This past Wednesday, I was invited to lunch with three former students. Two of these student took calculus-based physics with me; the third took first semester general astronomy with me. Of the first two, one (I will call him B) transferred to a nearby university after the first semester of physics and is majoring in mechanical engineering. The second (I will call him H) transferred to another state university campus and is triple majoring in physics, mathematics, and philosophy. The third student (I will call him M) has not transferred to a four-year school yet.
For some reason this (calendar) year, I have received a large number of emails from former students telling me how they are doing after transferring out of two-year college into a four-year environment and how much they appreciate the background they got in my classes.The common thread from students is that the way I structure my courses is a big reason they are doing will now. (I need to be very careful here becuase some will accuse me of claiming superiority over all others; it’s happened before and I must emphasize that that is NOT what I’m doing and have no remote intention of doing that.)
In my mind, the ultimate “assessment” (ugh how I hate that word nowadays) of my effectiveness as a teacher isn’t how many students enroll in my courses or how they perform on a given test. It is instead how my students do AFTER they transfer to a four-year institution and pursue their intended major. If they do well, then I consider myself to have done well in helping to get them there, at least in some small way. Unfortunately, something so simple doesn’t seem to be acceptable to administrators nowadays because it’s not readily quantifiable. I’m told that ANY positive feedback from students must be treated as being given under duress (yes, we were actually told that by a recently retired dean) and is therefore unreliable. I don’t understand how an administrator can be so blind.
Anyway, I have consistently been told by former students, and not just these three, that having a classroom enviroment where students can actually talk about physics, astronomy, and science and mathematics in general is a huge help in overcoming the stresses of traditional learning. B explicitly echoed this during lunch, saying that it was THE most important thing that has helped him. Talking about the physics helped him to understand it more than just working textbook problems. Given that B is an undergraduate taking a graduate course in analytical mechanics that emphasizes geometric methods, I assume he is telling the truth. More than once, H has told me that Matter & Interactions, together with beginning the course with special relativity prepared him well for his courses in modern physics, classical mechanics (Taylor), and classical electrodynamics (Griffiths). While M has not yet transferred, he echoed the same basic sentiments and now intends to take second semester astronomy next semester.
This lunch meeting was especially timely becuase last weekend, I attended the fall NCS-AAPT meeting at UNC-Asheville. Keynote speaker Gabriel Periz-Giz began his talk by saying that we need to devote more class time to actually talking about physics, not lecturing or doing silly and irrelevant labs or working sanitized textbook problems. He pointed out that he uses classroom time to present and discuss poorly framed problems (and he gave us an example from an AP C test) and even problem for which erroneous solutions have been published. Gabe also lamented the inertia that keeps these classroom discussions from happening so as to maintain the status quo of “covering material” regardless of whether or not students eventually understand anything.
My takeaway from all this is that I’m doing some things right and I’m apparently not harming students or impeding their success after they transfer. I take this as permission to keep doing this and to keep looking for ways to refine this approach in spite of the naysayers. I hope I’m right.
Because of Thanksgiving, this week was a short week, only two days (Monday and Tuesday). However, because of a bizarre institutional policy (described here) Tuesday ran on a Friday schedule. Therefore, my MW evening astronomy section only met once, the TuTh section didn’t meet at all, and the MWF section met on two consecutive days. It’s very difficult to ensure continutity with these shenanigans at this holiday-ridden time of year. I don’t mind holidays, but sometimes they’re an unnecessary and incompetently accommodated pain in the butt.
Anyway, we continued the buildup to our huge mystery: Why do the dates of earliest/latest sunrise/sunset not coincide with the solstices as we reasoned they should? This buildup contains so much that is directly relevant to students’ lives (ours too for that matter). Many students don’t know how time is measured (I’m speaking prior to atomic clocks of course) and how the measurement of time is classically related to astronomical observation. Many more don’t know why we have time zones or what a.m. and p.m. even mean. None know that they’ve lived their entire lives according to a fictitious celestial object, the Mean Sun, that can’t be seen and doesn’t cause sticks to cast shadows yet is what every mechanical clock ever invented is designed to track. I’ve gone faster through this material so far than I have in the past and becuase of that, I’ve done more lecturing than I usually do and I don’t like that. My goal is that all of this material will eventually take the form of activities, namely the Activity04xx series, but I just haven’t committed anything but rough drafts to paper yet. I’m still experimenting with different ways to introduce these ideas.
Next week, everything will come together with an introduction to the analemma (note especially this section, this section and this section) and from there, we can solve our huge mystery using graphical methods.
Comments and feedback are welcome as usual!
This week was a very short week, only two days, due to the Thanksgiving holiday. Furthermore, my instituion uses “flip days” and that took away one of the two days for my physics class. By the way, a “flip day” is a day on which the class schedule runs on another calendar day. In this case, Tuesday was “flipped” to a Friday. Ostensibly, this is to allow the same number of Mondays, Tuesdays, Wednesdays, Thursdays, Fridays, and Saturdays (sixteen to be exact) in a given semester and that’s a quite admirable goal in that it attempts to ensure students get everything they’re paying for. But administration says this is required by state law, and it isn’t as evidenced by their failure to cite the relevant specific law or policy (which I already know doesn’t exist) and as evidenced by my colleagues at other institutions in the system literally laughing at me when I describe this to them; I guess my colleagues’ institutions are all violating state law. I’ve been reprimanded for pointing out these facts so sadly, I suspect nothing will change. That’s unfortunate becuase these “flip days” interfere with students’ work schedules, especially evening studets, as they plan their semester schedules. Despite being published months in advance, no one reads an academic calendar that far in advance and really shouldn’t have to for things like this. Furthermore, these “flip days” interrupt continuity, which to me, is far more important than having X number of class meetings per semester. I honestly think we should experiment with doing away with fall/spring breaks and other non-legislated interruptions to the academic calendar. I think continuity is more important than specific numbers of meeting times. The bottom line is that my physics class only met once this week.
So what did we do? We continued working on solution portfolios! I’m seeing so much engagement and hearing so much wonderful collaboration and learning from mistakes that I’m seriously thinking about running the entire class like this near year. More on that in a future post. However, as a result of this burst in engagement I now have over fifty PDF files to look at, but I’ll take it!
We will pick up tomorrow with the chapters on energy, which I generally think of as one large megachapter.
Comments and feedback welcome.
I had planned to go into chapter 7 this week, but decided not to because no one in the class had begun working on their solution portfolio, a part of which is due at the end of this week. So I decided to let students use the class time to work on their portfolios.
The portfolios consist of problem solutions, both “regular” problems and computational problems, written up in LaTeX using Overleaf. For each chapter, I provided a list of problems from which students must select three. One of the three problems must be a computational problem. The problems are usually of medium to high difficulty (indicated by two and three dots respectively in the textbook) except in the early chapters where the problems are simpler and require more numerical effort than in later chapters (e.g. calculating a relativistic particle’s momentum). These are not trivial problems by any measure. I see students productively struggle with them and it’s wonderful to see the lights come on as they see the underlying physics.
We are behind where I would like the class to be at this point so I felt extremely guilty about using class time this way. However, I heard students say two things this week that encouraged me. One student said that he’d learned more from working on the portfolio this week than he had in all the previous weeks. Great! Still, students have ostensibly been working on problem sets all along (via WebAssign) and surely something was learned from that, at least by the students who actually did them. Another student said…get this…that “LaTeX is easier to learn than Microsoft Excel.” In at least one previous class, he’d been required to prepare PDF documents of some sort using Excel and he found that extremely difficult. He says LaTeX is far simpler for him. I never saw that coming.
I feel encouraged that students see the value in learning LaTeX because they’re already talking about how they will use it once they transfer to their four year institution of choice. I’m also encouraged by the fact that students are actually working the problems correctly. The mast majority of errors I’m seeing are LaTeX errors, but that’s good because it forces them to learn the LaTeX and hopefully makes them realize that taking a physics course isn’t just about learning from a physics textbook, even a great one like Matter & Interactions.
Despite the encouragement, the constant internal battle with “covering mass quantities of material” in the spirit of Halliday, Resnick, and Walker is always present. I cringe when I hear colleagues say that reformed textbooks like M&I are just smokescreens and don’t constitute “real physics.” I laugh and shake my head in confusion when I hear PhD colleagues say that M&I has a learning curve that is too hard for them…for THEM. Think about that…PhDs are supposedly the most highly accomplished members of our community and are, in most people’s words, ultimately qualified for any academic task and yet they find insurmountable difficulty in adopting a new approach to teaching introductory (INTRODUCTORY!) physics? Give me the proverbial break! As instructors, are we not more or less required to do what is best for our students regardless of any minor difficulty that may impose on us? If nothing else, it provides ample evidence that persons with so-called “terminal degrees” in the discipline seem to think that “terminal” applies to learning, at least on their part. If not that, then at least that they’re not always the best choice for teaching introductory physics.
Okay, well, I didn’t expect to go there so let’s just pretend that I didn’t. My point is that I’m consistently torn between “covering material” and doing what’s best for my students, because these two options don’t always overlap.
Comments and feedback are welcome as always.
This is the last full week of instruction before Thanksgiving.
First, a short rant. It’s unfortunate that students are racking up harmful absences. There is an institutional attendance policy, but we’re really not permitted to enforce it as written and yet it doesn’t change. This puts faculty in the dangerous position of having to decide when to enforce it and when to”compassionately” ignore it and break institutional policy. That’s a position I don’t want to be in. Either way, faculty are blamed (blamed for not being kind to the student by dropping them or blamed for ignoring institutional policy and being kind to the student) and “held accountable” so there’s no way to win. Administrators can willfully ignore published policy when they wish, but faculty can’t. The object is to keep as many students enrolled as possible and any attempt at pushing back against that is treated as ill behavior toward students. I just don’t see how an institution can work like this, but it’s my daily situation. Rant over.
This week we begin the fourth chapter, that on time. We don’t address what time is, becuase no one knows, but we do address the measurement of time because astronomers probably invented that. For our purposes, time is that which is demarcated by periodically occuring natural phenomena. HUH? In other words, we mark the passage of time (not time itself) by observing periodic natural phemonema. Sunrise. Noon. Sunset. Midnight. A stick’s noon shadow. A stick’s sunset shadow. Moonrise. Moonset. These are all observable periodic phenomena and we can model them all with our celestial spheres.
Our goal is to understand the analemma and how to use it to predict the dates of earliest sunrise, earliest sunset, latest sunrise, and latest sunset. They don’t occur on the most logical dates, and we want to understand why.
Measuring time requires the concept of hour angle, defined operationally as follows:
- Pick a celestial object (star, Sun, etc.).
- With a fingertip, trace out an arc from the north celestial pole to the object, continuing past the object (if it’s north of the celestial equator) to the celestial equator (if the object is south of the celestial equator you’ll hit the celestial equator before you hit the object) and stop. Your fingertip should always be on the celestial equator at this moment.
- Slide your fingertip along the celestial equator toward the celestial meridian (choose the shorter route, not the longer one), counting the number of time bumps you pass along the way. Stop when your finger gets to the celestial meridian.
- The number of time bumps you pass plus the fraction of the way from the last time bump you passed to the celestial meridian, expressed in hours, is the object’s hour angle.
The object’s hour angle tells you how much time elapses between rising and crossing the celestial meridian. It also tells you how much time elapses between crossing the celestial meridian and setting. By convention, objects on the eastern side of the celestial meridian have negative hour angles and objects on the western side have positive hour angles so you need to think in terms of absolute values to get these durations. Oh, and this means that double the hour angle’s absolute value tells you how much time the object is above the horizon.
At this point, we can investigate the duration of daylight (interval from sunrise to sunset) at the equator and at Hickory and begin to get an idea of seasonal variations and thus establish an operational definition of seasons.
The biggest benefit of this approach with the celestial sphere kits is that is completely eliminates the pitfall of thinking seasons are caused by a varying Earth-Sun distance. In this model, the Earth-Sun distance simply cannot vary and if students pay attention, they will notice this.
Next, we define a prime mover. A prime mover is just a name I made up for an object we’re going to track for the purposes of measuring the passage of time. Specifically, we’re going to observe the object and measure its hour angle. That hour angle can then be used to define a timescale unique to that prime mover. We will use Sun as our prime mover. At any given moment, the “time kept by our prime mover” is just Sun’s hour angle plus twelve hours. The twelve hours is needed as an offset to put the zero point at midnight, not at noon as it would otherwise be (hour angle is zero if the prime mover is on the celestial meridian).
There are actually TWO Suns! One is the Sun we’re used to, the true or apparent Sun, and the other one is an mathematical creation called the mean Sun. Each one can be used to establish its separate time scale.
We can now extend this and predict the times of sunrise and sunset for different locations.
Feedback welcome as always.
I’m posting this on the Monday after the week named in the title.
This week is a slightly short week becuase Friday is a holiday (Veteran’s Day) so the MWF section loses two hours of classroom time.
Because of concerns raised by some students and some by me, I rearranged the groups this week. Some groups consisted of dominant personalities and I wanted to spread some of that around.
We spent this week, once again, ensuring everyone had fluency with the parts of the celestial sphere. More students are beginning to admit they’ve not been spending time on this outside of class and I’m hearing the same questions over and over in class: “How do I change the date on the sphere?” “How do I change the time?” “How many ecliptics are there?” and several others. I don’t know what more I can do to encourage out-of-class participation other than bribery with grades and I don’t want to do that because I think it would spoil my efforts to get students to engage without being bribed. I don’t want to cave in.
Early in the week we again went over formulating one sentence explanations for various celestial phenomena. I kept hoping students would see some common threads in these explanations (e.g. that they almost all have to do with Sun’s changing location along the ecliptic, the ecliptic and celestial equator don’t coincide, etc.). Now, I would expect to be able to ask students to turn these explanations around and use them as evidence that the ecliptic and celestial equation can’t possibly coincide. Think about it! Here are two imaginary great circles on the sky and just by looking at shadows of sticks on sunny days and by looking at constellations on the celestial meridian at midnight we can ascertain that these two “invisible” great circles can’t overlap or coincide (even though they intersect) and we can even measure the angle between them! Getting THAT particular sense of amazement across has proven difficult, almost impossibly so, but there are a few students who really get it.
Late in the week, we did a kinesthetic activity where students paired up (each pair having an Earthling and a Lunatic) and simulated Moon’s phases and found the correlation between phase and time of rise/meridian/set. One student in the evening section knew, and verified, that a full Moon rises at sunset and sets at sunrise. This same student then articulated the most intelligent question I’ve heard all week: “Why would other phases follow this same pattern?” I quite literally jumped for joy when I heard this question becuase it’s precisely the type of question this little activity is intended to address.
Feedback is welcome.
As usual, I’m posting this the Monday after the week named in the title.
This week was all about chapter 6: energy and the energy principle. This is where Matter & Interactions really shines among introductory textbooks. I remember as a student being so confused by sign conventions that I honestly never knew when to include them or why they were even needed. The systems approach of M&I eliminates this whole bag of problems and why many educated faculty can’t (or won’t) see this huge advantage I’ll never understand. But, that’s not my problem.
The biggest revelation in chapter 6 is the origin of the concept of potential energy. It’s astonishingly simple, despite the fake complexity of traditional approaches. You define a system (this is the most important step). You identify interactions both internal to, and external to, that system. The work done by the internal interactions is defined (that’s the key word) as the opposite of a new quantity called the potential energy of the system. I’ve never like that term, though, because it’s quite vague. Stored energy? Energy that could potentially do work? Capacity to do work? Ack! All of these are bad in my opinion. I’ve seen it called interaction energy (my personal favorite that I try to promote) and configuration energy. I think either of these would be far better, but again, it’s up to individual instructors (keeping in mind that no one needs the community’s permission to introduce clearer terminology, as I’ve been told on more than one occasion…usually by grad students with no real teaching experience).
There’s no new physics in this name game, but it offers an extremely useful organizational structure: everything on the left hand side of the energy principle is internal to the system and everything on the right hand side is external. Changes crossing the system boundary from outside to inside carry a positive sign and changes crossing the system boundary from inside to outside carry a negative sign. I just don’t see how it could be simpler. Sure, these are all just conventions, but conventions should be used to make things simpler, not harder.
I tried to emphasize these points in class, but it’s so hard to tell how much sunk in. One student admitted to me that he’d not even begun his assessment portfolio yet despite having had weeks to work on it. Sigh. I just don’t know how I’m supposed to help students who flat out refuse to engage in their education and I don’t think I can be held “accountable” (note the quotes) in any professional way for the outcomes these students inevitably face.
To illustrate the simplicity of the energy principle approach, we did the typical (but interesting) case of an asteroid falling into Earth from “at rest very far away” and estimating its speed as it hits the top of our atmosphere. Accounting for other planets in the way is just a matter of adding an appropriate interaction energy term. This, along with other simplifying assumptions, makes the problem more interesting I think.
Feedback is welcome.