Physics
drorzel | August 19, 2009Kate recently signed up for Facebook, and I was talking to her earlier about some of the options for wasting tons of time entertaining yourself with Facebook, and mentioned the ever-popular trivia quizzes and "personality tests" and the like. Of course, I had to caution her that most of the quizzes are really lame, because the people making them up don't know how to make a good quiz.
Making up good questions is a skill that takes time to master. The key elements that the people behind most Facebook quizzes are missing are good distractors-- the plausible-sounding wrong answers that lead…
esiegel | August 19, 2009Last year, while watching the Beijing Olympics, I was blown away by how much faster Usain Bolt was than everybody else:
He became the first man to run the 100 meter dash in under 9.7 seconds. Now, I thought, that's really, really fast. But then, just a few days ago, there was a race between the "World's Fastest Men", and Bolt said he would break his own record. The result?
9.58 seconds. An average speed of 23.4 miles per hour (37.6 kph). It isn't like humans can't run faster instantaneously, as Donovan Bailey, for an instant, has been clocked at 12.1 meters per second (27.1 mph / 43.6 kph…
jstemwedel | August 18, 2009Recently, Steinn brought our attention to some of the difficulties involved in getting a scientific journal to publish a "Comment" on an article. He drew on a document (PDF) by Prof. Rick Trebino of the Georgia Institute of Technology School of Physics detailing (in 123 numbered steps) his own difficulties in advancing what is supposed to be an ongoing conversation between practicing scientists in the peer reviewed scientific literature. Indeed, I think this chronology of exasperation raises some questions about just what interests journal editors are actually working towards, and about how…
rallain | August 18, 2009I wrote two letters (for two different classes). These are letters from the students of the near future to themselves in the present. this first one is for a non-majors lab. In this lab, I let them turn in "informal" lab reports that they can then use on the midterm and the final exam. The thing is that a lot of students don't even turn this in. Here is the letter:
Dear Past Me,
How are you? I know how you are because I am you and I remember this day. Really, you should be asking how I am.
I am not doing so well. I just took the midterm for the physics lab and it didn't go too well.…
drorzel | August 18, 2009One of the blogs I hyped at the science blogging panel at Worldcon was Built on Facts, Matt Springer's blog explaining introductory physics concepts. You might not think that you want to read a blog that goes through freshman physics problems in detail-- I would've been dubious on the concept, had you explained it to me that way-- but it's really excellent stuff.
He's recently completed a series of posts on Maxwell's Equations, with one post for each of the four equations, plus one bringing them all together: Gauss's Law for Magnetism, Gauss's Law for Electricity, Faraday's Law, and the…
rallain | August 17, 2009I have been reflecting on my recent failure to realize that the Giant Water Slide Jump was fake (more analysis here). I think the guys that made this video did a really good job on several levels. First, the motion appears to do two important things:
shows constant acceleration in the vertical direction
shows constant velocity in the horizontal direction
That seems like such a simple thing, but it is surprising how often fake videos don't have those two elements. Maybe they were not close, but with the error associated with the panning and zooming camera, it seemed close enough. Also,…
ejohnson | August 17, 2009
In his regular life, graduate student Matt Springer teaches undergraduates the basics of physics: the mechanics of heat, rotational motion, the relationship between kinetic and potential energy, and more. Matt takes a similarly instructional approach on his blog Built on Facts, walking readers through equations and concepts that might have grown a bit fuzzy since their own undergraduate physics courses. In his latest series, Matt looks at each of James Clerk Maxwell's four famous equations describing the laws of electromagnetism. "It's difficult to conceive of much more impressive physics,"…
drorzel | August 17, 2009The results of the estimation contest are in. There were 164 serious entries (I excluded the $12,000 and $1,000,000 "guesses" from the final data). The mean value guessed by commenters was $83.30, and the median was not far off, at $77.12. The standard deviation was high-- $43.10-- but as you would expect with a large sample, the standard error (or standard deviation of the mean) was small, $3.37.
Or, in convenient graphical form:
That's a histogram with $20 wide bins showing the number of guesses in a given range. A pretty nice distribution, on the whole.
The red line indicates the actual…
rallain | August 17, 2009This is amazing. I can't believe that power companies are paying Blacklight Power money, but they are. I guess Blacklight Power must have great advertising. Ok, so what is this whole Blacklight-hyrdino thing? Honestly, I am not fully familiar with it, but basically this guy says that you can get energy by getting the electron in hydrogen to go to a lower energy level than ground state. Here are a few good links regarding this hydrino stuff.
Six Tiny Utilities Buy "Scientifically Impossible" Energy: CleanTechnica
Blacklight Power claims nearly-free energy from water - is this for real…
drorzel | August 14, 2009This wooden box sits on top of my dresser, and every afternoon when I come home, I dump the change from my pockets into it. It's getting close to full, as you can see:
I've got a couple of extra galley proofs kicking around, so here's a contest:
Guess the total dollar value of the change in this box.
Leave your guess in the comments. I will take the box to the bank next Monday, and have the change converted to folding money. At that time, the commenter whose guess is the closest to the actual dollar value of the change in the box (above or below) will receive a galley proof copy of How to…
drorzel | August 14, 2009I have a thousand things to do today, and blogging isn't high on the list. So here's a dorky poll to pass the time, because it's been a while:
What's your favorite Law of Thermodynamics?(polls)
We're working in the classical limit, here, so you're not allowed to choose a linear superposition of all four laws. Pick one as your favorite.
drorzel | August 14, 2009A cosmologist, a science writer, three best-selling science fiction authors, a best-selling mystery novelist, and a Nobel laureate walk into a bar--
Oh, wait, that's not the opening to a joke. That's the list of people who have provided blurbs for my book... Kind of an eclectic bunch, but I'm pretty psyched. I'm not quite sure why the final list of blurbs gets locked in this early-- we don't even have the cover copy written yet-- but it's set now, and they look pretty good:
"Chad Orzel teases out the mysterious and seemingly incomprehensible side of advanced physics and makes it…
esiegel | August 13, 2009Okay. Yesterday, I explained to you that the only thing that determines how the Universe expands is the amount of energy density in it. But many of you wanted more details. So, by popular demand -- including one insistence that there is no equation that tells us how the Universe expands -- here is the simplest explanation with math that I can come up with for the expanding Universe. If you hate or don't care about math, do not read this. This article is not for you. But if you're curious, read on.
Image credit: Wayne Hu.
First, let me tell you the underlying assumption behind all of it. You…
rallain | August 13, 2009What's the deal with the Chevy Volt? Well, obviously, it is a cool car. A plug-in hybrid. The problem is in how to quantify its efficiency. Normal hybrids (the non-plug in type) have only one type of energy input, gasoline. The Volt can take gasoline or electricity input. This makes it difficult to compare the efficiency of other cars. What is efficiency? There are several things you could calculate.
Actual MPG
This is the distance the car travels (the miles part) divided by how much gasoline it used (the gallons part). Pretty straight forward? Ah ha! Not so straight forward for…
drorzel | August 13, 2009One of our poetry contest winners has been reading his proof copy of How to Teach Physics to Your Dog, and posted some comments. Actually, it was posted last week, but I was at Worldcon, and not dealing with much of anything else.
The comments are pretty positive, but he asks a couple of questions along the way, and I figured I should respond to those here. So, below the fold are Adrian's questions and my responses:
I don't get what's so weird about the Quantum Eraser, other than things that are already weird in simpler double-slit experiments in any case. Once you've accepted that a photon…
rallain | August 12, 2009This Giant water slide video is extremely popular on the internets. Maybe you have not seen it (doubtful), then here it is:
This is such an incredible stunt that the very first question that comes up is - fake? or not fake? From my previous analysis, I can say:
Even though there is some slight perspective issues, the vertical acceleration seems to be constant and has a reasonable scale to give the acceleration of -9.8 m/s2
The horizontal motion is essentially constant (as a real jump would be)
The launch speed is about 19 m/s
The launch angle is 32.8 degrees
If the guy had no friction on…
drorzel | August 12, 2009ZapperZ links to an interview with David Saltzberg about careers for students with an undergraduate degree in physics. As is often the case, ZapperZ proclaims himself "disappointed" with things that I think are about right. In particular, he writes:
[W]hen asked on why one should major in physics, is the best that can be answered is that "... you really like it.. "? What happened to the fact that the skills one acquire majoring in it can be quite useful in one's career, be it in science or outside of science?
Actually, I think that really is the best reason for majoring in physics. Or any…
pontiff | August 10, 2009March is ages away, but it is time to start planning for the APS March meeting, to be held in the beautiful rose city, Portland, Oregon (Note to skiers that Mt. Hood is just a short distance away :) ) Anyway an important part of the March meeting are invites sessions and the quantum computing/information/foundations topical group GQI is in charge of a few of these sessions. Want to nominate a session or invited speaker? Now's your chance. Here's the email that was sent out Friday:
Dear GQI members,
This is an email to solicit from you proposals for GQI sponsored invited sessions and…
drorzel | August 8, 2009My talk was Friday morning at 10am, on the title given above. This wasn't my choice-- when I volunteered to be on programming, I said some general areas that I'd be willing to talk about, and left it at that. Somebody else made up the title and description for the talk, which made it very slightly like PowerPoint Karaoke. Happily, this is a topic I can easily discourse about, but I think in the future I'll try to remember to suggest more specific talk titles...
I've posted the slides for the talk on SlideShare, and will attempt embedding them below:
Worldcon09
View more presentations from…
rallain | August 7, 2009I have previously compared Tracker Video Analysis and Logger Pro - check that out here. Really, the only advantage Logger Pro has over Tracker is that maybe it is easier to use for simple things and maybe students are already familiar with it from other analysis.
There are other video analysis programs out there. There is VideoPoint - but this is not free and I don't think it has been updated in quite some time. Also, don't forget Video Graph. A great program for it's time, but that time was 1997.
So, this post is really about Tracker and its feature of calibration point pairs. What is…