October 20, 2010
You're taking your morning shower and a thought occurs to you. "In classical electrodynamics, an accelerating charge radiates. In general relativity, acceleration is equivalent to a gravitational field. Therefore a stationary charge should radiate simply by virtue of being in a gravitational field…
October 17, 2010
Here's a straightforward function of two variables, x and y:
Its domain is all real x and y, with the single exception of x = y = 0, which would make the denominator 0. But we have experience with functions such as sin(x)/x, where we can find the limiting value as x approaches 0 and just make a…
October 15, 2010
Generally speaking, if you play a movie backwards everything that happens is still physically possible. If I throw you a baseball and you catch it, reversing the video is just the equally plausible situation of you throwing the baseball followed by my catching it. If entropy is changing in the…
September 26, 2010
Death and taxes. And dead is dead, but taxes come in a huge panoply of forms. There's property taxes, excise taxes, sin taxes and income taxes. There's gas taxes and sales taxes and VAT taxes (yeah, I know) and death taxes.
With my politics I'm not a huge fan of any of them, but they are what they…
September 23, 2010
Whew! Back from a very successful wedding and honeymoon, moving into a new apartment, writing thank-you notes, and all the fun jazz that comes with being newly married.
But hey, we've got to get this blog cranking again at some point, and now's as good a time as any. We'll kick things back off…
September 2, 2010
This Saturday I'm getting married! The following week I'll be in Barbados relaxing on my honeymoon. While Barbados is a highly developed Caribbean economy with no shortage of internet access, in the interests of relaxation and matrimonial bliss I shall not be online. Posting will resume the…
August 29, 2010
If you go to the bank and open a savings account, the banker might tell you about the virtues of compound interest. He may say something like "Even if you never deposit anything, the rate of change of the money in your account is proportional to the amount of money in your account. The more you…
August 27, 2010
If you take a flashlight and shine it at a wall or through a prism or do pretty much anything with the light, you'll find that the effects of the light change in direct proportion to the amount of light the flashlight's putting out. Twice the light, twice the reflection from the wall. Twice the…
August 22, 2010
Here's an odd little bit of math for you this Sunday. It's defined in terms of recurrence. Recurrence happens when a function is defined in terms of itself. This happens more than you might think - one famous example is the Fibonacci sequence, which is informally defined by saying "To get the next…
August 18, 2010
A few days ago there was an interesting math problem posed on the right-leaning lawprof blog The Volokh Conspiracy. It's a cute problem in itself, and it makes a nice discussion example about the role of computers in modern physics. The problem is this:
Find a ten-digit number with the following…
August 17, 2010
Because I'm a bad busy person, this review of Chad Orzel's How to Teach Physics to Your Dog is only, oh, about 8 months late. You have probably all bought it already. But in case you haven't, I'll tell you what you're getting into.
If you wander over to your local bookstore's science section, you'…
August 16, 2010
The new academic year is starting, and if there's one thing students love it's a good word problem. If Sue is four times as old as John will be when Sue is one year than John... So in that spirit I was amused to find basically this kind of problem in a college physics textbook I was perusing for…
August 15, 2010
So I spent two weeks in Wyoming, participated in a wedding in Louisiana, moved two apartments worth of stuff, visited Louisiana again to get a marriage license for myself (20 days left!), collected data for an experiment demonstrating a new result we're trying to get published quickly (hot topic,…
July 22, 2010
I've been in Casper Wyoming the last few days at the Workshop of Quantum Science and Engineering, put together by Dr. Marlan Scully. The point of the workshop is to discuss the various work we're doing, exchange ideas, and all the other stuff that usually happens at these physics shindigs. We've…
July 15, 2010
It's a pretty nice time for quantum optics and laser physics at Texas A&M, with us moving into a brand new lab and acquiring several new laser systems. One of the systems we're moving isn't new (we've had it for a few years, and the technology is considerably older), but we're about to put it…
July 11, 2010
Again, apologies for the hideously scanty posting. Been in the lab doing some really interesting research which will with some luck get me in a really nice journal, as well as doing the various rounds of revision on the paper for some previous research. Also putting two talks together for a…
July 4, 2010
Happy birthday to the United States! It's one of the younger countries on the planet and yet has still managed to have one of the oldest continuous systems of government. Not too shabby. Here's hoping our current wobbles get straightened out and our next few Independence Days occur under more…
June 30, 2010
The laser pointer, much beloved of PowerPoint lecturers, cat owners, amateur scientists, and middle school boys at movie theaters, is actually a pretty amazing device. There's quite a bit you can do with a relatively cheap laser, and they're just plain fun. They're also relatively safe. The red…
June 24, 2010
I'm not normally much of a soccer fan, but the World Cup doesn't happen every day and it's pretty interesting to see all the excitement and high level of play. I personally think the rules need a little tweaking to reduce the tendency toward 0-0 and 1-1 ties, but I suppose the sport couldn't have…
June 18, 2010
On a web forum I frequent, a person asked if it would be possible to extract energy from the Earth's magnetic field. He was told no - static magnetic fields can't transfer energy. For all practical purposes this is true, but in fact we also know that the earth's magnetic field isn't static. It…
June 17, 2010
As you might expect for a guy who does experimental optical physics, I get to spend a tremendous amount of time in labs with some fairly snazzy lasers. Most of them are fairly specialized pieces of equipment that aren't really designed simply to dump huge amounts of power in industrial applications…
June 13, 2010
A while back I mentioned the St. Petersburg paradox. It's a hypothetical gambling scenario where you win money based on the outcome of a coin toss. If you get your first tails on the first throw, you get $1. If you get one head before your first tails, you get $2 dollars. If you get two heads…
June 9, 2010
This is a poster in a hallway here in the Texas A&M physics building:
Sort of an odd question, but an interesting one. Sound waves carry energy, and if that energy we being absorbed by your coffee because you were yelling at it, how long would you have to do so before it was piping hot?
But…
June 6, 2010
Back in 2003, I was a college freshman sitting in my first college math class - Honors Calculus I. On what was probably the second or third day of class, the professor gave us a surprise quiz. It was something like: "Give the formal statement of the principle of induction". It was my first graded…
June 1, 2010
Grab a particle and put it in a box.
According to elementary quantum mechanics, that particle isn't described by the classical model in which it can have any value of energy as it bounces around. Instead, the possible energy levels of that particle are described by a discrete set. When you measure…
May 27, 2010
Before we get to the heart of yesterday's quiz, let me briefly define solid angle for those who may not be familiar with it. Regular angles are measured in degrees or radians, and solid angles are to angles as square meters are to meters. Solid angle is more or less angular area, and is measured in…
May 26, 2010
Pop quiz! The picture below is a solar power facility wherein light from the sun is collected by mirrors and focused onto the top of a collecting tower. Fluid within the tower is heated by this light and the hot fluid is used to generate power. We won't care about that in this quiz though; we're…
May 23, 2010
You're a member of the French Resistance in the height of WWII. You're part of a network of resistance members who have to work with other resistance members they've never met before. For instance, an agent from Paris might have to meet up with an agent in Normandy to work together on sabotage…
May 22, 2010
I can't let this week go by without mentioning that it is - officially - the 50th birthday of the invention of the laser.
Officially, anyway. On the 16th of May 1960, Theodore H. Maiman produced the first working optical laser. There was actually recently a huge slap-fight in the letters to the…
May 19, 2010
Space Shuttle mission STS-132 is currently orbiting over our heads. It's scheduled to land a week from now. After that, there's two more launches and that will be that for the program. At that point the US will officially be out of the business of launching people into orbit, and there's not a lot…
