Quantum mechanics – things you should know

Diffraction of light through a grating. Image from http://commons.wikimedia.org/wiki/File:PatronRefraccionCD.jpg

The way sub-atomic particles behave is weird. They don’t fit very well into our everyday experience of the world, but the math and the experimental observations hold up. Chad Orzel has an interesting post on the seven things everyone should know about quantum physics that’s written in language a lay person can understand. This does not make the concepts much easier to grasp intuitively, because, as I mentioned before, quantum mechanics is weird, but it does explain things so we can begin to grasp the big picture of how the universe works. It also helps explain why they’re building the Large Haldron Collider. So though you may not know the answers, you’ll at least have an idea about what it’s about when your students ask.

The principles of macro-economics

With a national unemployment rate of 10%, most students are aware of the current recession. When they ask about what the government is doing about it, the answer is that they’re following the advice of a man who died over 60 years ago, John Maynard Keynes.

Keynes wrote the textbook on how to manage economies, particularly in response to recessions. If the economy is in a recession because people are not spending money, then his solution was for the government to spend the money instead. Friedrich Hayek, however, disagreed.

Hayek’s disagreement with Keynes is a disagreement about human nature. This is after all what economics is all about, how people behave. Hayek though that recessions are necessary for economies and societies adjust to changes. Economies go into recession because as things change, such as technology, some businesses will fail because their products are no longer necessary. Eventually new companies and industries will replace these, but as that transition occurs, there will be the general hardship of a recession.

So, if the government spends money to support the economy all it’s doing is preventing necessary change, which means that in the long run, the economy will be worse off than if the government just let the change occur. Necessary adjustments will have to occur sooner or later.

The thing which is most needed to secure healthy conditions is the most speedy and complete adaptation possible of the structure of production. – F. Hayek

Even today are ongoing arguments either way. The government, specifically the heads of the Federal Reserve and the department of the treasury, Ben Bernanke and Tim Gethner, is dealing with the current recession by following Keynes’ prescription. They are adding more money to the economy. Other economists disagree.

The video illustrates the differences between Hayek’s and Keynes’ view of the economy using a music video and a rap. It is a wonderful example of how serious issues (and you can see the sincerity of the creators) can be explained in a way that catches the attention. I like how the authors give the same message in two modes: the words explain the concepts and the video illustrate them (look out for Tim and Ben).

C.O.D.: Call of “Duty”

The Call of Duty video games are pretty popular among the boys in my class (the gender stereotypes hold up very well with this one). Last week they tried to convince me that there was enough educational value in the games to allow them to bring it in for their overnight at school. They even created a PowerPoint presentation to convince me. Unfortunately, for them, it was not particularly effective. While there was a lot of information about the missions and the types of weapons there was not so much in the way of facts or concepts they learned (Subsequently, however, one student mentioned that he learned about favellas in the game. Though I don’t want to think about what they were doing in the flavellas).

I would really have liked to have had them talk about “Duty”, as in the title, and moral responsibility. I dropped a lot of hints but too no avail. They were not successful in their petition, but we did have a good discussion about the purpose of warfare (if any), and how to make a convincing presentation (consider your audience). I may let them try again next time.

As a side note, The Onion, has a great video on the next version of the game which will be even more realistic (you spend most of the time in the game sitting around and then you get shot in the back unexpectedly and the game is over.) The video may not be appropriate for middle schoolers however, because there is a scene where the soldiers are sitting around bored and talking about what soldiers often talk about.

Waves and interference

There are lots of interesting interactive wave demonstrations on the web. The particularly interesting ones are the ones that show interference. Some of them make your eyes water. Others make your ears hurt. These simple animations show superposition (constructive and destructive interference) very nicely, but the language is a little advanced.

What I like about Dan Russell’s 2d animations is that they show the wave motion using particles. If you track a single particle with your eye you can see that while the wave moves from one side of the area to the other, the particles just move back and forth in the same general region.

Longitudinal wave
Longitudinal wave (from Russell, 2001).

I like this demo because you easily control the wave amplitude and lengths of two waves and it shows how they superimpose.

This animation of wave interference is nice because when you click on the 2d animation it shows the two waves’ effects at the point you’ve chosen as curves. You can choose points to show both constructive and destructive interference.

Constructive interference (screen capture from animation by Ng (Retrieved 2010)).

Destructive Interference (screen capture from animation by Ng (Retrieved 2010)).

This elegant but somewhat complex video shows the two dimensional sine waves generated by a rotating wheel.

Sine waves from a rotating wheel (from animation at Russell Kightley Media)

Gay marriage and civil rights

World homosexuality laws (from Wikimedia Commons).

Gay marriage is one of those current issues that allows for a fascinating perspective on civil and human rights. Although in many parts of the US racial discrimination and prejudice are still alive and pertinent, the issue has been decided; arguing for racial discrimination has no place in government policy and in the vast majority of society. The right of gay people to marry, however, still splits the country.

Terry Gross’ NPR interview with reporter Margaret Talbot is an excellent introduction to the topic based around the court case being argued in California right now. It starts with a discussion of fact that one of the lawyers arguing for marriage rights is a conservative, while the other is a liberal. This fact allows for a discussion that is much broader than a simple left-right political argument.

The interview also goes in to the role of the supreme court and its interpretation of the constitution in assuring civil rights for minorities. Loving vs. Virginia, the case striking down bans on interracial marriage, is a precedence that is key to the arguments of supporters of gay marriage.

Gross and Talbot also talk about the “orginialist” position that many conservatives take, where the Supreme Court must interpret the Constitution based on what the people who wrote it believed rather than allowing for the changes that have occurred over the past two centuries.

It’s a fascinating interview, that delves into a number of topics relating to government, courts and human rights, and uses intelligent, challenging, but not impossible language. Our next immersion trip deals with civil rights, and I plan on playing this podcast on the drive to our camping site. I suspect the students may not be too happy about this, but if it puts them to sleep, at least they’ll be well rested when we get to our destination.

Rock band and the choice of poetry

Popular music lyrics have been used to introduce students to poetry (Brenda Guerra has a nice lesson plan on the subject). We recently had an overnight at the school and the students elected to play Rock Band. It was clearly indicated that the songs they played would have to have language acceptable to the Middle School. Among the song choices they made was Bon Jovi’s “Living on a Prayer”.

I’d considered “Living on a Prayer” as one option for poetry reading but rejected it because I wasn’t sure that lines like, “she brings home her pay for love” would be quite appropriate. What I found most interesting was that even though they sung the song, they did not actually know the words. The game appears to only require them to make sounds of the right length and maybe pitch. So the singing sounded like, “Tommy used to blah blah blah blah.”

So now I think I’ll use the song, but I’m curious to see the response. Will the fact that it’s something they are aware of and play in a game make it more interesting to them? Or will it work the opposite way? We’ll find out.

This song also introduces issues of unions and the way the arts reflect society, both overtly and, in this case apparently, hidden in the music.

Seeing temperature, kinetic energy and color

We read that temperature is the average kinetic energy of a substance but you can (especially if you’re a visual learner) nicely internalize this from simple videos or animations. UCAR has a little animation with their definition of temperature. I however, adapted an interactive, 3d animation that I think does a nice job, and also introduces a couple of other interesting concepts too.

I’ve also used this model, at different times, to show:

  • The relationship between temperature and color emitted by objects. The main way we know the temperature of stars is because blue stars are hotter than red stars. Blue light has a shorter wavelength than red light, and things that are at higher temperatures emit shorter wavelengths.
  • Absolute zero (0 Kelvin) – where (almost) all motion stops and the objects stop emitting light.
  • Pressure in a gas – you really get a feel for the force exerted by the particles on the side of the box (although it might be even more interesting once I figure out how to add sound).

It is an interactive model, but it’s pretty simple because the only control is a slider that lets you set the temperature.

Finally, in the age of 3d movies, like Avatar, the models can be easily shown in 3d if you have the glasses (redcyan).

The model is easy to install and run on Windows, but you have to install the programming language VPython separately on a Mac (but that isn’t very hard). I have this, and a bunch of other models, at http://earthsciweb.org/GeoMod/.