Built on Facts

Archives for September, 2008

Orbits and Escape

How about a quick little circular motion exercise, since that’s what I’m teaching in my recitation at the moment? We know the force equals mass time acceleration, so how about we put the force of gravity on the right side and the force required for uniform circular motion on the left: And we’ll solve that…

The Begats of Physics

Several places in the Bible, there’s long lists of genealogies. The first chapter of Matthew, for instance, looks pretty much like this: …and Asa begat Josaphat; and Josaphat begat Joram; and Joram begat Ozias; and Ozias begat Joatham; and Joatham begat Achaz; and Achaz begat Ezekias… and so on. There’s a point to it. Ancestry…

Sunday Function

In our tour of the zoo of functions we’ve been spending time in the snake pit. These are the pathological functions of pure math, and are generally but not always useless in physics and pretty much everything else. But they’re very cool to look at! We’ll eventually get back to the useful domesticated farm animals…

Physics from All Around

Has anyone checked out ScienceBlogs’ new election site, A Vote for Science? It’s nominally about science issues in the presidential and congressional elections, but of course in practice it’s a pretty standard near-self-parody of the ultraviolet end of the political spectrum. Well, I’ve got an account there as well. Haven’t used it yet, but I…

Greatest Physicists #9 – J.J Thomson

#9 – J.J. Thomson The entire edifice of chemistry is a theme and variation on the study of the properties of atomic electrons. Tremendous sections of physics, from solid state to quantum optics to AMO and beyond hings almost entirely on electron behavior. Astrophysics, spectroscopy, and large chunks of high energy physics rely on the…

#10: Wolfgang Pauli Wolfgang Pauli was once asked to critique a paper of questionable merit. As he is said to have put it, “This is not right. It is not even wrong.” It was a good and concise statement of what physics requires – not merely interesting ideas, but ones that are both grounded in…

News and Apologies

No, I’m not dead or anything. There was no post this morning because I was absolutely bushed and bone tired. Homework, classes, teaching, and research over the last two days were ridiculous. The rest of the week looks not to be so bad. Funny how the whole “work” part of school never makes it into…

Vaguely Suspicious Homework Strategies

Yesterday some of my fellow students and I had this homework assignment which, long story short, amounted to doing some changes of variables. One part of the problem in particular was not very transparent until we realized we were missing a factor of a Jacobian. “I’m just going to write ‘The Jacobian enters in a…

Remember the post a while back where we tried to come up with a list of the 10 greatest physicists? I’ve been thinking and rearranging and I think I’ve come up with a list I’m reasonably happy with. There are quite a few great physicists I’m not happy at all about having to leave out,…

Sunday Function

Draw the graph of a function. Roughly speaking, if there’s no holes, jumps, or other choppy weirdness it’s a continuous function. The function is connected to itself like a curvy rope laid out on the ground, with no cuts. Now if that function has no sharp points, it’s a differentiable function. Again roughly speaking, imagine…