Monday, March 31, 2008

Traffic Jams Happen, Get Used to It

I've heard about this research study, but I didn't pay that much attention to it until I saw that they had a video of this effect that was rather neat. It also confirms what I had suspected for a while.

The study was done by a group of Japanese scientists/mathematicians about traffic jams that happened without any bottleneck[1]. In other words, there's no obvious obstacles, such as an on-ramp, or a constrictions, etc. that would be obvious causes for a traffic jam. All they did was increase the traffic density, and at some point, there's some "critical density" in which traffic jams simply occurs because people just don't all drive at the same speed.

What is need is that you can actually this taking place in the video that they have included. I've always suspected this. I drive roughly 31 miles each way to work every day. I sometime get stuck in a couple of slow spots where traffic either slows down or stopped for periods of time. Yet, as you you drive some more, you speed back up again as if nothing has happened, and you don't see any reason why the traffic slowed down. I tend to blame it on slow cars in the left lane, but I had no proof that was the usual cause. Now, I have some evidence to back my haunch! :)


[1] Y. Sugiyama et al., New Journal of Physics v.10 p.033001 (2008).

Time-Keeping Milestone

There are a couple of interesting reports in the latest issue of Science this week (Science 28 March 2008). Two papers have made the most accurate measurement of time-keeping to date. One uses the optical transition from ions[1], while the other uses neutral atoms[2]. They produced a time accuracy of up to 10^-17 and 10^-16 second, respectively, which is significantly more accurate than the Cs atomic clock.

However, as pointed out in the Perspective by Daniel Kleppner in the same issue, with an error budget that includes perturbation of the order of 10^-18 s, such precision now has to consider the effects of General Relativity.

When precision is pushed to new levels, ever more subtle effects must be taken into account. For instance, the error budget includes a small contribution, 1 mult 10-18, due to an uncertainty in the gravitational potential of the two clocks. This corresponds to a difference in their altitudes of 1 cm. This heralds one of the most interesting aspects of time keeping with optical clocks: The effects of general relativity that mix time with gravity are starting to approach a point that will require rethinking the basic concept of "keeping time."

The "two clocks" referred here are the two ion clocks used in the T. Rosenband et al. experiments - Al+ ion and Hg+ ion clocks. Having clocks that are now sensitive enough to detect effects of GR would certainly open up a whole possibility of testing GR even more.


[1] T. Rosenband et al., Science v.319, p.1808 (2008).
[2] A. D. Ludlow et al., Science v.319, p.1805 (2008).

Sunday, March 30, 2008

Gyroball - A "Nothing Ball"?

The controversy surrounding the existence of a "gyroball" in the sports of baseball continues. Recall that I reported on this a while ago of the skepticism that such a ball can be thrown. Now there's a new follow up to this issue where even more people are simply questioning why this is such a big deal.

Adair said it actually mimics a pitch in cricket that "probably goes back 100 years," its odd-duck spin more useful in that sport because the ball is bounced to the batsman. "It had various names," Adair said. "The 'googly' and the 'Chinaman,' because a British bowler of Chinese extraction threw it.'

"Properly thrown through the air, the gyroball does nothing. It's a 'nothing ball!'"

Or as University of Illinois physics professor Alan Nathan amended, "A 'qualified nothing ball.' Because if the batter is expecting a 'something ball' [with a break or a dip], that makes a 'nothing ball' effective."

Sort of a reverse psychology? :)

I wish they just play ball!


Saturday, March 29, 2008

Lawsuit: Huge Atom Smasher Could Destroy World

This news has been making the rounds around various blogs and news wires. A couple of wackos have decided to file a lawsuit against the US Dept. of Energy (DOE) and CERN to stop them from building the Large Hadron Collider (LHC) at CERN.

I debated on whether I want to dignify this stupidity by reporting it on here. But then again, it is going to be reported anyway. This news report has some brief description of the background of the yoohoos that filed the lawsuit.

Not included among the documents is Wagner's own indictment last month on identity-theft charges tied to an ongoing legal battle over a botanical garden on the Big Island of Hawaii, but you can read about that here.

Most physicists say Wagner's worries are unfounded. Micro black holes would evaporate nearly instantly instead of combining to form larger ones, they say, and the "strangelet" particles he frets would freeze the world would in fact fall apart quickly.

Wagner's own background is a bit fuzzy. He claims to have minored in physics at U.C. Berkeley, gone to law school, taught elementary-school science and worked in nuclear medicine at health facilities — but he doesn't appear to have an advanced degree in science.

Sancho's qualifications are even murkier, but the lawsuit identifies him as a Spanish citizen residing in the U.S., even if his presence makes the entire case a bit, um, quixotic.

And before someone accuse me of simply trying to attack the credibility of the wackos rather than address the "physics", let me point one very glaring and important observation here. There are already extremely energetic particles colliding with other particles in our universe. For example, the recent Auger Observatory results studied the origin of the these cosmic particles, that have energies in the 100's of TeV, something that CERN cannot even come close to. These particles have been around for million (even billions) of years, and have made gazillions of collisions. If such high energy collisions can create blackholes, we would have been swallowed and destroy by them already by now. Hello? Is this not obvious?

It looks like the crackpots are now getting a bit more daring. But now, rather than just being an internet nuisance, they are now being a pain-in-the-rear-end with their frivolous lawsuits. So anyone who thinks that these crackpots are just a "harmless" bunch of losers, think again. They're still losers, but they're definitely not always harmless.


Friday, March 28, 2008

Giant Magnetoresistance

The 2007 Nobel Prize in Physics was awarded to Albert Fert and Peter Gr├╝nberg for the discovery of the Giant Magnetoresistance, as reported earlier. I had also given a good link that explains what GMR is. Still, one can never have too many good explanations of what it is, so here's another one, this time, it's an article from Physics Central.

This is actually quite appropriate because it is another example on how basic research in strongly-correlated electron systems can produce something that becomes important in our daily lives. It is why basic research is important. One would hope that this message gets across to those people making funding decisions.


Thursday, March 27, 2008

Webcast: Nobel Laureate to lecture on "Blind Chance or Intelligent Design: The Need for Basic Research," April 8, 2008

Here is the announcement for the next series of Honeywell-Nobel Initiative lecture series:

Some scientific advances, such as the discoveries of X-rays and penicillin were stumbled upon through serendipity. Others, like streptomycin and nuclear reactors, resulted from targeted and specific research. Honeywell will be presenting a lecture and Webcast by Nobel Laureate Dr. Sheldon Glashow on “Blind Chance or Intelligent Design: The Need for Basic Research" at 9:00AM on April 9, 2008 in Beijing (9:00PM pm April 8, 2008 in Eastern Time).

Dr. Glashow’s many research accomplishments in theoretical physics include his prediction of the charmed quark (for which he was awarded the Oppenheimer Medal) and his seminal contributions to the unified theory of weak and electromagnetic interactions (for which he shared the 1979 Nobel Prize in Physics).

For the past quarter century, while he has continued his fundamental researches in particle physics and cosmology, Dr. Glashow has also focused on stimulating interest in science among high-school students and encouraging scientific literacy among non-science students at the university level.

Dr. Glashow will be delivering a lecture to students at Beihang University, Beijing, China on April 9. A live Webcast of his remarks, as well as related content, will be available for viewing from Honeywell Science.

The video of the recent lecture on Cosmic Background Radiation by George Smoot is now available online.


Under Control: Keeping the LHC Beams on Track

While people do have some idea of the size and the complexity of the LHC, most do not have a good 'scale' of the issues involved here. There are some astounding issues and problems that they have to deal with. Keeping the LHC beam under control, and what to do when it veers off course is a major issue.

This article tries to impart some idea on the control and contingency issues of the LHC beam. For example:

The complexity means that repairs of any damaged equipment will take a long time. For example, it will take about 30 days to change a superconducting magnet. Then there is the question of damage if systems go wrong. The energy stored in the beams and magnets is more than twice the levels of other machines. That accumulated in the beam could, for example, melt 500 kg of copper. All of this means that the LHC machine must be protected at all costs. If an incident occurs during operation, it is critical that it is possible to determine what has happened and trace the cause. Moreover, operation should not resume if the machine is not back in a good working state.

So this is not case where you can just simply pull the switch if something goes wrong. They have to make sure they dump the beam properly without causing damage to all the components along the ring.

This is, of course, a common issue at large particle accelerator facilities, including the Tevatron. I am still at awed at some of the things they are able to do, and at the scale that they are doing in. I some time wish the most of the general public has some clue on the level of complexity and the accomplishments at just being able to run such an experiment.


Wednesday, March 26, 2008

Accelerator in a Bowl

This is a cool demonstration to illustrate how they accelerate particles at the Tevatron at Fermilab.


Ettore Majorana And His Heritage Seventy Years Later

For those who are not familiar with the story of Ettore Majorana, this is probably a good introduction to his life, and his contribution to physics within such a short period of time till he mysteriously disappeared some 70 years ago. I consider him the Emelia Earhart or the Jimmy Hoffa of physics because of this disappearance, which still has not been solved.


Tuesday, March 25, 2008

An Inquiry Into the Reproduction of Physics-Phobic Children by Physics-Phobic Teachers

I know! I was intrigued by the title as well! :)

First of all, this is a paper that was originally published in Japanese, and this English version is, what appears to be, an almost direct translation. So there will be some awkward passages here and there. If you keep that in mind, everything should be OK (just think of literal translation and you'll be fine).

The authors studied the effect of teachers who themselves have little understanding or interest in physics on students. Somehow, the teachers disinterest in physics can (surprise!) transfers itself to the students.

It is interesting to note that, with the budget crisis in physics in the US and UK, we tout the high investments in science in Europe and Asia, particularly Japan, China, and Korea. But it is obvious from this report that even in Japan, they also face, to a lesser degree, problems in getting students to do physics, not just as a career, but in terms of being educated or literate in it.


Monday, March 24, 2008

Considering Science Education

There has been only one essay so far in which I flat out tell everyone to go read it. It was the Helen Quinn essay "Belief and Knowledge - A Plea About Language".

OK, so here comes another one. In the March 21, 2008 issue of Science, an editorial by Bruce Alberts is a MUST READ by everyone and anyone (Science, v.319. p.1589 (2008)). He argues why science education is important to everyone, and not just science students.

I consider science education to be critically important to both science and the world, and I shall frequently address this topic on this page. Let's start with a big-picture view. The scientific enterprise has greatly advanced our understanding of the natural world and has thereby enabled the creation of countless medicines and useful devices. It has also led to behaviors that have improved lives. The public appreciates these practical benefits of science, and science and scientists are generally respected, even by those who are not familiar with how science works or what exactly it has discovered.

But society may less appreciate the advantage of having everyone aquire, as part of their formal education, the ways of thinking and behaving that are central to the practice of successful science: scientific habits of mind. These habits include a skeptical attitude toward dogmatic claims and a strong desire for logic and evidence. As famed astronomer Carl Sagan put it, science is our best "bunk" detector. Individuals and societies clearly need a means to logically test the onslaught of constant clever attempts to manipulate our purchasing and political decisions. They also need to challenge what is irrational, including the intolerance that fuels so many regional and global conflicts.

I totally agree. If you have read the beginning of my series on revamping the intro physics labs, I've always argued that these labs can be a valuable tool to these students (the majority of whom are not physics majors) as an illustration on how we accept something to be valid, or how we arrive at some of our knowledge. We should emphasize the idea that using scientific technique to verify something is the strongest degree of certainty that one can have in any endeavor. It is why scientific evidence is different than anecdotal evidence. It is why astrology is not a science, whereas astronomy is. The fact that many still can't tell the difference is an important reflection on how these arrive at what they perceive to be true. This means that many of the decisions they make may not be based on valid information or evidence.

So think of what happens when they vote for their political leaders....


The Squeeze at Argonne And Fermilab

.. and this "squeeze" comes both in terms of funding and science.

Three months into the disastrous Omnibus bill, this article looks at the impact on the two national laboratories in the Chicago area - Fermi National Accelerator and Argonne National Laboratory.

To say that the mood and the morale are low is to put it mildly. One good thing about this article is that it highlights each of the facility that has been affected, and what kind of science and impact it has.

As far as I can tell, the outlook for the immediate future isn't rosy either. Even though the president's FY09 proposal calls for immediate increase in all affected areas, everyone here is almost certain that Congress is not going to pass this budget any time soon and will wait instead until after the general election. This means that we will be saddled with a continuing resolution, and will adopt the disastrous FY08 budget for the remainder of the year and into next year.

Things are not looking good for science in the US, despite all the lip service that has been given about its importance.


Sunday, March 23, 2008

The Science of Tangled Cord

Next time you have to untangled the cords from your electronics, you can at least think of it as a complicated physics process. :)

This news article describes a recent PNAS paper on this very issue.

Knot formation had been studied a lot by mathematicians, but not much by physicists. Smith was worried that the work wouldn't be taken seriously, but it ended up being published in the prestigious Proceedings of the National Academy of Sciences.

"The way that you get a knot is the string has to bend back on itself, coil back on itself," Smith said. As a string or cord tumbles, the end of it has a 50 percent chance of weaving to the left or the right of the coils, and under or over the coils, sort of like random braiding, Smith said.

The exact citation for this paper (which none of these popular newspapers ever give) is:

Dorian M. Raymer and Douglas E. Smith, PNAS v.104, p.16432 (2007).

Don't get all tied up with it.



Friday, March 21, 2008

Interpretation of Quantum Mechanics - The New Religion

First of all, a clarification and a qualification. Most physicists (at least the ones that I come in contact with throughout my years as a student and as a physicist) don't really care about the various interpretations of quantum mechanics. It really is a non-issues 99.9% of the time. So essentially, we practice Feynman's "Shut Up And Calculate" philosophy where the formalism and what empirical evidence that it can produce is what we care about.

Now, in one of my rants in "Imagination Without Knowledge is Ignorance Waiting to Happen", I mention about many crackpots who have argued that physicists simply want to keep the status quo as far as our understanding of the universe goes, that all we care about is upholding the current laws and theories. We can't, as some put it, work "outside the box". Some even compare to our "devotion" towards not wanting to drop our current understanding as a "religion".

This, of course, is stupid, and false, on many different levels, as I've mentioned in that blog entry. Still, there is one aspect of physics in which, I hate to say, is starting to look like a religion, and it has nothing to do whatsoever with what these crackpots have in mind. In fact, I don't think any of them could even comprehend these things well enough to know any better.

What I find in physics to be no different than a religion is the rabid devotion of some people, physicists included, to the various interpretation of quantum mechanics. These interpretations could range from the "popular" Copenhagen Interpretation (CI), to Many-World Interpretation (MWI), to Bohm Pilot Wave (BPW), etc.. etc. Now, again, to be fair, this issue comes up only in a very small percentage of practicing physicists. I tend to find more of these discussions on physics forums rather than in prominent physics journals. And certainly, amateurs and philosophers tend to be more fascinated by this issue than the overwhelming majority of physicists. So in physics, this "religion problem" isn't a widespread epidemic.

Still, those who are devoted to this is not doing physics any favor. I find that the rabid devotion to such various interpretation (rather than just a casual attitude about it) rather puzzling and contrary to how one accepts something to be valid in physics. This is why I find that the devotion to any such interpretation as being no different than a religion:

1. There's no empirical evidence that shows one being "better" than the other. All of them come up with the same analytical form within the formal QM. The similarities with religion is obvious here. This means that there's nothing to support which is better, and they all come up with the same answer, at best, so far.

2. Yet, the devotees in each camp tout why such-and-such is more "logical" or "rational" or "conceptually sensible", etc. Without empirical evidence to support such claim, this is nothing more than a preference based on a matter of tastes! We might as well argue for our favorite color, or, in this case, our favorite religion. This is no different than the different religions and the many followers that they have. Each one will tout the superiority of its belief system, or why it is the "truth", etc. Yet, in none of these are there any empirical evidence to separate and support these claims.

Now one could argue that isn't what is being taught in QM classes more along the lines of adopting the CI? I don't believe so, because in the end, it is the formalism that is more important, and there's no ambiguity at all there. And if it really is CI that is being instilled into these students, how come most of them grow up and adopt the "Shut Up and Calculate" point of view and not become a CI devotee?

I'm not saying that at some point, there won't be a "tie-breaker", be it a further refinement to these various interpretations that make them distinctly different from each other, and/or new tests would come out to allow for direct verification of each one. But until then, why are people "believing" in something that, at the very foundation, is simply a matter of tastes?


Thursday, March 20, 2008

Iron-Based High-Tc Superconductors

This certainly came out of nowhere.

There's another "high-Tc" superconductor joining the fun. This time, unlike the cuprates, it consist of iron-arsenic planes, and is doped with fluoride atoms. Currently, it has a Tc of 26K, but that would probably change.

From preliminary report, it seems that it is not phonon-mediated, but rather via spin-fluctuation. It would be interesting to see if it has the same phase diagram as the cuprates and if it also has a pseudogap state.

Update 04/18/08 : There's a rather good summary on this in a Science daily news.


What is the Matter with the Uuniverse?

More CP violation results out of KEK on the B meson.

To find out the team created pairs of matter and antimatter particles, called B mesons and anti B mesons, and measured how they behaved. The study has come up with a better estimate of earlier measurements that suggest that there is a difference in the rate of decay (they decay into a kaon and pion).

"We have measured two differences of decay rates between b and anti-b," says Prof Hou. " It is around 9 per cent for neutral B and anti-B, and 7 per cent for charged B and anti-B. The bigger mystery, and gist of our paper, is posing the question of why there is this difference."

But the end of the article mentioned about waiting for more results out of BaBar at SLAC. I thought SLAC is no longer doing any particle collider experiment and is already being converted into the LCLS? Did something changed? Or are still going to do limited collider experiment in between LCLS runs?


Addendum: I just finished reading the paper in Nature (Lin et al, Nature v.452, p.332 (2008)) and the Perspective on this work by Michael Peskin in the same issue of Nature. The BaBar result they are expecting is the analysis of the large, existing data that have already been collected. So it isn't from any future BaBar experiment. That clears things up a bit, at least for me.

More Addendum: See a report on this in PhysicsWorld.

Wednesday, March 19, 2008

HiRes Confirms GZK Cutoff

This could be one of HiRes last triumphs. It has now down a "negative result" experiment and confirms the GZK cutoff (link may be open for a limited time), signifying a threshold of energy for cosmic rays.

This energy ‘cut-off’ was predicted in 1966 by Kenneth Greisen of Cornell University in Ithaca, New York, and in the same year by Soviet physicists Georgiy Zatsepin and Vadim Kuzmin of the Lebedev Institute of Physics in Moscow. They predicted that there would be very few cosmic rays with energies greater than about 6×1019 electronvolts (eV) because of energy losses through interactions with the ubiquitous photons of the cosmic microwave background, the radiation that fills the Universe.


The Hummer is NOT More Environmentally-Friendly Than a Prius

It's amazing how a report that is full of holes can gain such a foothold once some talking heads on TV adopted it.

A while back, there was a rather dubious report called "Dust to Dust" that essentially drew up a conclusion that the monstrous Hummer is more "environmentally friendly" than the Prius, based on all the energy accounting that is being used to research, manufacture, and run the vehicles. has a brief synopsis of the whole thing. Luckily, they also tackled the validity of that claim and cited several prominent (and certainly, NOT dubious) research work. It essentially debunked that myth.

Moral of the story: never accept the validity of science/engineering issues from politicians, TV personalities, or popular news media.


More Challenges Against Non-Local Hidden Variables Theory

Science Daily is reporting a new experimental measurement out of NIST and Maryland that challenges the validity of a certain aspect of non-local hidden variables theory.

Experiments so far have ruled out locality and realism as a combination. But could a theory assuming only one of them be correct" Nonlocal hidden variables (NLHV) theories would allow for the possibility of hidden variables but would concede nonlocality, the idea that a measurement on a particle at one location may have an immediate effect on a particle at a separate location.

Measuring the polarizations of the pairs of entangled particles in their setup, the researchers showed that the results did not agree with the predictions of certain NLHV theories but did agree with the predictions of quantum mechanics. In this way, they were able to rule out certain NLHV theories. Their results agree with other groups that have performed similar experiments.

I may have missed it, but I don't recall ever seeing any experiment on entanglement that hasn't produced any result that's consistent with QM. One can argue that such-and-such an experiment doesn't rule out that and that theory, but QM is batting with 100% hits here with zero strike-out. I find that rather impressive, and impressively convincing.


Tuesday, March 18, 2008

Public Impatience With Science

Argonne's Director Robert Rosner spoke to the Chicago Council on Science and Technology, a not-for-profit organization is committed to promoting science and technology in the greater Chicago area. Some of the things he said bears repeating here, especially on the part where it takes decades for a basic scientific breakthrough to make it to the consumer.

Computers were around for 30 years before they became useful to business, and solid-state electronics consumer products didn't catch on until a generation after the transistor was discovered, said Rosner, director of Argonne National Laboratory.

"When a basic discovery is made, no one has any idea what it will lead to," said Rosner. And this disconnect is behind the financial crisis now afflicting Argonne and its sister institution, Fermilab.

"People believe that basic science can wait," said Rosner, "but the truth is that if you don't do the basic research today, you won't reap the fruits in 20 to 30 years. We have to invest now to benefit our children and grandchildren. But to a culture that expects instant results, such patience is a hard sell.

I think most people do forget that. Even within the sciences themselves, many forget that some of the advancement in biochemistry, for example, were brought about because of something that was developed in physics years before. Synchrotron light sources came out of research in high energy physics, and it took many decades before the field of biochemistry, medicine, and pharmacy realized that such facilities can be valuable to their work. This is just one example of something that came out of basic research that appeared to have no direct application at that time.

Just how do we convey that to the public and, especially, those politicians?

Edit: The original link appears to no longer work. However, there is a link directly to the Chicago Council on Science and Technology with a video of the talk.


What Makes A Successful "Letters"?

The "Letters" in this case is the Physical Review Letters (PRL), one of the top 3 most prestigious publication for physics papers. The Physical Review website has an editorial on what makes a suitable and successful PRL paper. With the criteria for acceptance being more tight, and with the editors at PRL now having a larger role in weeding out submission, it is more important to pay attention to these guidelines on what they are looking for.

A successful Letter of course begins with a valid result, one that is important and interesting. This is glib, however, because it lacks explanations of “important” and “interesting.” So, here are attempts to define each, in single sentences: An important result provides insight that changes the way others view and understand the topic, allows them to improve their own approaches, and thus leads to substantial progress. An interesting result will make readers glad to learn of it, because it is important to their own work or the work of others, or because it is science of uncommon beauty, aesthetically. In the context of a manuscript there is a third element: accessibility. Regardless of its content, a manuscript will be of lesser interest if it is impenetrable, and a manuscript that attracts fewer readers will be less important.

Present PRL policy incorporates these three concepts by seeking to publish work that should not be missed by researchers in the given field and also those in at least some related fields. Broader interest, in general, is better, as is greater importance, but the two are not independent. Work that is extremely important to a few might be as worthy as work that is moderately important to many, which again leads directly to presentation. A manuscript that can be understood only by a narrow audience will be less likely to be suitable for PRL, because it will lose its chance to be moderately important to a wide audience.


Monday, March 17, 2008

How Fundamental Particles Lose Track Of Quantum Mechanical Properties

We have another report on the study on the mechanism of the differences between the quantum world and our classical world. This is another study on the effect of decoherence on a quantum system that couples to an external "bath".

It would be interesting to compare this to an earlier report on the emergence of a classical system from a single-particle state after just one interaction. It is also interesting to see how Roger Penrose would handle this. He seems to think that our classical world emerges due to some coupling or interaction between the quantum systems and gravity, and that eventually destroys the quantum system and out comes the classical system. These two papers above seems to indicate that the mere act of decoherence might be sufficient to produce the classical world.


Revamping Intro Physics Laboratory - Part 4

Continuing with this series, here's another experiment that I would propose. This would still be something that can easily be done at the beginning of the semester, which means it doesn't require that the students would have already learned any physics related to it. BTW, in case people think that all the experiments that I'm going to propose are this "simple", that is not going to be the case. These "no physics" experiments are aimed only at the beginning of the semester and where we want to introduce to the students that physics is nothing more than a systematic way of deriving what is valid and how to figure out a way to understand the relationship between things. It reinforces the idea that one doesn't need to abandon all that we already know to understand physics. In fact, we need to bringing in our "common sense" and the sense of "play" to do physics, or at least, these physics experiments. As the semester progresses and, presumably, the students' understanding gets more sophisticated, the experiments should also evolve the same way.

OK, for this experiments, we will deal with springs and masses, so again, it shouldn't be something difficult. The task this time is simple:

You will be given a "mystery" object in which you need to determine its mass. You are given a set of springs, and a set of calibrated masses. In addition, you will also have access to a ruler and a stopwatch if you need them. Figure out how you can determine, as accurately as possible, the mass of this mystery object. You must describe explicitly how you go about doing this determination.

Now, of course, in many intro physics class, this type of experiment typically requires that they find the spring constant by looking at the extension versus force or mass applied to the spring. I'm going about this the other way. Forget about the spring constant for now. The key thing here is that the student learns about the relationship between the spring extension as different masses are added to the spring. This to me would be the most obvious technique that most of the students would do. They would find the extension of the spring with different masses. Then, when given mystery mass, they may have to do some interpolation or extrapolation to estimate the mass of that object.

Now, there's also a possibility that some students may do this differently. They could, instead, let each of the known masses oscillates one at a time and find the relationship between the mass and the period of oscillation. They won't end up with a straight line, but as in the previous suggested experiment, this is OK. While we tell them they need to do this as accurately as possible, in the end, we really don't care as long as they explain what they did and how they did it. So even if they had to extrapolate/interpolate by hand, this is perfectly fine.

Now, what we can do further is this. For the students that did the first method (hanging the mass and finding the spring extension), we can ask them this:

Now, often it is difficult to get the spring to be very still - the mass tends to oscillate up and down. So maybe it might also be a good idea to see if we can make use of this property to see if there's an additional relationship here between the mass on the spring, and the period of oscillation. Can you determine the mass of the mystery object this way? Does it give the same answer? It is always more convincing when two different methods give consistent answers.

For those who did the the second method (oscillating the mass and finding the period), you then say:

Oscillating the spring doesn't allow you to read off the mass very quickly, which is something you need quite often. So is there another way to determine the mass quicker? How about looking at how much the spring extends as you hang different masses? Can this lead you to a different way to measure the mystery mass? Does this value agrees with the one you got earlier? It is always more convincing when two different methods give consistent answers.

.. and voila, you've gotten them to do this in both ways! They also learn that in science, it is always more convincing when you can show a consistent result from two different techniques (although, to be technically accurate, these are not really two different techniques, but this is a good enough demonstration at this level). Now the fun starts if they come up with very different answers. This is where they need to figure out (with the help of an instructor) on what went wrong. To me, figuring out what went wrong is as important and what went right.

After the students have done both, you then can pose an additional question such as this:

What you have now is a graph that you always need to use whenever you want to determine a mass. Is there a way to know the mass of something without having to resort to using such a graph? Can we figure out a way in which, if we know how much the spring extends, we can simply punch that number in and out comes the mass?

I think you know where I'm going with this, don't you? Considering that the students should have a background in sufficient mathematics, they would have seen a straight line equation. If not, a bit of help and hand-holding is called for, which, at this point, should be alright.

So in essence, we have done the mass-spring experiment, but done in a different manner. Rather than giving out the necessary steps that the students have to do, we instead "coerced" them into doing them by a series of questions and tasks that we want them to accomplish by themselves. Inadvertently, they "discover" Hooke's Law by themselves.


Friday, March 14, 2008

"This Coincidence Cannot Be Accidental"

That's the most dramatic statement coming out of a newly-published paper in Science, and that was the title that Doug Scalapino used in his Perspective article on this paper in the same issue.

Just when we think that we know everything there is to know about conventional, metallic superconductors, Mother Nature throws a wrench at that fallacy. Reported today by Ayanajian et al.[1], metallic superconductors such as Pb and Nb still holds a mystery. This time, it appears that the exact phonon energies of the Kohn anomalies happen to coincide with the superconducting binding energies of the cooper pairs of that particular metal. This is something that was not expected, and current formalism of conventional superconductivity says nothing about such a thing. As Scalapino pointed out his is Perspective article[2],

... although the polarization created by the conduction electrons and the response to the ionic lattice contribute to determining both the Kohn anomaly and the pair binding energy, there must be something else at work that locks (the superconducting gap) to (Kohn anomaly energy). As noted, this could mean that there is some new physics that is not captured by the Eliashberg formulation.

I love it! I love unexpected surprises like this!


[1] P. Ayanajian et al., Science v.319, p.1509 (2008).
[2] D.J. Scalapino, Science v.319, p.1492 (2008).

Thursday, March 13, 2008

Dark Matter Music From CDMS

This is a bit out of the ordinary.

This is taken from Fermilab Today newsletter for March 13, 2008:

Karl Ramberg sometimes incorporates music into his artwork. But a trip with his brother, Fermilab physicist Erik Ramberg, added science to his palette. Karl, with the help of scientists, produced a full-scale, plastic model of a dark matter detector that translates its data into light and sound.

"The end result is that you get an experience, aurally and visually, of subatomic affects," Karl said. "You get a better understanding of what the data is saying."

The musical detector, a YouTube sensation, is modeled after the real Cryogenic Dark Matter Search, an underground experiment searching for dark matter particles. The actual CDMS experiment detects and records the energies of particles that strike its five towers. The model takes that one step further, expressing the data in color and tone according to particles and their properties. The idea for the model was inspired by a trip to the Soudan, Minn. mine that houses the CDMS experiment, where Erik, a CDMS collaborator, took shifts.

So this is essentially data translated into music.

It could pass for a New Age music, I would think. :)


Revamping Intro Physics Laboratory - Part 3 (Follow-Up)

OK, I got some very interesting responses to my suggestion of an experiment that can be done for an intro physics lab. I think I didn't explain myself too clearly on the premise and how I'm going to present it on here, so I should do that now.

While I tried to be explicit in describing the experiment and what would be a good way to do it, I don't actually want to reveal the whole hand. That's why I went along with the idea that there could be a dependence of the period with varying weights, because that is a very likely path that the students might attempt. If someone is thinking of actually trying to introduce this experiment in an intro lab, I don't want the possibility that some student might google it and find my blog where the whole thing has been revealed. :) That would defeat the purpose of them doing this without any kind of "previous knowledge".

So while I'm trying to be as clear and complete as possible in the experimental description, and the "philosophy" behind it, I don't really want to reveal everything either. In fact, I'm hoping that there WILL be students who decided to figure out if they can do it by changing just the weights. I consider discovering something that cannot work to be very educational. In fact, in science, knowing what doesn't work can be quite important (re: Michaelson-Morley experiment). They at least now know that changing the weights would not work. If they are curious enough, they'll try to find out WHY it doesn't work, and this is where the physics can be introduced.

Note that the experiment that I had suggested does NOT require that they have learned anything in intro physics. It is quite independent of the lesson they might have received in class. So in principle, this experiment could be done even during the first week of class. It doesn't require that they had learned about simple pendulum.


Wednesday, March 12, 2008

New WMAP Data Once Again Agrees With Cosmological Model

The more they test it, the more convincing it becomes.

The new report out of the new analysis of WMAP data on the neutrino background has again produced a result consistent with the Big Bang Nucleosynthesis.

As such, the cosmic microwave background provides an independent estimate of the number of neutrino “families” in nature: 4.4 ± 1.5. Despite having been inferred from a totally different cosmological epoch, this value agrees with constraints from Big-Bang nucleosynthesis, the first few minutes of the universe during which light nuclei were manufactured, and with precision measurements at particle accelerators which fix the number of families at three. The WMAP5 data also constrain the combined mass of all types of neutrino to be less than 0.61 eV.

“The discovery of the neutrino background tells us that our models are pretty much right,” says cosmologist Pedro Ferreira of the University of Oxford. “Stuff from particle physics that you’re not putting in by hand just drops out of them — that’s pretty cool if you ask me.”

Yes, very cool! :)


Revamping Intro Physics Laboratory - Part 3

OK, I haven't forgotten this yet.

To me, the biggest problem with the current structure of intro physics lab is that we give students a list of things they have to do and measure, and hand-hold them into getting the result. In other words, they don't have to think too much to complete the exercise. They may have to do a bit of thinking and understanding of physics to complete the write-up, but the actual part of performing the experiment requires simply the ability to follow instructions.

I believe that we should have a more open-ended experiment to be given to the students. So I'll give an example. Note that while thing is something that I've thought about for a while, I'm still writing this off the top of my head. So there may be other problems with it that I haven't carefully considered.

Give them a problem to solve such as something like this:

Construct a pendulum clock. To make this clock useful, it would be helpful if the pendulum can swing back and forth once as close to 1 second as possible. Then each complete oscillation will take just one second. That way, this clock and measure time in increments of one second. You may use a stop watch to calibrate your pendulum to verify that it makes a one-second swing. Try to build this as accurately as possible. You must describe in detail in your lab report how you accomplish this task and why you chose to do it this way.

Now, as apparatus, give them a length of string, a set of weights, and a stop watch, plus other necessary items for them to be able to mount the pendulum on something.

Here's what I expect to occur. You'll have some students doing this by trial-and-error. They'll mount a length of string, and then start changing the weights to change the period of oscillation. Of course, there's no guarantee here that there is JUST the right weight for that length of pendulum to produce a 1-second period of oscillation. So students doing it this way may face a problem, but that's OK, because at the end when we discuss on to do such a thing, they'll discover why their technique isn't the best way.

You'll also get a bunch of student who would use a fixed weight, but tries to vary the pendulum's length. Again, they may try this simply by trial-and-error, adjusting it a little bit at a time until the period is close to 1-second interval. This technique is of course, more "refined" than the earlier one, since there's a high possibility of getting the right period.

Of course, what should be done, rather than simply doing a trial and error method, is simply to use a fixed weight, then measure a set of period corresponding to a set of pendulum lengths. Using the table, one can plot period versus lengths, and from there, interpolate (or extrapolate, depending on the range of lengths that were used) the exact length to produce a period of 1 second can be read off. So after the experiment is done and the students write their report, the lab instructor can start a discussion on the best possible technique to get the most accurate result. One can even make it a bit more complicated and ask the students how accurate is their clock as they let it swing for a length of time. This is where if they constructed a clock that swings over a large angle of oscillation, they may discover that it doesn't keep time very well.

What this type of lab forces them to do is think on the relationship between two measured variables. The first group had to figure out how the period changes as they change the weights. The second group is finding out the relationship between the period and the length of the pendulum. There may be a 3rd group that may be changing both the length and the weights simultaneous. If they do, and they're doing this by trial-and-error, god help them! :) But no matter what, the students are forced to think of what to do, and why they're doing it, to accomplish the task. They are not told how to do it. The experiment and the equipment give are familiar enough to them that this isn't something out of the ordinary. In fact, when they were kids, they probably played with something like this. The curiosity with finding how to do things is the purpose of the lab exercise. It is really playing, it is just that now, they have to think on what they are doing, why they are doing it, and how to present it in writing.

Next time, I'll try to present another possible laboratory exercise along this line.


Tuesday, March 11, 2008

New Video on "Dark Matter" With Teacher Notes to Benefit Students, From Perimeter Institute

Hum.... a video on "dark matter" for high school students? With teacher's notes?

I haven't seen this yet, but this was the press release from the Perimeter Institute on something they are producing. If you have time and want to view it, you can directly go to this link.

Tell me what you think after viewing it. Do you think this can be an effective tool to introduce dark matter to students at that level? Would the teachers be able to understand it, even with the teachers guide?

Monday, March 10, 2008

A More Accurate Clock, and Fine Structure Constant Isn't Changing

Talk about killing 2 birds with one stone.

A new paper out of physicists from NIST has managed to accomplish to very important task. The first is the use of an optical clock that is way more sensitive and accurate than the atomic clock. Secondly, due to the highly sensitive and accurate nature of the clock, they have shown essentially that the fine structure constant isn't changing over time.

I wonder if the J.K. Webb camp will be responding to this report....


Review: The Mystery of the Missing Antimatter

This is a book review of Helen R. Quinn and Yossi Nir's "The Mystery of the Missing Antimatter". As the reviewer has noted, there are only 3 major mysteries in cosmology today: the nature of Dark Energy, the nature of Dark Matter, and why matter dominates antimatter in our universe today.

This might be something I might try to get in the next few months. Helen Quinn, if you've read this blog for any considerable period of time, wrote a while back an article that I had characterized as something all scientists and science students must read. So she certainly has a clarity of thought and a concise use of words.


'Expatriates' From Physics Careers Find Funding, Fulfillment in Medicine

I think the field of Medical Physics has not been getting enough publicity among incoming students, which is too bad considering the graduates from this field continually fetch good starting salary and continue to be highly sought after.

This news article highlights the migration into Medical physics by students who suddenly face funding shortage and cutbacks. Considering the economic outlook especially in the rest of physics, these setbacks may be a blessing for these students going into this field of study.


Sunday, March 09, 2008

Bill Foster Wins Election

It's no secret that I've mentioned about physicist Bill Foster campaign to win the House of Representative seat vacated by Dennis Hastert. He has done the upset and won the special election yesterday against Republican Jim Oberweis. So we have another physicists in Congress.

Unfortunately, this is only to serve the remaining term that was vacated by Hastert. We will have deja vu all over again this coming November when the two of them fight it out for the full term.


Friday, March 07, 2008

The Wave-Particle Duality of Light: A Demonstration Experiment

Other than the fact that I don't quite like the title, this is an excellent demonstration paper that was published recently in AJP. Very much like the J.J. Thorn et al. paper on the which-way experiment, these profound phenomena can actually be performed in an undergraduate physics lab.

First, the exact citation:

T.L. Dimitrova and A. Weis, Am. J. Phys. v.76, p.137 (2008).

They basically performed a Mach-Zehnder interferometer experiment using very low intensity light so much so that only one photon is in the apparatus at any given time. They also have a second stronger laser beam that traverse the same apparatus, but slightly displaced that exhibit the clear wave-like interference pattern.

So far, this is fine and dandy, and it would not have caught my eye because it would be a nice, undergraduate physics lab exercise. But at they end, they did something simple, yet, can be quite profound to a student. I'll quote what they said:

The demonstration, whose result is astonishing for students, is realized in the following way. First the fringe pattern is locked to a photodiode as explained in Sec. IV B, and the photomultiplier is moved to a fringe minimum, as characterized by a low photon count rate which can also be displayed acoustically. If now path A of beam 1 is blocked inside the interferometer, it is possible to hear (and see) a distinct increase of the click rate. This result demonstrates that if we give each photon the choice of taking either path A or path B, it has a low probability to appear at the detector. In contrast, if we force the photon to follow a specific path by blocking the other path, then the probability to arrive at the detector is much higher. The puzzling fact that a two-path alternative for each photon prevents it from reaching the detector, while blocking one of the paths leads to a revival of the clicks, is most intriguing for beginning students. This experiment is well suited for illustrating this remarkable quantum mechanical effect, which can be explained only if we assume that each photon simultaneously takes both paths A and B; that is, each photon, in the phrasing of Dirac, "interferes with itself."


It is something we know would happen, but the way this is demonstrated is so clear that I would say this is an experiment worth doing at every undergraduate level. Well done to the authors!!


Thursday, March 06, 2008

Campus Ceremony Will Celebrate New Stamp for Physicist John Bardeen

I mentioned about the new US Post Office stamps set celebrating American scientists which includes a stamp of John Bardeen. Well, if you happen to be at the University of Illinois campus today (March 6), there is a small ceremony to mark the unveiling of the stamp.

The U. of I. physics department will host Urbana Postmaster Kathleen J. Burr, regional U.S. Postal Service officials, university administrators, and family and friends of Bardeen (1908-1991) at the ceremony. The event is free and open to the public. It will begin at 12:15 p.m., in room 144 of Loomis Laboratory, 1110 W. Green St., Urbana.

I can only hope that those who don't know much about him will now have the impetus to learn more about what Bardeen has done and how he has directly influenced how we live today.


Follow-Up On Fredrick Seitz

I mentioned in a previous blog entry of the passing of Fredrick Seitz. Someone asked me why I didn't mention anything about his later-years opposition to Global Warming. After all, he was one of the more prominent skeptic of that effect.

I'm not sure why that would be relevant, frankly. The Fredrick Seitz that I know and admire came from his work on Solid State Physics. That was how he made his name, and that was how he became prominent. I'm sure he has his reasons for looking at the available data to be convinced that global warming isn't what it has been claimed. He's entitled to that. It's not as if he's supporting massive human extermination, which was the issue surrounding most German scientists during World War II.

So even though I don't agree with him regarding the issue of global warming, it remains a fact that he has a major influence in the field of solid state physics/condensed matter. Just for that, he deserves to be saluted.


Tuesday, March 04, 2008

Frederick Seitz Dies at 96

The name "Frederick Seitz" should be very familiar to anyone who has studied Solid State Physics. Seitz is one of the instrumental figures in Solid State Physics and may even be one of its founding fathers.

This distinguished physicist passed away this past March 2nd, 2008. Our modern civilization, in no small part, has be shaped by his work.

Thank you, and rest in peace.


The Best Years of Your Life?

It may not feel that way when you're embarking on pursuing your Ph.D, but it can be. This is an article from PhysicsWorld that reviews several students in the middle of their Ph.D program in physics. It has several good advices for anyone thinking of pursuing a physics Ph.D, especially if you are in Europe. This should plug some holes in my "So You Want To Be A Physicist" essay that essentially focused mainly on the US Ph.D program. Note the important difference between the US and UK/Europe program:

Having a research topic in mind is absolutely essential when applying for PhD positions in the UK and elsewhere in Europe, since you will usually begin working on your chosen research problem straight away. In the US, however, PhD students spend two years doing coursework and exams in all areas of physics and only then begin proper research.

“Most physics students in the US start their PhDs without a specific research field in mind,” says Jayatilaka. This adds at least an extra year to the process, but it makes the US a good option for those who want to learn a bit more physics before choosing an area to specialize in, or for students who want to undertake a PhD project in an area that they do not have much experience in.


Journal Club For Condensed Matter Physics

This is such a terrific idea.

The Division of Condensed Matter Physics of the American Physical Society (APS) has sent out e-mail highlighting the existence of a "Journal Club for Condensed Matter Physics". This is where prominent physicists recommend papers and preprints that they find important, fascinating, or have a passion for. You get a more in-depth review of the paper/preprint, especially a discussion on the salient point being made.

I will include this link in the Blog's Physics Links collection.


Monday, March 03, 2008

Physicists Successfully Store and Retrieve Nothing

This could easily fit in as an episode of the Jerry Seinfeld series.

It appears that there is such a thing as a "squeezed vacuum", and it takes some effort to store and retrieve this "nothingness".

To see what this is, begin with a normal light wave. Classically, this is a smooth wave of electromagnetic fields with equally spaced peaks and dips. But throw in quantum mechanics and things get more complicated. The precise height of the wave becomes uncertain, so the wave gets fuzzy (see figure). Physicists have learned how to manipulate that inevitable uncertainty--for example, making it smaller at the peaks and larger in between. That makes "phase-squeezed light." Now imagine turning down the intensity of the phase-squeezed light to zero. The wave itself goes away, but the waxing and waning uncertainty remains, creating a squeezed vacuum.

It's interesting that two separate groups produced work on this at almost the same time. This, of course, is not unusual, and PRL, Nature, and Science have been known to put such things in the same issue. It serves to reinforce the discovery.


I'm Back!

I'm back from a short vacation. It was great to be away for a while, but now I feel so out of touch with what has been happening. So I'll need at least a couple of days to get back up to speed. Hope I didn't miss any earth-shattering "we found proof of aliens" or "convincing evidence for the mechanism of high-Tc superconductors" news.