Black holes


How does a black hole work?


            A black hole is what is left over when a massive star has run out of fuel and collapsed. Why does that happen?

            There are two main, competing processes that shape stars. The fusion reactions are similar to tiny hydrogen bombs going off and tend to make the star bigger. At the same time, gravity tends to crunch all solar material and make the star smaller. These two forces are balanced throughout a star’s life, which typically lasts for billions of years.

             The size of a star is determined by this balance between gravity, making it smaller, and explosive forces, making it bigger, and this balance shifts only at the end of a star’s life, when the ultimate fate of any star is determined by its mass.

What happens to a star the size of our Sun? When nearly all the hydrogen is converted to helium, gravity will dominate and the star will collapse, ignite the nuclear ashes of helium, and fuse them into carbon. The star will then expand to the size of the orbit of Mars, at which point it is a Red Giant. After a few million years, the helium will be all burned out, the Red Giant will collapse, and the sun will become a cool cinder, called a Black Dwarf. Not a glorious end for our beautiful life-giving Sun!

            When all of the star’s hydrogen is used up, the fusion reactions stop, and the star’s gravity takes over, pulling material inward and compressing the core. This compression generates heat, which eventually leads to a supernova explosion, which blasts material and radiation out into space. This debris material goes into eventually making new stars. Stars are born, live out their lifetimes, and ultimately die.

            The story is quite different for a star three or four times the mass of the sun. Once nuclear fusion is done, the collapse doesn’t stop. The star not only caves in on itself, but the atoms that make up the star collapse so there are no empty spaces. What is left is a core that is highly compressed, very massive, and very dense. Gravitation is so strong near this core that light can’t even escape. The particles within the core have collapsed and crushed themselves out of visible existence. The star disappears from view and is now a black hole.

            If we can’t see a black hole, how do we know they exist? Though they’re not visible, we can detect or hypothesize about the presence of one by studying surrounding objects. Astronomers can see material swirling around or being pulled off a nearby visible star. The mass of a black hole can be estimated by observing the motion of nearby visible stars.

The core, or nucleus, of Galaxy NGC 4261, for example, is about the same size as our solar system, but it weighs 1.2 billion times as much as our sun. Such a huge mass for such a small disk indicates the presence of a black hole. The core of this galaxy contains a black hole with huge spiral disks feeding dust and material into it.

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I continue to write a weekly science column for the Tomah Journal and 2 newspaper in Juneau County are running some columns, soon to be joined by the Prairie du Chien Courier Press. The following question came from a student in the Warrens, Wisconsin area.


Why do some chemicals explode when they are mixed? 


            All chemical explosions are rapid and violent oxidation-reduction (redox) reactions that produce huge amounts of heat and gases that expand rapidly. A redox reaction is simply a reaction in which two atoms exchange electrons. Oxidation involves loss of electrons. Reduction means a gain in electrons. All explosions are exothermic, meaning heat is given off or liberated.

            It is the speed of the reaction that makes the difference between ordinary combustion and an explosion. Consider wood that is burning in the fireplace or campfire. The same oxidation-reduction process is taking place in the burning wood as is occurring with a firecracker. However, the heat and gas released with the burning wood happens much slower, not rapidly enough to cause an explosion as in the firecracker.  Another example of a very slow redox reaction would be steel that rusts.

            Gunpowder was the first man-made explosive, invented by the Chinese in the ninth century. A combination of sulfur and charcoal was the fuel, and saltpeter (potassium nitrate) was the catalyst that provided the oxygen. Gunpowder, or black powder, is a slow reacting explosion, causing a subsonic shock wave. That’s good for propelling a bullet out of a gun barrel. Deflagration is the term used to describe the slower burning explosion.

            Nitroglycerine  was discovered in 1860s.  Nitroglycerine is unstable, so Alfred Nobel invented the safer-to-handle dynamite in 1866.  Dynamite and TNT produce fast acting explosions with a resultant supersonic shock wave. Detonation is the term used for a first acting explosion. If dynamite were to be used in a gun barrel, it would blow the gun barrel apart.

            That prefix nitro is a clue that an explosion of some kind is possible. We burn 10 percent nitromethane fuel in our radio controlled airplane engines. Nitromethane  fuel is used in some dragster race cars.

            A fertilizer bomb destroyed the Federal Building in Oklahoma City in April, 1995 with the loss of 168 lives. Timothy McVeigh used over 4,800 pounds of ammonium nitrate fertilizer and nitromethane. There’s that word nitro again.

            The worst industrial accident in the United States occurred on April 16, 1947 in the port of Texas City, Texas. The freighter SS Grandcamp, loaded with 7,700 tons of ammonium nitrate exploded at 9:17 AM. The denotation killed 581 people and injured over 5,000. The blast knocked out windows in Houston, a distance of 40 miles.

            An explosion of twice the magnitude of the Texas City disaster was the N1 rocket disaster in the Soviet Union on July 3, 1969. The Russians planned to use the N1 rocket to beat the Americans to a moon landing. A loose bolt was ingested into a fuel pump of one of the thirty engines, triggering the massive blast. After this lost,  the Soviets never mounted a serious effort to go to the moon. Email questions and comments to:



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Summer in Tomah

It’s been a busy but beautiful summer for the Scheckels in Tomah, Wisconsin. Ann and I have been doing two-a-week science presentations in Wilton, Gays Mills, Tomah, Warrens, Mauston, and environs. Many of these are part of summer library reading programs. We use a lot of volunteers from the audience and it very rewarding to see many kids excited about being a part of a science demonstration. Yes, or program is fast moving and entertaining, but we take time to explain the science principals involved. We try to express how these science activities are involved in their everyday life.
We also enjoy riding bicycle in the hill country of southern Monroe County. A group of us bike on Tuesday, Thursday, and Saturday morning to breakfast in one of several pancake nooks, such as Camp Douglas, Sparta, Wilton, Clifton, or Oakdale. Plentiful rains have ensured a lust, green countryside. The corn and soybean crops look good. Second crop hay is being baled or chopped. The roadside chicory and Queen Anne’s Lace greet us at every turn. The views from the top of the Ridge, along Highway A, are spectacular.
I have been a part of a flying club here in Tomah for many years and enjoy flying the Cessna 150 over the verdant quilt work of fields, forests, and farms. But something new; I’ve taken up learning to fly a radio controlled plane and let me tell you, it is not easy. There is an active RC club in Sparta and I have been taking a few lessons. I did successfully fly a Tower Hobby 60 inch wing trainer successfully for a few flights. But disaster struck when I flew it into the rising Sun in the east and lost track of it. The repair job is coming along nicely!
Ann and I were very happy to help Dick and Sandy celebrate their 50th wedding anniversary which is in September. Every year the Bishop in La Crosse has a Mass and dinner for all the couples in the Diocese who have their 50th in the calendar year. The commemoration was last Sunday at the Diocesan Center in south La Crosse.

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On the road

Gays Mills 7 8 14 Wilton Library  7  7  14Ann and I have been on the road the past two days, doing science demonstrations to kids as part of their summer reading program. On Monday, it was down to Wilton where the librarian, Gina Rae hired us to do a one hour general demonstration program. So we did some great demonstrations on Bernoulli’s Principal, the science tenet that explains the lift of a wing on an aircraft, how a carburetor works, and a curve ball. We continued with sound and waves demonstrations, laws of vibrating strings, how sound is produced, and how organ pipes work. About 35 kids, had great time, very receptive audience.
On Tuesday, the Gays Mills library had Ann and I do an hour program around the theme of sound and waves. Pitch and frequency, waves, talk on a laser beam, singing rod. Highlight was having the 30 students play two songs using palm pipes.
We will be going down to Gays Mills for the next 3 Tuesdays, a different science theme each week. Next week is flight, aerospace, and rocketry.

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Why is asbestos bad for a person?
Asbestos is a generic term for a group of natural occurring minerals that have been mined and used in construction, industry, and the military since the 1880’s. The big advantage to using asbestos is its resistance to heat and combustion. Asbestos has superb insulating and sound-proofing properties in addition to being quite cheap.
The biggest producers of asbestos are Russia, China, Brazil, and Canada. Asbestos is still used in many developing countries.
Asbestos has been widely used in building materials and pipe insulation, brake linings, floor tile, shingles, fireman’s clothing, mats, fiber cement, and fire-resistant bricks.
There are different types of asbestos, the most common being white asbestos (Chrysotile) found in cement products, insulation, and auto and truck brake linings. White asbestos is also resistant to salt water, hence its popularity in ship construction.
Asbestos fibers are extremely small, about one-fifth the diameter of a human hair. The fibers can easily become airborne and inhaled into the lungs, where they remain permanently.
The medical damage can be severe. Asbestosis is scarring of the lungs and restricts one’s ability to inhale. Breathing becomes more and more difficult, until the lungs become useless. Mesothelioma is cancer of the lung lining. This is the disease we hear about on television ads.
People who get asbestosis and mesothelioma generally have been exposed to the material for long periods of time and high concentrations. Shipbuilders and certain factory workers fall into this category. The symptoms may not appear until 20 to 30 years after the first exposures. No safe limit has ever been determined. The longer the period of exposure, the greater the risk.
Thousands of tons of asbestos were use in WWII ships to wrap pipes, line boilers, and cover engines. There were 4.3 million shipyard workers in the United States in World War II. Estimates are that for every thousand workers, about 14 died of mesothelioma. An unknown number died from asbestosis.
Not only can asbestos exposure cause a wide variety of cancers, but also plaques, loss of lung function, heart enlargement, and breathlessness. The combination of smoking and exposure to asbestos greatly increases the risk of developing lung cancer.
Friability is a word you’ll hear when asbestos removal is being discussed. Friability is the ability of a solid material to be reduced to smaller pieces with very little effort. Asbestos may be friable if small particle are easily dislodged, enabling them to become small enough to become airborne, and to be inhaled into the lungs.
Most all products manufactured today do not contain asbestos. Asbestos was phased out of building products the1970’s an 1980’s. Fiberglass, mineral wool, and glass wool have replaced asbestos for insulation. Some product incorporate organic fibers and wood fibers. Stone fibers are used in gaskets and friction materials. Aramid is a synthetic product widely used in brake linings and is similar to Nomex, which is used in bulletproof vests.

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Misquito bites


Why do mosquito bites itch?


            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.           

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How do air bags activate?

How do airbags activate?
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”.

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