Physics
pontiff | September 24, 2008Over at Information Processing, the bit processor, Steve, has an interesting post up about your chances of getting a faculty job in high energy theoretical physics. (In between the best posts on the financial turmoil around 1, 2, 3.) If you're a high energy theoretical physics graduate student, and don't want to get depressed today, I would recommend avoiding the post so as to keep up your illusion of safety, but if you want a good dose of reality, check it out.
From the post you can see that the odds of getting a high energy theory job in physics are more close to none than even to slim…
rallain | September 24, 2008**pre reqs:** [Vectors and Vector Addition](http://scienceblogs.com/dotphysics/2008/09/basics-vectors-and-vector-ad…)
This was sent in as a request. I try to please, so here it is. The topic is something that comes up in introductory physics - although I am not sure why. There are many more important things to worry about. Let me start with an example. Suppose you are on a train that is moving 10 m/s to the right and you throw a ball at 5 m/s to the right. How fast would someone on the ground see this ball? You can likely come up with an answer of 15 m/s - that wasn't so hard right?…
drorzel | September 24, 2008So, the LHC has been shut down until next year, after a major helium leak in on section. This means it will be March or April of next year before collisions in the ATLAS detector create dragons that will eat us all.
Now you know why I didn't make a big deal of the "start-up" a couple of weeks ago. (Well, also, I was in Canada at a conference...)
If you're worried that this will delay the march of progress, though, fear not:
The failure occurred as the accelerator's two proton beams were being ramped up for a test run at 5 TeV. CERN had then planned to use the winter shutdown to make final…
drorzel | September 23, 2008Derek Lowe has posted an article about X-ray lasers in chemistry, which amused me because of the following bit:
Enter the femtosecond X-ray laser. A laser will put out the cleanest X-ray beam that anyone's ever seen, a completely coherent one at an exact (and short) wavelength which should give wonderful reflection data.
This is funny to somebody in my end of the science business, because we usually think of femtosecond lasers as have an extremely broad spectrum, not an "exact wavelength." It's a striking example of something I see all the time with chemists-- what chemists think of as "…
rallain | September 23, 2008In my classes, I like to bring up the question:
*Why do astronauts float around in space?*
The most common response to this question is that they float around because there is no gravity in space. Some people take this a small step further and say that there is no gravity in space because there is no air in space. This is why they claim there is no gravity on the moon (even though there is - more on this later).
I like to start off with the concept of gravity. Gravity is an attractive force between any two objects with mass. Your pencil and your dog both have mass so there is a force pulling…
pontiff | September 22, 2008I just saw the news that Alexei Kitaev, a pioneer in quantum computing and an incredible physicst/computer scientist, has won a MacArthur "genius" award. Awesome!
Kitaev was my next door neighbor while I was a postdoc at Caltech, and among the many highlights of my short life I count listening to Kitaev's amazing, confounding, brilliant and way over my head ideas. One event in particular I will always remember involved Alexei talking to theoretical computer scientists and, halfway through the talk, pointing out how Majorana fermions were essential to understanding what was going on in that…
rallain | September 21, 2008**pre-reqs**: [kinematics](http://scienceblogs.com/dotphysics/2008/09/basics-kinematics.php) *I don't think you need [part I of this](http://scienceblogs.com/dotphysics/2008/09/basics-making-graphs-with-ki…) if you don't want*
So, you still want to make a graph with that kinematics data? You think that graphs on paper are too barbaric? Well, if you are ready, you can use a spreadsheet. But be careful. If you don't know what you are doing, you can cause some damage (much like flying a 747 after reading a blog about it). Spreadsheets allow you to do a couple of things.
make pretty graphs…
rallain | September 19, 2008Today I was talking about electric potential. My favorite analogy for electric potential energy is gravitational potential energy. But electric potential is something different. Electric potential (commonly called potential) can be defined as:
So, V is the electric potential in units of Joules per Coulomb or Volts.
What about gravitational potential? I am sure some astrophysicist use gravitational potential. Maybe they even have some units for it, but I have never seen it. My students asked me if there was such a thing as gravitational potential. I said, sure. Here it is:
I picked…
drorzel | September 19, 2008Speaking of quantum (as we were), I've been meaning to link to the recent Scientific American article by Chris Monroe and Dave Wineland on quantum computing with ions. This is a very good explanation of the science involved, but you'd expect nothing else, given that the authors are two of the very best in the business.
What's especially notable about this article is that either they or the graphic design people at Scientific American came up with a really excellent visual example of quantum indeterminacy and entanglement, using ambiguous cubes. It's a clever way to illustrate the phenomena…
drorzel | September 19, 2008The Pontiff beat me to it, but my Ph.D. alma mater has scored a $12.5 million grant from the NSF to fund the Joint Quantum Institute as a Physics Frontier Center for the development of quantum technology:
The Physics Frontier Center (PFC) award, effective September 1, will fund 17 graduate students, seven postdoctoral scientists and seven undergraduates as well as an extensive and highly cross-disciplinary research program under the general title Processing Quantum Coherence. Ultimately the work may lead to development of a computer that exploits the strange phenomena of quantum mechanics…
pontiff | September 18, 2008The University of Marland's Joint Quantum Institute has won an NSF Physics Frontier Center. $12.5 million over five years. This is the first frontier center devoted exclusively to quantum information science. Congrats to UM! Press release below the fold.
UM Awarded $12.5 Million for Research Center at Frontier of Quantum Physics
COLLEGE PARK, Md. -- The National Science Foundation has awarded the Joint Quantum Institute $12.5 million over five years to create and operate a Physics Frontier Center at the University of Maryland. The Joint Quantum Institute is a partnership between the…
rallain | September 18, 2008**pre reqs:** [kinematics](http://scienceblogs.com/dotphysics/2008/09/basics-kinematics.php)
Suppose there is some experiment in which you throw a ball up and collect position and time data (with video analysis). What do you do with this data? Your instructor told you to make a graph, but how do you do that?
Here is the fictional data you (or I) collected:
Here is the text file with the data if you want to reproduce the graphs I make here [kinematics data](http://scienceblogs.com/dotphysics/kinematics_data.…
drorzel | September 18, 2008There's an article in yesterday's Inside Higher Ed about the supply of scientists and engineers, arguing that there is not, in fact, a shortage:
Michael S. Teitelbaum, a demographer at the Alfred P. Sloan Foundation, looked at what he called five "mysteries" of the STEM work force issue. For example, why do employers claim a shortage of qualified STEM graduates while prospects for Ph.D.s remain "poor"? Why do retention and completion rates for STEM fields remain low compared with students' aspirations? Why is there a "serious" funding crisis at the National Institutes of Health after its…
purepedantry | September 17, 2008Apparently, some people think that the name "Large Hadron Collider" fails to capture the terrific grandeur of the device's mission. The Royal Society of Chemistry had a contest to pick an newer, better name, but the winning name proved to be "Halo." No way can they call it that. That name is so copyrighted that angels are getting sued.
Over at Wired Science, they are running a web vote about alternative names for it. Go over and offer your suggestions.
My favorite: "Atom Smasher +5, Holy Avenger" by Gary Gygax
Hmmm...I always thought that Jennifer was a cute name. Hadron colliders are…
drorzel | September 17, 2008Two new recent posts take up the question of "spherical cows," the old joke term for absurd-sounding approximations that physicists make to turn intractable problems into easy ones. First, The First Excited State explains when N=N+1:
Everybody who's taken any sort of math class knows that a statement like N+1 = N is simply ridiculous. Everyone, that is, except for the physicist. Let's say that N is a really huge number, like if someone dumped an entire truckload of M&M's in your driveway. If you turned your back on me to watch the truck drive away, and I threw another M&M in the…
rallain | September 15, 2008I like computers, really I do. Computational physics is a good thing. However, there is a small problem. The problem is that there seems to be a large number of people out there that treat numerical methods and simulations as something different than theoretical calculations. You can tell who these people are because they refer to simulations as "experiments". But what do these simulations really do in science? What is science really all about?
**Science**
To me, science is all about models. Making models, testing models, upgrading models. Models. Some examples are the model of…
rallain | September 14, 2008**pre-reqs:** trig
Think of the following two things. Temperature and wind speed. These are two different things that you could measure, but there is one big difference. Wind speed has two parts to it - how fast and which direction. Temperature is just one thing (no direction). Temperature is an example of a scalar quantity (just one piece of information). Wind speed is an example of a vector quantity - multiple pieces of information. Here are some other examples:
**Scalar:** mass, money, density, volume, resistance
**Vector:** velocity (most physicist reserve the word "speed" to mean…
rallain | September 14, 2008Can you believe it? Have you seen this video?
Are you thinking what I am thinking? WOW. How could these people not follow my rules for cool internet video. Once again, here they are:
1Keep the camera stationary. This way I don't have to keep moving the origin in the movie.
2Don't Zoom. Same reason, this video followed that rule.
3Include a clear and obvious calibration object. A meter stick would work, or even a Kobe Bryant (I can look up his height). Maybe it could be a Ford F-150 that has a known length. Something!
4Include the mass and height of all people involved.
5Use high…
rallain | September 14, 2008Friction in Line Rider
Is there friction in Line Rider? Does it function as physics would expect? To test this, I set up a simple track:
Basically, a slope with a flat part to start with and to end with. Let me show you something simple before further analysis:
This is the x-position vs. time for the line rider on the first horizontal portion of the track (before he or she goes down the incline). This shows the rider…
drorzel | September 14, 2008Kate and I were talking about Garrett Lisi's utopian idea of a time-share netowrk for scientists (about which more later, maybe), and I mentioned the fine tradition of great discoveries being made while on vacation. It occurred to me, though, that there's a secret history story begging to be written about one of these.
Erwin Schrödinger famously discovered the equation that bears his name while on a skiing holiday in 1925. He was accompanied on this vacation by one of his many girlfriends, but which of them went on the fateful trip has been lost to history-- Schrödinger kept exceedingly…