Do “Gen Eds” make sense?

In a blog post today, Chad Orzel (chair of the physics department (last time I checked) at Union College) speaks out against a proliferation of “Gen Eds”. These are courses that teach basic skills that you’ll need either in life or in college, courses that are either divorced from content, or that are taught in a department other than the department of a student’s major and as such are “outsourced” skill-building necessary for their major.

Chad makes the argument that the proliferation of these things are bad, for a few reasons. By and large, I agree with him. Even beyond what he says, too often courses that are completely divorced from content can be vapid; the best ones, the ones that actually work, will apply some real content to make them work. (You can’t learn how to write without something to write about.) Students end up viewing these courses as hoops you jump through, boxes you check, rather than courses you’re actually supposed to take something away from and use in other courses. They then become less fun courses to teach, because the students aren’t intellectually engaged; instead, they think of you as primarily an obstacle.

Chad’s final statement is that departments who value these other skills (be it writing, public speaking, computer programming, or whatever) should find room for those skills within their major; if they can’t find room, then perhaps those skills aren’t important. I had a debate with a colleague this morning, who thought that Chad’s last statement was patently false. I believe he was misreading it, however; he seemed to be reading Chad as saying that “if you can’t find room, that other stuff isn’t important”. I hang on the “maybe” in Chad’s statement though; my colleague argued that conversationally, the maybe was a throwaway word and that Chad really was saying the other stuff was a waste of time. However, given the rest of what Chad wrote in the article, I think the point he’s trying to make is that by not finding room in your major, you’re indicating to the students that you think these things aren’t important; therefore, if you think they’re important, you damn well better find room in the major for them.

On a couple of points, I disagree, however. As Chad says, physics both outsources some of its basic skills to other departments (writing usually goes to English or similar departments, but most notably all sorts of the basic skills and knowledge you need for physics is taught by math professors), and provide outsourced “service” instruction for other departments (most notably, introductory physics for life science types (often (too often) pre-meds) and engineers). Now, I must admit that I have had moments in my life where I think that students would be better getting their math from physicists than from mathematicians. Mathematicians get worked up about proofs and (for instance) weird edge cases of limits, whereas physicists tend to like to be able to use the mathematical tools as they are useful in addressing physical theories and situations. (Mathematicians also have this terrible tendency to ignore units and dimensionality, and students come into physics classes thinking that that stuff doesn’t matter, creating headaches for all of us.)

There are a couple of reasons, however, why I still think that students (particularly at liberal arts colleges) should learn math from mathematicians rather than physicists. First, at a liberal arts college, the point of taking math classes is not just as a tool for physics. It’s also to learn math, as its own example of a human intellectual pursuit. On a more practical level, having everybody who needs calculus take that class in their own department splits the audience, and might lead (depending on the size of the school) to a whole bunch of classes with 5-10 people each learning calculus, instead of a smaller number of 20-person (ideally, more at some schools) classes learning calculus. Likewise, as a physicist, I can’t help but think that physicists are probably better people to teach physics to life science students than life science types. You can argue that, yes, if physics really is important for life scientists, then the life scientists should know it well enough to teach it at that level. But, again, I think there’s more to it than just getting what you need to do life science.

Indeed, in physics classes, we teach some math. There are some mathematical tools that might not come up in math classes. What’s more, we may “reteach” some of the math, to give physics students the “physics perspective” on math that they’ve already learned. (“Cheating with differentials” is an important skill that first-year physics students should learn, for example.)

The other area where I disagree with Chad is when he says this:

There’s a stark difference in style between the normal mode of writing in the two disciplines that just doesn’t cross that boundary– there’s some benefit to varying up the language used to refer to things in English papers, and trying to work in the occasional ornate turn of phrase, but in science papers, those both fail spectacularly. The goals in technical writing are clarity and precision, which means that you use the same words to refer to the same things throughout, as boring as that might seem. And you don’t use flowery language in places where it might cause confusion about what you did and what you measured and how you analyzed your data.

I strongly suspect that the writers that Chad is complaining about would, by and large, not be the writers that would be considered the best writers by English professors.  While, yes, there are stylistic differences when you’re writing for different audiences and with different goals in mind, I do strongly believe that there is a thing one could call “good writing” that is absolute.  In English papers, clarity is important.  Students too often seem to think that it’s all about bullshit and about using lots of self-important and gratuitously flowery language to make yourself appear all impressive.  I strongly suspect, however, that those papers do not tend to be the papers that receive the highest grades.  Yes, being interesting to read, and not sounding dull and repetitive is important, perhaps more important than strict precision in many cases, while in a science paper the priorities might be reversed.  But, the actual writing by some scholars (as exposed by things like the Sokal affair) aside, good writing in the humanities is also supposed to be clear. You’re supposed to be making your argument and supporting your argument clearly, not obfuscating it, or using a lot of flowery and creative prose to hide the fact that you don’t have an argument. Yes, sometimes, the style is the point, and you deliberately try to be obtuse. By and large, though, that’s not the type of writing that students are primarily supposed to be learning in their English classes, and the students who are best at that are indeed the ones who write clearly and realize that it’s not all BSing.

All of that being said– I don’t think there’s a lot of point in having a class called “writing”, or “public speaking”, or (God forbid) “critical thinking”. As I said, you learn how to write by writing about something. You can have a class where you look at a diversity of things and write about that, sure, but just calling it writing itself, reducing writing to a skill along the lines of typing, misses the thought and creativity that goes into writing well. (For the same reason, when I’ve taught a computer programming class here at Quest, I focus most of the class on the students writing a major project. You might think they should learn programming first and then attempt the major project. However, by having something they care about be what they’re spending their time on, ideally they are more motivated actually to learn the programming. Ideally, they learn by doing the major project. To be fair, while I think it’s worked pretty well, I can’t claim that this approach has worked universally for me.)

I still do think there is a place for “gen eds” at a liberal arts college, however. Not, definitely not, as explicitly “skills” classes. For all the reasons Chad said, students groan and mentally disengage if they have to take a wealth of courses with titles like “Rhetoric”, “Quantitative Reasoning”, “Critical Thinking”, and so forth. However, if you’re getting a liberal arts education, you should learn more than just your major. The whole point of going to a liberal arts college is to become broadly educated, to be generally familiar with the human intellectual endeavour. So, while, yes, focusing on something, learning something in depth (i.e. your major) is an important part of that, it’s not the be-all and end-all. Students should not only take classes, but ideally (if they “get” the liberal-arts ideal) should embrace taking classes that are outside of their major. I’m not just talking the classes that teach you skills you will “need”, but classes that expose you to other parts of human scholarship. And, who knows, you may well find out that some of what you learn in these other places broadens your perspective and gives you an ability to communicate with people who aren’t in your subfield, and gives you a flexibility of thought that you might not have hyperfocusing on just completing the prerequisites for whatever graduate program you seek to apply to.

A computer animation of a thermonuclear supernova

A year ago, I taught a 3D Computer Modelling and Animation class. Most of the class was focused on the students working on projects in groups of 1-3. During that time, I did a small project myself as well. I posted a still image from the project a year ago, and promised to post the movie. I’m only now getting around to doing that….

Here is a direct link to the movie. The text in this blog post, and the movie, are also available on the web here. The movie is currently in Ogg Theora format. At some point, I may also put online on that web page a file in another format.


sn1aprogenitor
Click to embiggen

Thermonuclear Supernovae

A thermonuclear supernova, also called a Type Ia supernova, occurs when a white dwarf star passes a critical mass (the Chandrasekhar mass). Too massive to support itself under the influence of gravity it starts to compress. This compression triggers runaway nuclear fusion, and the entire star blows itself away in a massive thermonuclear explosion.

White dwarf stars are whats left over when a moderate mass star (less than about 8 times the mass of the Sun) ends its life. Towards the end of its life, such a star will slough off its outer layers, which briefly (for a few ten thousand years) glow as a planetary nebula. The core of the star, which is probably somewhere between 0.4 and 1.4 times the mass of the Sun but only about the size of the Earth, is left behind. It’s made of Carbon and Oxygen, but given its mass and size is incredibly dense. It is supported by “Fermi degeneracy pressure”. To those who know some Quantum Mechanics, the electrons in the white dwarf are in a degenerate fermi gas. If you don’t know what that means, suffice to say that the electrons (and thus the nuclei that go along with them) are packed together absolutely as close together as the fundamental laws of physics (the same basic things that give us the Heisenberg Uncertainty Principle) will allow them to be.

Such a configuration in a star is only stable up to 1.4 times the mass of the Sun (which is the aforementioned Chandrasekhar mass). If it starts smaller than that, how does it get to the necessary size? It must have a source of mass somewhere. There are two possible ways for a white dwarf to reach the Chandrasekhar mass. First, if the white dwarf star has another regular star as a companion, and if it’s orbiting that star closely enough, it’s possible that the gravity of the white dwarf will be able to slowly pull some of the gas off of the surface of the other star and accete it on to itself. If the mass builds up to the critical mass, the white dwarf starts to collapse, and, boom, thermonuclear bomb 1.4 times the mass of the Sun. This is called the “single degenerate” scenario, beacuse there is only one white dwarf (the degenerate object).

The second possibility is called the “double degenerate” scenario. In this case, two white dwarfs, both of them less than the Chandrasekhar mass, come together. Neither one by itself has enough mass to explode. But, if the two come together and merge, the result can be a degnerate object that’s above the Chandrasekhar mass, and boom, supernova.

This movie depicts the single-degenerate scenario, where a white dwarf has a regular star (or perhaps a subgiant or giant star) as a companion. The mass pulled off of the companion builds up in an swirling accretion disk around the white dwarf. Mass from the inner part of the disk falls in on to the white dwarf until it reaches the critical mass and explodes.

Stages and Timescales

So that the movie can complete in a reasonable period of time, I play a little fast and loose with timescales. I’m going to describe the major steps of the movie, and talk about how everything evolves too fast in the movie as compared to in real life.

sdsn1a_progenitor

A star that is several times the mass of the Sun will live a few hundred million years before it becomes a white dwarf. If it’s close enough to its companion (which will be of lower mass than the star that left behind the white dwarf started as), it might start accreting matter from it right away. If it’s farther, it might not start accreting matter until the companion star approaches the end of its life and starts to swell. This can mean a delay of anywhere from millions to hundreds of millions of years after the first star becomes a white dwarf before it has accreted enough mass of its companion to reach the very final stages depicted in the movie here. It’s possible while this is happening that there might be sub-supernova explosions, as some of the hydrogen gas collected on to the white dwarf undergoes a (smaller, but still huge) fusion explosion; we might observe such an event as a nova.

You might object that the camera is moving through the system faster than the speed of light, and you would be right. But, what the heck, it’s an animation! I’m showing you what’s there, not what it would look like if you were really flying through the system.


sdsn1a_explosion

The explosion itself is instantaenous on astronomical timescales. There is some debate amongst theorists who model the explosions exactly how it happens, but even those arguing for a slower explosion still calculate that the explosion itself is over in about a second (e.g. Ciaraldi-Schoolman, Seitenzhal, and Röpke, 2013). The movie doesn’t really depict the thermonuclear fusion itself; it depictes the expanding blast wave of material blasted away and expanding as a result of the explosion. (Pictures of nuclear explosions we’ve created with our bombs on Earth are the same; the actual nuclear event is over instantly, and then the “explosion” is the expanding blast wave.) Watching the movie, you may think that the expanding blast wave is awfully sedate for such an extreme explosion. In fact, if anything it’s expanding too fast compared to how long it should take to expand in reality! If the star depicted in the video is a subgiant star, it probably has a radius that is at least several times the radius of the Sun. The white dwarf is a similar distance away from the surface of the companion star. If the white dwarf is 10 Solar Radii away from the surface of the star, that’s a distance of about 6,000,000 km. The blast from a supernova expands fast, but not at the speed of light. From memory (and I should really check this), we expect the blast wave to expand out at something like a third the speed of light. At that speed, it would take the blast wave a full minute to reach the nearby star! Things are far apart in astronomy. The 4-5 seconds it takes the blast wave to reach the companion star in the movie is almost certainly too fast.


sdsn1a_strip

The movie starts outside the explosion, but eventually the blast wave overtakes the camera and we see it from the inside… at about the same time that the blast wave is overtaking the companion star. What happens to the companion star? You might think it would suck to be next to a thermonuclear bomb one and a half times the mass of the Sun. And, it would. You might think you would be completely blown away. And, you would be. But a star wouldn’t. The gravitational force holding together the companion star is strong enough to allow it to survive despite the tremendous amount of energy deposited into it by being next to an exploding white dwarf. That being said, it is a lot of energy, and so we expect some fraction of the outer layers of the star to be stripped away. That indeed happens in this movie.


sdsn1a_zoomout

Finally, the movie zooms out, so that you can see the supernova in the context of its host galaxy. This supernova in the movie is really on the outskirts of the galaxy. It’s true that you find thermonuclear supernova more often in the outskirts of the galaxy than you do core-collapse supernovae (the other type), so it’s not unreasonable for the supernovae to be where I’ve shown it. I have made it rather optimistically far out, however. It’s also true that when it reaches maximum brightness, a supernova can be as bright as its whole host galaxy, which is qualitatively what you see in the movie. However, here is perhaps the greatest acceleration of time. It takes about 20 days for a supernova to reach maximum light after it explodes… not the mere handful of seconds that you see in the movie. However, the movie would be really boring if you had to sit and watch it for 20 days for the supernova to get as bright as the galaxy!

(You might be surprised by how long it takes for the supernova to reach maximum light; why isn’t it brightest right at the explosion? Parts of the exploding gas cloud are opauqe. Not all of it, and indeed as it expands, more and more of the outer layers become transparent. However, because the inner parts are opaque, the energy is effectively trapped inside the expanding cloud, and the rate at which it can be radiated away is limited by the surface area of the opaque part. So, as the supernovae gets bigger, it has more and more surface area, and so can get brighter. However, that’s only part of the story. The profile of rising and falling on the lightcurve is also driven by the detailed physics of what’s going on in the supernova. Some of the energy of the explosion goes into creating unstable nuclei that aren’t entirely stable, which then decay over time, releasing their energy into the expanding gasses.)

After maximum light, a supernova fades. Depending on how far away it is and how sensitive a telescope you use, it will be visible for weeks or months, or perhaps even years. In fact, if it’s close enough, it will be visible for thousands of years. At that point, though, we no longer call it a supernova explosion, but rather call it a “supernova remnant”. As an example, the X-ray and radio source Cassiopeiae A is the left over remnant of a thermonuclear supernova in our Galaxy that exploded in 1572.


Galaxy Image: NGC 1309, imaged by the Hubble Space Telescope. Hubble Legacy Archive, ESA, NASA; processing by Martin Pugh.

Music: Symphony No. 5 in C Minor by Ludwig van Beethoven, performers unknown; from the public-domain music site musopen.org

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Creative Commons License.

Friday Galaxy Blogging: NGC 5278

This is NGC 5278, as imaged by the Sloan Digital Sky Survey. This color image was built by putting together broadband ugriz images, with the g filter mostly mapped to the blue channel of the image, r to the green channel, and i to the red channel. (u influenced blue and z influenced red as well.)

This was one of the galaxies in Chloe Wightman’s keystone project at Quest in 2013; she was looking at Galaxy Zoo-identified merging galaxies, and comparing morpological features to optical emission lines.

sdss587735665840881790_beauty_color

Welcome to the new site

This will, hopefully, be the permanent location of my blog.

Yes, I hear you laughing at me for thinking something on the Internet might be “permanent”.

I also hope to start blogging again more regularly. I used to. I want to more. I want to do more posts like my M82 supernova post, and my Higgs Mechanism post.

As for why I left Scientopia, it’s because I couldn’t stand to see the abuse that a small number (one, in particular, although this individual wasn’t alone) heaped on Mark Chu-Carroll, the person who had been paying for the hosting of Scientopia and doing all of the work for it. It was really inexcusable. When, after a flare up, somebody came in and told us “all to be professional”, it was the last straw. I’m all for being professional. But when being professional means being polite and not calling out those who are engaging in smiling, moderately-toned, but inexcusable behavior, it’s all just pretend professional.

For more details about the recent downtime on scientopia, and why I’ve left the site, read Mark’s description of the history and the event.