Quiz Question

One of a continuing series

science-liquidoxygen

Photo from Wikipedia

Everybody knows that liquid oxygen is very cold and also that it is a powerful oxidizing agent. There is another property of liquid oxygen that is not as well known.

What amazing property does liquid oxygen possess?

Post your answer as a comment below.

Update

Nobody posted the obvious answer to this week’s Quiz Question. The answer to what is liquid oxygen’s amazing property is that it is paramagnetic. You can pick it up with a magnet. Who would have thought?

Quiz Question

One of a continuing series

This one will be trivial to most. Puzzling to some.

transmission

So, I have this special glass. See the illustration above. Disregard the colors. I put those in for interest. Color doesn’t have anything to do with the Quiz Question.

Light enters the pane of glass from the right. Only half of it emerges from the other side. Due to the index of refraction of the glass and the surrounding medium being the same, there is no surface reflection. Half of the light entering the pane is absorbed, and only half comes out the other side.

If I double the thickness of the pane, how much light comes out the other side? Post your answer in the comments section below.

Quiz Question

One of a continuing series

science-motorbattery

This Quiz Question requires understanding of some very basic physics. You have to figure out what this basic understanding is in order to come up with the answer.

Look at the diagram. Here we have the proverbial frictionless machine/assembly. It moves left and right without resistance. On the right side of the platform is an electric battery. On the left side is a flywheel driven by a motor. The motor is connected to the battery by an electric cable. Electric power from the battery will drive the motor.

The flywheel starts off perfectly still—not rotating. Then the electric circuit is completed, and the motor starts to drive the flywheel. Soon the flywheel is rotating at some considerable rate, said not rate not pertinent to the answer.

The question is: does the machine:

  1. move to the right?
  2. move to the left?
  3. neither move left nor right?

Post your answer in the comments section below.

Update

I received no solution to last week’s Quiz Question. Some explanation is in order. People need to realize some of these Quiz Questions are meant to appear difficult when they are not. This is one of them. All that is necessary to answer this is knowledge of basic physics. Here’s the explanation.

Know two things: Newton’s laws of motion and Einstein’s assertion of the equivalence of matter and energy. Here’s how it goes.

From Newton we know that, without an external force, the assembly pictured above will not move. That is to say, the center of gravity of the assembly pictured above will not move. That is critical.

Next, Einstein’s equivalence if mass and energy is exactly that. Matter and energy have the same properties. Energy, to an outside observer, behaves exactly like matter.

When energy is transfered from the battery on the right to the spinning flywheel, it’s the same as moving matter from the right side of the assembly to the left side.

Since the center of mass needs to remain motionless, the assembly will move to the right.

The Age Of Embarrassment

Fifth of a series

GlobalWarmingHickMentality

We haven’t had one of these in a while. So, what’s new?

A Real Climate Scientist Demolishes Bill Nye’s Global Warming Alarmism

All right, this one is a bit old—from last year even. That aside, I want to thank whoever posted this on Facebook for me to pick up. The truth be known, Facebook is a prime source of story ideas for this blog.

And this is refreshing. For once I’m not having to explain some fact-deprived meme from The Comical Conservative. This time we have Dr. Roy Spencer, an actual climate researcher, weighing in. And he has much to say about the evidence. Actually, he doesn’t. At least in the YouTube clip he doesn’t. Additionally, the item posted by Austin Peterson on The Libertarian Republic presents little in the way of evidence, either for or against the case for anthropogenic global warming (AGW). But Spencer is a real scientists working in the field, and it is worth knowing what he had to say in the interview.

Global warming alarmist talking heads like Bill Nye, Neil deGrasse Tyson and Al Gore are constantly paraded around as experts on climate.

I hope not. Because none of the three do research related to climate, and nobody would seriously refer to them as experts. What they happen to be are public defenders of the science behind AGW—speakers, if you like. In fact, you can discount Vice President Al Gore right off the bat, because his expertise is politics, and his training in serious science is close to vacant.

On the other hand, Bill Nye and Neil deGrasse Tyson have taken some college courses—Tyson more so—in physics, and the science of physics lies at the base of the study of AGW. In full disclosure, I have had college courses in physics, including four in the critical field of thermodynamics, and it is from this background that I come to agree with the argument for AGW.

To be sure, Dr. Roy Spencer has had these courses, and beyond that he has degrees in atmospheric science, including a Ph.D. in  meteorology from the University of Wisconsin–Madison. The Wikipedia entry for Roy Spencer lists a number of peer-reviewed papers critical of AGW, such as this one:

In 2007, Spencer and others published a paper in Geophysical Research Letters regarding negative cloud feedback in the tropics that potentially supports Richard Lindzen‘s Iris hypothesis, which proposes that as the tropical atmosphere warms, cirrus clouds decrease, allowing infrared heat to escape from the atmosphere to outer space. Spencer stated, “To give an idea of how strong this enhanced cooling mechanism is, if it was operating on global warming, it would reduce estimates of future warming by over 75 percent. […] Right now, all climate models predict that clouds will amplify warming. I’m betting that if the climate models’ ‘clouds’ were made to behave the way we see these clouds behave in nature, it would substantially reduce the amount of climate change the models predict for the coming decades.

This paper is available on-line from the American Geophysical Union, and I have retained a copy for your viewing:

https://skeptic78240.files.wordpress.com/2016/04/climatescience-spencer-01.pdf

Spencer’s objections to AGW, based on publication topics, appear to be related to the effects of clouds on solar energy loss. Some of his publications have received major push-back from other scientists. Of note is a recent work published in 2011 with William Braswell:

In 2011, Spencer and Braswell published a paper in Remote Sensing concluding that more energy is radiated back to space and released earlier than previously thought. Spencer stated, “The satellite observations suggest there is much more energy lost to space during and after warming than the climate models show. There is a huge discrepancy between the data and the forecasts that is especially big over the oceans.”

The paper was criticized by numerous climate scientists. Kerry Emanuel of MIT, said this work was cautious and limited mostly to pointing out problems with forecasting heat feedback.

The editor-in-chief of Remote Sensing, Wolfgang Wagner, later resigned over publication of Spencer and Braswell (2011), stating, “From a purely formal point of view, there were no errors with the review process. […] the problem I see with the paper by Spencer and Braswell is not that it declared a minority view …but that it essentially ignored the scientific arguments of its opponents. This latter point was missed in the review process, explaining why I perceive this paper to be fundamentally flawed and therefore wrongly accepted by the journal.”[22] Wagner added he, “would also like to personally protest against how the authors and like-minded climate sceptics have much exaggerated the paper’s conclusions in public statements”.

Spencer responded that Wagner’s assertion was wholly inaccurate, “But the paper WAS precisely addressing the scientific arguments made by our opponents, and showing why they are wrong! That was the paper’s starting point! We dealt with specifics, numbers, calculations…while our critics only use generalities and talking points. There is no contest, as far as I can see, in this debate. If you have some physics or radiative transfer background, read the evidence we present, the paper we were responding to, and decide for yourself.”

Andrew Dessler later published a paper opposing the claims of Spencer and Braswell (2011) in Geophysical Research Letters. He stated, among other things:

First, [they] analyzed 14 models, but they plotted only six models and the particular observational data set that provided maximum support for their hypothesis. Plotting all of the models and all of the data provide a much different conclusion.

At the very least, Spencer’s methods indicate a lack of scientific rigor. I went into this with the possibility of finding an additional factor, that factor being denial of AGW is strongly linked with political alignment and to a lesser degree with religiosity. Spencer’s Wikipedia contains two notes pointing toward religious influence:

Spencer is a signatory to An Evangelical Declaration on Global Warming, which states that “We believe Earth and its ecosystems—created by God’s intelligent design and infinite power and sustained by His faithful providence —are robust, resilient, self-regulating, and self-correcting, admirably suited for human flourishing, and displaying His glory. Earth’s climate system is no exception. Recent global warming is one of many natural cycles of warming and cooling in geologic history.”.[32] He believes that most climate change is natural in origin, the result of long-term changes in the Earth’s albedo and that anthropogenic greenhouse gas emissions have caused some warming, but that its warming influence is small compared to natural, internal, chaotic fluctuations in global average cloud cover. This view contradicts the scientific consensus that “most of the warming observed over the last 50 years is attributable to human activities”.

And:

In TCS Daily, Spencer wrote, “Twenty years ago, as a PhD scientist, I intensely studied the evolution versus intelligent design controversy for about two years. And finally, despite my previous acceptance of evolutionary theory as ‘fact,’ I came to the realization that intelligent design, as a theory of origins, is no more religious, and no less scientific, than evolutionism. In the scientific community, I am not alone. There are many fine books out there on the subject. Curiously, most of the books are written by scientists who lost faith in evolution as adults, after they learned how to apply the analytical tools they were taught in college.” In the book The Evolution Crisis, Spencer wrote, “I finally became convinced that the theory of creation actually had a much better scientific basis than the theory of evolution, for the creation model was actually better able to explain the physical and biological complexity in the world. […] Science has startled us with its many discoveries and advances, but it has hit a brick wall in its attempt to rid itself of the need for a creator and designer.”

Climatologist Patrick Michaels has defended Spencer, arguing that his religious beliefs have nothing to do with his climate change research.

Dr. Michaels holds a “Ph.D. in ecological climatology from the University of Wisconsin-Madison” and is a senior fellow at the Cato Institute, a libertarian think tank whose agenda includes opposition to AGW. He is correct in arguing that Spencer’s religious beliefs have nothing to do with whether he is correct in his conclusions. Most likely, there are many researchers supporting AGW who are also deeply religious.

What bears on religion and science is the matter of demonstrable science as opposed to personal opinion. Spencer has published his research, some of it valid, some not so much. Base on his research and that of others he voices the opinion that AGW is without merit. It’s here the value of his opinion comes into play.

When a person says in one breath that AGW is invalid science, and in the next breath he expresses belief in a mythical person who created the universe in six days and has power over our daily lives, then you can begin to doubt his conclusions regarding AGW. My observation from many years is that if a person’s thinking is horribly screwed up in one part of his brain, it’s time to closely examine everything else he says.

The Age of Embarrassment is still upon us, and there will be more on this. Keep reading. And may Jesus have mercy on your soul.

Quiz Question

One of a continuing series

Chuck-Yeager

On 14 October 1947 Army Air Force test pilot Chuck Yeager became the first person to exceed the speed of sound in an airplane (in level flight). The speed of sound at that altitude, 45,000 feet, was about 670 miles per hour. The speed of sound at sea level is typically 761 miles per hour. And that brings up the Quiz Question of the week.

Why does the speed of sound vary with altitude?

Post your answer as a comment below. If nobody has provided the correct answer by Friday I will provide an update with the answer.

Quiz Question

One of a continuing series

View the image below. It’s a scan from a high school text book.

SellGold

The problem is stated:

A scam artist hopes to make a profit by buying and selling gold at different altitudes for the same price per weight. Should the scam artist buy or sell at a higher altitude? Explain.

The concept being studied here is the variation of gravitational attraction with respect to distance from the center of the Earth. Don’t solve the problem. It really is quite simple. Instead, answer the Quiz Question of the week:

What’s wrong with this problem?

As always, post your answers as comments in the section below. If there are no correct answers by Friday I will post the solution then.

Update

A correct answer has been submitted. See the comments below. You don’t weigh gold and other precious stuff with a spring scale. You use a balance scale, which is not affected by gravity. That’s what’s wrong with this physics problem.

There’s more

Yes, that’s not all that’s wrong. the change in gravity is dwarfed by the change in density of the air. A bar of gold being weighed is buoyed up by the surrounding air. It will weigh less at the San Francisco bank than it would at the Denver bank. If you employ a spring scale. What if you use a balance scale? How will atmospheric density affect the measurement if you use a balance scale?

Not Now, Jody

One of a continuing series

Iconic police state image

Alan Diaz/AP Photo

Chapter Seven

I’m spending some time reviewing  It’s Now Or Never: A Call to Reclaim America by Georgia Congressman Jody Hice. Go back to the original post to get my overview of the book and the lowdown on the front matter. This is Chapter Seven, titled “The Rise of America’s Police State.”

As always, I’m going to review this chapter by posting selected quotes from the book and adding my own comments. Here’s for starters:

The Declaration of Independence states that God Himself has given us the rights and liberties that we enjoy. In essence, that is the meaning of ‘unalienable’ rights. They are rights recognized as not being man-made or man-given. Instead, it refers to that which is God-made and God-given and is therefore, beyond the scope and jurisdiction of human government. Our entire American political and legal system is based upon that unique premise. There is no other safeguard to defend the natural rights of humans apart from the recognition that they are divinely authorized. If we remove God, we will also remove all claims to American rights and liberty.

Dr. Jody Hice (2012-01-13). It’s Now Or Never: A Call to Reclaim America (p. 120). WestBowPress. Kindle Edition.

[Emphasis added]

 

I highlighted the significant passage. Allow me to translate: “If we remove an imaginary person created out of thin air by people living 3000 years ago in the Eastern Mediterranean, then we are S.O.L. This chapter is getting off to a rough start.

It’s been a few days since I read through this chapter, but my recollection is it goes like this: Our government is increasingly exercising its massive power to oppress the population. Congressman Jody Hice is going to explain all of this, and he’s going to provide some examples. Here is one:

The story behind the decision is quite interesting. It involves a Vanderburgh County married couple that was having a domestic dispute. The woman called 911 and law enforcement officers soon arrived on the scene. Once there, the woman told the police that her husband had not harmed her in any way, and couple went inside their home. An officer began demanding entry into the home and the man told him that everything was fine, and that their services were not needed. Nonetheless, the officer forced his way inside the home against the husband’s will. The husband then pushed the officer against a wall in protest of the forced entry. Another police officer, who was assisting the first one, shot the husband with a taser gun and arrested him. Shortly thereafter, the couple put forth a lawsuit claiming their Fourth Amendment rights had been violated.

Dr. Jody Hice (2012-01-13). It’s Now Or Never: A Call to Reclaim America (p. 122). WestBowPress. Kindle Edition.

 

The married couple lost their lawsuit in a decision much denounced by Congressman Hice. Not being a legal scholar (neither is the congressman), but I am sure it works this way:

  • There was a domestic dispute.
  • Somebody involved felt it important to call 911.
  • The police responded. That’s what they are supposed to do.
  • When the police arrived the husband said it was all a misunderstanding, and the police should go away.
  • The police are not so inclined in situations like this. Somebody phoned 911 and requested police intervention. Officers at the scene need to verify whether a threat actually exists. The police need to enter the residence and check on the safety of people inside.
  • The police do not need a warrant from a judge in cases like this. The husband was wrong in resisting the police.
  • Congressman Hice is flat wrong in his assessment of this situation. He has coughed this up and dressed it out in a way to present a distorted picture of the circumstances.
  • Congressman Hice is having considerable difficulty with the commandment relating to false witness.

The congressman cites another example:

The specifics involved a 9-year old girl (known as S.G.) in February of 2003, at an Oregon elementary school. An Oregon Department of Human Services worker and a uniformed armed deputy sheriff, without a court order and without notifying the child’s parents, entered the school and removed the young girl from her elementary classroom. Following the directives of government authorities, the school administrators did not object. S.G. was taken to an empty conference room and left alone with Sheriff James Alford and caseworker Bob Camreta, and for two hours they interrogated her about alleged sexual abuse at home, supposedly by her father. According to S.G.’s attorneys, when the caseworker asked the 9-year-old girl if her father touched her “all over [her] body,” she said “yes;” she was referring to affectionate hugs, kisses and piggyback rides. Camreta then asked “over and over again” if “some of those were bad touches.” Over and over again, S.G. said “no.”[142]

Dr. Jody Hice (2012-01-13). It’s Now Or Never: A Call to Reclaim America (p. 127). WestBowPress. Kindle Edition.

There is more to it than just the foregoing. If the description in the book is correct, the situation was gruesomely intimidating to the girl. Guns were visible. The girl was not informed she did not have to endure the questioning. After two hours of this she lied so she could leave and catch her school bus home.

The citation is to

 John Whitehead, “Alford v. Greene: A Case with Far-Reaching Implications for Parents’ Rights,” The Rutherford Institute, February 2, 2003, http://www.rutherford.org/articles_db/commentary.asp?record_ id=700.

The case eventually caught the attention of the Supreme Court:

Holding: Although the Court may generally review a lower court’s constitutional ruling at the behest of governmental officials who won a final judgment on constitutional grounds, here the case is moot because the respondent (the plaintiff below) no longer has a stake in preserving the court’s holding because she no longer needs protection from the practice at issue.

Plain English Holding: A government official can ask the Supreme Court to review a lower court’s ruling that he violated the Constitution, even if the lower court ultimately concluded that he could not be sued for that conduct.

Judgment: Vacated in part and remanded on May 26, 2011. Justice Scalia filed a concurring opinion. Justice Sotomayor concurred in the judgment, in an opinion that was joined by Justice Breyer. Justice Kennedy filed a dissenting opinion that was joined by Justice Thomas.

The Rutherford Institute has this to say, written by John W. Whitehead
(February 28, 2011):

On March 1, the United States Supreme Court heard oral arguments in Alford v. Greene, the first major case involving Child Protective Services to go before the United States Supreme Court in 21 years and one of the most important parents’ rights cases ever to reach the Court.

If it goes the right way–i.e., to bolster parents’ rights–it will mean that state agents will have to obtain a court order in order to question a child at school. If it goes the wrong way, which the Obama administration is advocating for, along with 40 state attorneys general, law enforcement agencies, social workers, prosecutors and defense attorneys, it will be a serious blow to parental rights as well as the rights of children in the public schools. And then there’s the possibility that the Court will either vacate the lower court opinion, leaving the police and other government agents free to question students at will, or sidestep the issue altogether and simply choose not to rule on it, declaring it moot because the young girl involved is no longer a child.

For some reason a lot of emphasis here is being placed on parental rights. I would have hoped the rights of a nine-year-old child would get more attention.

The facts are not disputed. The girl should properly have been questioned by a woman officer or even a woman counselor. Anybody less intimidating than two male police officers. Her right to get out of the situation should have been carefully explained to her. The school should have been more protective.

This next example requires some reading:

Take for example the early-morning terrifying experience of Anthony Wright on June 7, 2011, just days after the Supreme Court decision. At 6:00 A.M., federal agents started pounding on the door of his California home and before he could even open the door, government personnel entered the home and Wright was immediately overtaken by police. According to a neighbor’s eyewitness account, the agents forced entry into the home and then “dragged [Wright] out in his boxer shorts, threw him to the ground and handcuffed him.” His own words describe the scenario, “He [a federal agent] had his knee on my back and I had no idea why they were there.”[146] He was a victim of a raid from the Department of Education SWAT team. Furthermore, while Wright was being unconstitutionally mishandled, the federal agents took his three children (ages three, seven, and eleven) and detained them in a squad car while a search of the home was conducted. You would think this type of behavior was reserved for major felons or persons on the FBI’s ‘Most Wanted’ list. What crime had Wright committed? Evidently, the agents were not even looking for Mr. Wright. They were allegedly seeking information on his estranged wife, Michelle, who no longer lived at that address. So, what was her grievous crime? She was suspected of financial aid fraud! News reports said the raid was in regard to some delinquent student loans![147] Was this ‘show of force’ necessary for a delinquent school loan? A simple conversation would have been more appropriate and would have achieved the same purpose without frightening the children and abusing the rights of a private citizen.

Dr. Jody Hice (2012-01-13). It’s Now Or Never: A Call to Reclaim America (pp. 130-131). WestBowPress. Kindle Edition.

The book cites:

 John W. Whitehead, “SWAT Team Mania: The War Against the American Citizen,” The Rutherford Institute, June 13, 2011, http://www.rutherford.org/articles_db/commentary.asp?record_id=715.

That link is not working. This one gets you to the appropriate page:

For example, it was heavily armed agents from one such OIG office, working under the auspices of the Department of Education, who forced their way into the home of a California man, handcuffed him, and placed his three children (ages 3, 7, and 11) in a squad car while they conducted a search of his home. This federal SWAT team raid, which is essentially what it was, on the home of Anthony Wright on Tuesday, June 7, 2011, was allegedly intended to ferret out information on Wright’s estranged wife, Michelle, who no longer lives with him and who was suspected of financial aid fraud (early news reports characterized the purpose of the raid as being over Michelle’s delinquent student loans). According to Wright, he was awakened at 6 am by the sound of agents battering down his door and, upon descending the stairs, was immediately subdued by police. One neighbor actually witnessed the team of armed agents surround the house and, after forcing entry, they “dragged [Wright] out in his boxer shorts, threw him to the ground and handcuffed him.”

This is not the first time a SWAT team has been employed in non-violent scenarios. Nationwide, SWAT teams have been employed to address an astonishingly trivial array of criminal activity or mere community nuisances: angry dogs, domestic disputes, improper paperwork filed by an orchid farmer, and misdemeanor marijuana possession, to give a brief sampling. In some instances, SWAT teams are even employed, in full armament, to perform routine patrols.

There is hardly any way to read this without thinking excessive firepower was being employed. An Internet search for additional information produced scant results. One item may bring clarification:

In a statement to FoxNews.com, Education Department Press Secretary Justin Hamilton confirmed that its Office of Inspector General executed the warrant with the presence of local law enforcement authorities.

“While it was reported in local media that the search was related to a defaulted student loan, that is incorrect,” the statement read. “This is related to a criminal investigation. The Inspector General’s Office does not execute search warrants for late loan payments.”

Hamilton declined to comment on the specifics of the case, citing an ongoing investigation.

“We can say that the OIG’s office conducts about 30-35 search warrants a year on issues such as bribery, fraud, and embezzlement of federal student aid funds,” the statement continued.

At the very least, Anthony Wright has now become Kenneth Wright. It is also possible the case involves actual criminal activity. The book provides no additional clarification.

Regarding Congressman Hice’s keen interest regarding overbearing police action, my own brief Internet search found little to none regarding Congressman Hice and some recent instances:

  • The killing of Michael Brown in Ferguson, Missouri
  • The killing of Tamir Rice in Cleveland, Ohio
  • The death of Freddie Gray in police custody in Baltimore, Maryland
  • The death of Eric Garner while being arrested by Staten Island police
  • The bizarre arrest and death of Sandra Bland in Texas

A later book, perhaps.

Coming next, Chapter Eight, “Parental Rights Vs. Guardian Government.” There should be something here of interest to everybody.

Keep reading. And may Jesus have mercy on your soul.

Quiz Question

One of a continuing series

This never came up on a quiz, although I did once take a course on Interplanetary Navigation. See the diagram.

InEllilipticalOrbit

Your spaceship is in an elliptical orbit around the evil planet GOP. In one month’s time the planet is going to explode. You need to get away. Fortunately you have just enough fuel left to achieve escape velocity. You wait for the optimum point in your orbit to fire your thrusters.

What is the optimum point?

Question 2: In which direction do you fire your thrusters?

Question 3: Why?

Solution

I’m going to review the solution along with comments that have been submitted to the post and also on Facebook. Two comments were posted to the blog. Here they are:

Well, you really need to increase your orbital energy. So you need to fire your thrusters in the same direction as your current velocity vector in order to achieve the maximum increase in orbital velocity. Now if you fire at apogee, you will mainly just increase your perigee. That is NOT desirable. I watched the newly launched MUOS 4 “secret” communication satellite for a couple of hours two weeks ago because there was a chance that it would fire its thrusters. But it didn’t. 😦

http://spaceflightnow.com/2015/09/02/video-liftoff-of-atlas-5-rocket-to-deploy-navys-muos-4-satellite/

Exactly when the planet lines up with both the radii. (That is either on the left most or the right most point of the orbit in the diagram.)

The planet speed varies in the orbit. The planet is traveling the fastest at these points (and is slowest at the vertical points in the diagram.)

After you get into the orbit of the planet (with enough fuel to achieve escape velocity you won’t have any fuel left) so the speed of the planet — at this fastest point — will help you get out with the planet’s speed at that point which is the maximum speed you can achieve under these conditions.

Here are the comments from Facebook:

Steven Breed If the question is only whether the spaceship escapes or not, then only energy matters because that is what determines whether a binary system is gravitationally bound. If you want to optimize the spaceship’s escape in some way, then its position in the orbit probably does matter.
Steven Breed I re-read the question. It’s asking from where can the escape be accomplished using the minimum of fuel (since the spaceship only has the minimum necessary). Expending the fuel at the bottom of the orbit optimizes the result, I believe. The spaceship gains the most at this point because it isn’t burdened by having to carry the fuel back out to higher potentials. I’ve cheated a bit because, although I haven’t read the appropriate Heinlein, I did read this in 2010: Odyssey Two by Clarke some years back.
Prasad Golla Yes, that’s right the total energy is the same irrespective of the position in the orbit.

Of course, Steve Breed, with some history of studying physics, nailed it on the second try. A number of things are correct:

  1. The energy of the spaceship in orbit is constant. While a satellite is orbiting a planet there is nothing adding or subtracting energy (almost). When the satellite is farther from the planet it has higher potential energy with respect to the planet’s gravitational field, but its velocity is lower, and so on.
  2. A rocket engine is not a constant power device. When a spaceship is still sitting on the pad right after firing its engines, the engines are not developing any power, because there is no forward motion of the rocket. The power delivered by a rocket engine is the product of its constant thrust and its variable forward velocity. Actually, rocket engines develop more thrust when operating outside the atmosphere.
  3. When the spaceship is at perigee its speed is greatest. If the rocket engines are fired at this point while the spaceship is pointed in the direction of motion, then the rocket engines develop the most power, and the most energy is imparted to the spaceship.
  4. The spaceship is best able to escape the evil planet GOP by firing its rockets at perigee, with the thrust along the line of forward motion.

This was explained in Robert Heinlein’s novel The Rolling Stones, in 1952. I read it when it was serialized in Boy’s Life magazine, so I was aware of this bit of science before I took a bunch of physics courses in college.

Quiz Question

One of a continuing series

We were given this problem in physics. Here is an explanation:

This is a standard principle of physics. See the image. A (hypothetical) light wave front from a source far away is incident on a solid wall. The wave crests are for the purposes of this demonstration parallel. The waves that hit the wall are stopped or reflected, and the remaining ones keep going as before:

Diffraction-01

Not really. The next figure shows what’s wrong with that interpretation. Considering the light wave as an electrical and magnetic field traveling through space, then the arrow points to a place adjacent to the electrical field that is vacant. The electric field will propagate into this space.

Diffraction-02

See the next figure. The wave front adjacent to the edge of the wall will curve toward the available space, effectively bending the wave front.

Diffraction-03

Here’s the result of this action. If you take a metal plate and make a small hole in it and then aim a beam of light at the hole, some light will pass through the hole. If the light is monochromatic, and you place a screen to the right of the plate in the figure, then you will see that the illumination on the screen conforms to the graph in the next figure. I copied this figure from Wikipedia and did some slight editing:

Diffraction1

Well and good. Now suppose you use electrons (or protons) instead of light waves. The same thing happens. See the next figure:

Diffraction-04

These electrons (electrons are round and black) and are headed for the hole in single file, but when they emerge from the hole they spread out like shot from the muzzle of a shotgun. Why?

The standard answer is that on a certain level electrons, in fact all particles and even macro objects, behave like waves. We were given the problem of deriving the diffraction of electrons (any sub-atomic particle for that matter).

While I was taking the course I went around and bought up a bunch of other physics books. One of them had a novel way of approaching this problem. It did not involve treating the electrons as waves. How else can you derive the diffraction pattern without resorting to wave analysis? I will give a hint later this week.

UPDATE

Enough of this. The answer lies in application of the Heisenberg uncertainty principle. Also in paying attention. This Quiz Question was resolved in a previous post, which discusses the diffraction of particles due to Heisenberg’s uncertainty principle.

Sex And Heat Transfer

All this happened 44 years ago. I was working for this small engineering company in Austin, and we had a contract to design a tokamak fusion device. We produced the design drawings, and artist Tony Bell took them and came up with a rendition of the completed system.

tokamak

As you can see from the drawing, at the center liquid nitrogen is fed into the machine to chill critical components. The liquid nitrogen temperatures were going to present a problem, and that’s where this topic came from.

At the center the temperature was going to be  −195.79 °C. The air in the lab was going to be in the 20 °C range. There was a lot of concern the liquid nitrogen chill was eventually going to reach the outer surface of the machine, and frost was going to form. This was something we did not want. I was given to job of determining what the outer surface temperature was going to be.

My boss was a mechanical engineer who had gone to Rice University, and one of his courses was heat transfer. The professor was in the process of writing a text book on heat transfer, and he was using the draft as the text for the class. He handed out (sold?) copies of the draft. The title on the front was Sex and Heat Transfer. The professor explained that with a bunch of college students there might not be much interest in reading a book titled Heat Transfer, but he figured students might actually pick up and read a book titled Sex and Heat Transfer. My boss handed me a copy.

The notes were useful, and although I still don’t know a lot more about sex, I did pick up enough knowledge about heat transfer to work through the problem. Here is how it works. Look at the figure:

HeatTransfer-01

The rectangle represents a thickness of material, for example a metal plate. On one side the temperature is −40 °C. On the other side the temperature is 40 °C. In between the temperature is going to be in between. Heat is going to flow from the warmer side (the right) to the cooler side (the left). How fast does the heat flow? That’s already been worked out.

HeatTransfer-02

In this equation H is the amount of heat transferred through a plate of thickness L, and an area A during a time T. t1 and t2 are the two limiting temperatures. The factor k is a characteristic of the material. It’s called the thermal conductivity of the material. The greater the value of k the better the material conducts heat.

That given, let’s examine the situation that existed for the tokamak. On the inside there’s a surface cooled by liquid nitrogen, on the outside there’s a room full of air at 20 °C. Heat flowing from the outside air to the surface cooled to −195.79 °C has to pass through multiple layers of materials of different thickness with differing coefficients of thermal conductivity. Here’s a graphical representation:

HeatTransfer-03

There’s a high temperature (t1) on the left and a low temperature (t2) on the right. This shows four layers of material between the two regions, but there could be any number. The key thing to note is there is a monotonic change in temperature across the combination. The temperature never goes down and then back up again.

What you are left with is to solve for the temperatures at each boundary layer with a significant condition that needs to be satisfied: Considering this is a steady-state situation (temperatures are remaining constant) then the heat flow per unit time is the same through each of the layers. In fact, the heat flow through all vertical planes drawn through the above diagram must be the same. No heat is lost. No heat is generated. What comes out on the right is the same that goes in on the left, at the same rate—the same number of calories per second.

So, I did this and then what? It wasn’t much help. It didn’t solve the problem of whether frost would form on the outside, the warm side. That’s because the final heat barrier is the air layer adjacent to the outside of the apparatus. You cannot ensure that the air next to the outside surface remains at 20 °C. The layer of air adjacent to the outside surface will be chilled by the cold outer surface.

To ensure frost does not form on the outside surface you have to blow warm air on it. If you don’t do anything then there’s a possibility the air next to the outside surface will chill down to the freezing point, and frost will form. After all the computations the solution is to place fans as necessary to keep the outside warm enough to prevent frost from forming.

And that’s the way engineering is done.