Physics
drorzel | June 28, 2010Last week, Dmitry Budker's group at Berkeley published a paper in Physical Review Letters (also free on the arxiv) with the somewhat drab title "Spectroscopic Test of Bose-Einsten Statistics for Photons." Honestly, I probably wouldn't've noticed it, even though this is the sort of precision AMO test of physics that I love, had it not been for the awesome press release Berkeley put together, and this image in particular (grabbed with its caption):
This is a nifty paper, and deserves a little explanation in Q&A format:
Is this another New Scientist style "Einstein was wrong" paper? No. If…
drorzel | June 28, 2010There is a proposal for a Physics Q&A site along the lines of Stack Overflow for computer stuff. Like many such projects, this largely conflates "physics" and "theoretical particle physics," so I'm not sure how much of a contribution I can really make. I've got plenty of theorist readers, though, so if this seems like the sort of thing you would like to have exist, click the link above.
rallain | June 27, 2010Sometimes I get asked to do some demos for kids. I like this, it is fun. This week, I was asked to do just such a demo. Kind of as a historical record, I am going to document what I did.
The audience
It is always important to think about who you are talking to. Is this a group of high school physics students? High school teachers? Middle school teachers? Kids? It could be anything. In this case, I was meeting with a group of kids from ages 8 to 12 as part of a science camp.
The Objective
Is there a reason for the demo show? In this case, there was no stated objective. That means I can…
ksnyder | June 25, 2010It was a time of fierce (but friendly) international competition, when physicists still built things with their own two hands. Dotted with barracks and trenches, Brookhaven was yet to fully transform its face from army camp to research institution.
In the early 1950s, the physics community was at the horizon of the boom of discoveries that define our understanding of the universe.
Before quarks, neutrinos, and CP violation could be found, scientists needed a tool much more powerful than Brookhaven's Cosmotron -- the leading particle accelerator of the time. The problem: building an…
rallain | June 25, 2010The oil spill is still in the news (sadly). One thing that keeps coming up is the speed that the oil bubbles rise to the surface. This is important in different oil-capture methods. The common statement is that smaller bubbles of oil can take quite a long time to reach the surface and larger bubbles can take about 2 days.
This is one of those cases where things do not scale quite the same. Suppose there is a spherical oil bubble rising at a constant speed. Here is a force diagram for such a bubble:
If this drop is going at a constant speed, then all these forces have to add up to the…
esiegel | June 24, 2010"The Universe is made mostly of dark matter and dark energy, and we don't know what either of them is." -Saul Perlmutter
When I was starting out as a graduate student, one of the most exciting (and daunting) tasks facing me was to piece together a scientifically accurate and useful picture of the Universe, including its composition, structure, and history. (And I owe a huge shout-out to my PhD advisor, who helped me immeasurably in that task.)
The big question facing me, as far as I was concerned, was deciding whose ideas were right, and which were the ones I should spend my time and energy…
drorzel | June 24, 2010Next in line of questions from readers, we have tbell with:
Since science is a self-correcting process (maybe only at a statistical level, not necessarily an individual level), it would be cool if you would relate the last time you were seriously wrong about some aspect of science or research, and how you altered your thinking as a consequence.
This is kind of a tough one to answer, because I'm an experimentalist. Most of the mistakes I make in the process of research are problems of a technical nature, like "I totally thought that would work, but the impedance of the vacuum feed-throughs…
drorzel | June 24, 2010Starting at the beginning of the uncomfortable questions left by readers, we have Tex asking:
If physics is the basic science that underlies almost every other science, why do American high schools usually teach it in the 3rd or 4th year, after biology and chemistry? Shouldn't it be the other way around? Physics first, then chemistry, then biology?
Physics is the final course in the standard American high school curriculum for two reasons, as far as I can tell: history and math. History is the less convincing of the two, as it amounts to "the courses are in that order because they've been in…
drorzel | June 23, 2010I don't remember who pointed me at this transcript of Deepak Chopra interviewing Michio Kaku, but if I remember who it was, I fully intend to hate them.
DC: Is our conversation affecting something in another galaxy right now?
MK: In principle. What we're talking about right is affecting another galaxy far, far beyond the Milky Way Galaxy. Now when the Big Bang took place we think that most of the matter probably was vibrating in unison.
DC: So it was already correlated?
MK: It was already correlated. We call this coherence or correlation. As the universe expanded, we're still correlated, we'…
drorzel | June 22, 2010A press release from Harvard caught my eye last week, announcing results from Markus Greiner's group that were, according to the release, published in Science. The press release seems to have gotten the date wrong, though-- the article didn't appear in Science last week. It is, however, available on the arxiv, so you get the ResearchBlogging for the free version a few days before you can pay an exorbitant amount to read it in the journal.
The title of the paper is "Probing the Superfluid to Mott Insulator Transition at the Single Atom Level," which is kind of a lot of jargon. The key image is…
drorzel | June 21, 2010An experiment in Germany has generated a good deal of publicity by dropping their Bose-Einstein Cendensate (BEC) apparatus from a 146 meter tower. This wasn't an act of frustration by an enraged graduate student (anybody who has worked with BEC has probably fantasized about throwing at least part of their apparatus down a deep hole), but a deliberate act of science: They built a BEC apparatus that is entirely contained within a two-meter long capsule inside the evacuated drop tower at the Center of Applied Space Technology and Microgravity (which in German leads to the acronym ZARM, which…
rallain | June 21, 2010Of course I am talking about Arnold Schwarzenegger. After looking at how many bullets he carries in Commando, I remembered this scene (also from Commando) (warning: maybe some not great language and some killing. You have been warned)
If you don't want to watch that clip, here is a shot (sorry for the quality).
Clearly Arnold is strong, but there is more than strength involved here. Oh, don't bring your "he did it with wire stuff". I am not buying that. Also, I am talking about THE Arnold - he is real. I am not talking about the character in the movie (not real). Now for some physics…
drorzel | June 21, 2010The Virtuosi has quickly become a staple of the daily Links Dumps here, but the recent series of posts on experimental physics deserve greater prominence, so here they are:
Life as an Experimenter- Day One
Life as an Experimenter- Day Two
Life as an Experimenter- Day Three
Life as an Experimenter- Reflections
The individual day posts provide an inside look at what it's like to do experimental condensed matter physics, specifically using beam time on an accelerator to do diffraction studies of materials. It's got everything you would like to see in such a story-- equipment failures, sleep…
drorzel | June 19, 2010As I was heading out with SteelyKid to do some shopping, I noticed that the mail had arrived, including a large book mailer from my agent. I was a little puzzled as to what that could be, but left it for my return. Where I was pleased to open the envelope and find:
That's a copy of Como Ensinar FÃsica ao Seu Cachorro, that is, the Portuguese translation of How to Teach Physics to Your Dog. I can't directly read a word of it, of course, but having written the original, I can identify some key amusing phrases, such as "Coelhos feitos de queijo" and "Cuidado com os esquilos perversos," which is…
gboustead | June 17, 2010
The full replay of Hidden Dimensions: Exploring Hyperspace, featuring Brian Greene, Lawrence Krauss, Shamit Kachru, and Linda Dalrymple Henderson, is now available for streaming for a limited time. If you haven't had your mind blown yet this morning, I recommend you head over to our livestream replay pages pronto, grab a tall cup of coffee, and prepare for perspective-scrambling kernels from some of the greatest living physicists.
Watch now >>
rallain | June 16, 2010Somewhere on the internet, I came across this Cracked.com article on movie myths about guns. The article wasn't too bad, but I really liked this video they included from Arnold's movie Commando.
The myth for this particular clip was that guns never run out of ammo in the movies. Right away, I thought: I wonder how many bullets he shot? BRING IT ON.
First, I am going to find the fire rate of Arnold's weapon. Oh, I know I could look it up on Wikipedia or something - but I am not going to do that. I am going to determine the fire rate from the clip.
After capturing an audio segment where…
rallain | June 15, 2010Pre Reqs: electric potential, electric field, work-energy
To start, remember that for a constant electric field the change in electric potential energy would be:
WARNING: that is only for a constant electric field. I know you will be tempted later to use this for a different electric field, but DON'T DO IT. But if not that, then how do find the change in electric potential for a point charge? Let me start with a conceptual question. Suppose there were two point charges, both positive but one is held in place. If I hold the other point charge a distance r away from the other charge and…
drorzel | June 15, 2010Tommaso Dorigo has an interesting post spinning off a description of the Hidden Dimensions program at the World Science Festival (don't bother with the comments to Tommaso's post, though). He quotes a bit in which Brian Greene and Shamit Kachru both admitted that they don't expect to see experimental evidence of extra dimensions in their lifetime, then cites a commenter saying "Why the f*** are you working on it, then?" Tommaso offers a semi-quantitative way to determine whether some long-term project is worth the risk, which is amusing.
I was reminded of this when I looked at the Dennis…
oracknows | June 15, 2010I don't know if I need to get out the infamous paper bag or--even worse--the Doctor Doom mask out yet. As you may recall (if you are a long time reader, anyway) is that the mind-numbing stupidity of certain MDs has driven me to want to hide my face in utter shame at the embarrassment caused by my fellow physicians. Most frequently, it has been everyone's not-so-favorite creationist neurosurgeon with dualist tendencies, Dr. Michael Egnor. So bad was he that I compared him one time to Deepak Chopra.
Damned if P.Z. hasn't led me to another highly embarrassing physician woo-meister. Worse, it's…
grrlscientist | June 15, 2010tags: Foucault's Pendulum, physics, rotation, Pendulum, Jim LaBelle, Dartmouth University, wow, streaming video
This video features physics and astronomy professor Jim LaBelle, as he discusses the truly fascinating science behind a classic physics experiment, Foucault's pendulum, while seated next to Dartmouth University's pendulum in Fairchild Tower.
While scientists already knew that the Earth had a rotation, they had struggled to come up with a way of definitively proving this was so. In 1851, French scientist Leon Foucault gave a sensational demonstration in the Paris Pantheon proving…