Vector Potential, Electromagnetic Induction and 'Physical Meaning'

This is a nice paper exploring the "meaning" of the vector potential that every physics student encounter in classical E&M.

"Vector potential, electromagnetic induction and 'physical meaning'", G. Giuliani, Eur. J. Phys. 31 871 (2010).

{the paper is available for free downloads during the first 30 days of online publication. Paper was published online on 8 June 2010}

This is a good paper for undergraduate students to read, because it clearly shows why the vector potential is not only amazingly useful, but also why it is important. One only needs to see that the vector potential is one of the few quantities that are involved in the quantum Hamiltonian.

What is also interesting about this paper is that there is quite a discussion on what is meant, at least in physics, by the phrase "physical meaning".

These considerations lead us to the crucial point; the physical meaning of a theoretical term relies, primarily, on theoretical grounds. We suggest that a theoretical term has a physical meaning if

(C1) its elimination reduces the predictions—experimentally testable—of a theory; or, in a weaker sense, if

(C2) its elimination reduces the descriptive proficiency of a theory.

Maybe this is a more meaningful definition, rather than discussing what is "real". It reduces the criteria of what has a physical meaning to something more testable, rather than just simply being a matter of tastes or personal preference. This then puts new light into the maddening discussion on whether time is an "illusion". As I've argued earlier, try removing any time dimension out of the Lagrangian/Hamiltonian formulation. Now, do you still have a complete description of the dynamics of the system? Does the removal of time reduces the predictions of a large section of physics, if not all?

Damn right it does!

Time has a physical meaning, and that statement is physically meaningful.

Zz.

Stolen Galileo's Finger On Display

I mentioned this earlier about the discovery of the missing Galileo's finger. It seems that it is more than just a finger. There's a tooth, and a thumb (which is also a finger too, no?).

In any case, they will now be on display in Florence.

A tooth, thumb and finger cut from the body of the famous renaissance astronomer Galileo will go on display this week in Florence after an art collector found them by chance last year.

The body parts, along with another finger and a vertebrae, were cut from Galileo's corpse by scientists and historians during a burial ceremony 95 years after his death in 1642.

'The laymen and masons that were attending the ceremony thought that they should have some souvenir of Galileo's body,' Paolo Galluzzi, director of Florence's Galileo Museum said.

I think I'll pass on this one...

Zz.

Dimensional Analysis in Physics and the Buckingham Theorem

Here's a paper that might be useful to physics students:

"Dimensional analysis in physics and the Buckingham theorem", T. Misic et al., Eur. J. Phys. 31 893 (2010).

Abstract: Dimensional analysis is a simple, clear and intuitive method for determining the functional dependence of physical quantities that are of importance to a certain process. However, in physics textbooks, very little space is usually given to this approach and it is often presented only as a diagnostic tool used to determine the validity of dependences otherwise obtained. This paper presents the basics of dimensional analysis in two cases: the resistance force of the fluid that occurs when a body moves through it and the speed of propagation of waves on water. After that, a general approach to dimensional analysis based on the Buckingham theorem is shown. The material presented in the paper could be useful to both students of physics and physics graduates.

You can get a free download of the actual paper during the first 30 days that it appears online. This paper appeared on 8 June 2010.

Zz.

Chicago's Museum of Science and Industry is FREE This Week

Chicago's Museum of Science and Industry offers free admission only this week! (ends Friday, June 11, 2010).

So if you want a good excuse to go, this might be it.

Zz.

The Search For Dark Matter

Two videos from PhysicsWorld on the search for dark matter. Both of these are looking for dark matter in underground laboratories.





Zz.

Street Corner Science: Ask A Nobel Laureate - Follow-Up

I mentioned earlier about Nobel Laureate Leon Lederman setting up a table in downtown Chicago this past Sunday to answer questions from all-comers. This is a news report on that occasion.

Those were some of the burning questions dozens of science fans asked Nobel laureate Leon Lederman, who set up shop Sunday near the Michigan Avenue Bridge. The Chicago Council on Science and Technology sponsored the event to show people that science is accessible, said President Alan Schriesheim.

Jonathan Shobrook, 11, of Highland Park, asked about a theoretical particle called the Higgs boson, known as the "God particle." Physicists believe Higgs may give mass to all things and could explain how the universe is put together. Shobrook, who will enter seventh grade this fall, showed Lederman a chart he made about the particle.

I hope they do this again, either with Lederman, or with someone else.

Zz.

The Physics of Hockey

... as in ICE hockey, in case people from other parts of the world get confused since many areas consider "hockey" to be FIELD hockey.

With the Chicago Blackhawks and the Philadelphia Flyers tied in their Stanley Cup championship series, a reporter from the Chicago Tribune decided to ask a University of Chicago physicist on the "physics" of hockey.

A couple of good ones that were asked are:

Q: What principles of physics are at play with the slap shot?

A: Hockey players are taught to swing the blade so it hits the ice about one foot behind the puck. As the hockey stick slides across the ice, it can bend to almost a 30-degree angle. When the blade strikes the puck, it launches the puck at more than 100 miles an hour because of all the energy in the bent stick. If the player cleanly strokes the puck without striking the ice, the maximum speed would be much lower. You really have to get the stick bent.

Q: Why is ice slippery, allowing both skates and puck to glide across it?

A: That question has a long, interesting history that goes back to the 1860s, when (renowned physicist ) Michael Faraday theorized there is a very thin layer of water on ice, demonstrating it by holding two ice cubes together, resulting in them freezing together.

Later there was a theory that skaters could glide across the surface of ice because the pressure of the skater's weight on the blade causes the ice surface to melt. That proved not to be true.

Faraday was right, there is a thin layer of water on the ice surface even at 328 degrees below zero Fahrenheit, but we still don't know why. Because it is so ubiquitous, it's hard to think of water as a weird organic chemical with a lot of strange properties. Ice floats because water in its solid state is less dense than in its liquid state — for example, the opposite of alcohol.

Of course, this is sports. There has to be some silly moments.

Q: Why is Philadelphia Flyers defenseman Chris Pronger such a jerk?

A: There are some questions that physics simply has no answers for. This is one of them.

Zz.

More Exercise = Higher GPA?

It is difficult to differentiate between the cause-and-effect observation versus the correlation observation when we deal with public health. So I wouldn't pass this out as a fact, but I'll just mention it.

It seems that the latest study presented at American College of Sport Medicine's annual meeting shows a correlation between college students who engages in daily 20 minutes of vigorous physical activity and higher GPA.

A study presented Thursday at the American College of Sport Medicine's annual meeting demonstrated the relationship and reinforced the notion that exercise reduces stress, improves performance and increases a sense of well-being.

Joshua Ode supervised the study at a university in the northern U.S., of students ages 18-22. Ode said, "If the students are improving in the classroom, it may create a better campus environment. You're creating more successful students, which is the goal of universities."

Researchers studied 266 undergraduates and defined moderate activity as those exercises which don't make you sweat or breathe hard, and vigorous activity for those which do, of any type. Their findings were consistent regardless of gender or major.

So then, let's examine this in light of the common stereotypes. We associate engineers, physicists, etc. as nerdy, wimpy looking guys, which presumably are thought to be smart and, therefore, would tend to have higher GPA. Don't look like they exercise much. Yet, we also often associate muscular, athletic, and physically fit guys as dumb jocks, not someone who would tend to have higher GPA.

So the stereotypes are in contradiction to the study, assuming that we buy into one or the other, or none. And yes, I'm being wishy-washy here. :)

Zz.

Q&A with Nobelist George Smoot

A very informative (and somewhat "entertaining", depending on what you deem as entertaining) video of a series of questions and answers with Nobel Laureate George Smoot.



Zz.

James Franck

In this month's issue of Physics Today, there is a short biography of James Franck. This is another example of one of the giants in physics that most of the public are not aware of. So it is a good article to read just to familiarize yourself on the contribution that this person has made. It also gives you some background on name given to the institute at the University of Chicago that focuses on condensed matter physics.

Zz.

Journal of Physics: Condensed Matter - 2009 Highlights

The IoP's Journal of Physics: Condensed Matter has produced its highlight papers from 2009. And the good news is, you get to read all of the highlighted papers for free until end of 2010.

So don't miss it. There are some very good ones here.

Zz.

2010 World Science Festival

The third annual World Science Festival in NY City is upon us again. Check out their website for all the amazing events being planned for this year's festivities.

The presence of Stephen Hawking will certainly jack up the interest in this event.

As the presence of Dr. Hawking suggests, this year’s festival has a decidedly cosmic flavor. The Webb telescope model will preside over a star-gazing party hosted by, among others, John Grunsfeld, the former NASA astronaut and Hubble Space Telescope repairman, on Friday night. Telescopes will be available, or you can bring your own. Meanwhile throughout the week visitors to the Broad Street Ballroom in Lower Manhattan can hear what black holes might sound like as they are being formed. Astronomers hope to record them with the Laser Interferometer Gravitational Wave Observatory, a vast expanse of lasers and mirrors set up in Washington State and Louisiana to measure the twitching and pulsing of space-time in response to cosmic catastrophes.

Don't miss it if you're in The Big Apple.

Zz.

OPERA Made First Detection of the Tau Neutrino

The collaboration between Italy's INFN and CERN has announced the first ever detection of the tau neutrino, and the muon-tau neutrino oscillation.

The project's source of neutrinos is a proton accelerator at CERN in Geneva that slams protons into a graphite target, producing particles called pions and kaons that quickly decay into muon neutrinos.

Because the neutrino beam that is created is not affected by electrical or magnetic fields, the proton accelerator must be pointed directly at detectors in the laboratory under Gran Sasso mountain 453 miles away in central Italy, between the towns of L'Aquila and Teramo. When neutrinos are produced, they continue in the same direction of the proton beam, arriving at Gran Sasso in 2.4 milliseconds.

A splendid discovery that confirms one of the aspect of the Standard Model, but ironically, also confirms that the Standard Model needs to be tweaked. This is on top of the electron neutrino-muon neutrino oscillation that was confirmed several years ago.

Zz.

Graduation Speaker Perpetuates Myth

At some point, you just have to shake your head and accept that for most part, the damage is done.

The 2010 graduating class of Cresset Christian Academy, presumably in Durham, North Carolina, was told this myth during its graduation ceremony:

It’s the people who’ve believed in the impossible in this world who have been able to accomplish the greatest dreams, she said.

“There are always going to be people who are what I call ‘Dream Chisellers’,” she said. “But you always have to believe that you can.”

Smith also held up the bee as an example of the impossible being possible. Given what we know of physics and aerodynamics, she said, the bee’s fragile, thin wings should not be able to support its bulbous body. But yet, it does fly.

She left a paper cutout of the bee in each of the graduating seniors’ folders, and encouraged the graduates to hold to their belief in Jesus Christ and belief that there is a perfect plan for them in life.

What she meant was given what SHE THINKS SHE KNOWS about physics and aerodynamics....

It is sad that a graduation speaker won't do some simple, basic homework to check up on her facts. Instead, she continues to perpetuate this myth that we can't account for why the bee can fly. This is seriously wrong. For a bumble bee, a very common example when used with such a myth, we know perfectly well how it can fly.

So there's a bunch of impressionable high school graduates who will be walking around thinking that physics cannot explain why a bee fly, and that this is an impossibility that has been shown to be possible. Someone needs to yank this person to the side and straighten her out before she does any more damage with such lies.

Zz.

More On Einstein's "Sexy Ad"

I mentioned about the lawsuit against GM about their recent ad using Einstein's head on top of a muscular body. This news report has a picture (at least partially) of that ad.

Well, the picture is a little bit disconcerting (if not disturbing). Still, I don't think it is that big of a deal, especially if GM did get a permission to use Einstein image.

Zz.

NRC Report On Global Warming

The National Research Council has issued three separate reports recently on global warming.

Advancing the Science of Climate Change
Adapting to the Impacts of Climate Change
Limiting the Magnitude of Future Climate Change

The strongest conclusion out of these reports is: Climate change is occurring, the Earth is warming, and these are largely caused by human activities.

Lest people think that these reports are simply a rehash and done by the same people who did the IPCC, the report from this week's Science (Science 28 May 2010 p. 1085) indicated otherwise.

But this was no rehashing of the IPCC report, which has taken considerable flak of late. The new NRC reports draw on the past 5 years of peer-reviewed literature, which was published too late for inclusion in the IPCC analysis, Matson emphasized. They also reflect findings from more than a score of reports from the U.S. Global Change Research Program and earlier efforts from NAS. The membership of the three NRC panels also had little overlap with that of the IPCC's working groups, says economist Gary Yohe of Wesleyan University in Middletown, Connecticut, an IPCC veteran who was on the NRC panel on adapting to climate change. Yohe says he was surprised to find at the panel's inaugural meeting that three-quarters of his fellow members were unfamiliar to him.

Zz.

Don't Mess With Al

... Al, as in Albert Einstein.

Hebrew University, who holds the rights to Albert Einstein's image, has sued General Motors. It seems that GM used Einstein's image in one of their print ads. GM, on the other hand, claimed that they received permission.

The Detroit automaker grafted the Nobel Prize-winning German scientist's head onto the body of a buff, shirtless man in a Nov. 30 ad in People magazine.

The ad had the slogan "Ideas Are Sexy Too."

Hebrew University of Jerusalem filed suit against GM earlier this month federal court in central California. The suit quotes Forbes magazine in 2008 as saying Einstein earned $18 million a year, fourth among deceased celebrities. He died in 1955.

I haven't seen the ad, and I don't know about you, but somehow, this ad sounds rather ... er ... creepy.

Zz.

Autobiography of Robert Laughlin

There are many physicists that I find fascinating. It doesn't mean that I "worship" them or anything, but I find their stories to be quite captivating. Often, these are anecdotal stories told by colleagues, former students, etc...

I love Robert Laughlin's book that tried to argue against reductionism, because it introduces an alternative concept at looking at the world than what has been popularized. I've already heard many anecdotal stories about him from others, but it is always nice to hear about his life stories from the person himself. More than anything, is autobiography on the Nobel website is not your typical run-of-the-mill autobiography, and several years ago, I remember spending time reading the whole thing. I happen to come across it again recently when doing a search on something, and found myself reading it all over again.

So, if you haven't had the chance to read it, do yourself a favor and read his fascinating life story so far.

I suppose what I like about his story is because he hits the same points that I've been making, which are:

1. Some of the best theorists tend to be those who pay close attention to experiments. His argument that experiments are the "eyes and ears" aimed at Mother Nature, to me, is spot on.

2. That you can have the motivation to study and want to do physics not because you have a grandiose ambition to "study the universe", but rather because you are fascinated by the simple and small things. Laughlin was first interested in how a television work, and simple basic electronics. I remember being curious at how a top can not only spin, but precesses around an axis without topping over. It doesn't have to be about finding and solving for the grand unified theory. In fact, I haven't found any physicist that I know who first got interested in physics because of such glorified ambition.

Zz.

Ask A Nobel Laureate David Gross

Here's another opportunity for you to ask a video question to a Physics Nobel Laureate on YouTube. This time, it is to David Gross, Nobel Prize winner in 2004, along with H. David Politzer Frank Wilczek, for "... the discovery of asymptotic freedom in the theory of the strong interaction".

To make your question a little bit more relevant to the person you're asking, it would be beneficial to at least read a little bit of some background info on what he is an expert in. So go review his Nobel Prize lecture as a start.

Zz.

Want To Go Into Medical School or Law School? Major in Physics

Latest statistics from the AIP reveals a rather interesting result. It appears that an undergraduate major in physics might be the best major for a student intending to go into Medical School or Law School in the US, if we go by the MCAT and LSAT test scores.

From the average MCAT scores by different majors shows that physics majors score the highest average. The LSAT statistics also shows that physics majors get the highest mean scores.

Now, of course, it's hard to do any kind of cause-and-effect simply based on such correlations. In other words, did learning physics and having a physics background helps in preparing for such tests? And more importantly, how did these different majors do in the actual Medical or Law school? But still, it is a very powerful result where in both exams, physics majors are doing so well.

Zz.