Archive for the 'Science Education & Outreach' category

In Which I Compare the Slashdot Commentariat to the 17th-Century Catholic Church

Aug 14 2011 Published by under Astronomy & Physics, Big Bang & Cosmology, Cosmology, Physics & Astronomy, Science, science & society, Science Education & Outreach

I am regularly struck, when giving public outreach talks, or when hearing the topic of Dark Matter discussed amongst the general non-Astronomer public, at the separation between acceptance of Dark Matter between astronomers and the general (informed) public. (The general public at large probably doesn't have enough of a clue about Dark Matter even to have a wrong opinion, alas!) Most astronomers know the evidence, and accept that non-baryonic dark matter is a real component of our Universe. Many in the public, however, seem to view Dark Matter as a horrible kludge, an ex-rectum fudge factor that astronomers have invoked in order to explain discrepancies between observation and theory. Indeed, topics related to this will be the subject of my upcoming August 16 365 Days of Astronomy podcast.

For a popular level discourse on the evidence for dark matter, I shall point you to two sources:

And now I can get to the snarky bits of this post. Yesterday, on Slashdot there showed up a post entitled CERN Physicists Says Dark Matter May Be An Illusion. In the paper indirectly referenced by the Slashdot article, a theoretical physicists explores the idea of negative gravitationally charged antimatter and the polarization of the vacuum as an explanation for the rotation speeds of galaxies (the mainstream explanation for which is, yes, Dark Matter).

What's interesting is the tone of the Slashdot comments. Some are informative, and ask exactly what I ask: what about the Bullet Cluster? However, a fair number of the comments show the same tenor as these excerpts:

I hope so. Dark matter is the ugliest kludge to the standard model ever.

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Agreed. I have always had a hard time stomaching the theory that dark matter and dark energy exist. It seems far too much like aether, i.e. something made up to fill a gap in knowledge without much evidence backing it up.

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Yay for phlogiston [wikipedia.org] and aether [wikipedia.org]. Dark matter might end up on the list of ideas that physcists turned to in order to explain things that had other explanations. La plus ca change

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Dark matter, too, has never been observed, and possesses properties of matter previous unseen or indeed thought impossible, and exists solely to bridge a gap between our model of how things should behave, and how things actually behave. This does not bode well for it.

There is a strong general sense among a large (majority? hard to tell) subset of the Slashdot commentariat that astronomers are all on the wrong track and propping up a failing theory, and that dark matter is a kludge that just can't be right.

The thing is, they're wrong. They just know that Dark Matter can't be real, because they are not comfortable with the idea that a substantial fraction of the Universe is made up with stuff that we can't see, that doesn't even interact with light. Much as... the 17th century Catholic church just knew that Galileo (and others) were wrong about Heliocentrism, because it's obvious to everyday observation that the Earth is still and the Sun is going around it. (Also, the Bible says so.) And, just as the leaders of the Catholic church completely discounted (and indeed refused to look at) Galileo's observation of Jupiter's moons orbiting Jupiter (and, crucially, not the Earth), armchair pundits completely ignore (probably mostly through ignorance!) the wide range of evidence for Dark Matter that goes beyond the "accounting error" represented by the motion of stars in galaxies, and galaxies in galaxy clusters. (Those motions are indeed one part of the evidence for Dark Matter, and historically formed the first evidence for it, but they're far from all of the evidence nowadays.) They cling to notions of how science ought to work, and how the Universe ought to be made up in a familiar way that seems natural to us humans, and use this to assert that an entire field full of scientists must all be on the wrong track for having a different model.

Specifically with regard to comparisons to the luminiferous aether, I would point you to my June 2010 podcast: "Dark Matter: Not Like the Luminiferous Ether". (And, yes, I'm conscious that I've spelled aether two different ways in this paragraph!)

Indeed, I would say that the comparison between denial of Dark Matter and denial of Heliocentrism goes deeper than that. The Copernican Principle is that the Sun, not the Earth, is at the center of... well, today we would say the Solar System, but in Copernicus' day that was also what was thought to be the whole Universe (the stars not at the time being understood to be things like the Sun). An extension of this is the Cosmological Principle, which stated succinctly says "you are nowhere special". We're not at a special center of the Universe, we're just at a typical random place in the Universe pretty much like any other. Observations (of galaxy distributions, of the Cosmic Microwave Background, and so forth) bear up this assumption or postulate, which is why we call it a principle. Think about it in broader terms, though. We are made up of "baryonic matter", which is Physicist for "stuff made of protons, neutrons, and electrons". In light of the Cosmological Principle, however, why should we expect that most of the Universe is made up of the same general kind of stuff as we are? In the face of evidence otherwise, many still insist that most of the Universe must be made up of baryonic stuff that interacts with other baryons and our familiar photons. Is this not just as much hubris as insisting that the Earth, where we live, must be the center about which all the other Solar System bodies orbit?

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"Galaxies in Collision" : public online talk today at 10:00AM PDT

May 21 2011 Published by under Astronomy & Physics, Science Education & Outreach, Second Life, Second Life Events, Technology and Society

As of this writing, in just over an hour I'll be giving a talk in Second Life on the topic "Galaxies in Collision".

Second Life is an online virtual world. Basic accounts in Second Life are free. I regularly give these talks as a part of MICA, the Meta-Institution of Computational Astronomy. Most Saturday mornings at 10AM pacific time (17:00 UT if we're during Daylight Savings), MICA has a public outreach astronomy talk. (However, like many academic institutions, we tend to slow down and get spotty over the summer.)

This talk will be at the MICA Large Amphitheater.

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"More Things in Heaven and Earth" -- the interaction of physics and astronomy

Feb 23 2011 Published by under Astronomy & Physics, Science Education & Outreach

365 Days of Astronomy is a daily podcast about astronomy, entirely recorded by volunteers. The topics are all over the place; some are about amateur astronomy, some are about the history of astronomy, some are about recent discoveries in astronomy. I've done a number of these over the last couple of years, and am doing more this year.

I recorded today's podcast— and, if I am to be perfectly honest, I have to admit I recorded yesterday, way after when I was supposed to get it in. The topic is the interaction between fundamental physics and astronomy. I talk a little about ancient physics, where the realm outside the sky and the Earth were viewed to be separate realms. Newton's universal gravitation unified those two realms. Some chemical elements were discovered originally in astronomical objects, and it was from observations of astronomical objects that we learned about neutrino oscillations.

You can check out today's entry if you want to hear more.

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Online talk tomorrow morning : "Neutrino: Placeholder Particle"

Feb 05 2011 Published by under Astronomy & Physics, Science Education & Outreach, Second Life

I'll be giving a talk in Second Life tomorrow morning at 10AM pacific time. (That's Saturday, Feb 5, at 18:00 UT.) This is part of a regular talk series; follow that link to find the slides and audio recordings from most of the previous talks I've given in the series. Remember that a Second Life account is free! Come and hear the talk. You can also ask questions in text chat, which I generally try to respond to as the talk is ongoing.

Tomorrow's talk is entitled "Neutrino: Placeholder Particle". I'll talk about the history of the discovery of the neutrino. Even Pauli, the guy who proposed the neutrino, was uncomfortable with making up a new particle that nobody had seen to explain things that seemed to be missing from other observations. There are clear parallels to Dark Matter today, with many being uncomfortable that we've got most of the Universe made out of stuff that we can't identify. I'll also talk about our current state of knowledge of the neutrino, and I hope to get into the issue of how the "mass neutrinos" are not the same as the "flavor neutrinos", and even though there are three of each, there are still only three total neutrinos. (It's a Schrödingers Cat sort of thing.)

Here's the abstract I sent to Paradox Olbers, the organizer of the MICA talks:

Sometimes critics of nonbaryonic dark matter will characterize it as a "placeholder particle"-- the name we give to the fact that we can't find particles doing the things that we see happening gravitationally. Of course, dark matter is not new in astronomy; Uranus, for instance, was originally detected indirectly. Nor are palceholder particles new in particle physics. The neutrino was originally proposed more than 20 years before it was first observed. In this talk, I'll go over the history of our discovery of the neutrino, and how it was in fact astronomy that led to some relatively recent important discoveries about these elusive little particles.

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One-Slide Explanation of Tides

Jan 22 2011 Published by under Astronomy & Physics, Science & Culture, Science & Religion, Science Education & Outreach, Second Life

I realize that this Bill O'Reilly quote is two weeks old, which in Internet time is a substantial fraction of the age of the Universe. And, the Internet being what it is, a top conservative commentator can't say something this butt-ignorant without having bloggers jump all over him within seconds. So, yes, I realize that I'm way, way behind the times, sort of like somebody getting all snarky to the dinosaurs because they didn't invest in programs tracking near-Earth asteroids. But, still, I think it bears repeating, to remind ourselves collectively the kind of people who are shaping the agenda of an entire political party in the USA right now.

Here's my one-slide explanation of how the tides work:


Click image for larger version

This slide does go along with some speaking, normally. Indeed, it is one (of 28) slides that I'll be using in the talk I'm giving in Second Life in about half an hour, all about interacting galaxies and whether or not they're connected to the phenomenon of active galactic nuclei. (Really, tides are relevant to this story!)

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Online talk tomorrow morning: "Observational Evidence for Black Holes"

Jan 08 2011 Published by under Astronomy & Physics, Science Education & Outreach, Second Life

Tomorrow morning, I'll be giving a public lecture entitled Observational Evidence for Black Holes. This is part of a regular series of talks sponsored by MICA, Saturday mornings at 10:00 AM pacific time (1:00 PM Eastern, 18:00 UT). They're open to anybody.

These talks are in Second Life. A basic Second Life account— everything you need to attend the talk— is free. Go to the Second Life page I just linked in order to sign up. Once you've downloaded the Second Life viewer, and have created an account and logged in to Second Life, you can follow the link on our Upcoming Public Events page to find the talk.

Here's my blurb for tomorrow's talk:

Black holes are a theoretical prediction of Einstein's Relativity. But do they really exist? The answer is a nuanced "yes." We have observational evidence for two sorts of black holes. In our Galaxy, we observe black holes that are several times the mass of the Sun. At the core of almost every big Galaxy, we find a supermassive black hole that's a million or more times the mass of the Sun. In this talk, I'll give an overview of the evidence that these objects are in fact black holes. I'll also point out that the observational definition of "black hole", meaning those things that we know exist, isn't exactly the same as the definition of the objects predicted by Relativity, although most astronomers suspect and assume that what we observe are in fact the things that Relativity predicts.

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My "365 Days" Astronomy Podcasts

Dec 24 2010 Published by under Astronomy & Physics, Science & Culture, Science Education & Outreach

365 Days of Astronomy is a podcast series that was started in 2009 for the International Year of Astronomy. It continued through 2010, and will continue into 2011 as well. It's a contributor podcast; there are monetary contributors who sponsor podcasts and help keep it going, but also the podcasts themselves are contributed by all and sundry. Nancy Atkinson is the editor, and the long-suffering one who deals with people who never get their podcasts in on time.

I've done a number of these, including today's. Here are the links to the summaries and podcasts that I've done in this series:

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More thoughts about teaching on the block system

Dec 24 2010 Published by under Academia, Astronomy & Physics, Quest University Canada, Science Education & Outreach

So, yes, it's been nearly two months since my last post, and posts were few and far between even then. Well, right now I'm on winter break (and have been for almost a week), and I'm back into a state of mind where I can post. There may be a torrent of them in the next several days; we shall see.

A few months ago, as I was just getting started here at Quest University, I posted about teaching on the block. The block system is how classes are organized here, in the same way as Colorado College. Students take one class at a time, and hyperfocus on it. That also means that I'm teaching one class at a time, but cram a full semester's worth of teaching into 18 extremely intense days. When I'm teaching on the block, I can do almost nothing else. It really does take away your focus. It's not just the hours. Yes, because I try to be available to my students, many days I'm spending several hours talking to students in my office outside of the three "contact" hours in class. (There are also students who aren't in my class, but with whom I talk, either just because they drop by, or because I'm taking them on as a mentor for their last two years, or because they want to talk about future classes and independent studies.) However, it's also the "energy" level. I put energy in scare quotes, because of course it's not something that's measured in Joules and that would be recognizable as energy to a physicist, but it's the sort of "energy" that we mean when we tell each other that we're feeling particularly low energy today. There's only so much creativity and intellectual effort that one can put into something until one is exhausted, until the point of diminishing returns is indistinguishable from its asymptote. (This is why the notion that grad students are supposed to work 80 or 100 hours a week, and the schedule that medical residents or programmers on a "death march" are put on, are fundamentally absurd.)

I'm learning other things about teaching on the block— things that, to be fair, I was told about ahead of time. The most important lesson is probably "less is more". This is true of teaching in general. When I first started at Vanderbilt, there were seminars about teaching for the new faculty where they basically told us this. (Faculty would say that every time they taught the same class again, they'd try to cover less than the previous time.) This is even more true on the block. The format just does not lend itself to "survey" classes (of which I have to admit that I'm dubious anyway!). Because you're working closely with students for three hours, probably three consecutive hours, each day, it's far more suited to getting into stuff in depth than it is to driving by a large number of topics.

This last block, I taught a first course in calculus-based physics. I used Thomas Moore's books Six Ideas That Shaped Physics. I'm finding that (with one or two caveats) I like these a lot. There are six books. At Pomona, he uses three each semester. Each chapter is designed to go with a single 50-minute lecture period. Already, you can see that I have to adapt a little. I find, however, that three chapters is far too much for a single 3-hour class meeting. Thomas Moore goes through three books a semester, and I'm doing the same thing right now: three books in December, three books in January. However, next time I teach this, I think I'm only going to use two books each course. That does make me a little sad, as the third book from Physics I is Relativity, and I think it's very cool that if students only take one calculus-based physics course, they get some Special Relativity. (I also really like the way he does Relativity, emphasizing the metric (or the "invariant interval"), and getting to that before the "cool effects" of time dilation, simultaneity, and length contraction.) However, my observation is that we rushed through the material too fast, and that students didn't digest the material as well as I had hoped. On many things, I wished we had a second day to work through problems and work with the things we were working on. So, in the future, I'll do Conservation Laws and Newtonian Mechanics in the first physics course; Relativity and Electromagnetism in the second; and save Quantum Physics and Thermodynamics for the third. (That will be two years from now; Quest isn't big enough at the moment to teach introductory calculus-based physics every year.)

As time goes by, I hope to find a way to keep up with blogging while teaching on the block. However, if I'm slow to post, it's almost certainly because teaching on the block really does take over your life. It may only be during the summer, or during blocks I'm not teaching (which at the moment appear to be being taken over by planned independent studies!) that I will be able to keep up with blogging!

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Why P=nkT is better than PV=NRT

Oct 08 2010 Published by under Astronomy & Physics, Science Education & Outreach

If you've ever taken a Chemistry course, you've run across PV=NRT. That is, of course, the ideal gas law. Real gasses approximate ideal gasses; the noble gasses (Helium, Neon, Argon, Krypton, Xenon) probably approximate it best. It tells you that the pressure times the volume of a gas is equal to the number of moles of that gas, times the ideal gas constant, times the temperature in Kelvins.

So, fine. It's useful, and I've used it a lot. My problem is that as a physicist, I think that moles are an extremely gratuitous unit. Sure, I recognize that you're more likely to be dealing with 32 grams of O2 than 32 individual molecules, but still, it's yet one more concept that doesn't do much for me. What's more, the ideal gas constant is a constant that, at least as its name suggests, is of limited utility.

I much prefer this formulation:

P = n k T

All of the same information is there. However, instead of the ideal gas constant, we've got Boltzmann's Constant, which is a much more fundamental constant. Yes, all the same information is there— except that it doesn't come in units containing moles, so you don't need to know the definition of moles to use it— and Boltzmann's constant shows up as is in a lot of other equations.

On the left, we have pressure, the same as before. On the right, we have the number density of the gas. The variable n, instead of being just a number, is the number of particles per volume. OK, I will admit, that's going to tend to be a huge number. If I did my calculations right, for a gas at room temperature it's going to be something like 3×1025 m-3. So, I will admit that that is one advantage of the chemist's way of formulating it: the numbers are easier to deal with.

The rest of the right is kT. What's neat about that is that if you do physics (and probably chemistry as well, and probably many other natural sciences), you're used to seeing kT all the time. Boltzmann's constant times the temperature times a number of order 1 is the average kinetic energy of a particle in a gas that's at temperature T. This (other than aethetically preferring k to R) is the primary reason I prefer this formulation of the ideal gas law. It's got a piece in it that lets you directly connect this to other physics. "Aha", you say, "this law is somehow related to the average energy of individual particles!" And, sure enough, if you realize that pressure is the rate at which particles are crossing an imaginary wall, times the amount of momentum that each particle carries with it across that imaginary wall, you realize that it should be related to the kinetic energy of that particle.

There's another thing here. If you look at "nkT", you'll realize that that is just a number of order 1 times the kinetic energy density of the gas. kT is (close to) the kinetic energy of each particle, and n is the number of particles per cubic meter (or per cubic centimeter, if you like cgs units better). This leads immediately to the realization that the units of pressure are exactly the same as the units of energy density— something that seemed perverse to me the first time I came across the stress-energy tensor of relativity, as I'd been brainwashed into thinking they were entirely different things by the obscuration inherent in PV=NRT. To be sure, pressure and energy density aren't the same thing, but they are related. (One could say that energy density is momentum flux in a temporal direction, and pressure is mometum flux in a spatial direction, but you need an appreciation of spacetime for that to be illuminating.)

It may be just me as a curmudgeonly physicist talking back to chemists who've figured out a more convenient way to deal with it. I've certainly come across curmudgeonly physicists who express disbelief and either horror or amused condescension that astronomers would use a unit so silly as the "Astronomical Unit"... and their reaction is simply the result of them not being used to it, and not realizing that that unit is extremely convenient for star systems, just like their fermi is extremely useful for atomic nuclei. However, I do really think that from a clarity of concept point of view, P=nkT is a much better way to state the ideal gas law than PV=NRT.

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Do science students do their reading?

Sep 27 2010 Published by under Academia, Quest University Canada, Science Education & Outreach

Many science professors hold it as an article of faith that students do far less of the reading in their classes than they do in humanities and social science classes. I heard this expectation expressed at the APS workshop for new faculty I went to several years ago, and in other presentations I've heard about physics and astronomy education. The technique Just In Time Teaching was invented partly as a way of allowing science classes to make better use of textbook reading. Is it not a waste to spend classroom time in information transmission, telling students in a linear fashion what they could just have easily read from the textbook? Physics education research has shown that active learning is much more effective in getting the students to really understand the concepts.

When I've heard talks about this, the view I've heard expressed is that it would be crazy to expect students to come to a literature class without having done the reading. They would be completely unable to participate in that day's discussion. On the other hand, the view is, the norm is that students don't do the reading for their physical science classes, except perhaps in a last-ditch attempt to figure out how to do homework problems ("find an example that matches!").

In my statistics class that met this last September (ending last Friday), all of the students had a project; they chose a question, obtained data, and analyzed it. One student, Julian Seeman-Sterling, surveyed students at Quest to find out how much of the reading they did. Below are a couple of his results:

Histogram about Reading

You can tell just looking at the histograms that there's no appreciable difference between the amount of reading that students claim to complete in the natural sciences as compared to other disciplines. And, indeed, Julian ran a statistical test on these, and there's no evidence of any difference. (Note that Julian calls "physical science" what is more commonly called "natural science"— that is, it includes things such as biology.)

I do have to say that I was surprised to hear that, but of course it all comes with caveats. These are the results of a survey of students at Quest. Quest is an unusual place; students only take one class at a time, and it's very intensive. They don't have stacks of reading for many different classes to do; they only have the one class. As such, they tend to be very engaged with the one class they are taking. Also, these are the results as reported on the survey. As Julian pointed out during his presentation in class, he couldn't know if they're really true without following a lot of students around throughout their day... and that wouldn't be entirely practical.

So, do students do less of their reading in physics and astronomy than they do in their humanities courses? I don't know. Julian's data suggests that that is not the case at least at Quest.

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