September 30, 2008
In physics, you come up with an idea, formulate it mathematically, find the theory's predictions about the real world, and test those predictions by experiment. This works because God is subtle, but not malicious (to borrow Einstein's words). In more concrete language, the laws of physics fit…
September 29, 2008
Update: I seriously feel guilty for writing politics in a physics blog. I personally sometimes get annoyed at reading politics on other non-political blogs, and I imagine you do too. That's why I happily encourage you not to read anything I write tagged with politics unless you like that sort of…
September 29, 2008
#7 - Erwin Schrodinger
Schroedinger, Erwin! Professor of physics! Wrote daring equations! Confounded his critics!
That's the first couple of lines of Cecil Adams' brilliant epic poem about Schrodinger's cat. Why does Schrodinger deserve an epic poem? Because he's the 7th greatest physicist, that…
September 27, 2008
Due to some homework which is taking longer than anticipated, today's Sunday Function will have to be a bit quick. It's no less interesting for that.
Define a function Q(n) on the natural numbers, such that Q(n) = 1 for a prime number and Q(n) = 0 for a composite number. In other words, it's just…
September 27, 2008
The debate? Didn't watch it. I'm keeping my "not watching the debates this year" record spotless. Not because I don't want to keep myself informed but because modern TV debate formats don't let anyone do anything but go for the best soundbites, zingers, and gotchas. That said I'll probably read…
September 26, 2008
Mean-spirited reactionary politics below the fold. If you're a kind-hearted liberal here for the physics, you might want to skip this post, have a nice tea instead, and calmly meditate on Obama's recent rise in the polls.
I've had several conversations with people over the past few days about the…
September 26, 2008
The Terminator?
Which headline do you think would sell more papers?
INTELLIGENT ROBOTS KILL 20,000, NO SIGN OF STOPPING
or
AUTO FATALITIES DECLINE 50%
In a nutshell, this is the PR problem of technology. Technological progress is taken for granted, and technological problems are trumpeted to the…
September 25, 2008
We're holding a rock, and we drop it. What happens?
There's lots of methods for treating this problem. We've done it with Newton's laws of force, and we've done that in more than one way. We've done the Lagrangian formulation in terms of minimizing the classical action. I don't think we've done…
September 24, 2008
#8 - Paul Dirac
Dirac was a physicist of incredible brilliance even by the standards of the great physicists. You can't turn a corner in quantum physics without bumping into something he discovered.
Solve the ubiquitous and vitally important quantum harmonic oscillator problem using the wave…
September 23, 2008
Hey, I just wanted to draw some attention to this great post of Chad's about femtosecond lasers and laser bandwidth in physics and chemistry. Those lasers are near and dear to my heart, as they're one of the main focuses of my research group.
And just so you have some original content, here's the…
September 23, 2008
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…
September 22, 2008
Richard Feynman once said of large numbers that "astronomical" was no longer the best adjective. "Economical" was. There are more dollars in the national debt than there are miles in a lightyear.
Today we're getting a some exposure to one of those numbers: $700 billion. It's the size of the…
September 22, 2008
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…
September 21, 2008
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…
September 20, 2008
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…
September 19, 2008
#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…
September 18, 2008
#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…
September 17, 2008
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…
September 16, 2008
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…
September 15, 2008
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, but 10 is a…
September 14, 2008
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.…
September 13, 2008
One of my favorite writers, the extraordinary David Foster Wallace, is dead after ending his own life. He was 46.
My first exposure to his work was his beautiful mathematics book Everything and More: A Compact History of Infinity. He brought his extraordinary skill as a narrative fiction writer…
September 13, 2008
Yesterday I was watching Discovery's Project Earth, avoiding doing homework and grading. It's an interesting show, with ideas ranging from the interesting to the preposterous. The episode I saw proposed launching little lenses into space to scatter a small fraction of the sun's light away from…
September 12, 2008
"It's not the heat, it's the humidity."
This is said by people all over the country, especially so in the coastal south where 90+ degree heat is made that much worse by air thick enough to swim in. But heat is usually an inconvenience. Hurricanes are another matter. It's not the wind, it's the…
September 12, 2008
There's a comic strip called Non Sequitur. Not one of my favorites, but occasionally there's a pretty good one. Here's an example. We have a kid speculating about firing a gun on the moon. He asks:
If you were on the moon, which is a vacuum, and tried to shoot a gun, would it fire? After all…
September 11, 2008
You're probably more tired of politics than I am, but somebody has to be the voice of reason around here. I apologize to my physics-loving nonpolitical readers and urge those of you fitting that description to avoid anything I write with the politics tag. It will all be over soon.
Maybe it's…
September 11, 2008
Reader nanoAl had an interesting observation about the post on applying an electric charge to the earth. We were trying to find out how much electric charge would need to be applied to the earth and the moon to cancel out their gravitational attraction. The answer was suprisingly little. Here's…
September 10, 2008
If you're here for the physics and not the politics, skip this entry. I wouldn't blame you. It irritates me to read politics on science sites too, but with the election only about two months away it's hard to resist the temptation. Here we go.
Neurotopia links to an article criticizing Sarah…
September 10, 2008
Ever wondered why it takes a tremendously huge rocket to launch people from the earth, but the Apollo astronauts managed to launch from the moon in a comparatively tiny lunar module? Easy, the whole thing was faked and NASA forgot to come up with a plausible explanation!
Wow, it was almost…
September 9, 2008
There's been a lot of discussion about NASA administrator Mike Griffin's leaked email about the future of the space station. It's a fascinating, honest, and cogent look at where we stand now at the crossroads of the Shuttle and the eventual Ares/Orion system. He's precisely right on the facts.…
