May 6, 2009
Sorry for the light blogging this week. Finals are this week and next, and so I'm pretty swamped. Today I'm going to pose a straightforward but slightly counterintuitive probability question, of the sort that in modified forms aren't so uncommon in physics:
A densely populated authoritarian state…
May 4, 2009
Our excellent physics blogger Chad Orzel has a post up about the thermodynamics of Goldilocks. Seems it's a little questionable to have the porridge configured as it was in the old tale. A few wags in the comments complain that in a story with talking bears physics is the least of the concerns,…
May 3, 2009
"I'd like to open a savings account," you tell your banker.
"Excellent!, the banker says, "our savings accounts have an interest rate of 5% and an annual percentage yield of 5.127%. It's a great deal and I think you'll like it."
5% interest is a great deal on a savings account these days. But…
May 2, 2009
Well, we've explored some groundwork in three previous posts and so it's time to put it all together. Why exactly do bosons have such weird behavior at very low temperatures, with a large fraction of their number crowding into a single quantum state? Let's plow on. If you're not familiar with…
April 30, 2009
Normally I stay mostly on the physics beat, trying to mostly stay out of the controversy arena except occasionally when my lunatic reactionary politics crops up in something like my Social Security piece a while back. But all things considered I much prefer to a nice, collegial, uncontroversial…
April 29, 2009
That Professor Goddard, with his 'chair' in Clark College and the countenancing of the Smithsonian Institution, does not know the relation of action to reaction, and of the need to have something better than a vacuum against which to react - to say that would be absurd. Of course he only seems to…
April 28, 2009
Yes, it's Tuesday. Busy weekend, including a Relay for Life (you should find your local one and donate!). Today we'll get back on schedule a bit and make this one a rather more utilitarian than usual Sunday Function, playing into the last step we'll need in order to complete the Bose-Einstein…
April 25, 2009
[This post is tremendously nerdy Star Wars fan ranting. There is no physics. You have been warned!]
Let me get this straight: I tremendously enjoyed Star Wars: Episodes 1-3. I enjoyed them in all their badly-acted, incoherently characterized, effects-dependent glory. Every single one of them I…
April 24, 2009
"Everybody listen up!" shouts the high school PE coach, "I'm splitting you up into N teams of equal size. I'm going to make the selection of players randomly, so with any luck the teams will be of equal skill. The players with high skills all the way down the continuum to the players with low…
April 23, 2009
Today we're going to have to do some groundwork to set up for a step we're going to need a post or two from now. It has to do with density in a slightly more abstract context than usual.
Imagine you want to know how many people are living in a particular region. You can multiply the population…
April 22, 2009
It's been a while since we've worked on some slightly more heavy-duty physics, so I'm going to spend the next couple of days going through the basics of the theory of Bose-Einstein condensation. Let me set the stage:
Particles can be divided into two classes based on a quantum mechanical property…
April 21, 2009
Reader Timothy writes in with a question:
It seems that the north pole would get more daylight during the summer solstice than the equator does during an equinox. During the summer solstice, the north pole would get the equivalent of (24hrs)sin(23.5 ° ) = 9.57 hours of sunlight from directly…
April 19, 2009
"So," Herr Schrodinger says to us, "I'm looking for a function of x. It needs to be equal to the negative of its second derivative, up to a constant factor. When x is zero, the function itself should be zero. And when x equals L for some constant L greater than zero, the function also needs to…
April 18, 2009
An emailer sends in a link to a comment on The White Coat Underground. It's in the context of naturopathy, the idea that medical problems ought to be treated with natural means. Some of it's a good idea - eating right, exercising, that sort of thing. Those sort of things aren't going to cure…
April 17, 2009
It was a dark and stormy night. Well, it was day. And it wasn't all that dark either, but it was very stormy. Yes, in College Station today it was pretty miserably wet and so was everyone on campus. Even if you had an umbrella.
Not actually very glorious.
Well, I thought, I wonder if you could…
April 16, 2009
Let's say you've got one of these, and you're dusting off your computer:
(img source)
As you spray, you'll notice the can getting cold. You've probably noticed this in similar contexts: propane tanks getting cold, helium tanks getting cold, compressed air tanks running pneumatic tools getting…
April 14, 2009
I almost titled this entry "Rocket Porn" but I wasn't sure if the management would appreciate it. Still, to the space enthusiast this is definitely pretty enthralling.
These photos are straight from my old college roommate, now an engineer at NASA's Stennis Space Center. He works in a building…
April 13, 2009
I can't think of a way to relate this to physics, but it's just too cool not to share. In New York City there is an artist named Kacie Kinzer. She created small cardboard robots that can do precisely one thing - roll forward continuously. Well, that and look cute.
Attached to these robots is a…
April 12, 2009
Today is Easter Sunday, the most sacred and second most widely observed holy day in the Christian calendar, celebrating the resurrection of Jesus. Friday was Good Friday, the remembrance of the crucifixion. Thus after spending three days buried, Jesus rose from the dead.
Wait, three days? Let's…
April 11, 2009
Mike the Mad Biologist links to a piece arguing that Social Security is fine thank you very much. Rumor to the contrary is pure political propaganda, and the fact that many young people think they'll never see a dime is a result of simple fearmongering.
I am sorry to say that they're not right.…
April 10, 2009
Earlier this week I wrote up a brief outline of an experiment to measure the speed of sound using only your singing talent. I'd like to be able to do the same thing with the speed of light. But it's a lot harder because light is so friggin fast. As with sound, the speed of a traveling wave c is…
April 9, 2009
I have a project for you, since I know practical physics is pretty popular around here. This one involves orbital dynamics, optics, and astronomy. The required experimental apparatus is just your eyes, a clock, and an internet connection.
There are these satellites orbiting overhead by the name…
April 8, 2009
So not only did I miss the Saturday and Sunday posts, but also the Monday and Tuesday ones as well. Gah! It's honestly quite a bit more difficult to keep to the one-per-day regimen this semester than I though. Nonetheless I'll try to stick to that schedule to the greatest extent possible. KBO.…
April 3, 2009
I'm going to be out of pocket most of this weekend, though with any luck I'll still have the standard Saturday miscellany and Sunday Function posted. Today I'll be on the road, and leave you with a slightly useless bit of trivia:
The average density of books in my apartment is 1.83 per square…
April 2, 2009
I've wanted to do some writing about statistical mechanics, but it's difficult to do without it turning into deathly boring strings of equations. There's ways to make it interesting, I'm sure, and I think webcomic artist Randal Munroe has found one:
Full size at the link. "Hmm," thought I when I…
April 1, 2009
This is a pulley, pulled straight off Wikipedia:
On the test that my students had last week, there was a question involving pulleys connected in a sort of eclectic arrangement. The objective was to find the tension in certain ropes which were holding the pulleys up.
Imagine instead of being…
March 31, 2009
I have a Fermi problem for you. By the very nature of a Fermi problem, a precise answer is impossible, we're merely looking for a justified order-of-magnitude estimate. Here goes:
During last week's Earth Hour event, what amount of CO2 was not released that otherwise would have been? What is…
March 30, 2009
Before we figured out that the universe was a very large open space with lots of stuff scattered about, the ancients had some interesting ideas on how the sky worked. Roughly speaking, celestial phenomena came in three kinds. There are the stars, which remain a constant, fixed background. There…
March 29, 2009
The quadratic formula. With the exception of the Pythagorean Theorem, it's probably the single most common mathematical formula people carry from high school. It's not a function as such, it's something that solves a function. Let me give an example:
Pick a number x, square it, add twice x to…
March 28, 2009
Saturdays I tend to use for soapboxing on things which may or may not be related to physics. Today I think it will be free speech. There's a Supreme Court case involving Hillary: The Movie in the context of McCain-Fiengold campaign finance law. Suffice it to say that free speech is non-…
