Physics
drorzel | January 26, 2007Matt Leifer doesn't blog all that often, but what he posts is very good. It tends to be extremely high-level stuff about foundational problems in quantum theory, mind, so it's not for the faint of heart, but if you get into that sort of thing, it's fascinating. Wednesday's post on dechoerence is no exception:
[L]et me start by defining two problems that I take to be at the heart of understanding quantum theory:
1) The Emergence of Classicality: Our most fundamental theories of the world are quantum mechanical, but the world appears classical to us at the everyday level. Explain why we do not…
drorzel | January 25, 2007I've been collecting a bunch of little news squibs from the IoP and the APS over the last week or so, and I keep saying that I'm going to do a nice long post explaining each of the experiments. And my actual job keeps eating my life, what with candidate interviews, committee meetings, class prep, and lab set-up. And, of course, those news items are becoming less current with every passing day...
In lieu of a lengthy and detailed explanation of each, then, here's a short list of physics stories that have caught my eye. If there's a great clamor for a more detailed explanation of any of these,…
drorzel | January 24, 2007Some news for those interested in open-source publishing and "Open Science": Dave Bacon is announcing the debut of scirate.com, a sort of social-networking site for physics preprints:
The idea came from the observation that while the arxiv is a amazing tool, one of the problems was that the volume of papers was high and, to put it bluntly, the quality of these papers was not necessarily so great. So the question became, how do I do something to filter out the arxiv? Now, of course, everyone will want a slightly different filter. One person's noise might be indeed another persons operatic…
drorzel | January 23, 2007It's going to be a very busy day, in ways that will keep me away from the Internet for most of the day, so you'll need to entertain yourselves. Here's a question for the science-minded:
What's your favorite science textbook of all time?
It could be your favorite book from when you were a student, or it could be your favorite book to teach out of, but if you've got a favorite textbook, leave the name in the comments. Obviously, my expertise in dealing with textbooks is mostly in physics, but I'll throw this open to all sciences, so go ahead and nominate that biology book you can't get enough…
drorzel | January 18, 2007I'm giving an exam this morning, and there's yet another job talk at lunch, followed by an afternoon of trying to finish all the stuff that's been pushed aside by candidate talks and interviews, so I'm a little too busy for detailed blogging. Sounds like time for a couple of audience participation entries...
I'm running out of good Dorky Poll topics, having already done fundamental forces, fundamental particles, and the like. This one may be too arcane, but what the hell:
What's your favorite example of an elision in a textbook or paper?
That is, what's the best trick you've seen for…
drorzel | January 16, 2007This is the first post I'm doing for the "Basic Concepts" series. When I asked for suggestions, I got a good long list of stuff, and it's hard to know quite where to start. I'm going to start with "Force," because physics as we know it more or less started with Isaac Newton, and Newton is best known for his work on forces. In fact, as-you-know-Bob, the SI unit of force is the "Newton," in ol' Isaac's honor.
(I should note that this particular discussion is adapted from a lecture that I give in the introductory mechanics class, so there's also a "path of least resistance" argument for starting…
drorzel | January 15, 2007"Thoreau," guest-posting at Unqualified Offerings, has a nice post commenting on a Physics Today article about the use of language in science, by Helen Quinn. The article is pretty standard stuff for anyone following the "culture wars" debates here-- use of the word "belief" to describe scientific conclusions causes confusion, and attempts to put science on the same level as faith. She calls for scientists and science writers to use "Scientific evidence supports the conclusion that" instead of "scientists believe."
Thoreau rightly points out that this issue is somewhat overblown, in that the…
drorzel | January 15, 2007Over at Cosmic Variance, Sean has an idea for an Undergraduate [Particle Astrophysics and Cosmology] Theory Insitute, a six-week summer course that would cover a bunch of the basic tools and techniques of the field, and prepare students to do theoretical research in those fields. The proposed syllabus:
Special relativity, index notation, vectors, tensors.
Lagrangian and Hamiltonian mechanics.
Classical scalar field theory.
Gauge theories and electromagnetism.
Basics of Lie groups, SU(n).
Non-abelian symmetries.
Spontaneous symmetry breakdown, the Higgs mechanism.
Topological defects.…
drorzel | January 13, 2007One of my favorite experiments in physics has released a new set of results in Physical Review Letters, putting experimental limits on the size of any extra dimensions of the sort predicted by string theory:
We conducted three torsion-balance experiments to test the gravitational inverse-square law at separations between 9.53 mm and 55 µm, probing distances less than the dark-energy length scale λ~85 µm. We find with 95% confidence that the inverse-square law holds (|α|
You'll need a subscription and a Ph.D. to read the whole thing (though you may be able to find it for free on the ArXiV…
drorzel | January 12, 2007In a back-channel discussion among ScienceBloggers, John Wilkins suggested that it might be interesting to do occasional posts on really basic concepts in our fields-- the sort of jargon terms that become so ingrained that we toss them around without realizing it, and end up confusing people. A lot of these terms often have a technical meaning that is subtly (or not-so-subtly) different from the use of the word in everyday language, which provides a further complication.
The original example given was "vector," which turns up a lot in mathematical discussions, and loses a lot of people (it's…
drorzel | January 12, 2007For tedious reasons, I find myself faced with giving what will basically be a pure math lecture next Friday. I need to introduce a bunch of mathematical apparatus that we will need in the coming weeks, and I know that the Math department doesn't cover these topics in any of the classes that these students have taken. If I want them to be able to use this stuff, I need to teach it myself.
Formal mathematics is probably my least favorite part of teaching physics. I'm very much inclined toward the "swashbuckling physicist" approach to math, in which we cavalierly assume that all sorts of picky…
drorzel | January 11, 2007There's been lots of news from the AAS meeting in Seattle this week, but the best from my perspective is that high school physics enrollments have neevr been higher:
Presenting new data that encourage this outlook, [Michael] Neuschatz [senior research associate at AIP's Statistical Research Center] will show that enrollment in high school physics classes is up and likely to continue increasing. The data show more than 30 percent of high school seniors have taken physics classes, more than ever before. This percentage has been rising steadily since the mid-1980s.
In addition, the percentage…
drorzel | January 10, 2007PhysicsWeb provides me with yet another blog post topic today, posting a lament about the death of letter writing, which makes life more difficult for historians:
Now that e-mail has replaced letter writing as the principal means of informal communication, one has to feel sorry for future science historians, who will be unable to use letters and telegrams to establish facts and gauge reactions to events. In addition to the Copenhagen episode, another example of the role of letters is Stillman Drake's startling conclusion, based on a careful reading of Galileo's correspondence, that the…
drorzel | January 9, 2007In the last week, The IoP's Physics Web has posted two news updates that fall into the category of "regrettable physics," here defined as "the sort of work that makes Daniel Davies say mean things about physicists." I'm talking here about the application of physics concepts to fields where they're neither immediately relevant nor particularly wanted.
The first gets bonus black marks for the title "Physicists Make Religion Crystal Clear" (which, I realize, isn't the fault of the authors, but really...). This reports on forthcoming work applying solid-state models to the growth of world…
drorzel | January 9, 2007A lot of people have commented on this New York Times article on science budgets, mostly echoing the author's lament about the negative effects of operating at 2006 funding levels. I really don't have much to add to that, but it's worth reminding people where the blame for this belongs:
Last year, Congress passed just 2 of 11 spending bills -- for the military and domestic security -- and froze all other federal spending at 2006 levels. Factoring in inflation, the budgets translate into reductions of about 3 percent to 4 percent for most fields of science and engineering.
Congressional…
drorzel | January 8, 2007Paul Davies's forthcoming book Cosmic Jackpot is subtitled "Why Our Universe Is Just Right for Life," so you know that he's not going after small questions, here. The book is a lengthy and detailed discussion of what he terms the "Goldilocks Enigma," and what others refer to as "fine-tuning"-- basically, how do you account for the fact that the universe allows us to exist? A small change in the values of any of the constants of nature would very likely make it impossible for life as we know it to exist. And yet, here we are-- so how did that happen?
Though this book won't be released for a…
drorzel | January 6, 2007While working on a review of a book that talks about the fortuitously bio-friendly constants of nature (review forthcoming, don't worry), I mistyped "ratio of proton to electron masses" and "ratio of proton to electron charges." Which is, of course, 1, and thus not a terribly interesting ratio.
But that got me wondering: is there a solid fundamental reason why that ratio is one? This is, could you have a self-consistent universe in which the electron and proton had different charges-- say, a proton having twice the charge of an electron? That wouldn't be a useful sort of universe, of course,…
drorzel | January 4, 2007One of the standard elements of most academic hiring and promotion applications, at least at a small liberal arts college, is some sort of statement from the candidate about teaching. This is called different things at different places-- "statement of teaching philosophy" is a common term for it, and the tenure process here calls for a "statement of teaching goals."
I spent hours and hours on this, because I get a little obsessive about written work. It did get read closely by the ad hoc committee, at least-- at my first meeting with them, they asked a couple of questions about details of…
drorzel | January 4, 2007I've got lab this morning, so I don't have time for detailed physics blogging today. Happily, there's a new edition of the physics-centered blog carnival Philosophia Naturalis posted today, which should provide plenty of physics content to get your day off to a good start.
drorzel | January 3, 2007A little bit before Christmas, I spent an afternoon swapping mirrors out of one line of the apparatus. I was losing too much of the laser light before it went into the chamber, and replacing the mirrors increased the power entering the apparatus by a factor of two or so.
Here's a picture of the two types of mirrors, side-by-side:
"Well, of course you had to replace them," you say. "The one on the left is a perfectly nice mirror, but the one on the right is utter crap. You dolt."
The thing is, the mirror on the right is the type I was putting in. The one on the left is the type that wasn't…