High School Physics Free-For-All

Mark at 9:23 am, April 16th, 2007

Once per year, I spend a morning visiting a local high school to discuss physics with a class of talented seniors. This is a program organized by a wonderful teacher - Ranald Bleakley - who I met through the Saturday Morning Physics program that I have run at Syracuse for the last five years.

Ranald spends the entire school year teaching physics to these students, covering the classic subjects - mechanics, electricity and magnetism, etc. - and trying to connect these ideas to frontier topics in modern physics. Because these are all bright, motivated and college-bound students, they generate a large number of questions, many of which Ranald handles. Nevertheless, a pile of unanswered questions inevitably accumulates, and it is my job to try to get through some of these during my visit.

Although I didn’t attend high school in the U.S., there are enough similarities to the British system that I always find it strangely nostalgic to walk the corridors again after all these years. There is a certain smell, and a certain atmosphere of restrained mayhem that one can just sense as soon as one walks through the doors.

The students in Ranald’s class are always a great deal of fun - smart and curious and easy to interact with after the first few minutes when they’re first getting used to speaking to me. So, what was the number one question they had? “We’ve heard a lot about this thing called string theory - what’s it all about?” It doesn’t matter where you go - people are talking about it!

I was able to give them a little review of the regimes of validity of General Relativity (GR) and Quantum Field Theory (QFT), talk about physical situations where both theories seem to be needed, and hence discuss the problems that their incompatibilities present. I then sketched out what string theory is, and why we think it is attractive - namely that it seems to provide a consistent theory of quantum gravity. This discussion also allowed me to make some useful distinctions between Theories (with a capital “T”, if you like) such as GR and QFT, which have made numerous verified predictions, and theories (with a small “t”), such as string theory, which many scientists find extremely attractive, for good reasons, but which have yet to confront experiment.

A second question was a standard one I get in public lectures, although these students seemed to have more background than the general public, - “We know that the universe is expanding; do we know if it is infinite in size or not, and whether it will expand forever or eventually recollapse?”

This is an interesting question, to which cosmologists for a while often gave a set of technically wrong answers. What we think we measure, through combining results from a number of experiments such as the WMAP satellite and the Hubble Space Telescope, is the local spatial geometry of the universe (the geometry of spatial slices). This is determined by the local energy density in the universe.

If the matter in the universe consisted only of regular matter (dark matter, baryons, and radiation) for all time, then one could indeed infer the ultimate destiny of the universe from such measurements, since positive spatial curvature implies more than a critical density and hence ultimate collapse, while flat (which seems to be what we measure) or negatively curved spatial geometries imply eternal expansion. However, the possibility of a cosmological constant (which may be causing cosmic acceleration) ruins this connection, meaning that one could, in fact, live in a positively curved universe that expands forever.

Furthermore, our measurements of the local spatial geometry tell us nothing about the topology of the universe - i.e. its connectedness, and whether it is finite. For example, there actually exist so-called compact hyperbolic manifolds, which are homogeneous and everywhere negatively curved, but in fact are of finite volume. One can construct these in analogous ways to making a torus from an infinite flat plane (and this means also that if the universe is flat, we also don’t know if it is finite or infinite).

One can, of course, perform measurements to see if the universe is finite on a given scale (because if so there would be correlations in light coming from beyond that distance on very different parts of the sky. The furthest away light we have is the CMB, and current tests have not revealed the telltale signs of cosmic topology in it. Therefore, our best knowledge of the universe is that, even if it were negatively curved, it could be finite or infinite, but if finite, then only on so-far unobserved scales.

Later questions included

“I understand that when some stars die they end up as neutron stars, and others end up as black holes. What’s the difference?” This allowed me to discuss some quantum mechanics - the Pauli exclusion principle and degeneracy pressure.
“How do astronomers measure distances?” This gave me a chance to talk about the cosmological distance ladder, parallax, cepheid variables, type Ia supernovae, and much more.
“Why do you spend your time studying these things?”

This last question led into a discussion of what an academic’s life is like, and then a chat about what kinds of other careers open up to you when you have a physics degree, with the associated critical thinking and problem solving skills.

This type of public outreach is extremely rewarding and requires basically no preparation. Most cosmologists and particle physicists can provide coherent answers to the questions above straight off the tops of their heads. The students seem to enjoy the time, get their questions answered, and provide good donuts by way of thanks.

And another thing - it’s worth commenting on the makeup of the class this year. I counted around fifteen students, only three of whom were men. I don’t know whether this was anomalous, and I certainly don’t want boys to be discouraged from taking physics, but it was wonderful to see so many young women enthusiastic about science.

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25 Comments on “High School Physics Free-For-All” rss feed

michael pierce on Apr 16th, 2007 at 10:06 am

Great fun!

Along similar lines, the internet savy scientist may enjoy participating in one of the online science-public-outreach programs such as :

Newton “Ask a Scientist” BBS
http://www.newton.dep.anl.gov/

Mad Science Net
http://www.madsci.org/
Cecil Kirksey on Apr 16th, 2007 at 10:45 am

Mark:

You said “talk about physical situations where both theories (GR and QFT) are needed”. Hmmm. I would be very interested in knowing what “physical situations” (translated as being observable) that requires these two theories. As far as I know there is no experimental or observational data that is in conflict with GR. So is there a need for a union of QFT and GR other that the esthic claim? Thanks for your time.
Mark on Apr 16th, 2007 at 10:48 am

Hi Cecil. “Physics situations” means situations that arise in physics - not that have been actually measured yet. Particular situations I have in mind are at the center of black holes and at the earliest times in the universe. These need a union of QFT and GR.
JJ on Apr 16th, 2007 at 11:53 am

…but it was wonderful to see so many young women … Period.
Mark on Apr 16th, 2007 at 11:59 am

JJ. I know you’re making a joke, but it is comments like that, in the wrong context, that are one of the things contributing to the uncomfortable environment that deters some women from entering physics. In my post I’m talking about their interest in physics, and in that context there really isn’t a place for a discussion of them in the way your comment implies.
Stephen Uitti on Apr 16th, 2007 at 12:36 pm

I’ve done this sort of thing, but for fifth graders. Lots of fun. I came prepared with a talk to fill the time. But also, i encouraged these kinds of questions, and abandoned the talk as needed.

Wish i had more time to do this sort of thing.
mollishka on Apr 16th, 2007 at 12:41 pm

I like the question of whether or not the universe is infinite (and what its actual topology is like). It’s great because the Earth itself is an excellent analogy: standing in Kansas, it sure looks flat, but you can’t tell what’s happening past that horizon because it’s just so big.
efp on Apr 16th, 2007 at 8:08 pm

I don’t know whether to laugh or cry. I hardly ever meet a student… a college student… with the inquisitiveness or knowledge to ask such questions. Even among physics majors. Most of the time I’m defending the heretical opinion that yes, a college graduate should have to know how to divide two numbers. I have to get the hell out of Indiana.
Mark on Apr 16th, 2007 at 8:24 pm

Hi efp. These were great students for sure. They’ve also had a great teacher and an intensive year of courses - that helps. Since I’m married to a Hoosier, I am forbidden from commenting on your final statement
Cecil Kirksey on Apr 16th, 2007 at 10:03 pm

Mazrk:

Can you please explain how any potential quantum effects inside a black hole could EVER be measured??? I am the pesky redhead in the back of the room. Thanks. CV is my favorite physics site because the bloggers here tend to respect the commenters and provide a good dialogue. Thanks again.
mollishka on Apr 16th, 2007 at 11:21 pm

efp: It’s not just Indiana.
Charly on Apr 17th, 2007 at 1:11 am

it’s excellent that you’re doing this, Mark! I would really love to do this in the near future, and perhaps have it as a periodic event when I become a professor. I would like to see more people excited about physics, or at least become more aware of what’s going on around them. Most people have no idea what physics really is, what physicists do (hang around in the lab and draw incline planes and boxes?) and how rewarding a career in physics can be.
Mark on Apr 17th, 2007 at 6:30 am

Hi Cecil,

The quantum nature of a black hole is key to understanding the information loss paradox and the end state of black hole evaporation. If, for example, certain extra diensional theories are correct, then we should see mini black holes evaporating at our upcoming colliders, and such considerations would be important. More generally though - black holes do form, and we’d like to know what goes on in that process, although getting data may be hard.

There are many questions about early universe cosmology that may depend on a clear quantum gravity theory - the resolution of the singularity, the origin of space and time, the origin of perturbations, … The right quantum gravity theory may tell us a lot about these, and observations of, for example, gravitational waves, may allow us to test the predictions.

These are frontier topics for sure, but they are important and definitely require a quantum gravity theory for a complete understanding.
Mark on Apr 17th, 2007 at 6:30 am

Thanks Charly!
Matt on Apr 17th, 2007 at 9:56 pm

Mark - As an incoming first year at Syracuse, what opportunities are afforded graduate students to do outreach and whatnot? I have done a bit of High School teaching (mostly as a sub), and while it was draining, I still seem to have some interest in spreading my fascination with physics to the next batch of students.
Mark on Apr 18th, 2007 at 6:14 am

Hi Matt, sounds like you’re an incoming grad. student - right? Welcome! We don’t have any formal setup for grad. students to be involved in outreach (your first year is going to be extremely busy, trust me). But there are lots of other opportunities at various points. Drop by and talk to me about it in the Fall when you are here.

Two examples:
- Our Cosmic Connections project involved a number of graduate students (we even paid them!)
-When I did this same visit to the high school last year I took two of my graduate students along and we answered questions together. This year our schedules didn’t quite allow this but I’ll be taking them next year.

Hope to see you in the Fall.
Peter Erwin on Apr 18th, 2007 at 2:05 pm

This is an interesting question, to which cosmologists for a while often gave a set of technically wrong answers.

Yes, I remember those days (having once substituted for my advisor for a day in teaching an Astronomy 100 class, and discussing just those wrong answers)…

One can construct these in analogous ways to making a torus from an infinite flat plane …

I think you mean a finite flat plane, yes?
Mark on Apr 18th, 2007 at 3:05 pm

Hi Peter. We’ve all given the wrong answer at some point in the past (if we’re old enough)

I actually do mean an infinite plane. If one takes the covering space of flat geometry - the infinite plane - and mods out by a freely-acting subgroup of the isometries (translations in this case), then one will obtain a finite torus.
Peter Erwin on Apr 19th, 2007 at 6:07 am

Mark,

I actually do mean an infinite plane. If one takes the covering space of flat geometry - the infinite plane - and mods out by a freely-acting subgroup of the isometries (translations in this case), then one will obtain a finite torus.

OK, you’ve blown past my limited knowledge of topology, so I’ll take your word for that ;-). Though I’d suggest that, pedagogically, it’s easier to explain finite plane -> torus examples, as in the case of mapping opposite edges of a square onto each other the way video games sometimes do (Asteroids being a classic example).
Mark on Apr 19th, 2007 at 6:23 am

I know what you mean Peter, but there are two reasons I wouldn’t want to do that in the case of cosmology. First, a finite plane has edges (and so isn’t a manifold), and the last thing one wants to do is get people thinking the universe can have an edge (they already do, and one has to disabuse them of this misconception early in public talke usually). Second, the point here is that local geometry doesn’t tell you about topology (and whether the universe os finite or infinite). It is the infinite plane and the torus, say, that have the same geometry, different topology, and one is infinite and the other finite.
limes on Apr 19th, 2007 at 8:56 pm

I wish that there was one person - one person - like the people you describe in my 11th grade physics class. But there isn’t. So I get to look forward to spending the rest of the year sitting through a million variations of the “Explain basic algebra to me, please!” request. No one in our grade likes physics. The one girl who pretends she does has been failing her tests and making a great show of reading the “general relativity” section of next year’s textbook and nothing else. Our class would never have anything as interesting as an actual practicing physicist in our class because everyone else is too busy discussing last night’s hockey game or Grey’s Anatomy.

So I guess what I’m really saying is that I’m jealous of those seniors you talked to.
Mark on Apr 19th, 2007 at 9:09 pm

Sorry to hear that limes. Do I gather from your comment that you are a student? If so, why don’t you try suggesting to your science teacher that you try to invite a practicing physicist to talk to your class one day? If you let me know where you live, I may even be able to suggest one to ask.
limes on Apr 19th, 2007 at 9:53 pm

Indeed, I am of that wild breed known as “student”.

I doubt our teacher will let us (we have an optics unit to do), but it might be a neat idea. Do you know anyone in the Ottawa/Gatineau area who might think of doing it?
Mark on Apr 19th, 2007 at 10:24 pm

Hi limes. How about someone from the Carleton University Theoretical Particle Physics group, for example Heather Logan?
Gavin Polhemus on Apr 21st, 2007 at 9:23 am

Mark,

Thanks for promoting outreach to high schools. I visited high schools and enjoyed the experience enough that I took a part time job as a high school teacher. I’ve got a single class of 31 students, all of whom have taken a year of physics previously. It is great fun, and lots of work.

In addition to teaching my class, I spend much of my time answering questions from other teachers and students outside of my class, and I occasionally give presentations to other classes. Every semester I go to all of the Geo-Space classes and give a lecture on the expanding universe. Geo-Space is the course for students who need a science course to graduate. They have minimal math skills, and very limited science background, but they are always engaged and ask great questions. Don’t think that you need to be talking to the best students if you go to visit a high school, just use lots of pictures from the Hubble Space Telescope and take plenty of time explaining. I spent three days teaching group theory and particle physics in an advanced math class (after the teacher asked me “Is group theory useful for anything?”). I even gave a talk to our Theory of Knowledge classes who were doing a unit on perception. I presented the evidence for dark matter, an example of perception at the frontiers of physics.

I’d really like to see high school teaching become a viable career path for more Ph.D.s but there are some serious obstacles. Foremost is money. I am making “in the high four figures,” as I like to put it. Next year I will have two classes, so I will make almost exactly what I was making as a graduate student ten years ago. Clearly underfunding of education is a serious problem generally that should be fixed in a comprehensive way. However, as scientists interested in outreach I think we should be looking at ways to fund involvement of scientists in primary and secondary education beyond the occasional drop in appearance. I would love to hear some ideas on this.

The second big challenge is isolation from the research community. My background is in string theory and it had been my hope that working only part time in the school would allow me to dedicate time to reconnecting with the field. However, it is a challenge. I live right by Colorado State University, but they don’t do string theory. (I’ve considered switching fields to something that they do.) The University of Colorado is just over an hour away and I should get down there more often for conversations. It seems that the internet should be a great tool for getting connected, but I haven’t figured out how to make that happen yet. I’d be very interested in suggestions on this topic as well.

Many Ph.D.s leave science for other fields and disconnect from the subject they love. I feel very lucky to have found a career where I can talk about physics everyday with interested and intelligent people. I hope I can figure out how to sustain it and make this an opportunity for more scientists. Science education would benefit tremendously.

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