Wednesday, July 31, 2013

Did He Just Learned Physics?

In this video and news report, the BBC business editor is trying to learn quantum physics.

The title of this report is misleading, because one doesn't learn quantum physics (or any science for that matter) like this. Rather, one is learning ABOUT quantum physics. There is a difference here, and I've mentioned this quite a while back in context with my take on the many pop-science books out there.

While learning about science should be highly encouraged, especially among the general public, we should never mistaken it as learning science, because this practice provides information only at the superficial level.


Tuesday, July 30, 2013

Same Paper, But Two Entirely Different Emphasis

See, this is essentially what is different between this blog, and the outlandish stuff they have elsewhere that tries to capture people's attention by drawing onto something that's improbable.

Last week, I highlighted a paper in PRL on the estimate made on the lifetime of photons based on current measurements. This upper limit also is related directly to the upper limit on the mass of photons, if any. In that blog post, I tried to highlight what is well-known and well-established, rather than try to make extrapolations on things that are still up in the air.

But that is not what is done here. This news report, also reviewing the same publication, decides to go with a different route, which is highlighting the speculative, attention-grabbing possibility, no matter how remote, how unlikely, and how improbable it might be. It focuses a lot on the minute possibility of photon decay, and decaying into "lighter" produced that could travel faster than the photons themselves.

If photons do break down, the results of such decay must be even lighter particles, ones that would travel even faster than photons. Assuming photons have mass, "there is only one particle we know from the Standard Model of particle physics that might be even lighter — the lightest of the three neutrinos," Heeck said.

It is sad that, rather than emphasizing the result that was published, news account on something like this would venture into citing remote possibilities and highly speculative conjectures. The result itself got buried. Rather, an improbable consequence of a possible outcome is the one that was brought to the forefront! This is a shameful attempt at sensationalizing a result! It is no different than the sensational front page news from supermarket tabloids.


Monday, July 29, 2013

Still No Sign Of Violation Of Lorentz Symmetry

The more they test it, the more precise they measure the validity of the foundations of Relativity. This time, the measurement comes from a new technique of measuring the the transition energy between two electron energy states of dysprosium.

The team chose dysprosium because it has a pair of closely-spaced energy states that involve orbitals where electrons travel at very different speeds. Because of this speed difference, a change in the electron’s kinetic energy due to a change in the atom’s orientation would affect the two states very differently. The researchers illuminated a beam of dysprosium atoms with two laser beams to excite them to state B (via another state) and then drove the transition to A with a precisely calibrated microwave beam. To measure the transition energy, they found the microwave frequency most effective at driving the transition. The team repeated the experiment many times over a period from 2010 to 2012.

The orbitals of the atoms were oriented to some extent by the polarization of the exciting laser beams. So if the electrons’ kinetic energy depended on their direction of motion, the team would have seen a daily oscillation in the transition energy from the earth’s rotation. Similarly, if there were any effect from the earth’s position in the sun’s gravitational field (violating local position invariance), there would have been an annual oscillation.

There are many different ways to violate Lorentz invariance, so researchers in the field have developed a standard set of parameters to characterize different types of violations. Hohensee and his colleagues measured eight of the nine parameters that describe any dependence of the electron’s maximum attainable speed on the speed and direction of the lab’s reference frame. They significantly improved limits from previous experiments for four of them, one by a factor of 10. Their new limits on local position invariance for electrons are 160 times more precise than previous ones.

Friday, July 26, 2013

The Physics Of High-Speed Trains

While the accident in Spain is certainly a tragedy, it is also an opportunity to examine the physics involved for us to understand a bit more of a possible cause of the accident. This article in The New Yorker has a simple enough description of it that anyone without any mathematics or science degree can understand. It tries to explain why there is speed requirement or limit of curved tracks.

One of those forces is centrifugal (“to flee from the center”) force, the inertia that makes a body on a curved path want to continue outward in a straight line. It’s what keeps passengers in their seats on a looping roller coaster and throws unsecured kids off carousels. Centrifugal force is a function of the square of the train’s velocity divided by the radius of the curve; the smaller and tighter the curve, or the faster the train, the greater the centrifugal force. As it increases, more and more of the weight of the train is transferred to the wheels on the outermost edge of the track, something even the best-built trains have trouble coping with. That’s where the concepts of minimum curve radius and super-elevation, or banking, come in.

Banked curves, in which the outer edge of the track is higher than the inner edge, balance the load on the train’s suspension. Since gravity pulls a train downward and centrifugal force pulls it outward, a track banked at just the right angle can spread the forces more evenly between a train’s inner and outer wheels, and help to keep it on the track.

But banking the tracks isn’t a cure-all—a passenger train can tilt only so far before people fall out of their seats. So the minimum curve radius comes into play. Imagine that a curved portion of track is actually running along the outer edge of a large circle. How big must that circle be to insure that a train’s centrifugal force can be managed with only a reasonable amount of banking? 

It is interesting to note that this is the type of question that we deal with in first year intro physics.


Wednesday, July 24, 2013

The Lifetime Of Photons

I see questions on the mass of photon a lot on online forums. The idea that a photon has a mass has numerous implications, including a non-zero longitudinal polarization. Another consequence is that a photon having a mass is not stable and will eventually decay. Thus, it should have a lifetime.

This latest paper examines and calculates the lower limit of a photon's lifetime based on our best upper limit of the photon's mass (additional review of this work can be found at PhysicsWorld).

For a photon to decay, it must have a mass—otherwise there’d be nothing lighter for it to decay into. A photon with nonzero mass is not ruled out by theory, but experiments with electric and magnetic fields constrain the mass to less than 1054 kilograms. Heeck assumed this upper limit and worked through a generic model in which photons decay into even lighter particles, which could potentially be neutrinos or some more exotic particles.

As a constraint, Heeck considered the CMB, the relic emission from the hot, opaque plasma that persisted for several hundred thousand years after the big bang. The CMB spectrum matches very closely a perfect blackbody, which implies very few, if any, of the CMB photons decayed on their 13 billion year journey. Heeck calculated that the minimum lifetime is 3 years in the photon’s rest frame. This might seem ridiculously small, but the photons are extremely relativistic. When time dilation is taken into account, a visible wavelength photon in our reference frame would be stable for 1018 years or more.
In other words, it is horribly longer than the age of our universe by many orders of magnitude! I'd say the odds of observing such a decay is zero.


Tuesday, July 23, 2013

Physics Departments Without A Single Female Faculty Member

Before we start, let me emphasize that I'm a man, but I've been involved in promoting women participation in science, and especially physics, for years. Anyone who has followed this blog would have read several items on this issue, and also my activities in this area to promote women in science. I definitely think that there is an under-representation of women in physics, and one of the ways to improve that is to make the field more enticing and more familiar to them, both in terms of the subject matter, and the working condition.

Now, having said that, you know what's coming next is not going to be pretty. This is a news article that reports on a recent statistical analysis/modeling done by the American Institute of Physics. It aimed to address that fact that fully 1/3 of the physics departments here in the US do not have a single female faculty member. But one shouldn't stop there, because the statistics included schools with small number of faculty members (often less than 10), and these tend to be the schools that do not have any female faculty members.

The AIP ran a simulation that takes into account the number of available female faculty members and the available positions, and came out with the conclusion that the lack of female faculty members in these departments is consistent with the statistical distribution, and not due to any inherent bias.

A new report from the American Institute of Physics -- based on simulation analysis -- concludes that the large number of departments without a single woman is to be expected and is not the result of discrimination. Some experts on women and science, however, disagree.

The institute's report says that there are two factors that explain the distribution of women among departments: the size of departments and the total number of female faculty members available. There are many departments with only two or three physics faculty members, the report notes. So "it is unlikely that these departments will have a woman among the faculty because the overall representation of women among all physics faculty members is low," the report adds.
To put it simply, say that you have 100 balls. On the table, you have many compartments of various sizes, some able to contain 20 balls, while others are big enough to have only 2 balls. If you toss those 100 balls up in the air and let them land randomly into those compartments, the argument here says that naturally, the smaller compartments will have a higher probability to end up with having NO balls.

Whether one buys into the parameters set up for the simulation is another matter. But taken at face value, I don't see anything wrong with this. It is certainly a first attempt at trying to figure out if the lack of any female faculty members in these small departments are due to some inherent bias, or simply out of statistics. It is a scientifically valid methodology to START and investigate an issue. Now the next logical step is to re-examine if the parameters used are valid, or accurate. Maybe some of the assumptions used are debatable, etc., and thus, the simulation should be tweaked.

What annoys me is the response being given to this study. I certainly expect disagreement with the conclusion, but the counter-argument that has been given is purely speculative!

Janet Bandows Koster, executive director and CEO of the Association for Women in Science, said via e-mail that the report "a disappointment."

She urged physicists to study the concept of "implicit bias," which she said might have something to do with the pool of women in the discipline. "We know that most people are reluctant to accept that they are biased, and scientists in particular pride themselves on their impartiality. Yet scientists are humans raised in societies, and thus are subject to collective messages that suggest men are suited to science because they are independent and analytical whereas women are better suited to care-giving and cooperative enterprises."

It's too easy, she said, to focus only on the relatively small number of women in the field. "Inferring there is no hiring bias because the 'n' is so small for female faculty is essentially like granting a papal indulgence to physics departments across the country," she said.
I'm sorry, but that is stupid! You are countering a statistical analysis with nothing more than a speculative fishing expedition! That's like saying you don't agree with Special Relativity because you don't like the look of the equation!

And no one here is saying that there is no hiring bias. A statistical analysis such as this can't come to such conclusion. What it does say is that the lack of female faculty members in 1/3 of the physics depts. cannot be attributed to gender bias as the main factor, because statistical analysis alone can account for that observation! As scientists, we need to know what statistics say, and what they don't!

The PROPER way to counter something like this is to look at the validity of the parameter used, to see if the model is accurate, and to show where it might have missed something, NOT to simply insinuate that there are biases. For someone who is supposed to represent an association of women in SCIENCE, she sure used a lot of hand-waving, unsupported argument to counter a scientifically-derived conclusion.


Monday, July 22, 2013

Alan Sokal Attacks Psychology Theory

I mentioned Alan Sokal and his infamous hoax before (in case you haven't heard of it). Sokal is back in the news, but not due to any hoax that he has created. This time, he's attacking a psychology theory that made use of something out of physics.

In the paper, the trio critique an application of what psychologists call the "positivity ratio" -- the ratio of a person's positive feelings to his/her negative feelings. In 2005, two psychologists wrote that people "flourish" if the ratio meets or exceeds 2.9 -- that is, if positive emotions occur at least three times as often as negative ones. A pretty intuitive concept in the abstract sense, but one Sokal and his co-authors say cannot be described by the equations the psychologists borrowed from physics.

"We find no theoretical or empirical justification for the use of differential equations drawn from fluid dynamics, a subfield of physics, to describe changes in human emotions over time," the trio wrote in their article. "Furthermore, we demonstrate that the purported application of these equations contains numerous fundamental conceptual and mathematical errors."

The trio's article, "The Complex Dynamics of Wishful Thinking: The Critical Positivity Ratio," was published online July 15, 2013 in American Psychologist.

Somehow, this fits in perfectly with an earlier comment on psychophysics babble.


Sunday, July 21, 2013

Why Do Physicists Gravitate Towards Jobs In Finance?

This is a take on why physicists gravitate towards a job in the finance world.

Then again, perhaps it is not surprising that so many physicists wind up working in finance. After all, they are good at using mathematics to solve real-world problems and the money is good. There is more to it than that though. There are mathematical links between physics and finance that go back at least to 1900, when Frenchman Louis Bachelier wrote his Theory of Speculation, in which he used the mathematics of a random walk to analyse fluctuations on the Paris stock exchange. Five years later, the same ideas were used by a young Albert Einstein to explain why pollen grains zigzag when they are suspended in water. His explanation invoked the idea that very large numbers of tiny molecules, much smaller than the pollen grains, are responsible for kicking the grains around. This was a crucial insight and provided one of the earliest convincing confirmations of the existence of atoms. To make the parallel with the financial markets, we might say that stock prices are kicked around by myriad unknown factors in the marketplace. Today, these ideas have been developed into a means of computing the value of sophisticated financial instruments and the management of risk.

Now, I'm skeptical with the first assumption that there are physicists who "gravitate" towards a job in finance. I am not sure to what extent these people AIMED for such a job, or rather if they took it due to other circumstances. Would they have taken it if they had other jobs in physics that pay close to what they would be making? Did they graduate with the intention of take such jobs in finance?

Furthermore, I've mentioned a few articles in which these theoretical model in finance and areas dealing with social and human interactions and activities (what is often called as psychophysics) are being called into question.

In any case, this is an article that covers what is going on in the UK, and it doesn't look to be that much different than what is happening here in the US.


Friday, July 19, 2013

"The Story Of Energy" - Physics Reporting At Its Worst!

Again, if this was another obscure, backwoods article, I wouldn't give a hoot. But this comes in with Scientific American tags! I do not know in what capacity this is part of Scientific American, but they ought to be ashamed of themselves to be associated with this type of garbage.

This article was written by a "Clarissa Ai Ling Lee". A search turns info that this is a Ph.D candidate at Duke University, majoring in Literature, and specializing in "..... in science and technology studies and comparative media studies."

There are so many convoluted, metaphysically-injected theme, or outright mistakes, that one just doesn't know where to start. For example:

In our three-dimensional world (even it we count time, that merely allows the curvature or space to be accounted for, and not much else),

Holy cow! Is she that ignorant, and is actually proud to share it with the world? I suppose those time-reversal symmetry (or lack of it) events are of no use. After all, we didn't use time in there just merely to allow for the curvature of space! Unbelievable!

But it gets better...

Cosmic rays, as high-energy charged particles, are sets of naturally occurring particles found through the process of atmospheric nuclei decay.

Now this is utterly wrong. High energy cosmic rays especially, a non-terrestrial. It originates elsewhere in the universe. So it definitely is not a produced of "atmospheric nuclei decay". Even a quick search on Wikipedia can correct that! How lazy can one get?

And if you can stomach it, here a winner when she attempts to describe beta decay:

According to the law of conservation, the disintegration of neutron should produce equal part electrons and equal part protons, but this was found not to be the case. Therefore, Enrico Fermi named it for a particle which is supposed to exhibit zero mass and zero charge (a sort of 'virtual' particle at that time) so as to counteract the 'shortfall' that would have resulted from the proton and electron not being consistently emitted as a 'neutrino.' 
 Did you have to rub your eyes and read that twice?

A beta decay produces EQUAL amount of proton and electron. There was never a problem with charge conservation. It was a problem of spin/momentum conservation!

And oh, she has picked an area we should study:

They want to know how understanding a specific property of strong interaction at the subatomic level can help explain why so much of our universe is constituted of dark matter. 

Bet you didn't know that, did you, that the strong interaction, at the subatomic level, no less, can help explain our dark matter. Yes sir!

The rest of the article, if you have the patience to read it, is a mumbo-jumbo of words with a generous dose of meta-physical flavor (a very popular trick) and enough word salad that it makes it difficult to be falsified and comprehended.

And aren't we glad that this is just Part 1! Can't wait on what other bastardization that is in store next!


Thursday, July 18, 2013

Energy Theater?

I've read the "press release" of this work, but only had a quick glance at the paper. But that should not stop you from having a look at it.

This activity for elementary/primary level education is meant to give a rather visual representation of the concept of energy, the ability of energy to transform from one form into another, and the conservation of energy principle.

In the current study, the researchers report their ongoing examination of an activity that they have created, called "Energy Theater." Energy Theater is specifically designed to help learners visualize energy and how it dynamically changes form and location. In Energy Theater, learners (K-12 science teachers in this study) each play the role of one "chunk" of energy, and indicate with hand gestures what form that energy has (e.g., chemical, motion, gravitational, thermal). Different objects are represented by loops of rope on the ground, and learners can move from object to object, demonstrating energy moving between those objects. While energy is not actually a material substance, this metaphor can help learners think about how a fixed amount of energy can flow between different objects.

For example, the group may be given the problem of, "Show what happens when a hand pushes a box across a table." Participants would first stand in the area representing the hand, making the gesture for "chemical energy." One by one, they would move to the area representing the box, changing their gesture to "energy of motion." Other scenarios might include how energy flows when an incandescent light bulb is turned on. The group must work together to decide how the "theater" will play out for a particular situation, making complicated decisions about just where and when the energy will flow and take different forms. 

It sounds rather convoluted to me, but that is probably because I haven't had the chance to actually see it. Maybe something like this can sink in easier with students at that age and level.

In any case, you should be able to read the actual publication that appeared in PRST-PER that gives free access.


Wednesday, July 17, 2013

Particles, Fields and The Future of Physics

If you have about an hour and a half, you could do worse than viewing this lecture by Sean Carroll of CalTech on elementary particles and the future of physics.


Light Stopped And Stored For More Than A Minute

Advances in this field of storing light have been astounding. It was only a few years ago that we had the amazing accomplishment of light being stopped and then "played back" out of Lene Hau's lab. And there have been more advances since then (read here). Now comes this latest paper (free access to the actual paper is available at that link).

There are two major accomplishment that are notable with this one:

1. They managed to store light and all of its coherent information for more than a minute, and

2. They are using a solid state medium, rather than atomic gasses, which will make this more viable for storing quantum information.

While solid-state devices would be preferable for applications, stopping light in solids is more challenging: stronger interactions between atoms and their environment severely limit the attainable coherence times. But the effect has been demonstrated in a special class of solids: crystals doped with rare-earth (RE) ions cooled at cryogenic temperatures. Since the atoms are naturally trapped in the crystal, the motion of RE atoms is limited and the transitions of interest take place between electronic levels (e.g., the 4f electrons of praseodymium) shielded from the crystal environment by outer full electronic shells (5s and 5p). This makes the coherence properties of these crystals exceptional.


Tuesday, July 16, 2013

"The 1905 Relativity Paper and the "Light Quantum""

Galina Weinstein has a rather nice article uploaded on arXiv recently on the history of the "light quanta" per Einstein's 1905 paper. In particular, she explored why this issue, or rather, the "light complex" that Einstein mentioned in his photoelectric effect paper, was never included directly in his Special Relativity paper. Rather, there was an implication that SR's validity actually depends on the correctness of the photoelectric effect paper and the energy of the light quanta.

Note that in the article, Einstein clearly considered that it is the idea of the light quanta, and NOT Special Relativity, that was truly revolutionary. He thought that Special Relativity was simply an extension of classical electromagnetism.. This is the view that John Ridgen has also taken in proclaiming that it is the photoelectric effect that is a truly revolutionary idea, more so than Relativity (link requires free registration).


Zero Gravity Coffee Cup

This video is more about fluid mechanics in microgravity, but hey, coffee is important too, even in space! :)


Sunday, July 14, 2013

Neutrinos - Nature's Identity Thieves

Here's a video explaining a bit about the flavor-changing neutrinos.


Thursday, July 11, 2013

Physics Discussion Gave Birth To Emoticons

We all know that high energy physics led to the invention of the World Wide Web at CERN. Now comes a history lesson from Symmetry Magazine which credited a physics discussion giving birth to the ubiquitous emoticons that we all have used.

On Sept. 16, 1982, Neil Swartz, a computer scientist at CMU, posed a physics problem to his computer science colleagues on the department’s “bboard,” a form of early online message board similar to today’s Facebook group. Bboard users often posted science puzzles for one another to solve and had been discussing the riddle of whether a canary could fly in an elevator during free fall.

Swartz presented a new scenario, which involved a lit candle mounted on an elevator wall and a drop of mercury on the floor.

“The cable snaps and the elevator falls,” Swartz wrote. “What happens to the candle and the mercury?”
That evening, fellow computer scientist Howard Gayle responded with a facetious message titled “WARNING!”

“Because of a recent physics experiment, the leftmost elevator has been contaminated with mercury,” Gayle wrote. “There is also some slight fire damage. Decontamination should be complete by 08:00 Friday.”

Despite posts noting that the warning was meant in jest, some people apparently took the notice at face value, believing a mercury spill had actually taken place. Various bboard users began joking about different symbols that could identify posts that weren’t meant to be serious.

Eventually, Scott Fahlman, then a computer science research assistant professor, proposed using :-) for joke posts—or, given the preponderance of joke posts, simply using :-( for serious ones.

There ya go! And there are still people who question the value of physics??!!



Wednesday, July 10, 2013

Eugen Merzbacher 1921 - 2013

This is a bit late.

Many physics students, especially graduate students, would recognize that name. Merzbacher's QM text is one of the more popular texts being used at both the advanced undergraduate level and graduate level. This famous author and physicist passed away last month.

You may read the obituary here and a brief description of his life here.


Friday, July 05, 2013

Molecular Wires With 2000% Change In Magnetoresistance!

Holy magnetic wires, Batman! This thing blows away those colossal magnetoresistance material! What's bigger than "colossal" for us to give a name to this thing?

A new paper appearing in Science today is reporting the properties of a molecular wire that has the capability of having a 2000% increase in its magnetoresistance, and all at room temperature!

Ironically, the new molecular wires aren't made with magnetic materials at all. Rather, their MR effect relies on the conductivity of nonmagnetic organic dye molecules called DXP, which the Italian automaker Ferrari once used to give their roadsters their trademark red color. Unlike conventional inorganic metals in which electrons zip through a crystalline lattice, in organics electrons must hop from one molecule to another, like pails of water being passed by a bucket brigade. To create a MR, material researchers need to switch off that bucket brigade in the presence of a magnetic field.

In organic materials researchers do this with a little help from quantum mechanics. A tenet of quantum mechanics called the Pauli Exclusion Principle states that no two fermions (particles in a family that includes electrons) can occupy the same quantum state. If two electrons with the same quantum state try to hop onto the same DXP, they can't. The bucket brigade turns off and resistance skyrockets.
Of course, we all know (don't we?) that this is the field that has been responsible for invention of computer magnetic storage disks, etc. So kids, this is another example of real-world, practical application of physics, and quantum mechanics in particular.


Thursday, July 04, 2013

First Direct Measurement of Van der Waals Force

In an amazing feat of experimental ingenuity, the first direct measurement of Van der Waals force between two atoms has been accomplished.

This latest research was done by researchers at the Laboratoire Charles Fabry (LCF) in Palaiseau and the University of Lille. "What we have done here, for the first time to our knowledge, is to measure directly the Van der Waals interaction between two single atoms that are located at a controlled distance, chosen by the experimenter," says Thierry Lahaye, who is part of the LCF team.

Controlling the distance between normal atoms – while measuring the force between them – is extremely difficult because the relevant distances are tiny. To get round this problem the team used Rydberg atoms, which are much larger than normal atoms. Such atoms have one electron in a highly excited state. This means that they have a very large instantaneous dipole moment – and therefore should have very strong Van der Waals interactions over relatively long distances. They also have unique properties that allow them to be controlled with great precision in the lab.
You can also read more review of this work at APS Physics, and, get a free copy of the paper.

Nice piece of work.


Monday, July 01, 2013

Where Is The True North Pole?

This video might make you even more confused than before.