Larry Scheckel

QUESTION:

Why do mosquito bites itch?

ANSWER:

            It’s not the bite that itches, but our body’s reaction. The mosquito uses her piercing needle proboscis to penetrate the outer layer of skin. I use “she”, because only female mosquitoes bite. (no sexist jokes please).

            Once the straw-like proboscis gets down through the epidermis, the mosquito searches for a blood vessel in the dermis layer underneath. She secretes a bit of saliva that contains an anti-coagulant that keeps the blood flowing smoothly. She does not want her “soda straw” to clog up. When the blood sucker (no IRS jokes please) is finished with her meal, she flies happily away but leaves behind that saliva.

            Our marvelous immune system senses an invader and produces a histamine to combat the foreign intruder. The histamine gets to the site of the attack and causes the blood vessels to swell. That’s the source of the reddish bump (wheal).

            When the blood vessels expand, nearby nerves are irritated. That irritation is the source of the itching. This entire process takes time, so a person may not realize they’ve been bitten for an hour or two.

            That itching can turn out to be a good thing. It tells us that we have been bitten. Mosquitoes carry some really bad stuff. In the United States it is encephalitis and the  West Nile Virus. In more tropical climates, malaria is the big concern. The itch may be a clue to a potential cause if a person comes down with one of those maladies.

            Some people develop an immunity to mosquito bites and are not affected. On the other end of the spectrum are those that develop swelling of limbs. Benadryl, an antihistamine, is useful, as is Calamine lotion. Ice packs provide relief, same with  aloe, a cream used in many sunburn remedies. 

            Mosquitoes are most active at sunrise and sunset when the air is most calm. Those flying syringes are lightweight creatures and can’t operate when it is windy.

            One of huge obstacles to building the Panama Canal at the beginning of the 1900s was the prevalence of yellow fever and malaria in that tropical climate. The French had lost 22,000 workers in their attempt to build the Canal decades before.

            Colonel William Crawford Gorgas was appointed to solve the problem. Mosquitoes lay their eggs on the surface of standing water. When the larvae hatch, they live just below the water’s surface, breathing through a siphon in their tails. Eliminate the standing water and you eliminate the mosquito. That is just what Colonel Gorgas’s crews did; draining swamps, filling some wetlands, spraying standing pools, fumigating residences, quarantining infected individuals, and providing screened verandas as sleeping quarters. 

            By 1906, one year after the start of the eradication program, only one case of yellow fever was reported and when the construction was finished and the Panama Canal opened, in 1914, there were none.           

Email questions and comments to: lscheckel@charter.net

QUESTION:
How do airbags activate?
ANSWER:
Airbag deployment has saved thousands of lives and allowed people to survive a crash that otherwise might have resulted in serious injury or death.
An airbag is a stretchable fabric that can be tightly packed into various locations in a vehicle and can be deployed in milliseconds by filling the bag with a gas to help cushion the driver and passengers.
The most important part of the airbag is the crash sensor. A motorist wants the airbag to deploy in a crash, but not when he bumps into a car ahead while texting during a traffic jam!
The crash sensor responds to different inputs, the most important being a sudden stop, Other sensors measure wheel speed, seat occupant status, and brake pressure. Some sensors can activate seat belt locks and automatic door locks, in addition to airbag deployment.
There are two basic airbag sensors; electrical and mechanical. One common sensor is termed a “ball and tube”, in which a ball is held by a small magnet. When a collision occurs, the ball is dislodged from the magnet, rolls forward in the tube, and hits a switch that activates the airbag.
Another popular and modern airbag sensor is the MEMS accelerometer, a small integrated circuit with internal micro mechanical elements. The mechanical element moves with a rapid stop, causing a change in capacitance which is detected by the electronics on the chip. The chip activates the airbag. Most autos have some sensors inside the car, and some on the outside.
Once a sensor detects an actual crash, the next step is bag inflation. And it has to be fast, so fast that the driver’s head doesn’t smash into the steering wheel. The bag must be inflated with nitrogen gas within 55 milliseconds. A millisecond is one-thousandths of a second.
The decision to deploy an airbag in a frontal crash is made within 15 to 30 milliseconds of the start of the crash. Airbags are fully inflated within 75 milliseconds. The bag has to deploy at a speed of about 200 mph. If the deployment is too slow, the passengers risk injury from the airbag moving toward the passenger at the same time the passenger is moving toward the airbag.
Some manufacturers use an igniter pin that is driven into a sodium azide packet that produces the gas used to inflate the airbag. Then the bag has to deflate on its own once deployed. The gas escapes out tiny vent holes.
The automobile people say the airbag can hurt a person if they are out of position. That’s why they preach that seatbelts must be worn if airbags are to be effective. Airbags are placed in the steering wheel for the driver and dashboard for the front passenger. That dashboard airbag on the passenger side is larger and more expensive than the driver’s airbag, simply because it is bigger. Side doors hide airbags. Modern cars can wrap a person in a cocoon of airbags.
Deployed airbags have been known to kill kids in the front seat. Most states have rules for kids in the front seat. Those laws are based on age and weight.
Airbags have been used by spacecraft landing on Mars, the F-111 fighter/bomber, and the Army’s Blackhawk and Kiowa Warrior helicopter.
Mecedes-Benz was the first production car to install airbags. They started in 1980. A poignant milestone occurred in April, 1990. Two cars, both Chrysler LeBarons, both equipped with airbags, collided head-on at Culpeper, Virginia. The estimated combined speed was 70 mph. One car strayed over the centerline initiating the crash. One driver had a cut on his elbow and a bruised knee. The other driver had a bloody nose and minor bruises. Both walked away. The press headlined the accident as “dueling airbags”.

QUESTION:
How does lightning form?
ANSWER:
Lightning; one of nature’s most awesome, beautiful, and deadliest phenomena. Lightning is an electric current caused by a static discharge. In a thunderstorm, raindrops and frozen bits of water make contact and rub against each other and soon the clouds are filled with electric charges. It’s very similar to a person shuffling across the room in bare feet and touching a metal door knob. A tiny lightning bolt jumps from hand to door knob.
Negative charges form at the bottom of clouds and positive charges accumulate at the top of clouds. Like charges repel each other. Negative and negative charges repel. Positive and positive charges repel.
The ground beneath a cloud will become positively charged because the negative charges in the ground under the cloud are driven away or repelled by the negatively charged cloud. The term for this event is called “charging by induction”.
Now we have “negative” cloud sitting above a “positive” ground. Unlike charges attract.
Charge concentrates or builds up on anything that is sticking up, such as a tree, mountain, fishing pole, or person.
A tiny leader charge goes up from these sharpened points, and a huge charge comes down from the cloud and that is the bright lightning flash that we see. The average lightning bolt carries 30,000 amperes of current. In comparison, a typical toaster uses 10 amps. The air is heated to over 50,000 degrees Fahrenheit. The color varies from clear white to yellow orange.
Thunder is not the angels in heaven clapping and applauding, as our Mother told us kids. Thunder is the shock wave created by heating the air. The light flash we see travels at the speed of light, or 186,000 miles a second, almost instantaneously. The sound from lightning, or thunder, moves 1,100 feet a second. Light moves about a million times faster than sound. It takes sound five seconds to travel a mile. You want to know how far away the lightning is from you? Count the time between flash and thunder and divide by five to get the distance in miles.
Thunder is often heard as a rolling, slowly dissipating rumble. The sound from various portions of the long stroke reach the ear at slightly different times.
Cloud to cloud lightning is of little concern. Although a few planes have been disabled by lightning and crashed, modern aircraft are equipped with static discharge wicks that drain the charge and prevent radio interference and also drain the charge. Aircraft are frequently struck by lightning with no ill effects. Charges reside on the outside of a conductor and airplanes are very good conductors.
Obviously it is the cloud to ground lightning that is the most dangerous. Cattle under trees are killed, forest fires are started, and buildings are damaged.
In the summertime, we often see lightning on the horizon, but we not hear the thunder. We kids on the farm called it heat lightning or sheet lightning. It really is lightning from a distant thunderstorm that can be as much as 100 miles away. The lightning, aided by the refraction or bending or light in the atmosphere, can be seen from a great distance. But the thunder from that lightning travels 10 or 15 miles, at best.
Periodically we would see a tree that had been struck by lightning. The lighting strike heats the sap in the tree to steam, and the resulting explosion bursts parts of the tree into many splinters. Well, isn’t there some little sap in every family tree?
Lightning kills about 30 people every year in the United States. Most of the deaths are caused by people doing outdoor recreational activities such as fishing, camping, and playing golf. One of the safest places to be is inside a metal car or inside your house, away from the window.
Lightning is not strictly an Earth event. Lightning has been observed on Venus, Jupiter, and Saturn.

QUESTION:
How long would it take for someone to walk around the world?
ANSWER:
It is close to 25,000 miles (circumference) around the Earth. The average walking speed for most people is about 3 miles per hour. So we’re looking at 8,300 hours of walking. Let’s figure a 10 hour walking day. That puts us at 830 days of walking, or about 2.7 years.
Such a feat (no pun intended) would require about 50 million steps, many pairs of shoes, good health, determination, and stamina. It would be an epic demonstration of human endurance and courage.
But a walk around plant Earth is complicated. There is no path entirely on land that would permit a 25,000 mile continuous trek. One would have to take a boat or plane for a substantial part of the trip.
According to the Guinness Book of Records, the first verified walk around the Earth was made by Dave Kunst. It took four years, 21 million steps and 22 pairs of leather shoes for Kunst to complete his record-making 14,450-mile walk in 1974. His brother John accompanied him, but he was killed by bandits in Afghanistan. Dave Kunst completed the journey with another brother, Pete.
Kunst and his brothers hiked across Europe, North America, Asia, the Middle East, and back to Europe.
The Guinness Book of Records lists Steve Newman as the first do walk around the world solo. It took Newman four years to cross 20 countries for a distance of 15,000 miles.
Jean Beliveau, a neon sign salesman from Quebec Canada, started his walk in 1998 at age 45. He hiked 45,000 miles through 64 countries in 11 years.
George Meegan holds the record for the longest unbroken walk. From 1977 to 1983, he walked 19,000 miles from Tierra Del Fuego, the southern tip of South America to the northernmost part of Alaska. Meegan covered the entire Western Hemisphere and the most degrees in latitude ever on foot.
There are ways of getting around the Earth besides walking. Some notable circumnavigations would include the Magellan-Elcano voyage. Magellan set out from Seville, Spain in 1519 with 5 ships and 270 men. One ship, the Victoria, with 18 men returned 3 years later. Four ships were destroyed or lost and Magellan himself was killed by hostiles in the Philippines.
The first airplane circumnavigation was carried out by the United States Army Air Service in 1924. The team of fliers took 175 days to go 27,340 miles. Four Douglas built aircraft were used and three finished the journey.
One of the most remarkable trips around the globe was the nine day 1986 non-stop, and non-refueled flight by Dick Rutan and Jeana Yeager. Their composite (fiberglass, carbon fiber, Kevlar) aircraft, Voyager, had 17 fuel tanks. Their Voyager aircraft can be seen at the Smithsonian National Air and Space Museum in Washington, DC. A replica is on display at the Experimental Aircraft Association Museum at OshKosh, Wisconsin.

QUESTION:
What temperature is twice as hot as 0 degrees?
ANSWER:
Short answer: A temperature of 273 Celsius (Centigrade) is twice as hot as 0 degrees Celsius. That is a very tricky question and one that does not lead to an easy explanation.
Part of the complexity is that we typically use two temperature scales, Fahrenheit and Celsius (Centigrade). Also, the temperature can be positive or negative on both temperature scales.
Temperature has to do with how much energy there is in the air. Temperature measures the average molecule motion. That energy of motion is all gone when you get down to a temperature of -273 Celsius, which is -460 degrees Fahrenheit, stated as 460 degrees below zero. This temperature is called “absolute zero”. At absolute zero there is no movement of molecules. There is no heat.
The solution is to choose a meaningful zero point for temperature. Scientist came up with a new temperature scale called the Kelvin scale. This scale is used to calculate the temperature, pressure, and volume of gases.
The Kelvin and Celsius scales are the same, but they start at a different point. Kelvin starts at 0 degrees. Celsius starts at -273 degrees. The rule is K = C +273.
A cold winter day of 0 Celsius (32 Fahrenheit) is 273 Kelvin. A normal body temperature is 98.6 Fahrenheit, and 37 Celsius and 310 Kelvin. Do you feel a fever coming on?
How did we come up with 273 Celsius as an answer to the question posed; what is the temperature that is twice as hot as 0 Celsius? If we double 273 K (0 Celsius), we get 546 degrees Kelvin. That is twice as warm as 0 degrees Celsius. Convert that back to Celsius by subtracting 273 from the Kelvin, and we have 273 Celsius.
While that may be a scientific answer, it does not fit our everyday sense of hot and cold, and how much clothing we should wear to stay warm or how dangerous it is to work in the heat of the day.
So the question is sometimes referred to as a trick question or one that does not have a meaningful answer. Me thinks it just might be a question posed by science teachers to their students to get them to think about heat, cold, temperature, calories, and multiplying by 0 !
If you are traveling by car in the early morning hours, say around 5 AM, you can pick up CBC Radio, 990 AM on the dial, from Winnipeg, Canada. Also, CJBK 1290 AM from London, Ontario in Canada. Both stations come in loud and clear, via “skip”. The radio signals bounce off the ionosphere located high in the heavens.
Of course, our more enlightened neighbors to the North have adopted the metric system and the temperature in their weather reports are given in Celsius. The wind is given in knots, not miles per hour. So there is a neat little limerick to help us Americans “decipher” the temperature:
30 is hot
20 is nice
10 is cool,
and 0 is ice.

QUESTION:
What color is your brain?
ANSWER:
The brain has forever been referred to as gray matter. Truth be told, the brain is pinkish fleshy in color. The very center of the brain is an off-white shade. The brain is very soft tissue having the consistency of tapioca pudding.
The brain uses about 20 percent of the total oxygen intake. Oxygen is used to make glucose, which is the brain’s source of energy. If the brain’s oxygen is cut off, permanent brain damage occurs after four minutes. Hypoxia means low on oxygen and anoxia is total lack of oxygen.
A whole slew of things can go wrong with the brain. Heart attack, suffocation, drowning, high altitude, and head injury or blunt trauma can all put a damper on a healthy brain.
A stroke is caused by a disruption of blood flow to a certain part of the brain. An aneurysm happens when an artery wall in the brain is weakened. The damaged area can swell and apply undue pressure to the surrounding tissue. Tumors are growths caused by run-away cell division. Malignant, or cancerous tumors, invade surrounding tissue causing massive damage. Benign, or non-cancerous tumors, do not spread or attack other tissue, but they can apply pressure to adjacent brain tissue.
The abuse or misuse of legal and illegal drugs can damage nerve cells in the brain which leads to permanent brain damage.
Dementia is a general term that describes a wide range of brain declines, such as memory loss, demise of thinking skills, and the inability to perform everyday activities. Alzheimer’s account for about 75 percent of cases.
There are three main parts to the brain; the cortex, the limbic, and the brainstem.
The cortex handles the most complicated things, such as thinking, making decisions, recognizing sights, words, sounds, and sensations. We depend on the cortex for playing sports and music and for writing.
The limbic is involved with survival. The limbic lets us know when we need to eat, drink water, and put on a coat when we get cold. The limbic warns us of dangers and makes us aware of threats. The limbic also is where we experience pleasure and happiness.
The brainstem connects the brain to the spinal cord that runs down the backbone. The brainstem controls heart rate, breathing, and other vital organs. If the brainstem is badly damaged a person can lose consciousness and lapse into a coma. The cortex needs the brainstem to keep it alive.
The brain weights about three pounds and has a volume of the 1300 cc (cubic centimeters). Brain weight and size varies with the size of the individual.
Don’t read any further. Parental guidance is recommended!
Sometimes a medical examiner or coroner will order an autopsy of a body. The reason, of course, is to establish cause of death. As part of most autopsies, the brain is removed.
The medical examiner uses an electric saw, called a Stryker saw, to make a round cut through the top of the skull. The cap of skull bone is removed. The medical examiner employs a scalpel to cut the tissue that connects the brain stem to the spinal cord. The brain can be pulled out, stored in a solution, and is now available for further examination.
Albert Einstein’s brain was removed within a few hours of his death in April, 1955. It is well worth reading about the journey his brain took in the next 50 years.
OK, the gruesome part is done and you can start reading again!
The brain is a wonderful instrument. Our brain is who we are. Our body is just along for the ride, so to speak, and quite utilitarian. The brain is so complex, it has been referred to as one of the last frontiers of the unknown. Outer space and the deep ocean have also been put into the categories of “last frontiers”.
Each of the 100 billion neurons in the brain has about 1,000 connections to other neurons, creating a huge network of 100 trillion synapses. These synapse connections are “on” or “off”, like transistors in a mega computer.
Our brain is so magnificent and exquisite that it behooves us to take good care of it, for no other reason than it is the only one we will ever have. Realize that it is not wise to endanger our brain by drug or alcohol misuse, or failure to wear cycling helmets or wear seatbelts. And like muscles, we know we should exercise the brain by lifelong learning.

The Ask A Science Teacher book is published by Experiment Publishing, New York City. I am so very proud of this book, as it has been carefully copyedited and fact checked. The release date was December 17, 2013. It is available on Amazon.com and is in Barnes and Noble stores across the United States. Ask A Science Teacher will also be found in smaller and independent book stores. Below is a Q & A from the book.
QUESTION:
Why do we have leap year?
ANSWER:
We have a leap year every four years because the Earth does not revolve around the Sun in an even number of days. There is no reason why it should; it would be a freak accident of nature if the Earth rotated on its axis a whole number (no fractions) of times for every one full orbit around the Sun.
The Earth needs 365.25 days to go around the Sun. That extra quarter, or one-fourth, day, added up four times, means that we need to add a day to the yearly calendar every four years. That extra day, every four years, is February 29 in the Gregorian calendar that we all follow. We had leap years in 2008, and 2012, and the next ones will be 2016, 2020, and 2024.
However, it gets a bit more complicated. Technically, the Earth does not need 365.25 days, but rather 365.2422 days. (We could also say this as 365 days, 5 hours, 48 minutes, and 46 seconds). That extra day every four years overcompensates for the error.
Here’s the fix. Over a period of 400 years, the totaled errors amount to three extra days, so the calendar leaves out 3 leap days every 400 years. There are February 29ths in the 3 century years, (integer or whole number multiples of 100) that are not whole number multiples of 400.
The year 1600 was a leap year. The years 1700, 1800, 1900 were not leap years. However, the year 2000 was a leap year. The years 2100, 2200, 2300 will not be leap years.
The year 2400 will be a leap year. The year 2500 will not be a leap year, and so on.
There are a few simple steps to determine a leap year. First, the year must be evenly divisible by 4. If the year can also be evenly divided by 100, it is not a leap year, unless the year is also evenly divisible by 400, in which case it is a leap year.
If this seems complicated, and it is, just get a calendar from Barnes and Noble; they are sure to have it done properly. That’s what I plan to do in 2100!
The name ‘leap year’ is derived from the fact that a fixed date on the calendar advances one day of the week from one year to the next. However, in a leap year, the day of the week will advance two days, from March forward, (no pun intended) because of the extra day of February 29.
For example, Christmas Day in 2010 was on a Saturday, on a Sunday in 2011, on a Tuesday in 2012, and on a Wednesday in 2013. Christmas Day “leapt over” from Sunday to Tuesday in the leap year of 2012.
It is a tradition in Britain and Ireland that women may propose marriage on leap years. In Greece, marriage in a leap year is considered unlucky. In some countries, if a man refuses a marriage proposal from a woman on leap day, he is expected to pay a penalty, such as a gown or money. In other countries, if a man turns down a marriage proposal on leap day, he is expected to buy the woman 12 pairs of gloves, supposedly to hide the embarrassment of not wearing an engagement ring.

Airport runway lengths.

Our newest book, ASK A SCIENCE TEACHER, released by Experiment Publishing, contains 80 new Questions and Answers concerning science and everyday life. Below is one of the new Q & A.
QUESTION:
How do they decide how long airport runways should be?
ANSWER:
The length of airport runways depends on several factors, including the types of aircraft the airport will serve, the airplane’s itinerary, the altitude, winds, surrounding terrain, and the proximity of tall buildings and towers.
Large, heavy, aircraft need a longer runway to achieve the high speed required to give the wings lift. As for itineraries, more fuel is needed for longer flights, so a higher take off speed is used to lift the larger weight. Some fully loaded Boeing 747 planes weigh close to a million pounds.
Another factor is the elevation difference between airports near sea level, like the one in San Francisco, and those in the mountains, like Denver’s airport. The air in Denver, the “Mile High City,” is quite a bit less dense than the air in San Francisco, and so there’s comparatively less lift during takeoff in Denver. So an aircraft in Denver must reach a higher takeoff speed on the ground, requiring a longer runway to give the aircraft time to reach that higher takeoff speed. As a rule of thumb, the runway length is increased by seven percent for each 1,000 feet of elevation above sea level.
For Denver, the figuring goes like this: 1.07 to the fifth power equals 1.4. We can multiply 1.07 times itself five times and we come up with 1.4. So the runway lengths at Denver should be 40 percent greater than the airport runway lengths at San Francisco. That holds with reality: The new runway at Denver is 16,000 ft long, while the longest runway at San Francisco is 11,870 feet in length.. The required takeoff distance for the fully loaded Boeing 747-400 at sea level is 11,100 feet, and at Denver’s high altitude, a plane needs roughly 5,000 ft more runway to generate the required lift.
An additional need for a longer runway is based on air temperature. Warmer air is less dense than cold air, so warm air has less lift. Pilots refer to this as “density altitude.” Dry air is slightly more dense than moist air. Ideally, airplanes want to take off in air that is low (low altitude), cold, and dry.