Sunday, July 31, 2011

US Physics Graduate Degrees - Through 2008

The latest statistics from AIP is out on the graduate physics degree in the US. This latest data covers up to 2008.

The overall number of PhD being granted has increased since the local minimum in 2004, with the largest movement made by a significant increase in US citizens being awarded PhDs.

Several interesting facts can be seen from the data:

1. It still takes slightly more than 6 years to get a PhD (starting from a B.Sc degree) in the US (Fig. 6). The average is 6.2 years.

2. The largest number of PhDs still comes out of Condensed Matter Physics (Fig. 7). In fact, if one were to count "Material Science" and "Surface Physics" as part of this subject, the number is even larger.

3. The one that caught my eye was Table 6. It asks for a response to the question "“If You Had To Do It Over Again, Would You Still Get a PhD in Physics?” Most US citizens overwhelmingly said yes, either to doing it at the same institution, or at a different institution. However, non-US citizens seem to have a consistently larger percentage of either not wanting to do it all over again at the same institution, not doing a PhD in physics, or even not getting a PhD at all! It would be fascinating to dig a little bit deeper here to see what's going on.

These statistics are always intriguing to read. To me, it is still the most definitive survey of students and professionals in this field in the US.


Friday, July 29, 2011

Pendulum Waves

During the week when people are huffing and puffing about possible hints of the Higgs, what am I more fascinated with? These pendulum waves!

These are so cool!

What it shows: Fifteen uncoupled simple pendulums of monotonically increasing lengths dance together to produce visual traveling waves, standing waves, beating, and random motion. One might call this kinetic art and the choreography of the dance of the pendulums is stunning! Aliasing and quantum revival can also be shown.

How it works: The period of one complete cycle of the dance is 60 seconds. The length of the longest pendulum has been adjusted so that it executes 51 oscillations in this 60 second period. The length of each successive shorter pendulum is carefully adjusted so that it executes one additional oscillation in this period. Thus, the 15th pendulum (shortest) undergoes 65 oscillations. When all 15 pendulums are started together, they quickly fall out of sync—their relative phases continuously change because of their different periods of oscillation. However, after 60 seconds they will all have executed an integral number of oscillations and be back in sync again at that instant, ready to repeat the dance.

I will put the video here, but you should read the webpage given in the link above for the explanation, and useful references.

So you can have the Higgs, the supersymmetry, the dark matter, etc. I'll take any of these "mundane" stuff any day!


Thursday, July 28, 2011

Faster-Than-Light Expansion? Not So Fast, Buddy!

This is a very common question that I come across. Is the universe expanding faster than the speed of light? If so, then isn't this proof that SR basic postulate is incorrect?

Most people who asked that question usually don't have an understanding of General Relativity. But even for those who do, especially students studying that subject, a serious confusion can occur when it is applied to outlying, sufficiently-far away celestial bodies, where speed greater than c can be achieved.

This is a nice paper, to be published in AJP, that addressed this issue, and the restriction on the application of the Hubble Law.

Abstract: Naively applying Hubble's law to a sufficiently distant object gives a receding velocity larger than the speed of light. By discussing a very similar situation in special relativity, we argue that Hubble's law is meaningful only for nearby objects with non-relativistic receding speeds. To support this claim, we note that in a curved spacetime manifold it is not possible to directly compare tangent vectors at different points, and thus there is no natural definition of relative velocity between two spatially separated objects in cosmology. We clarify the geometrical meaning of the Hubble's receding speed v by showing that in a Friedmann-Robertson-Walker spacetime if the four-velocity vector of a comoving object is parallel-transported along the straight line in flat comoving coordinates to the position of a second comoving object, then v/c actually becomes the rapidity of the local Lorentz transformation, which maps the fixed four-velocity vector to the transported one. 

It also contains several references that tackle this apparent faster-than-light issue in terms of universe expansion. Hopefully, this will answer that vexing and common question.


Wednesday, July 27, 2011

No Asymmetry in Antiproton-Electron Ratio

A new measurement on the mass ratio of antiproton-electron shows no difference with the proton-electron mass ratio. So no asymmetry found so far with this one.


Sports Versus Physics

Here's a video on a lot of issues related to sports, and the physics involved. The description says that this is from a 2004 lecture. Still, it actually is quite fascinating, if you have roughly 45 minutes to spare.


Bookmaker Putting Odds Of Higgs Discovery At 1/3

I guess you can place bets on anything. This is true for the odds at a Higgs discovery this year. An Irish bookmaker has reduced the odds of a Higgs discovery this year from 12/1 to 1/3 after the recent report at this year's European Physical Review conference.

Paddy Power is now offering odds that favour finding the Higgs sometime this year. At 1/3, a £3 bet will pay out a measly £4 if the Higgs is discovered before January. By contrast, the same bet last week would pay a whopping £39.

Ha! Can't even make money out of gambling on the Higgs!BTW, those who work at CMS and ATLAS could be considered as having "insider" information. I'd buddy up with those people if I were you before making your bets! :)


Tuesday, July 26, 2011

Physics Central At Comic-Con

The folks at Physics Central were at Comic-Con last week and passing out physic comic books to the attendees.

Looks like they had fun, and a long and tiring outing. I'm guessing that what they handed out was their publication on Spectra comic books, which you can download from their site.


Monday, July 25, 2011

Aharonov-Bohm Effect

Physical Review Focus this week highlights the landmark paper by Yakir Aharonov and David Bohm of the effect of the electromagnetic potential that the phase of the wavefunction of a quantum particle.

In quantum mechanics, the electromagnetic potential alters the descriptions of charged particles only by shifting their phase--that is, by advancing or retarding the crests and troughs in their quantum wavefunctions. In general, however, such a phase change does not lead to any difference in the measurable properties of a particle.

But in 1959 Yakir Aharonov and David Bohm of the University of Bristol, England, devised a "thought experiment" that linked the potential to a measurable result. In their scenario, a beam of electrons is split, with the two halves made to travel around opposite sides of a cylindrical electromagnet, or solenoid. The magnetic field is concentrated inside the solenoid and can be made arbitrarily weak outside by making the cylinder extremely narrow. So Aharonov and Bohm argued that the two electron paths can travel through an essentially field-free region that surrounds the concentrated field within the electromagnet.

In this field-free region, however, the electromagnetic potential is not zero. Aharonov and Bohm showed theoretically that electrons on the two paths would experience different phase changes, and that recombining the electron beams would produce detectable interference effects. That is, the intensity of the recombined beam would vary according to whether the phase-shifted wavefunctions reinforced or canceled each other--a measurable physical effect directly related to the potential, contrary to standard wisdom. However, the phase shift can also be calculated from the strength of the magnetic field, so that interference can be interpreted as an effect of a magnetic field that the electrons never actually pass through. Aharonov and Bohm argued that physicists must accept that in quantum mechanics the electromagnetic potential has genuine physical significance. They expanded on this point in a second paper in 1961.

This effect now bears their names. It's a triumph of theoretical physics and of quantum mechanics. This discovery is a Nobel Prize caliber.

P.S. I think the link gives you a free download of the actual paper.


Sunday, July 24, 2011

Amazing Water Fountain Illustrates Basic Kinematics

Rhett Allain at Dot.Physics found this video of an amazing water fountain show at a Japanese mall. While the whole thing is jaw-dropping, there's a small puzzle that anyone seeing it might start to wonder. Why do all the patterns made by the water show get bigger vertically as they fall down?

This, of course, can be explained by simple kinematics that any First Year intro physics student can understand. Allain explained it clearly in his blog entry that you can read for yourself. But again, this is another one of those "mundane" observations that I really love and it is fun to figure out why such things occur.

For your convenience, here's the video in question.


Saturday, July 23, 2011

Weak Hints Of The Higgs

Finally, after years of results where large energy range are excluded for the Higgs, we are starting to get hints of the Higgs signature, and it came out of ATLAS and CMS at the LHC. Both were reported at this week's EPS meeting.

Both experiments found excesses in the 130-150 GeV mass region. But the excesses did not have enough statistical significance to count as evidence of the Higgs.

Scientists measure statistical significance in units called sigma, written as the Greek letter σ. These high-energy experiments usually require 3σ  level of confidence, about 99.7 percent certainty, to claim they’ve seen evidence of something. They need 5σ to claim a discovery. The ATLAS experiment reported excesses at confidence levels between 2 and 2.8σ, and the CMS experiment found similar excesses at close to 3σ.

Still, there's a very long way to go (and more data collection and analysis) before one can actually claim discovery. Unlike pseudosciences where even a weak correlation seems to be sufficient to claim that a phenomenon exists, in high energy physics, not only do you need a high confidence level that your result isn't simply due to chance, but you also need another independent detector, measuring things differently, to agree with your result! The fact that both ATLAS and CMS are getting almost the identical result is a very good start. And it is only a start.

Interestingly enough, the energy range where this is detected is also accessible at the Tevatron. I wonder if CDF and DZero might zero in (no pun intended) in this range and see what their data looks like with various background subtraction schemes.


Friday, July 22, 2011

Pioneer Anomaly Has A "Dull" Explantion

Whether we like it or not, the Pioneer anomaly may finally have an explanation that should put to rest all the other exotic, wild theories.

The quartet’s painstaking analysis of telemetry data suggests that the anomalous acceleration of both spacecraft is decreasing with time. While the exact nature of this decrease is not certain, there is a good chance that it is exponential. This would be consistent with the decay of radioactive material with a half-life of about 27 years. Both spacecraft have radioactive power sources that are still running – so mystery solved.

Well, not quite. Both spacecraft are powered by plutonium-238, which has a half-life of about 88 years. However, the team believes that the more rapid drop in acceleration could be the result of degradation and changes to the thermal properties of the spacecraft over time. When these factors are considered, claim the researchers, a half-life of 27 years seems reasonable.
 This sounds like a tedious, painstaking task. So bravo to them for the monumental effort.


We Are Not Special

Sorry kids. Contrary to what your parents told you when you were young, you and I and everyone else are not special. Well, we are not special in terms of our place in the universe.

Y'see, once upon a time, we thought that we are at the center of the universe, and everything revolves around us. We believed that we are in a privileged location in the universe. Well, someone by the name of Copernicus, and later on, Galileo, practically destroyed that delusion.

Yet, there are still ideas (some call them theories) even today that still want to place us at this special location in the universe, and if they do that, they said that they can explain the universe accelerating expansion without any need to invoke dark energy. As always, Mother Universe can throw a wrench into the best-laid theory. This latest wrench comes in the form of the latest observational data that basically conclude that the universe is homogeneous at a length scale up to a gigaparsec.

In a paper appearing in Physical Review Letters, Pengjie Zhang at the Shanghai Astronomical Observatory and Albert Stebbins at Fermilab show that a popular void model, and many others aiming to replace dark energy, don’t stand up against telescope observation.

Galaxy surveys show the universe is homogeneous, at least on length scales up to a gigaparsec. Zhang and Stebbins argue that if larger scale inhomogeneities exist, they should be detectable as a temperature shift in the cosmic microwave background—relic photons from about 400,000 years after the big bang—that occurs because of electron-photon (inverse Compton) scattering. Focusing on the “Hubble bubble” void model, they show that in such a scenario, some regions of the universe would expand faster than others, causing this temperature shift to be greater than what is expected. But telescopes that study the microwave background, such as the Atacama telescope in Chile or the South Pole telescope, don’t see such a large shift.
 So for now, we are nothing special in our place in the Universe. But that's OK. I still like myself, and I still like you!

Edit: read another review of this work here.


"Speed Of Gravity Is 9.8 m/s^2"

OK, if you think I was nitpicking when I criticized the use of the phrase "rate of speed", you'll have an aneurysm with this one! So look away now! :)

I was driving into work this morning, and I happen to be listening to a local station here - 93.9 Lite FM (I know, it makes me sound kinda lame!). Still, the show Valentine in the Morning can be quite funny at times when they discuss certain topics. But this morning, following up on their geography quiz, they had a science quiz with a set of questions related to science. One of the questions that was asked was "What is the speed of gravity?"

Immediately, the host of the show (Valentine) answered "9.8 m/s^2!" And he was deemed by the person asking the question to be CORRECT!

Now, I think I don't need to explain why this is NOT correct, do I? I do? Oh brother!

1. Just looking at the units alone, one can tell something isn't kosher. Speed (and velocity) has units of length/time. The units given "m/s^2" is length/time^2, which is acceleration.

2. 9.8 m/s^2 is the acceleration due to gravity at Earth's sea level. It's a value at a specific location. It means that it isn't a constant, and certainly changes when one is elsewhere. g is different at higher elevation, and even more different on the surface of the moon.

3. As far as we know (and this has yet to be explicitly verified experimentally), the "speed of gravity" is equal to the speed of light. If sun suddenly disappears, we'll now about it not instantaneously, but at the same time that our sky goes dark a few minutes later.

The issue here isn't that the answer is wrong. More importantly, is that while people remember certain information, the CONTEXT of what they remember can be faulty. Facts are useless if they dangle in mid-air and without understanding what they mean and how they are used. Seeing something like this kinda let me to believe that there's a lot more people who think that speed of gravity is 9/8 m/s^2. Could this be that this is another example where what you say (or teach) is not what they understand?


Thursday, July 21, 2011

Stability of Bicycles on Rollers

A lot has been made of the stability of riding a bicycle. In most elementary, intro physics text, this is used as an example of conservation of angular momentum. But of course, most of us know that the stability in riding a bicycle involves a bit more than that (such as steering into the direction of tilt, etc.).

This is a rather interesting paper[1] that investigate the stability of riding a bicycle on rollers. The bicycle isn't moving, but the wheels are still turning. So if one thinks that the stability in riding a bicycle is due mainly to conservation of angular momentum of the wheels, this is a very good test because here since the motion isn't there, but the wheels can still turn, thus preserving the angular momentum.

So what do they observe?

Riding a bicycle on rollers is unique because of the absence of the forward inertia which aids in bicycle handling for stability, instead of isolating and restricting the degrees of freedom in handling. Adopting one’s riding style to ride on rollers is quite difficult, with many avid cyclists falling off their bicycles on the first few attempts. Given that all riders struggle somewhat with the apparatus, but some more than others, the degree of struggle to ride on rollers may also indicate how different riders rely on specific factors for bicycle stability, which has not been addressed in many studies up to now. We use the example of riding bicycles on rollers as a test case on the individual factors that lead to bicycle stability.
The paper gives quite a few references to various treatment on the issue of stability on bicycles.


[1] P.A. Cleary and P. Mohazzabi, Eur. J. Phys. v.32, p.1293 (2011).

Wednesday, July 20, 2011

High-Tc Superconductivity At 25

This is a wonderful historical account (and the internal fighting) of high-Tc superconductivity as it turns 25 this year. The link is open for free only for a short period of time, so read it while you can.


New Evidence For Spin-Charge Separation in 1D System

A new report out of an experiment on the 1D system of blue-bronze shows a severe violation of the Wiedemann-Franz Law, which is a very good indication of a spin-charge separation.

The experimental group, led by Professor Nigel Hussey of the Correlated Electron Systems Group at the University of Bristol, tested this prediction on a purple bronze material comprising atomic chains along which the electrons prefer to travel.

Remarkably, the researchers found that the material conducted heat 100,000 times better than would have been expected if it had obeyed the Wiedemann-Franz law like other metals.  Not only does this remarkable capability of this compound to conduct heat have potential from a technological perspective, such unprecedented violation of the Wiedemann-Franz law provides striking evidence for this unusual separation of the spin and charge of an electron in the one-dimensional world.

Strangely enough, the press release here made it seemed as if this is the first such instance of the violation of the Wiedemann-Franz Law. This is certainly not true since I've cited at least one other before. A quick search on Google Scholar will also reveal other previous observations.


Tuesday, July 19, 2011

Your Workout May Cause The Building To Shake!

Who needs a volcanic eruption or an earthquake? Just a group of people doing a vigorous Tae Bo workout is enough to send a tremor to a 39-story building in Seoul, Korea.

Prime Group, owner of the 39-story TechnoMart commercial-residential high-rise in Seoul, said 17 middle-aged people were working out to the pop song "The Power" by Snap on July 5 when their movements set the upper floors of the tower shaking for 10 minutes, according to a report from the Korea JoongAng Daily.

Scientists recreated the event in the 12th floor gym, according to a report in the Korea Times.

Of course, being there is a reason for that to happen:

“It just happens to be that the vibration cycle caused by Tae Bo collided with the vertical vibration cycle unique to the building,” Chung told the Korea Times. The action amplified the building's vibration and caused the shaking, he said.

In other words, it's a variation to the infamous Tacoma Narrows bridge incident, without the completely collapse of the structure!

Still, I wonder if there will be a different effect if the gym moves to a different floor....


How To Reproduce "Washboard" Road

This is an informative review of a work on figuring out the physics of washboard roads. It's based on work done quite a while back (2007) and published in PRL[1].

This is another one of those "mundane" stuff that perks up my interest and what got me into physics in the first place. Of course, these things APPEAR to be mundane, but the physics of these things have wide-ranging impact and application. It is just that the phenomena that manifest the principles looks so benign. Still these are the stuff that I find most fascinating. You can go solve the mysteries of dark matter and CP-violation. Just give me rippled roads and grapes that bounce up and down in sodas!


[1] N. Taberlet et al.,Phys. Rev. Lett. v.99, p068003 (2007)

Monday, July 18, 2011

T2K Results On Neutrino Oscillation

I mentioned earlier of the results out of T2K of the muon neutrino oscillation into electron neutrino. The paper has now been published in PRL, and it is also reviewed in APS Physics this week. That means you get a free copy of the paper as well!

As I've mentioned, this seems to be consistent (roughly) with the recent MINOS results.


Saturday, July 16, 2011

"Do You Watch "The Big Bang Theory"?"

I get that question a lot from people who I've just met. When they find out that I'm a physicist, other than asking what's going on at the LHC, they tend to ask if I watch the popular TV series "The Big Bang Theory". Unfortunately, my answer to that question is "No, I don't".

I know that it is a wonderful comedy depicting scientists/physicists (nerds?), and that other famous physicists have made cameo appearances on the show, but I've never had the inclination to watch it. It's not that I have anything against it. However, my TV channels (and I have 4 TVs in the house) are stuck on HGTV, Food Network, Bravo, TLC, Travel Channel, PBS, BBC America, Animal Planet, Tennis Channel, and Discovery. I normally don't watch any network TV shows (ABC, CBS, NBC, FOX), so that means I don't watch the Big Bang Theory.

Now and then, some of my friends would ask me certain episodes of the show, because they said that these episodes would probably had been a lot funnier if they understood some physics and the inside joke that went along with them. That's probably true from what I've read on the research done for that TV series. I gathered that there's a big college following for that show, which isn't surprising.

Still, I have never watched, and don't plan on watching, "The Big Bang Theory".


Friday, July 15, 2011

New Hope For Sanford Lab at Homestake

After the National Science Foundation (NSF) balked at funding DUESL, the Dept. of Energy (DOE) appears to be the steward of the underground laboratory at Homestake. In the new proposed congressional budget, a $15 million funding has been allocated to building this lab.

The combination of federal funding and support from the scientific community means the associated laboratories being built underground for experiments into dark matter and neutrinos -- which were the objects of Nobel Prize-winning research at the 4,850-foot level of the mine decades ago -- should be finished and can begin operation next year.
But the scale of this laboratory has been cut back significantly from the original plan for DUESL envisioned by NSF.

The Deep Underground Science & Engineering Laboratory, or DUSEL, was originally conceived as a complex of laboratories at different levels down to 7,400 feet below the surface and costing $1 billion or more. That structure seems to be fading into the realities of a tight federal budget and a shift in responsibility for the project from the National Science Foundation to the Department of Energy.

It is a transition that will at least for now limit the scope and cost of the underground laboratory work and mean DUSEL will not be part of the project lexicon.
 One can only hope that the scaled-down project will get that funding, and this becomes the newest US National Laboratory.


Thursday, July 14, 2011

No Link Yet Between Cellphone Use And Brain Tumor

Another new studies that could not find any link between prolonged cell phone usage and brain tumors.

Y'know, people can make many speculative arguments back and forth on the issue of cell phone use and brain cancer. The FACT that we have right now are:

1. no established and clear link between cell phone and cancer, and
2. no physical mechanism for cell phone signals to cause cancer.

These are what we have currently. While people certainly are free to exercise caution if they want to, one should not confuse personal preferences and speculation with hard, valid evidence.

I'm more worried about drivers who use their cellphones while driving than I am about the cellphones causing cancers. If people are SO worried about their safety, why aren't they up-in-arms about that? There are enough documented evidence of accidents (including fatal accidents) that were direct results of using cell phones while driving. Instead, we get MORE publicity out of something that hasn't even been well-established, AND people who seem to already believe in them.

Makes no sense....


Another Bastardization of Quantum Mechanics

I hoping that I would stop finding things like this, but I think that is asking way too much.

This "author" seems to think that quantum physics can explain god. Go figure!

There are several puzzling stuff that he wrote in that article, but I'm going to focus on just a couple:

Energy makes up matter, electrons are a form of matter, so electrons are made up of energy, which means photons. Light being comprised of streams of individual particles then forces electrons to inhabit only specific energy levels when in orbit around the nucleus of an atom. When an electron gives up or receives energy, it is doing so in the form of giving up or receiving photons of light (of which it is comprised). Since photons are seen to come in discrete packets and not continuous streams of energy, then an electron is limited to exchanging energy solely in multiples of these minimal packets of energy; no fractional amounts of a single photon are allowed. When in orbit around the nucleus of an atom, then, if an electron is to move closer to or farther away from the nucleus (i.e., raise or lower its energy), it can do so only in multiples of a photon's energy. This translates into there being very specific energy levels that an electron can obtain in orbit around the nucleus. It's like the steps on a ladder: You can't climb up half a step. The steps would be the energy levels and the spacing between the steps determined by the size of a photon.

Wow! Where do we start? First of all, this is false: "Light being comprised of streams of individual particles then forces electrons to inhabit only specific energy levels when in orbit around the nucleus of an atom". The discrete energy levels of the atom is due to a "central force" of the nucleus and the electron. You solve the Schrodinger equation, and you get all of these discrete energy states. It has nothing to do with the fact that light consists of photons. That's bogus.

It is obvious that he's confused because he went on to say this: "Since photons are seen to come in discrete packets and not continuous streams of energy, then an electron is limited to exchanging energy solely in multiples of these minimal packets of energy; no fractional amounts of a single photon are allowed." He obviously doesn't know that (i) I can cause an exited state in an atom via electron bombardment as well (example: fluorescent lamp), and (ii) the energy level in an atom does not increase by constant amount. The energy difference for hydrogen, for example, is different between n=1 to n=2, n=2 to n=3, n=3 to n=4, etc.. etc. So when he says "if an electron is to move closer to or farther away from the nucleus (i.e., raise or lower its energy), it can do so only in multiples of a photon's energy." it clearly shows that this part of the physics is something he didn't get.

Oh, but it gets better!

This insistence on discrete energy levels dictates how atoms interact with one another, which forms the chemistry of bulk matter -- everything from the stars to ourselves. So it can be seen that the nature of the very littlest of things can have a tremendous impact on everything else, on the nature of our reality. The formation of matter in our reality is, at its essence, the result of brain waves.
 Of course, when someone says that, he or she has no clue on what condensed matter physicists study, and the fact that More Is Different! When atoms conglomerate to form bulk material such as metals, semiconductors, insulators, etc., they no longer behave as individual atoms, but now have a COLLECTIVE behavior. This collective behavior can be very different than the individual behavior. For example, the discrete energy levels may disappear and form BAND of continuous energy states. This is how we get the conduction band in metals, the band gap between conduction and valence bands in semiconductors, etc. The discrete orbits in atoms have been "mixed" or hybridized to form new properties that are not present in atoms. In fact, there are many phenomena that are EMERGENT out of such collective behavior, none of which can be derived simply from knowing the behavior of individual atoms. Examples are magnetism, superconductivity, etc.. etc..

Yup! Chalk this up to another bastardization of quantum mechanics!


Wednesday, July 13, 2011

Fusion Power

This is an Op-Ed in the NY Times by Stewart C. Prager, director of the Princeton Plasma Physics Laboratory, on why investment in fusion power research is critical.

But an abundant, safe and clean energy source once thought to be the stuff of science fiction is closer than many realize: nuclear fusion. Making it a reality, however, will take significant investment from the government at a time when spending on scientific research is under threat.

Harnessing nuclear fusion, the energy that powers the sun and the stars, has been a goal of physicists worldwide since the 1950s. It is essentially inexhaustible and it can be created using hydrogen isotopes — chemical cousins of hydrogen, like deuterium — that can readily be extracted from seawater.
 Of course, in the current political climate in the US, funding and commitment to fusion technology in the US is lagging behind several nations.

However, even though the United States is a contributor to this experiment, known as ITER, it has yet to commit to the full program needed to develop a domestic fusion reactor to produce electricity for the American power grid. Meanwhile other nations are moving forward to implement fusion as a key ingredient of their energy security.

Indeed, fusion research facilities more modern than anything in the United States are either under construction or operating in China, Germany, Japan and South Korea. The will and enthusiasm of governments in Asia to fill their energy needs with fusion, as soon as possible, is nearly palpable.
Again, not surprising, and it's the same old story. The US is slowly but surely falling behind in an increasing number of scientific areas. I wouldn't be surprised at all that, 50 to 100 years from now, this period for the last 10-20 years will mark the beginning of the decline of the American civilization, just like the decline of other great civilizations of the past.


Tuesday, July 12, 2011

Can Quantum Theory Be Derived From More Fundamental Principles?

It is an intriguing question and certainly something that a number of theorists have been working on. The latest in such a development is the latest paper published in PRA this week, and covered this this week's APS Physics (you also get a free download of the actual paper)[1].

Abstract: We derive quantum theory from purely informational principles. Five elementary axioms—causality, perfect distinguishability, ideal compression, local distinguishability, and pure conditioning—define a broad class of theories of information processing that can be regarded as standard. One postulate—purification—singles out quantum theory within this class.

Quantum mechanics continues to be one of the most puzzling and amazing theory of our time.


[1] G. Chiribella et al., Phys. Rev. A v.84, p.012311 (2011).

Monday, July 11, 2011

James Webb Space Telescope On the Chopping Block

It is unfortunate that we get this more frequently nowadays. Another major scientific endeavor is now on the chopping block in the latest US Congressional budget proposal. The funding for the James Webb Space Telescope, which is supposed to replace the aging Hubble Space Telescope, is being cut.

Read the article on Wired on why it is important to save this project, even with the cost overruns. Again, if you care about this, and you are a US citizen, you need to make your voice heard with your representatives. Government agencies such as NASA, DOE, NSF, etc. cannot, I repeat, CANNOT lobby Congress to save their projects, whereas political organizations and special interest groups can! So unless they hear from you, your politicians will only tend to hear just one side of the story.


Sunday, July 10, 2011

Soda Cans Beat Acoustic Diffraction Limit

I love experiments such as this. It is one of those experiments that uses ordinary objects, but produces astounding results, AND, gets published in PRL, of all places!

We have heard about optical metamaterial and how such materials can become left-handed and also defeat the diffraction limit. Well now, an acoustic metamaterial made up of soft drink cans (link open for free only for a limited time) has been made, and it can defeat the acoustic diffraction limit!

Lerosey and his colleagues took a similar approach to an experiment they performed in 2007 and later described theoretically for electromagnetic waves1,2. The group generated audible sound from a ring of computer speakers surrounding the acoustic 'lens': a seven-by-seven array of empty soft-drink cans. Because air is free to move inside and around the cans, they oscillate together like joined-up organ pipes, generating a cacophony of resonance patterns. Crucially, many of the resonances emanate from the can openings, which are much smaller than the wavelength of the sound wave, and so have a similar nature to evanescent waves.

To focus the sound, the trick is to capture these waves at any point on the array. For this, Lerosey and his team used a method known as time reversal: they recorded the sound above any one can in the resonating array, and then played the recording backwards through the speakers. Thanks to a quirk of wave physics, the resultant waveform cancels out the resonance patterns everywhere — except above the chosen can.

The work will be published in PRL (I'll put a reference to it here when it is published).

Edit: A review of this work can be found on PhysicsWorld website.


Saturday, July 09, 2011

The Physics Of Six Flags

For those who don't know, "Six Flags" is the name of a number of amusement parks here in the US (and probably in some other parts of the world as well).

This is a rather cute study of the mechanics at a Six Flags park. Of course, it mainly deals with rollercoaster dynamics (and a vertical drop). But at least there is real data being gathered here. I often wonder if those class trips under the guise of a physics outing actually have any meaningful and educational values. Now, if the kids could do something like this, that's a different matter.


Friday, July 08, 2011

What Is A Higgs Boson?

This is a rather informative and concise (and short) video out of Fermilab explaining, in simple terms, what a Higgs boson is (and what a Higgs field is). This would be something appropriate for the general public.

I wish they had done this sooner, certainly at the height of all that frenzy with the LHC. Still, better late than never, and the explanation is simple enough that those without any physics background can have some idea on what it is.


Physics World Invisibility Issue

If you can find it and see it, this month's issue of Physics World is dealing with the whole issue of "Invisibility" or "cloaking" that has been in the news during the recent years. Since the discovery of metamaterials and left-handed material, this phenomenon of cloaking has been a rather "sexy" news item and has frequently garnered a lot of publicity.

You can get a free download of this issue of Physics World (upon registration).


Thursday, July 07, 2011

A Table Design Inspired By Quantum Physics?!

Another cringe-worthy moment! Wow! Two in a day!

It appears that a designer has come up with a "Quantum Table", which presumably a design inspired by, what else, quantum physics!

Before I go barf, I have two questions to ask:

1. What makes this designer think he/she knows anything about "quantum physics" to be able to be "inspired" by it?

2. What is it about this table that has anything to do with quantum physics? I looked at the photo, and if someone didn't tell me that it was inspired by quantum physics, I wouldn't have guessed. And considering that I think I know a lot more about quantum physics than the average Joe (and presumably, this designer), one would think that I would have noticed any "resemblance".

From the looks of it, I think this is a Spaghetti Table, if you want my opinion.


The Quantum Physics Of Harry Potter

I will admit that I cringed when I read the title, and it didn't go away after I read the news article.

A postdoc at University of Waterloo’s Institute for Quantum Computing and a magician will try to "illustrate" some of the principles of quantum mechanics by invoking similarities between it and the world of Harry Potter. Then, supposedly, the magicians will use magic to "... explain the sometimes hard-to-fathom quantum world... "

So why Harry Potter?

“When I really think about what’s going on in the quantum world, to me it just seems like magic. Some of the stuff we’re doing is crazy,” Shalm said.

“I’m a fan of Harry Potter, and I thought ‘we’re actually doing some very similar things in the lab.’ It seemed like the perfect vehicle to explain some of the things we’re doing in quantum mechanics.”

Oy vey!

First of all, I'm all for trying to convey to the public not only important concepts in physics, such as quantum physics, but also informing the public on what we do in our work. There's no argument there, and in fact, I highly support it. More of it should be done. Period!

However, is it really a good idea to interweave something that is hard-core since, with very stringent test and verification, with "magic" and the supernatural, pseudoscience world of wizardry? Just because there are some similarities doesn't make them compatible and agreeable with each other. It might give the impression that quantum mechanics is nothing but "magic" and hocus pocus.

I've criticized many sources before when they bastardized quantum mechanics and used the similarities between it and some mystical beliefs as the justification for the validity of that mystical beliefs. In quantum mechanics case, there are plenty of ways to engage the public to want to learn a bit about it. The subject matter itself is already interesting enough that it doesn't need to piggyback onto something like Harry Potter movies. And then to pair it off with some magic show?

I wrote earlier on why I think that quantum mechanics is so difficult to comprehend, especially to the general public. Because of the lack of connection with everyday world, many aspect of quantum mechanics will appear as if it came out of thin air, like magic! In reality, it is the mathematical formalism that grounds us, but this is something that the public cannot comprehend or has the skill to use. So paring quantum mechanics with magic can only reinforce the fallacy that it IS truly magic, and things can be invented, appear and disappear weely neely without any need for rules and physics constraints/descriptions. This is not the message that I want to convey to the audience.

This presentation will take place on July 14 and 15, presumably in Waterloo, Canada. If anyone attends this, I would appreciate if you could post a comment on what you think of it.


Wednesday, July 06, 2011

Photon Drag Image From Slow Light

This is a very fascinating experiment to show the photon drag effect in a fast-moving medium. By passing light through ruby (a "slow light" medium), the image made by the light tilts differently based on the direction of rotation of the medium from clockwise to counterclockwise. Not only that, they also see an increase in the tilt when they ramp up the photon intensity. They attributed this affect to multiple absorption and re-emission in the medium.

To test this idea, Franke-Arnold's group shone a rectangular beam of green light into a cylinder made of ruby, which they spun at up to 30 revolutions per second. Ruby is a well known slow-light material, and transmits light with a group velocity of just a few tens of metres per second. By changing the rotation of the ruby from clockwise to counter-clockwise, the researchers could detect a rotation of the light rectangle by about one-third of a degree (see figure). What is more, when they ramped up the intensity of the light, the rectangle's rotation increased to about 10° – probably because the photons were then undergoing several absorption and re-emission cycles.



Tuesday, July 05, 2011

Antineutrinos Might Be Different Than Neutrinos

The latest result out of MINOS seem to indicate that muon antineutrino seem to have a different oscillation than muon neutrinos.

A test of CPT symmetry was recently performed by the MINOS experiment at Fermilab, which, due to its magnetic field, is the first experiment to distinguish μ- and μ+ tracks and separately measure the disappearance of muon neutrinos and muon antineutrinos [1]. (Previous experiments have measured a mixture of neutrino and antineutrino oscillations.) Remarkably, as reported in Physical Review Letters, MINOS appears to observe a difference between muon neutrino and muon antineutrino disappearance

This seems to be consistent with an earlier report out of MiniBooNE.

If this effect is real, then as the article pointed out, the consequences will be highly profound.

If the apparent difference between muon neutrino and muon antineutrino disappearance is not due to a statistical fluctuation or to nuclear effects, then we would have to consider new physics beyond the standard model. Indeed, global fits to the world neutrino and antineutrino oscillation data [5] encounter tension between the neutrino and antineutrino data sets and favor different neutrino and antineutrino oscillation parameters. One possible beyond the standard model solution involves nonstandard interactions [6], which would affect neutrinos and antineutrinos passing through matter (as is the case for MINOS) differently. A more extreme possibility is that Lorentz symmetry is violated [7] or CPT symmetry is violated [8], and that neutrino oscillation parameters are different from antineutrino parameters. If this were the case, then the impact on nuclear and particle physics would be profound.

Stay tune. With all the new experiments about to come on line, there's plenty of surprises in store!


Monday, July 04, 2011

Lifing A House With Balloons

Looks like the scenario as depicted in Disney/Pixar's "Up" continues to get quite a mileage for discussion.

This is Physics World blog, several interesting topics were discussed and linked to. This includes the topic that we had discussed before, which is the scene from "Up" where huge amount of balloons were used to lift Carl's house.

If you enjoyed the film Up, you might want to peruse the paper that asked how many helium balloons would actually be required to lift a small wooden house – like the one in the film – as well as a common brick house found in the UK. The authors found that it would take almost 10 million helium balloons to lift the small wooden house and 400 million helium balloons to lift a typical UK house! They note the downfalls of this particular method of relocation though, by concluding that the balloons would “deflate very quickly at high altitudes” and that the “foundations and drainage of the house would be removed, making the structure very unstable, if by some miracle the journey is possible.” Pity, balloons would make moving so much easier!

Hum... I think they might have missed something. I went and look at the paper (freely available in that blog article if you follow one of the links). This is what the authors said in the discussion:

Since the air density decreases with altitude this would not be enough to let it climb indefinitely, even assuming that no helium can escape from the balloons. This is because the air density (and therefore the buoyancy force) is inversely proportional to N. This means that N would have to be even higher to reach an altitude of normal aeroplanes (37000 ft or 11277m [5]).

At an altitude of 11277m the air density is approximately 0.3471kgm-3 [6] which is more than 3 times smaller than at sea level. This means that N would have to be more than 3 times greater than that calculated previously at this altitude than at sea level.

The balloons will also deflate over time which will also be exacerbated by altitude, even at different altitudes close to sea level [7]. This is due to the diffusion in the balloons [8] to a space of much lower pressure, which at an altitude of 11277m is going to be a massive effect.

Hum... As the balloons rises to higher altitude, it is true that the air density surrounding the balloon becomes less. However, because of that, one can also argue thatm, for ordinary balloon that has elastic skin, the VOLUME of the balloon is also expanding. So in this case, the displaced volume gets bigger, which will add to the buoyancy. Whether the additional buoyancy can compensate for the decrease in air density, that I haven't calculated. I'm sure that depends on the elasticity of the balloon, etc.

When balloon detectors are sent very high up into the upper atmosphere, if you look at the launch on earth, you'll see that the balloons were not completely inflated because of this reason. If you sent things up already fully deflated, the drop in air density (pressure) will cause the balloon to want to expand even further and will eventually cause a rupture in the balloon.


Friday, July 01, 2011

Raman Spectra of Graphene and Carbon Nanotubes

Mildred Dresselhaus discusses Raman spectroscopy of graphene and carbon nanotubes.