Physics
rallain | May 4, 2009I got a great question (several actually) from the students participating in the Adopt a Physicist program. The question went something like this (not a direct quote):
Why is it that the stuff we study in physics class is 100 year old stuff?
I am sure the students phrased this better than that, but you get the idea. The first response is that most of the most of the topics covered in introductory physics is more like 300 years old (Newton). Needless, why do most course cover old topics?
First, to answer this question I would ask the following:
What is the purpose (goal) of the introductory…
drorzel | May 4, 2009SteelyKid is not yet at the stage where I can usefully read to her-- she likes sitting on my lap while I read just fine, but she's more interested in trying to eat the pages than listening to the story. I was reminded this morning, though, that when she gets to bedtime-story age, I'm going to face some real dilemmas. Some of the classic stories teach dangerously wrong lessons about physics.
Take, for example, the story of Goldilocks and the Three Bears (referred to at the end of the previous post). In the usual telling, Goldilocks comes upon the Bears' house and finds three bowls of porridge…
drorzel | May 4, 2009I'm an experimentalists through and through, and have always known better than to attempt real theory. On two occasions, though, I've been forced to do a little bit of computer simulation work in order to interpret my results. One of these was for the time-resolved collisions experiment, and worked out well. The other was when I was a post-doc, and was... less useful.
The situation we were dealing with in my post-doc work was a Bose-Einstein condensate of rubidium that we chopped into several pieces with an optical lattice. Whenever you do this, there is necessarily some uncertainty in the…
rallain | May 2, 2009So, I am mowing the lawn. What to do better than thinking while I mow? Sometimes mowing is no fun. It is just a type of maintenance. How much of what we do is maintenance? I first thought about this when I was thinking about getting a new car. Wouldn't it be great if you didn't have to get the brakes changed or the tires rotated? I hate taking the car to the shop to get these things done (yes, if I was motivated I could do them myself). Here are some other maintenance things:
Mopping the floors
Paying bills
Keeping files organized on your computer
Brushing your teeth
How much of…
rallain | May 2, 2009There are a couple of things I should probably not talk about. One of them is photons. But no matter what you think about photons you will probably agree that this is not a very good description of electromagnetic radiation. (from comos4kids.com)
Structure of Energy:All EM energy waves travel at the speed of light when in a vacuum. No matter what their frequency or wavelength, they always move at the same speed. Some properties of waves, such as diffraction and interference, are also seen in EM radiation. Scientists have figured out that there are tiny particles in these waves. The…
esiegel | May 1, 2009Who is correct here? We don't know, you don't know, it is uncharted territory. Would you bet the entire human history and the existence of our solar system on it?
I wouldn't.
--from a user comment on my old website on the topic of the Large Hadron Collider
Back when all the hype and hoopla concerning the LHC startup had people afraid that the Large Hadron Collider would create a black hole that would eat and destroy the Earth, I tried to quell some of these fears. At my old site, I wrote three articles explaining why the Earth was safe, and why -- even if the worst-case scenario came true…
drorzel | May 1, 2009Like Sauron creeping into Dol Guldur, Quantum Diaries has returned to darken the blogosphere once more, driving Tommaso Dorigo before it--
Oh, wait. More good science blogs is a good thing, not a creeping menace. Even if they are particle physicists.
Anyway, in a move that is unrelated to the return of Quantum Diaries, and, in fact, happened two weeks ago, Tommaso Dorigo, a survivor of the original Quantum Diaries, has closed up shop and moved to ScientificBlogging.com. Had I known he was thinking of moving, I would've pushed the Corporate Masters to invite him to ScienceBlogs so we could…
rallain | April 30, 2009ZapperZ already beat me to this, but if it is worth doing once it is worth doing again. Here is a video of an electric motorcycle that can apparently go from 0 to 60 mph in 1 second.
What acceleration would this have? If you want, you can look at my stuff on kinematics, but this case is pretty straight forward. Really, as straight forward as one could get. Let me start with the definition of acceleration: (in the x-direction since this is a 1-d problem)
I know both the change in speed and the time, so this is easy. I can make it even easier using google. The acceleration is 60 mph/s.…
drorzel | April 30, 2009I have two labs today, and a lunch meeting, so no time for detailed blogging about science. It's been a while since I did a Dorky Poll, though, so here's one to keep people entertained while I'm working:
What's your favorite color?
"What's dorky about that?" you ask. You need to give your answer in wavelength units. For extra bonus dorky points, specify an atomic transition of approximately that wavelength.
Personally, I'm kind of partial to the blue-green lines in helium, right around 501 nm. That's a nice color. The violet line in the hydrogen spectrum, around 435 nm, is also pretty good.…
drorzel | April 29, 2009I got email this afternoon from Andrei Derevianko, the leader of the research project badly described by the press release mentioned in the previous post. He sounds a little surprised by the whole thing (though not much more surprised than I am that my griping on the Internet got brought to anybody's attention), and explains what happened:
The original story (that I have went through with a writer) is posted here: www.unr.edu.
Unfortunately, the release writers have added introductory paragraph and the title without consulting with me (I was travelling giving talk about our result).
Now…
drorzel | April 29, 2009A wonderfully incoherent press release came across my EurekAlert feeds yesterday, with the headline "Particle physics study finds new data for extra Z-bosons and potential fifth force of nature." You can tell it's going to make no sense at all from the very first sentence:
The Large Hadron Collider is an enormous particle accelerator whose 17-mile tunnel straddles the borders of France and Switzerland. A group of physicists at the University of Nevada, Reno has analyzed data from the accelerator that could ultimately prove or disprove the possibility of a fifth force of nature.
As the largest…
drorzel | April 28, 2009So, the President gave some sort of speech to a bunch of smart people yesterday (video, transcript), and hearts are a-flutter all over the science blogosphere, as President Obama promises great things for science:
We double the budget of key agencies, including the National Science Foundation, a primary source of funding for academic research, and the National Institute of Standards and Technology, which supports a wide range of pursuits - from improving health information technology to measuring carbon pollution, from testing "smart grid" designs to developing advanced manufacturing…
rallain | April 28, 2009In the second Cat in the Hat book (I think it is the second one), the Cat reveals that he has more smaller cats under his hat. They are labeled A - Z with Z being so small you can't even see. Question: What is the sequence of sizes for successive cats? How big would Cat Z be?
Here is the first picture that Cat reveals Cat A. It is not trivial to measure their relative sizes because they are in different positions. I drew two circles, one around each head and looked at the circle sizes.
So, Cat has a head that is 165 px tall and Cat A has a head 61 px tall. Let me call the total length…
drorzel | April 27, 2009Back in the stone ages, when I was a student and walked uphill through the snow to class, if you wanted assistance on a homework assignment, you needed to track the instructor of the class down in person, either by going to their posted office hours, or calling them on the phone to set up an appointment. With the introduction of modern communications technology, it is now possible to interact with your instructor electronically, and get help on your homework at times when you couldn't hope to meet them in person.
While this is a tremendous improvement over the old way of doing things, here…
rallain | April 26, 2009It's odd that I have talked about these forces so much. First, I talked about how centrifugal forces were not real and the difference between centrifugal and centripetal forces. Then I talked about how sometimes, fake forces are good. Finally, I talked about the origin of the words centrifugal and centripetal. (note: "talked about" means wrote a blog post)
In thinking about centripetal forces, I realized that I could come up with a situation in which the centrifugal force is the centripetal force. This is great. I can end all the confusion between centrifugal and centripetal by making a…
rallain | April 24, 2009A student in my office temporarily confused the words centripetal and centrifugal. This started me thinking about these two words. They mean different things, but do sound and look similar. I have previously talked about the difference between fake and non-fake forces, but let me quickly define these two:
Centripetal: This is the force needed to make something move in a circle. The force could actually be a number of things such as: friction, gravity, tension in a rope or any combination. Centripetal force is a name for a real force that has the role of making something move in a circle…
rallain | April 24, 2009I have already indirectly talked about this before, but I see it more and more. Say you have a show. It has to be more than entertaining, it has to educational. How do you make things educational? Describe the physics behind the concepts - right? Fine. How do you explain stuff? It's simple. Just make some diagrams with arrows. Be sure to use words like "force", "velocity", "acceleration". You know, physicsy words. Everything will be fine.
Everything will not be fine. First, I love MythBusters. They are awesome. I know they are not scientists, and that is maybe why I like them.…
drorzel | April 23, 2009I'm speaking, of course, about this past weekend's Bloggingheads conversation between Jennifer Ouellette and Diandra Leslie-Pelecky. They both blog at Cocktail Party Physics, and Diandra has written The Physics of NASCAR.
It's a good Bloggingheads, covering a wide range of topics related to physics, sports, and entertainment. Jennifer talks about the work of the Science and Entertainment Exchange, Diandra talks about how NASCAR people know more about physics than you might think, and they both have worthwhile comments about the diificult job of explaining complicated technical subjects in…
rallain | April 22, 2009Some time ago I was looking for materials to possibly build a foucault pendulum. Of course the first step is google. There was a site that suggested two old issues of Scientific American, and it happens that we have tons of old Scientific Americans in the store room. I found the two that I needed. I will talk about foucault pendulum in second, but let me show this picture.
This is a device to prevent elliptical motion of the pendulum. Part of it has a ring of nickel. Now for the quote:
"The nickel ring, perhaps appropriately, should have the dimensions of a U.S. five-cent piece, with a…
drorzel | April 22, 2009We had a talk last night by Alan Lightman of MIT, a theoretical physicist and novelist, best known as the author of Einstein's Dreams. He spoke for about an hour about his own background, and the similarities and differences between the worlds of science and the arts.
One of the differences he mentioned was the way the different disciplines handle names. He claimed that science is deeply concerned with naming things, because naming a thing in some sense defines it-- the word "electron" carries with it a whole host of properties that are shared by all electrons in the universe. In the arts, on…