Physics
ejohnson | May 26, 2009
Our physicists-in-residence at ScienceBlogs enjoy catching a few waves every now and then—but what kind? In the most recent installment of his Dorky Poll series, Chad Orzel asked his readers at Uncertain Principles which they preferred: Waves which oscillate perpendicular to their direction of motion—transverse waves—or longitudinal waves, which oscillate in a parallel direction. Matt Springer of Built on Facts had a ready answer for Chad: "Transverse or longitudinal waves, purely as a matter of aesthetic preference? Transverse all the way, of course."
Dorky Poll: How Do You Like Your Waves…
drorzel | May 26, 2009We no longer do what is possibly my favorite lab in the intro mechanics class. We've switched to the Matter and Interactions curriculum, and thus no longer spend a bunch of time on projectile motion, meaning there's no longer room for the "target shooting" lab.
It's called that because the culmination of the lab used to be firing small plastic balls across the room and predicting where they would land. In order to make the prediction, of course, you need to know the velocity of the balls leaving the launcher, and making that measurement was the real meat of the lab. The way I used to do it,…
rallain | May 25, 2009When I was talking about balancing a stick, I mentioned the moment of inertia. Moment of inertia is different than mass, but I like to call it the "rotational mass". What does mass do? Things with larger mass are more difficult to change their motion (translational motion). A similar thing is true for the "rotational mass". Things with larger rotational mass are more difficult to change rotational motion. Here is the demo.
Demo for Moment of Inertia from Rhett Allain on Vimeo.
Why do I like this demo? First, it uses ordinary things. I consider juice boxes to be pretty ordinary.…
rallain | May 25, 2009I was wondering around the blogosphere and read some stuff about introductory physics labs. In particular, I was looking at ZapperZ's Revamping Introductory Physics and Dr. Pion's Objectives for a Lab. Both of these are good posts. Here I thought I would add make take on this subject as I am picking the labs I will use for the summer session of introductory (algebra-based) physics labs.
When I first started teaching this lab, my goals for the course were a lot like Dr. Pions. Namely, I would like the students to improve in the following areas:
Critical thinking
Writing and communication…
drorzel | May 24, 2009Friday morning at DAMOP was probably the thinnest part of the program, at least for me. Annoyingly, this was the day that my cold (or possibly allergies-- whatever it was that had my head full of goo) let go, so I was the most awake and alert I managed for the entire conference.
I watched a few talks in the ultracold molecules session, where I heard about the remarkable progress being made in producing large numbers of ultra-cold molecules, generally diatomic alkali molecules (Rb2, KRb, LiCs, etc.). This is an area where relatively standard techniques seem to work surprisingly well. This is…
drorzel | May 22, 2009The release date for the forthcoming How to Teach Physics to Your Dog is December 22, seven months from today, and I got a look at some sample pages yesterday, so things are moving right along. To mark the occasion, and give you something to entertain you while I'm spending another day at DAMOP, I thought I'd offer some video:
This is me reading the dog conversation that goes with Chapter 3, on the Copenhagen Interpretation. The cheap computer microphone doesn't do that great a job picking up the Dog Voice, but it'll give you the basic idea. The images that go with it were mostly taken by…
drorzel | May 21, 2009Thursday at DAMOP was a little more broken up than usual for me at one of these meetings, because the nagging cold I have was bugging me more, and also because I needed to check my email a few times. There was still some neat stuff, though.
The early-morning session was the toughest call of the meeting: there was the undergraduate research session, a session on ultracold Rydberg atoms, and a session on complicated states in BEC, in widely spaced locations. I ended up skipping the undergraduate session in favor of hearing Chris Foot talk about a rotating optical lattice (which simulates some…
pontiff | May 21, 2009He of uncertain principles asks Which do you prefer: transverse waves, or longitudinal waves? The fact builder chimes in with a clarification of a common misconception.
Myself, certainly I'm going to go for transverse waves. Not only are all the cool waves transverse (well sort of), electromagnetic waves, gravitational waves, stadium waves, etc, but you can't surf on a longitudinal wave.
And of course, how cool are gravitational waves? So cool they produce this mesmerizing action on a ring of particles:
Interestingly while light is often used as the quintessential example of transverse…
rallain | May 21, 2009I made a gamble and my gamble failed. It really wasn't my fault. In the preview, they showed this huge barrel thing dropping on a see saw. It looked something like this: (I could search for 30 minutes for a picture of this online, or just draw it)
At first glance, this looked JUST like that video of the pile driver shooting the skydiver up in the air. You can see how I would make that mistake. To make up for my mistake, I will give a very simple analysis of the see saw myth. The basic idea is that something comes down, hits the see saw and sends the other thing flying up. If I assume…
drorzel | May 21, 2009Technically, the meeting started Tuesday, but all that happened was a welcome reception, which I missed due to travel. The real beginning of the meeting was Wednesday morning, with the traditional unscheduled half-hour welcome from local dignitaries. That was followed by the Prize Session, featuring the frighteningly smart Misha Lukin, who was awarded the I.I. Rabi Prize for being really freaking brilliant. The abstract he sent in was kind of vague, but he mostly talked about stuff related to the quantum computing in diamond stuff that I've blogged about before.
I'm fighting a bit of a cold,…
esiegel | May 20, 2009When I was a teenager, my choice of food was basically determined by three criteria:
It needed to be ready in under 10 minutes.
It needed to have enough calories to make me not hungry anymore.
And it needed to be (marginally) edible.
That was really it. And so it won't surprise you to know that a portion of my diet at the time consisted of -- you guessed it -- Hot Pockets. And to be fair, they don't actually look so bad on the box.
For those of you who don't know, a Hot Pocket is a frozen Pop-tart filled -- instead of with fruit -- with nasty meat and sauce. You're supposed to stick it in…
drorzel | May 20, 2009I made it to Charlottesville, and am all checked in to the Econo Lodge, which is a little more Econo than I was expecting. It's an old-school motel, with rooms that open right into the parking lot, the sort of place where the towels are tiny and scratchy, the pillows and mattresses are thin, and the tap water tastes like cigarette smoke. Still, it's not like I'm going to be doing much more than sleeping here.
I promised some entertainment in my absence, so this seems like a good time for a Dorky Poll. I'm going to be spending a lot of time over the next few days listening to talks about the…
rallain | May 19, 2009Some of the other blog sites have talked about physics vs. chemistry. It seems this started with The experimental Error blog. Tom at Swans on Tea added a very excellent point to the discussion and the discussion continues at Uncertain Principles.
So, here is my take on the subject. Physics essentially deals with the fundamental stuff. You know, Maxwell's equations, the four forces, the particles, quantum mechanics. Chemistry is the study of substances and their interactions. First, let me attack chemistry. Here are some things I don't like:
Photo electron. What is a photo electron?…
jstemwedel | May 19, 2009There's an interesting article in the Telegraph by Eugenie Samuel Reich looking back at the curious case of Jan Hendrik Schön. In the late '90s and early '00s, the Bell Labs physicist was producing a string of impressive discoveries -- most of which, it turns out, were fabrications. Reich (who has published a book about Schön, Plastic Fantastic: How the Biggest Fraud in Physics Shook the Scientific World) considers how Schön's frauds fooled his fellow physicists. Her recounting of the Schön saga suggests clues that should have triggered more careful scrutiny, if not alarm bells.
Of…
drorzel | May 19, 2009I'm leaving this afternoon for Charlottesville, VA and the 40th annual DAMOP conference. At this meeting, we will once again be confirming the prediction of the bosonic character of interesting talks. Bosons, as you know, are quantum particles that happily occupy the same state as other bosons, and as you can see from the meeting program, the most interesting sessions are bunched together in a few time slots on Wednesday and Thursday. Thus, interesting talks are clearly bosonic in nature.
(The same basic physics has been demonstrated dozens of times previously, at other meetings and…
rallain | May 18, 2009Another electric motorcycle post. (Here is the post on the wind-recharged drag racing motorcycle) This new one is a solar powered motorcycle. The site claims that the bike can go 50 miles on a full charge (from Gas2.org). This is easily possible, but how long would it take to charge with normal solar panels? Here is an image of the bike.
Questions to be answered: How much energy would the bike need to go 50 miles? How much power (average) could you expect to get from the solar panels? And...how long would it take to charge this sucker. I am sure you can store enough energy in a…
drorzel | May 18, 2009Thoreau offers without qualification some observations about the different approach to books taken by sciences vs. humanities. Specifically, he notes that despite frequent claims that it is the Most Important Book Ever, nobody actually reads Newton's Principia Mathematica
This is totally different from humanities. In humanities, people make a point of reading the original thinkers. They don't just say "Well, philosopher so-and-so influenced lots of other people and got the ideas rolling, so let's read somebody influenced by him and maybe a Cliff's Notes version of the original." They…
grrlscientist | May 18, 2009
What: A public presentation, "Not Even Wrong: The Failure of String Theory & the Continuing Challenge to Unify the Laws of Physics"
Where: Brooklyn Society for Ethical Culture, 53 Prospect Park West (corner of Prospect Park West and 1st Street), Brooklyn, NY [map]
When:Monday, May 18, 7:30 p.m.
Cost: free and open to the public.
Peter Woit is a mathematician and physicist at Columbia University who will discuss string theory and why it is controversial, as well as prospects for new experiments and a better understanding of the mathematical theories used to describe the physical world…
drorzel | May 17, 2009The Experimental Error blog considers the difference between disciplines (via Tom):
I often contemplate the differences between these two areas of study. Also, I hear fellow undergrads argue for one or the other, usually divided along the lines of their respective major. Anymore, I think they're so interrelated that I find it hard to find a difference between the two, except for the phases of matter that they most often deal with.
Back in the days when science was new, Physics dealt with understanding the fundamental laws of the universe, and it was Chemistry that was making the attempt at…
drorzel | May 16, 2009From Tuesday to Saturday, I will be at the 2009 DAMOP meeting at the University of Virginia in Charlottesville, VA. I have been to Charlottesville three times before, and based on that experience, I know these things:
The White Spot is worth a visit if you're a fan of greasy spoon diners.
Getting stuck in an elevator with half a rugby team kind of sucks.
It's damnably difficult to find good bagels in the South.
Getting stuck in an elevator on your way to bed after a wedding reception really sucks.
Yes, that's right, I have been stuck in an elevator in Charlottesville, VA not once, but twice…