Physics
drorzel | November 15, 2008As mentioned briefly the other day, I recorded a Bloggingheads.tv Science Saturday conversation with Jennifer Ouellette on Thursday. The full diavlog has now been posted, and I can embed it here:
This was the first time I've done one of these, and it was an interesting experience.
I'm rocking the handset in this because of the aforementioned cell phone service problems, and because the whole thing was very hastily arranged, and I wasn't able to obtain a headset for the landline. If they ask me back again, I'm definitely getting one.
On the other hand, being tied to the handset did restrain…
rallain | November 14, 2008Here is a video of a guy jumping 35 feet into a pool of water only 1 foot deep.
UPDATE: Apparently, that video went away. Here is another version.
How does this work?
I don't think I even need to do a video analysis of this motion, all the important info is given. I will assume that air resistance did not play a signficant role (and that is a good assumption - or good enough - see this for example: motion of a falling tennis ball). So, here is the situation.
Part 1: guy falls 35 feet 5 inches (10.8 meters).
 on quantum physics arguing against the use of photons in teaching quantum physics. Part I gives a very nice introduction to quantum physics, which is why I linked it, but Part II goes a little off the rails. There's not as much physics content, and it ends with a list of phenomena that are able to be described by semi-classical models of light, leading up to a question:
So, if there are no photons, why are they in all the textbooks? That is a great question. I am glad I asked it. I really don't have a great answer…
drorzel | November 13, 2008Bora's beating the drum for submissions to this year's science blogging anthology. He doesn't seem to be suffering from a lack of submissions, but if you've got something you would like to see re-printed in dead tree form, submit it before December 1. I'm not clear whether this will be going through Lulu again this year, or if they have a regular publisher interested.
It's earlier than I would normally do this sort of thing, but Bora's post got me wondering about what I consider my best posts of the year. This isn't by any means a comprehensive list, just what I came up with in a few minutes…
rallain | November 12, 2008Numerical calculations are grand. Of course, they are just another form of normal calculations - like I have said before. So, I have mostly used [VPython](http://vpython.org) for my calculations on my posts. But there is a new game in town: [Easy Java Simulations](http://www.um.es/fem/Ejs/). What is the difference between these two? Which is better for students? Which is better for me? What are their strengths? What other questions are there? What other questions are there?
**VPython**
Let me start with [VPython](httP://vpython.org) since I am more familiar with that. VPython is…
rallain | November 11, 2008One of the fundamental aspects of physics is the study of light and how that interacts with matter. I have been putting off this post - mainly because I am not a quantum mechanic (I am a classical mechanic). There are lots of things that could be done in this post, but I am going to try and keep it limited (and maybe come back to the interesting points later). Also, most of my posts are aimed at the intro-college level or advanced high school level. This will be a little higher. If you are in high school, there is still a lot of stuff for you here.
Let me summarize where I am going to…
drorzel | November 11, 2008Sometime commenter "Dr. Pain" asked, on a mailing list, for book recommendations for his son, who "wants to read up about physics, especially weird modern physics." He adds some qualifications:
Kid's books on physics are way too elementary for him, but the typical "naive adult" book is over his head. Does anyone have any good recommendations for something that would be an interesting introduction to physics at a young teen level?
I'm somewhat embarrassed to admit that I don't know anything to recommend for this. Partly because it's been so long since I was in middle school, and partly…
drorzel | November 11, 2008In the recent discussion of Many-Worlds and making universes, Jonathan Vos Post asked what science fiction treatments of the idea I like. The answer is pretty much "none," because most SF treatments are distractingly bad.
For example, last night I finished Neal Stephenson's Anathem, a whopping huge brick of a book setting up an incredibly imaginative alternate Earth, with a detailed intellectual history paralleling our own. It's got all sorts of great stuff, but it lost me when it started talking about parallel worlds, because it munges together the Many-Worlds Interpretation of quantum…
drorzel | November 10, 2008SteelyKid has recently begun to figure out her hands. As I noted last week, within the last couple of weeks, she's started to be able to reliably grab things near her. Just within the last few days, she's discovered that she has two hands, and they can interact with each other:
She's started grabbing one hand with the other, and exploring them. I've also seen her start to use both hands in concert, holding a hanging toy steady with one hand, while manipulating bits of it with the other, like a good little scientist.
Hands are, of course, critical to science. You can't be a good scientist…
pontiff | November 9, 2008If you want to have a productive day I suggest avoiding Assembler.
Via: "Phd"ed Man
rallain | November 7, 2008On MythBusters this week, Adam and Jamie tested the bullet-proofness of various objects. The one that sticks in my mind is the ipod. The said there was a report of a solider being shot by an AK-47, but he was saved because the bullet hit his ipod. To test this, Adam shot an AK-47 at an ipod and it went through. Their conclusion was that he was also wearing body armor. I am not sure I like that conclusion. Why would someone report that the ipod saved him if he was also wearing body armor? Maybe they would, but not sure.
I was thinking, maybe the bullet went through the ipod because they…
drorzel | November 7, 2008If, like me, you have long thought that the world needs more thrillers based on quantum physics, the students and post-docs of the Ultrafast Group at Oxford have got a short film for you: The DiVincenzo Code, in six parts on YouTube.
It doesn't make any less sense than a Dan Brown novel, and the production is impressively good. Ian Walmsley's turn as the evil Dr. Eve is not to be missed, particularly part V where he does the Mad Scientist Dance.
(Via the Pontiff.)
drorzel | November 7, 2008In a comment on a post from last week, Neil B. Asks a good question about my snarky response to the "make-your-own-universe" kit:
[Y]ou never explained why this "universe creator" could be considered based on a misapprehension. Considering the way multi-worlds QM theory is usually presented, IIUC; why would you (anyone?) say it doesn't work as advertised?
The short and unhelpful answer to this is "See Chapter 4 of my book when it comes out." I spent a lot of time wrestling with the best way to understand this stuff, and I think it came out all right.
The longer answer is, well, complicated.…
rallain | November 6, 2008I just watched two episodes of the discovery show [Time Warp](http://dsc.discovery.com/tv/time-warp/time-warp.html). Really an interesting show. There are many videos that I could see some analysis project for (too bad I am like 20 projects behind schedule - I think of things faster than I can do them). There is one problem though. It seems like all of the people on the show like to use physics terms, but they use them incorrectly. This DRIVES ME NUTS. You can't have "energy going this way". Energy is a scalar, not a vector. You can't have "force flowing through this". You can't "put…
drorzel | November 6, 2008Getting back to science, at least for the moment, I was puzzled by a press release from RPI, with the eye-catching headline Solar power game-changer: 'Near perfect' absorption of sunlight, from all angles. The article describes work published in Optics Letters (that I haven't been able to put my hands on yet), developing new anti-reflection coatings to enhance the absorption of light by silicon solar panels:
An untreated silicon solar cell only absorbs 67.4 percent of sunlight shone upon it -- meaning that nearly one-third of that sunlight is reflected away and thus unharvestable. From an…
rallain | November 5, 2008[Here is a LiveScience article on cars that run "mostly" on air](http://www.livescience.com/technology/081103-air-car.html). I also hear students talking about this - how the world will change when cars run on air. This is misleading. These cars do not really run on air. It is not like you put them outside and BOOM - instant energy.
A better way to say this is that these cars run on energy STORED in compressed air. How do you store energy in compressed air? You need a compressor that typically runs on electricity. Where does that energy come from? Probably coal or natural gas.
It…
rallain | November 4, 2008**Pre Reqs:** [Work-Energy](http://scienceblogs.com/dotphysics/2008/10/basics-work-energy.php)
You need to be familiar with work and energy to understand this. If you are not familiar, look at the pre requisite link. Ok? Now, let's begin.
Suppose a ball moves from point A (3 m, 3 m) to B (1 m, 1 m) at a constant speed as shown in the diagram below:
Suppose there is some other force (like my hand) also exerting a force on this ball to make it move along this path at a constant speed. What is the work…
drorzel | November 3, 2008Continuing the series of descriptions of candidate technologies for making a quantum computer (previous entries covered optical lattices and ion traps), we come to one that's a little controversial. It's the only remaining candidate I can describe off the top of my head without doing some more background reading, though, so I will plunge ahead boldly...
Liquid state Nuclear Magnetic Resonance (NMR) was first suggested as a technology for quantum information processing in 1997, and some demonstration experiments followed very quickly, as there's relatively little infrastructure required. The…
rallain | November 1, 2008I have been meaning to post something useful lately, but I am currently at the southeastern section of the APS. Anyway, I saw [this link on digg](http://www.hyperevo.com/new%20site/index.php?subaction=showfull&id=1225…)
Apparently there is a message in the source code on the digg page. Funny stuff.
drorzel | November 1, 2008Via Boing Boing, a "conceptual artist" is selling a make-your-own-universe kit:
According to [a slightly garbled explanation of quantum mechanics], any kind of measurement causes the universe to split and this is the basis of Keats' new device. His universe creator uses a piece of uranium-doped glass to create a steam of alpha particles, which are then detected using a thin sliver of scintillating crystal. Each detection causes the creation of a new universe.
The kits sell for $20.
For a limited time only, though, I'll make you a better offer: if you send me $15, I won't send you an art…