it behind should a predator grab them by the tail. Some geckos are also able to shed their entire skin.
• Geckos are the only lizards that have a “voice”. They can create different sounds that help attract potential mates.
• Most geckos lack a moveable eyelid. Instead, they use their tongue to help keep their eyes clean and moisturized.
• The Geico gecko was born from the common mispronunciation of the name Geico. So many people kept pronouncing it gecko that Geico’s add agency began to brainstorm about the possibility. Given that it had been shown animals create a strong connection with people in advertisements, the Martin Ad Agency began using the gecko in commercials in 1999. Since that time, the Geico gecko has become one of the most popular advertising personalities in the United States. In 2005, it was voted as America’s favorite advertising icon.

References:

• The Mystery Of Geckos Sticky Feet
• Geckos Footprint
• Gecko Setae
• Van Der Waals Forces
• Electronegativity
• The Physics Of Geckos
• Gecko Facts
• Geckos By Encyclopedia
• The Geico Gecko
• Image Source