Physics
rallain | April 21, 2009I am not sure if First Excited State posted this as a blog entry, but it was mentioned on twitter. Question: why are sparks blue? My first gut response was that this is the blackbody color. Wrong for several reasons. The short answer is that sparks are blue because of the colors given off from nitrogen and oxygen when they are excited.
In order to make this post longer than necessary, let me say something about blackbodies. A blackbody is an object that emits radiation due only to it's temperature. Since it does not reflect anything, it looks black at room temperatures. You can make a…
rallain | April 21, 2009First: Car Talk is awesome. I wish I could come up with some class activities that help students become as good at trouble shooting and critical thinking as Tom and Ray are. Anyway, they are quite entertaining.
So, my Dad called and told me he heard a discussion on Car Talk about the effect DC to AC converters and accessories plugged in to it and how they would effect gas mileage. I skimmed through the last Car Talk podcast, but couldn't find it. He must have heard a re-run on the radio or something (he doesn't really believe in podcasts). Let me calculate the effect a number of things…
esiegel | April 21, 2009The Sun is doing something interesting, and has been for the last few years. As a solar physicist noted last year, there really haven't been many sunspots lately. Look at 2001 (left) and 2009 (right) for the difference in sunspot activity.
But there's more. In addition to virtually no sunspots, the Sun is having fewer solar flares, hit a 50-year low in solar wind pressure, and is at a 55-year low in radio emissions. This is in addition to sunspot activity, which is at a 100-year low!
Well, Professor Mike Lockwood, an expert in long-term solar variations, has been keeping tabs on our Sun. As…
esiegel | April 21, 2009You've seen it a bunch of times when you're reading the specs on a new car: the number of foot-pounds of torque that it puts out. Well, the 2009 New York Auto Show just happened, and I was reading the synopsis of a new Mercedes that just came out:
369 foot-pounds of torque, it says. (That's 500 Newton-meters, for you mks/SI folks.) Torque is the amount of "turning power" you have, much in the same way you turn a wrench. 369 foot-pounds means that if you had a wrench that was 1 foot long, and applied a force of 369 pounds directly perpendicular to that wrench, you would get 369 foot-pounds of…
esiegel | April 20, 2009In celebration of April 20th, I thought I'd show you a method for making fire that's so neat it will work -- without fuel or chemicals -- both on Earth (left) and in space (right).
We're going to do it without a match, without a lighter, and without friction. That's right, the next time someone needs a light, I'll show you a way to make one that even beats rubbing two sticks together!
Image credit: Gideon Mendel/CORBIS.
Have you ever read the book Fahrenheit 451? The title refers to the temperature -- 451 degrees Fahrenheit (233 Celsius) -- at which paper will spontaneously, in the…
drorzel | April 20, 2009A couple of physics stories in the last few days have caught my attention for reasons that can be lumped together under the Vizzini Effect-- that is, they say things that involve unconventional uses of common words. Take, for example, the Physics World story Physicists distinguish between the indistinguishable, which starts off:
Spurred on by their work on building one of the world's most accurate atomic clocks from strontium-87 atoms, researchers in the US have now discovered that "forbidden" collisions can occur between these atoms.
Strontium-87 atoms belong to a class of objects known as…
drorzel | April 18, 2009SteelyKid is fascinated by the John Archibald Wheeler tribute issue of Physics Today:
"I find his popular writings much more digestible than the Big Book of Gravity," she says. "Misner, Thorne, and Wheeler is much too big to put in my mouth."
drorzel | April 17, 2009Via the arxiv Blog, a review article has been posted by the Haensch group with the title"Testing the Stability of the Fine Structure Constant in the Laboratory." The fine structure constant, usually referred to by the symbol α is a ratio of fundamental constants-- the electron charge squared divded by Planck's Contant times the speed of light (e2/hc)-- and usually assumed to be constant. Some beyond-the-Standard-Model theories of physics, though, include effects that could cause this ratio to change over time.
For this reason, people have been looking to see if the fine structure constant is…
rallain | April 16, 2009I have been meaning to write about this for quite some time. Really, I wanted to reply to Chad's article on science at Uncertain Principles, but you know how things go. So, here are my key and interesting points about science in random order.
Science is all about models (not ball bearings)
Science is about making models. What is a model? A model can be lots of things. It can be a mathematical relationship, a conceptual model, or even a physical model. One model I like to use is static friction. For many cases, the frictional force can be modeled as:
This model says the frictional…
drorzel | April 16, 2009Physics World has a nice news article about a new experimental development in quantum computing, based on a forthcoming paper from the Wineland group at NIST in Boulder. I'd write this up for ResearchBlogging, but it's still just on the arxiv, and I don't think they've started accepting arxiv papers yet.
The Physics World piece summarizes the key results nicely:
Now, Brad Blakestad and colleagues at the National Institute of Standards and Technology (NIST) in Boulder, Colorado have created a junction in an ion trap in which there is practically no heating. Constructed from laser-machined…
pontiff | April 15, 2009Over 9 months ago I decided to apply for teaching tenure track jobs. Then the economy took what can best be described as a massive, ill-aimed, swan dive. Thus creating an incredible amount of stress in my life. So what does a CS/physics research professor do when he's stress? The answer to that question is available on the iTunes app store today: arXiview. What better way to take out stress and at the same time learn objective C and write an iPhone app that at least one person (yourself) will use?
What is arXiview? It is yet another arXiv viewer (there are two others available, last I…
drorzel | April 15, 2009A recurring problem in academic science is trying to correctly identify a single author. For example, I was reviewing a grant that made reference to a group, but not a specific paper, and needed to sift through a few pages of search results in order to determine which of the people with that surname was the one I was looking for.
I'm somewhat fortunate in that the combination of my last name and first initial is not common. The Harvard/ Smithsonian Astrophysics Data System turns up all of my papers and nothing else when searching for "Orzel, C." The INSPEC database comes up with one bogus…
drorzel | April 14, 2009Over at Faraday's Cage, Cherish has had a Huck Finn moment with regard to paper writing style:
I know that I'm not supposed to use the first person plural when writing papers. Frankly Scarlet, I don't give a damn. I am going to say, "we did this" and "we did that".
This made me blink a little, because I've never thought that was a rule. In fact, one of the things I had beaten into my head when I was a grad student writing papers was that scientific papers ought to be written in the first person plural and the active voice.
There definitely seems to be a belief that scientific writing should…
drorzel | April 13, 2009I've remarked several times that I think condensed matter physics gets slighted in public discussions of the field, especially relative to its usefulness. Particle physics gets all sorts of press, but in practical terms, it is essentially useless-- whether CERN or Fermilab locate the Higgs boson or not will make absolutely no difference in the lives of the average person. Condensed matter physics, on the other hand gets basically no press, despite the fact that modern technological civilization would be impossible without an understanding of condensed matter physics.
(I should note here that…
rallain | April 13, 2009Previously, I showed how to analyze a cat video with Logger Pro. Logger Pro is nice, but so is Tracker Video. I also posted a comparison between Tracker and Logger Pro. Now, here is the same tutorial on the same video using Tracker Video.
Record your screencast online
I am not going to go through the analysis, since it would be the same as with Logger Pro.
rallain | April 12, 2009I already talked about increasing the temperature of a pool. My father commented that he thought the pool level rose by like half an inch when the temperature increased (by about 10 degrees F). So, this leaves the question: Is my father crazy, or is this possible? Or are both true?
Does water expand when it warms up? Yes, except when it melts. Why does this happen? Liquids are actually very complicated, but here is a basic answer. Take a look at this PhET gas simulator, I know it is for gases not liquids. I think we can make it behave like a liquid if you increase the gravity to the…
rallain | April 11, 2009It is spring break, so we are at my parents house for a couple of days. The kids like it because there is a pool, a heated pool even. It really isn't that cold outside, but yesterday the water measured at 62 oF. So, with some help from the kids, we cleaned out the pool and turned on the heater. We also put a cover on it, hopefully to help it heat up some more.
This is perfect for a quick calculation. Is it reasonable that the pool could get up to a swimable temperature by tomorrow? Let me first make some assumptions and data:
15,000 gallons of water in the pool. This is about 57 m3.…
rallain | April 10, 2009I am so pumped up that MythBusters is back on. Not only do I like the show, but it offers so many blogging opportunities. Their latest show featured car crashing myths. One of the myths from the episode was a redo of the myth where two trucks crash head on simultaneously crushing a smaller car in the middle.
The first test was very similar to the previous time they tested this, but faster. They towed two 18 wheelers to crash together around 50 mph and smash a stationary car. The results were impressive. However, they did not have the result of the car completely contained in the…
jstemwedel | April 10, 2009This morning, I came upon the younger Free-Ride playing a game.
Younger offspring: I'm playing "launch the bear".
Dr. Free-Ride: Oh, really?
Younger offspring: Yeah. I put the bear on the edge of the piece of cardboard and hold my hands on the other end with the fingers on top, and then I flip it!
Dr. Free-Ride: And there goes the bear.
Younger offspring: Yeah! I flip to try to get the bear past this finish line I made on the floor.
Dr. Free-Ride: That's pretty cool. Have you tried using something longer to do the flipping?
Younger offspring: Like this blue box lid? Let's see ... FLIP!…