September 8, 2008
There's got to be what, probably one or two Metalocalypse fans in the readership? The rest of you will probably be pretty confused, but bear with me. Quick primer: the show is about an absurdly successful but actually incompetent death metal band called Dethklok.
The season finale was last night…
September 7, 2008
Take as our starting point this function, defined on the positive whole numbers:
All it does is add together the fractions above, stopping when you hit the fraction specified by your particular choice of n. As you increase n and thus add more fractions to the sum, you'll end up with a plot of the…
September 6, 2008
Friday I met my first ScienceBlogger in person. Nick Anthis from The Scientific Activist was in town, and as he's a former Aggie we got to trade a few stories about the university and the different kinds of work we're doing. He's a cool dude! It was very nice meeting him, and I think it might…
September 5, 2008
I've taught seven recitation sections as a graduate student, and this semester I'm teaching three more. Between them it's several hundred hours of standing in front of a classroom teaching. That's nothing compared to career teachers and professors, but it's a decent bit of experience as far as TA…
September 4, 2008
Teaching Physics 201 has me digging out some of my old favorite concept-y problems. Nothing dramatic in the mathematics, but at the 201 level you can't even assume knowledge of derivatives. But you can try to catch their minds with interesting examples. Here's a classic one:
You've got the earth…
September 3, 2008
Physics is a continuous thing, progressing steadily forward with only rare dramatic leaps. This is not the kind of style that makes for flashy news stories in the popular press. When there are interesting things being reported, they're usually wrong. "Faster than light" laser pulses, quantum…
September 2, 2008
In honor of Physics 201 which I'm teaching this semester, I present a very elementary statics problem.
Here we have a board of uniform composition and weight W. It has length l and the supports are separated by a distance s. What are the two forces (call them A and B) on the boards?
The board…
September 1, 2008
Fundamentally, you can start off with the Standard Model. It's not perfect, but it's a pretty good description of the particles and forces of nature especially at the mostly low energies of our soar system. Using quantum mechanics you can built up those particles into distinct nuclei, and…
August 31, 2008
We can't graph here, this is bat country! Complex bat country.
...well ok, let's stop and take a look anyway. But no graph.
You've seen this jewel of mathematics. It's Euler's identity.
It comes from the more general expression right below this paragraph, which is today's Sunday Function. You…
August 30, 2008
First, a Public Service Announcement: As a decade-long former south Louisiana resident who was in Baton Rouge for Katrina, I have some advice. If you're in Louisiana anywhere south of about Alexandria, now's the time to start packing. You might be ok sticking around till Saturday night or…
August 29, 2008
I really loathe politics, and have mostly tried to avoid writing about it. But finally something interesting has happened, and it's worth a brief comment.
In physics we like to talk about symmetry. Conservation laws and symmetry are intimately related, and you can learn a lot about one by…
August 29, 2008
Top 10 lists are silly. But they're fun, which is why there's so many of them. In a week or two, I'm going to start a brief biographical series with a little bit of information on the lives and works of the great physicists.
The top 3 are obvious (Well, to me anyway). The top 5 - I think I have…
August 28, 2008
Nine dayes they fell; confounded Chaos roard,And felt tenfold confusion in thir fallThrough his wilde Anarchie, so huge a routIncumberd him with ruin: Hell at lastYawning receavd them whole, and on them clos'd,Hell thir fit habitation fraught with fireUnquenchable, the house of woe and paine.-…
August 27, 2008
Physics professors have this annoying habit. They'll present a problem to be solved, figure out how to describe it in mathematical terms, and declare that the physics is done and the rest is just math.
Well yeah, but that's kind of like drawing a blueprint for a house and then declaring to your…
August 26, 2008
We all know what the formula for kinetic energy is. Take the mass, multiply by the velocity squared, divide by two. In 1905, Einstein raised his hand and said that we're not quite right. In fact the actual expression for kinetic energy is
where c is the speed of light and
That doesn't look…
August 25, 2008
This is one of those times when being a non-anonymous blogger is a little inconvenient. Nonetheless, I think I can make things a little vague and change a few names and I'll be ok.
As I mentioned a couple of days ago, I'm taking two classes. I thought nothing of it when I signed up for them; they…
August 24, 2008
If you're a regular reader of this site, you might remember a post about this fascinating specimen from the collection of unusual functions. I'm only showing it on the interval [-1,1] for reasons that will become apparent, but outside that region the growth tapers off rapidly and the function…
August 23, 2008
Don't think I've forgotten about the falling electron question from a while back. Short version: an accelerating charge radiates. So if you let an electron fall in a gravitational field, it should radiate. But a person (or detector) falling along beside it does not perceive the electron as…
August 22, 2008
Congratulations to all the Olympic athletes who have competed thus far, especially Michael Phelps, Nastia Liukin, and Shawn Johnson. Gymnastic events are all great to watch, and I don't think you could find a more colorful analyst than Bela Karolyi. The balance beam is probably the most classic…
August 21, 2008
You can break the laws of your local jurisdiction. It might not be a good idea, but if you want to drive 60 in a 45, you can. You'll pay a hefty fine if you get caught, but you'll still have been able to do it.
There's no penalties for breaking the laws of physics because you can't break the laws…
August 20, 2008
This is Zhang Juanjuan, immediately after applying an impulse to an arrow. Impulse is something which gets less airtime than work in freshman physics, but it's nonetheless very important. It's sort of momentum's version of work.
You'll remember from Monday that there are two main things to keep…
August 19, 2008
This is more technology than strictly physical science, but I'm professionally interested in laser physics. My own area is mainly attosecond pulses at modest average power, still, the applications of broader laser technology are always instructive.
Boeing has been working on laser weapons…
August 18, 2008
This is Liao Hui, not doing any work. He did work to get the weight over his head, but despite the tremendous force he's applying to this 348 kilogram [Update: Thanks to commenter Ducklike for correcting this to 158 kg] weight he's not doing any work in this picture. The weight is stationary.…
August 17, 2008
You all know what the natural log function looks like. Take the number 1, divide it by the natural log, and then find the antiderivative of that function. You'll get the logarithmic integral function. It looks like this:
Sometimes the lower limit of the integral is changed to 2 instead of 0,…
August 16, 2008
Greg Laden responds to the recent change in policy allowing teachers with concealed carry permits to carry in one particular public high school in north Texas should they so choose. If only the teachers had guns.... (Texans = Morons). Here's CNN's original story.
The school is a 30-minute drive…
August 16, 2008
A quick Olympic question: How would a native of China pronounce the j in Beijing? All the commentators pronounce it like the J in the French je suis, but I've heard that in China the pronunciation would be closer to the J in jingle. I have no idea if this is true, and I'm not at the university…
August 15, 2008
What's the temperature inside a microwave oven?
I've seen some thermodynamics textbooks start off with a preliminary definition of temperature that amounts to "The temperature is what a thermometer says it is", since temperature is really a concept that fundamentally is derived from energy and…
August 14, 2008
I think it's time for a good old practice problem. This is a pretty basic one, which you might encounter as a freshman physics major. The general concept of dealing with inelastic collisions is one that you never escape, and from special relativity to quantum mechanics this type of thing keeps…
August 13, 2008
MarkCC on Good Math, Bad Math has been posting lately on encryption and privacy. As usual, technology has increased the number of ways the government can read your mail, but it has also increased the ways you can hide your communications as well. Modern open-source encryption is very secure and…
August 13, 2008
In quantum mechanics, particles like electrons can be observed in one of two spin states: up or down. The theory, however, doesn't require the state to be completely determined before we look at it. Any given electron doesn't have to be in one of those spin eigenstates; it can be in a…
