As the advent calendar moves into the E&M portion of the season, there are a number of possible ways to approach this. I could go with fairly specific formulae for various aspects, but that would take a while and might close out some other areas of physics. In the end, all of classical E&M comes down to four equations, known as Maxwell's equations (though other people came up with most of them), so we'll do it that way, starting with this one: This is the first of Maxwell's equations, written in differential form, and this relates the electric field E to the density of charge in…

Having covered most of what you need to know about classical physics, the traditional next step is to talk about electricity and magnetism, colloquially known as "E&M," though really, "E and B" would be more appropriate, as the fundamental quantities discussed are the electric field (symbol: E) and the magnetic field (symbol: B), whose effect is given by today's equation: This is the "Lorentz force law," giving the force experienced by a particle with charge q moving at a velocity v through a region with both electric and magnetic fields. This is, in some sense, what defines those…

We kicked off our countdown to Newton's birthday with his equations of motion, so it seems fitting to close out the section on classical mechanics with another of Newton's equations, this time the Law of Universal Gravitation: Like all the other equations to this point, I'm cribbing this from the formula sheet for my just-completed intro mechanics class, which means it's in the notation used by Matter and Interactions. This is sub-optimal in some ways-- I prefer to have subscripts on the r to remind you which way it points, but I don't care enough to re-do the equation. So, this is the…

Tom Stites: Taking stock of the state of web journalism » Nieman Journalism Lab The buzz about how bloggers and citizen journalists will save the day, once almost deafening, has died down to a murmur, although the buzz about Twitter, Facebook, and cellphone video cameras saving the day has picked up thanks to their powerful contributions to coverage of major breaking stories, from the Arab spring to Occupy Wall Street. But the triumphant march to the digital future, at least when measured in terms of original reporting, has yet to lead anywhere near triumph. Yet the picture is not entirely…

Today's advent calendar post was delayed by severe online retail issues last night and child care today, but I didn't want to let the day pass completely without physics, so here's the next equation in our countdown to Newton's birthday: This is the final piece of the story of angular momentum, the undefined symbol from the right-hand side of the angular momentum principle: torque is defined as the cross-product between the radius vector pointing out from the axis of rotation to the point where the force is applied, and the vector force that acts at that point. As with the definition of…

Three quick items relating to science in book form: 1) It's that time of year again when every media outlet of any consequence puts out a "Year's Best {Noun}" list, and John Dupuis is checking the lists for science books so you don't have to. It looks like a pretty reasonable year for science in the best non-fiction-book-list world, but you can see for yourself. 2) In the "good books about science coming next year" category, the line-up for The Open Laboratory anthology of outstanding science blogging has been announced. I'm very pleased to report that my write-up of the OPERA preprint was…

Now that we've defined angular momentum, the next equation on our countdown to Newton's birthday tells us what to do with it: This is the Angular Momentum Principle, and as with energy and momentum before it, this relates the time derivative of the angular momentum (that is, how quickly it's changing its value) to a quantity related to the interactions with other objects, in this case the torque. So, why is this important? As with energy, with the proper choice of system, we can often ensure that there is no net external torque on the system, in which case the right-hand side of this…

Print - What Really Happened Aboard Air France 447 - Popular Mechanics Human judgments, of course, are never made in a vacuum. Pilots are part of a complex system that can either increase or reduce the probability that they will make a mistake. After this accident, the million-dollar question is whether training, instrumentation, and cockpit procedures can be modified all around the world so that no one will ever make this mistake again--or whether the inclusion of the human element will always entail the possibility of a catastrophic outcome. After all, the men who crashed AF447 were three…

The Pip turned one month old yesterday, so to celebrate, here's a picture of the whole family: OK, it's not a photograph, but look! SteelyKid drew that all by herself! (The labels on the drawing were done by one of her preschool teachers; the printed text was added by me when I obscured the given names of SteelyKid and The Pip.) This one's going to be on the fridge for a while. For those who insist on photos, there are a couple below the fold: First, a traditional Appa-for-scale shot: (Picture by Kate, with my camera.) And while it's hard to take pictures of SteelyKid these days, she really…

Catching Up To the Future: An Appreciation of William Gibson | Tor.com William Gibson is one of those writers whose name is in the process of becoming an adjective--consider Kafkaesque, Ballardian, Pynchonesque: words for which the meaning has become osmotically absorbed even by people who haven't necessarily read the authors' books. Now we have Gibsonesque (or perhaps "Gibsonian"? The jury remains out). As with all such things, it's not necessarily easy to define--if it was, we wouldn't have needed to adjective-ize the name to begin with. Vishnu Parasuraman on the problems with the BCS -…

One of the things that is sometimes very frustrating (to me, at least) about popular physics books is that they rush very quickly through the physics that we already know, in order to spend time talking about wildly speculative ideas. This not only gives some of these books a very short shelf life, as their wilder speculations get ruled out, but it does a dis-service to science. Because as cool as some of the things that might be true are, the stuff that we already know is pretty awesome in its own right, and even more amazing for being true. Happily, Frank Close's new book, The Infinity…

Moving along through our countdown to Newton's birthday, we come to the next important physical quantity, angular momentum. For some obscure reason, this gets the symbol L, and the angular momentum for a single particle about some point A is given by: This is probably the most deceptive equation we'll see this season. Yesterday's definition of work clearly showed its vector calculus roots, but to the untrained eye, this just looks like a simple multiplication: You take the momentum (p) and multiply by the distance (r) from point A, and you're all set. To those with a little mathematical…

"In the first place God made idiots. This was for practice. Then He made School Boards." -- Mark Twain In last night's post about a school board member failing 10th grade standardized tests, I may have unfairly slighted our students. In response to a comment in which Rick Roach, the school board member who couldn't pass 10th grade math, implied that nothing on the test would be of any practical use, I wrote: As someone who quite regularly has to teach introductory physics to students who struggle with it because they have a shaky grasp of tenth-grade math, I'm really not any happier with the…

Following the basic pattern established at the start of our seasonal countdown to Newton's birthday, today's equation defines a piece that was left hanging in yesterday's post: This is the technical definition of "work" in physics terms. It's also probably the scariest-looking equation to this point, as it explicitly involves vector calculus-- there's an integral sign, and a dot product. The basic concept is simple enough, though: you look at the force F exerted on an object, multiply it by the distance dr that the object moves under the influence of that force, and then add up the Fdr…

You Khan't Ignore How Students Learn | Action-Reaction People's reactions are not indicators of effectiveness. Pre/post testing is needed to indicate effectiveness. Ah, but perhaps there is a relationship between people's reaction and effectiveness? The research indicates otherwise. In the very research study that Khan says is valid (and then dismisses), student actually did better after watching the videos they described as confusing, and made no gains after watching the videos they described as easy to understand. Additional research indicates that when an instructor switches over to IE…

A blog run by the Washington Post featured a post on Monday about an adult taking and failing a standardized test, who was later revealed as school board member Rick Roach: Roach, the father of five children and grandfather of two, was a teacher, counselor and coach in Orange County for 14 years. He was first elected to the board in 1998 and has been reelected three times. A resident of Orange County for three decades, he has a bachelor of science degree in education and two masters degrees: in education and educational psychology. He has trained over 18,000 educators in classroom management…

It's hard to go more than a couple of days without seeing another "imminent death of publishing" article somewhere, predicting the ultimate triumph of ebooks, There's one category of books that I expect to remain safe for the foreseeable future, though, namely books that are specifically constructed to be aesthetically pleasing. In other words, coffee-table books. Clifford Pickover's new Physics Book is one of these. It's a very attractive and well-made book, pairing some 250 full-page images representing milestones in physics, paired with one-page descriptions of the underlying scientific…

For the sixth day of our advent countdown to Newton's birthday, we have the first equation that really departs from the usual notation. I've gotten to kind of like the way the Matter and Interactions curriculum handles this, though, so we'll use their notation: This is what Chabay and Sherwood refer to as the Energy Principle, which is one of the three central principles of mechanics. The term on the left, ΔE represents the change in the total energy of a system, while the two terms on the right represent the work done on that system by its surroundings, and any heat energy flow into or out…

How Doctors Die « Zócalo Public Square It's not a frequent topic of discussion, but doctors die, too. And they don't die like the rest of us. What's unusual about them is not how much treatment they get compared to most Americans, but how little. For all the time they spend fending off the deaths of others, they tend to be fairly serene when faced with death themselves. They know exactly what is going to happen, they know the choices, and they generally have access to any sort of medical care they could want. But they go gently. Paris Review - Document: The Symbolism Survey, Sarah Funke…

I'm still getting back up to speed with the blog, as well as the huge backlog of stuff I've read during the past few months when I was too busy to blog. Thus, I am semi-officially proclaiming this Book Review Week. I'll post one review a day of books I was sent by publishers looking for a mention on the blog. We'll start off with The Manga Guide to the Universe, which is from the same organization that brought us The Manga Guide to Relativity. This one is, as the title suggests, a cartoon introduction to astronomy. As is standard for the Manga Guide series, this has a framing story involving…