Lifting Lemon

This is a simple experiment, and variations of this have been done in many classroom demonstrations, I'm sure. But it still becomes a topic of discussion as to why it happens, as demonstrated by the discussion on this video's YouTube page.



This link provides an explanation for this effect.

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Angry Birds At The Kennedy Space Center

You know it was bound to happen. When Angry Birds went into space, all the signs pointed to it partnering with NASA to come up with some educational tie-in. So now it has happened.

At NASA's invitation, the online game birds are roosting at Kennedy Space Center for the next 1 1/2 years in an effort to lure youngsters to the cosmic wonders of math and science.

The huge interactive exhibit opened March 22 and immediately packed in the kids, including this reporter's 7-year-old son, who couldn't get enough of the mirrored maze and design-your-own Angry Bird and play-the-game stations.

Too bad they didn't have this when I was there last December. Maybe I'll make it back there some time soon before the exhibit goes away.

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RToBad

Too eTooad 

Tooor

e here: http://www.star-telegram.com/2013/03/27/4733211/space-centers-angry-birds-exhibit.html#storylink=cpy

Philosophy Of the Higgs

A rather fascinating article that throws itself into the debate between physics and philosophy.

You can read the rest of the article for yourself. However, it seems that we can boil it down to the last two p paragraph in the article.

So then, should we physicists listen to philosophers?

An emphatic "No!", if philosophers want to impose their preconceptions of how science should be done. I do not subscribe to Feyerabend's provocative claim that "anything goes" in science, but I believe that many things go, and certainly many things should be tried.

But then, "Yes!", we should listen, as philosophy can provide a critical assessment of our methods, in particular if we consider physics to be more than predicting numbers and collecting data, but rather an attempt to understand and explain the world. And even if philosophy might be of no direct help to science, it may be of help to scientists through its educational role, and sharpen our awareness of conceptional problems in our research. 

I have no issues if I have to live with that. What it is saying is that philosophy doesn't really have any contribution on the physics itself. However, it may have some usefulness in the PRACTICE of physics, which isn't surprising because doing physics is a human endeavor.

However, there is still the nagging feeling that while physics can stand on its own to show how (i) it is useful and (ii) it has changed our perception of the world that we live in, the field of philosophy appears to be less able to stand on its own and depends very much on what comes out of science.

I think philosophy of science should not consider itself primarily as a service to science, but rather identify and answer questions within its own domain. I certainly would not be concerned if my own research went unnoticed by biologists, chemists, or philosophers, as long as it advances particle physics. On the other hand, as Morrison pointed out, science does generate its own philosophical problems, and philosophy may provide some kind of broader perspective for understanding those problems. 

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Solid State Higgs At The 2013 APS March Meeting

I mentioned the other day of the leg up that condensed matter physicists had on the high energy physicists in the hunt for Majorana fermions. The score so far is 3-0 in favor of condensed matter physicists.

It turns out that one can also argue that condensed matter physicists also beat their high energy physics counterpart in discovering the "Higgs"!

In 1981, Peter Littlewood and Chandra Varma, two solid-state theorists at Bell Laboratories in Murray Hill, New Jersey, realized that a mysterious effect seen in a niobium selenide superconductor could be explained by the jiggling of the invisible field that causes electrons in the material to pair up and move as one without resistance. Mathematically, the disturbance in the field looked very like one that is associated with the Higgs particle found by particle physicists.

This shouldn't really be a surprised, because as I've mentioned somewhere in this blog, and as stated in the article, the concept that arose to become the Higgs mechanism came right out of condensed matter:

It wouldn’t be the first time that particle physics stood on the shoulder of condensed-matter physics. When Peter Higgs, a theorist at the University of Edinburgh, UK, put together the idea known as the Higgs field in 1964, he built on a theory developed a year earlier, by theorist Phil Anderson, now at Princeton University in New Jersey, to describe the interactions of superconducting electrons. Higgs took the idea further, interpreting the field as a medium in empty space that would pull on particles, giving them mass. The Higgs bosons that made up the field would be invisible unless the field was jiggled in the right way, as occurs in high-energy collisions at the LHC.

That session on solid state Higgs at the APS Meeting sounded like a hoot. Seems like a lot of people are claiming Higgs-like scenario in their systems. Anyone attended that and can add a report or two?

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2013 US Spending Bill

The US legislators have finally finished some form of a spending bill for FY 2013 (several months late, if anyone is counting). Science Insider has a summary of how each of the science funding agencies within the US government fared with such severe budget cuts. It certainly looks like DOE's Office of Science suffered quite a blow.

The US is enjoying the fruits of its investment in science from way back in the 60s and 70s. The effect of a continuing downward trend in support for basic science since the 80s will be felt in the next 10 years. When historians 50 to 100 years from now look back and try to figure out when was the turning point that started the fall of the great US civilization, this will be a huge marker.

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Antiproton's Magnetic Moment Upholds CPT Symmetry

An amazing new measurement of the antiproton's magnetic moment by the ATRAP collaboration has improved the accuracy of the measurement its magnetic moment by 3 orders of magnitude. The new measurement agrees with the proton's magnetic moment to within the experimental error, thus still upholding the CPT symmetry.

The ATRAP Collaboration enters the fray with their own test for CPT violation. They look for a difference in the magnetic moments of the proton and antiproton. To enable this test, they precisely measure the magnetic moment of a single, trapped antiproton, achieving the most sensitive measurement to date of this quantity. They compare their result to the known value of the proton’s magnetic moment and find that the magnitudes are equal within experimental uncertainty, as predicted by the CPT theorem. 

The link above gives you free access to the paper.

Still haven't found anything yet that clearly violates the CPT symmetry.

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CPT

Sign of Annihilating Majorana Pairs

We now have more evidence of the presence of Majorana fermions in a condensed matter system.

I earlier pointed out 2 separate experimental evidence that are consistent with the existence of Majorana fermions in such systems. Now comes the 3rd evidence.

To help confirm recent observations, Aaron Finck and his colleagues at the University of Illinois at Urbana-Champaign have created a new system that uses a semiconducting indium arsenide nanowire hooked up to two superconducting leads. Theoretical models predict that two Majorana quasiparticles will appear at the two ends of the nanowire when a strong magnetic field is turned on. The team observed the presumed signature—a conductance peak in the wire at zero voltage. They also witnessed the splitting and re-forming of this peak as they varied the magnetic field and electron chemical potential. Although these peak modulations could arise from electron scattering effects, the authors show that their data are consistent with the wave functions of the two Majorana quasiparticles extending towards each other inside the nanowire, which leads to their transformation (or annihilation) into a more mundane collective state.

So now, in the race to find these Majorana particles, it's 3 for condensed matter, 0 for high energy physics.

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Alka-Seltzer Rocket

This is a fun demo. However, I'm not sure if this is suitable for very young kids. Someone could get his/her eyes poked! :)




And has been posted in the first comment, who the heck still has those photographic film canisters anymore? :)

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From Mars to the Multiverse

The 2012 Isaac Newton Medal lecture given by Martin Rees.




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Exoplanet Physics Project

Here's an interesting project aimed towards high-school level. This is IoP's Exoplanet Physics Project.




The synopsis says this:

The Exoplanet Physics Project is an extra-curricular science club designed to promote the practical uses of physics in society. They are available to Year 9 students from Partner Schools. Classes work in teams and are matched with an AS or A2 level physics Advisor from another school in England. Advisors are available to talk to students and support them throughout the project via an online blogging platform that is both easy to use and secure. You can register for the project or become an advisor on the Stimulating Physics website: http://www.stimulatingphysics.org/pupil-support-the-exoplanet-physics-project.htm

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What Are The Odds They Share The Same Name?

I'm sure many of you have come across the same thing.

Here in the US, the college football ranking and the choosing of teams to fight for the national championship is determined by something called the Bowl Championship Series (BCS). Of course, those of us in physics, and especially in Condensed Matter, already had a BCS name used since 1957 - the landmark Bardeen, Cooper, and Schrieffer paper on the theory of superconductivity.

Recently, I came across another name coincidence that is shared in popular culture. I watch HGTV channel quite often. In the many HGTV commercial promoting the channel and their various shows, they often play this tune, which eventually stuck in my head. I later found out that this is actually a song titled "Home" performed by a singer named Phillip Phillips, who won Season 11 of American Idol. Of course I didn't know that since I've never seen the TV show. But I thought it was a interesting coincidence because there's a well-known physicist in condensed matter (why is it always condensed matter?) at UIUC of the same name. In fact, there's a press release on a new paper that he and his co-authors had recently published on high-Tc superconductors (oh, it's that superconductivity connection once more!).

So what are the odds? After all, it really isn't a common name, or name combination. Have you come across the same thing where something in physics shares the same name with popular culture?

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Phonon Laser - Part 2

3 years ago, I highlighted a report on 2 papers advancing the concept of phonon/acoustic laser. This week, it looks like significant progress has been made.

Now, the paper of Mahboob et al. reports a significant step towards this goal. The authors create a purely mechanical system of three energy levels that is reminiscent of a three-level laser scheme (see Fig. 1, top panel). In a three-level laser, atoms are excited by an optical pump (usually another laser or a flashlamp) from the ground level (1) to a higher energy level (3), and then quickly relax through spontaneous emission and accumulate in the upper laser level (2). If the population of level 2 exceeds that of level 1 (a condition known as population inversion), photons resonant with the 1→2 laser transition get amplified through stimulated emission: the medium acts as an optical amplifier and, when placed within a cavity, lasing occurs if the gain exceeds the losses.

The link given above gives you access to the actual paper, so don't miss it.

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Old Videos Of Ernest Lawrence?

This is annoying. Berkeley Lab released a bunch of old footage, but the videos have no accompanying explanations. They just dumped them out on YouTube and left it at that!

Anyway, from what I could gather, all the videos involved Ernest Lawrence. They start from his demo of the cyclotron, all the way to his acceptance of the Nobel Prize.













It's a shame that such historically significant footage were not accompanied by detailed descriptions.

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Feynman's Double Slit Experiment

Either I'm psychic or I have excellent timing in these things.

I showed an illustration of the double slit experiment just a couple of days ago using both single photons and single electrons. Well guess what? Physics World today highlights a modern version of the double-slit experiment using electrons, and supposedly, this one is the closest to Feynman's original thought experiment.

The electrons were created at a tungsten filament and accelerated across 600 V and collimated into a beam. After passing through the double slit, they were detected using a multichannel plate.

The intensity of the electron source was set so low that only about one electron per second was detected – which ensured that only one electron at a time would ever pass through the slits. At this rate it took about two hours for a pattern to build up on the detector – a process that was recorded in real time (see video below). Measurements were repeated with the mask in a series of positions: first blocking both slits, then one slit, then none and then the opposite slit. As expected, the double-slit pattern was seen when the electrons had access to both slits, but not seen when one slit was blocked.

The link shows a video of the accumulation of the signal. You also get free access to the paper since this is a New Journal of Physics article.

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Topological Insulators Found In Nature

Looks like Mother Nature knows how to cook these things way before many of us know about it.

Newly-found samples of kawazulite found in gold mines in the Czech Republic shows properties of being a topological insulator, and may in fact have a higher quality than made-made ones.

In search of materials that display these properties, Gehring and his colleagues examined a natural sample of kawazulite, which contains bismuth, tellurium, selenium and sulphur, found at a former gold mine in the Czech Republic. Lab-made samples of kawazulite have already been shown to be topological insulators, but no one had checked for the property in natural samples.

The team cleaved off single crystalline sheets 0.7 millimetres wide and applied the standard test for a topological insulator: photoelectron spectroscopy. This involves measuring the properties of electrons dislodged when ultraviolet light is fired at a material’s surface. Their results confirm that the electrons’ energy and momentum distribution matches predictions for a topological insulator.

Feng Liu, a materials scientist at the University of Utah in Salt Lake City, notes that the team’s natural sample contains fewer structural defects than its lab-made counterparts, reducing unwanted conduction in the bulk. “It may turn out to be cheaper to use a natural supply of topological insulators,” says Liu.

Obviously, these material are not in such high demand right now. But wait till something useful can be made out of these things.

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What's The Difference?

OK, I have two figures here for you:

A.

B.

Other than the orientation and the pixel density, can you tell what is what in these two, and what are the differences?

No?

What if I tell you that one is a 2-slit interference experiment using single electrons, while the other is a 2-slit interference experiment using single photons. Can you tell which is which?

You are not at fault if you can't, because I won't be able to either, just from looking at the figures. Figure A is the single-photon interference experiment, while Figure B is the single-electron interference experiment (G. Matteucci et al., Eur. J. Phys. v.34, p.511 (2013)). The effects look the same for both.

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Observing Matter-Antimatter Oscillations

This result out of LHCb on the B-meson matter-antimatter oscillation has been getting a little bit of publicity lately (see the PhysicsWorld coverage). The paper has now appeared on PRL, and you can get a free copy of the paper at the APS Physics link.

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"Admissions Criteria and Diversity in Graduate School"

I only managed to read through this article yesterday, so this is a bit late for something that has appeared for a while.

This is a rather interesting article that first appeared in the APS News. It examines that effect of using a GRE cutoff score as a basis for graduate admission in physics, and how this may contribute to a reduced diversity for American students.

Justifying using the GRE becomes significantly more complicated, however, when the test results are dissected by race and gender. The figure plots QGRE scores by race/ethnicity and gender for US citizens whose intended graduate major was "physical sciences". The top and bottom of the lines are the 75th and 25th percentiles of the score distributions, respectively; the tick is the mean. This pattern is qualitatively unchanged when controlling for undergraduate GPA. Note the implications for diversity of using 700 as a minimum acceptable score: nearly three quarters of Hispanics would be rejected, and significantly more than this for American Indians, African Americans, and Puerto Ricans; similarly, women are filtered out at a higher rate than men. Mixing cut-off scores with these racial and gender disparities sets the foundation of a glass ceiling erected by the lopsided treatment of minorities and women before they even set foot in grad school. 

The author certainly presented some compelling statistics on why the GRE cutoff rule not only does not provide a good prediction on a student's performance in a graduate program, but also contributes to racial and gender disparities in admission.

And this brings me to another, slightly different item of discussion. The article looks at the diversity among the US students in physics. Many of us who went through the STEM educational program often see not only US students, but a large population of international students in these programs. In fact, in many schools, especially smaller ones, the number of international students can outnumber US students. This is definitely true in physics and engineering. There is a large population of international students from China, India, Korea, South America, etc.. So while there may not be as much "diversity" in the US student population in STEM fields, I find that there is a huge degree of diversity for the overall student population in these fields of study, more so then students in the liberal arts, economics, law, etc. Did you take an elective course in literature, art history, philosophy, etc.? How diverse in terms of racial/national origin were the students? How about those majoring in those fields?

Students in STEM areas have a larger opportunity to interact and experience students from other cultures and nationalities over a longer period of time. Often, they go through the degree program together. They tend to be more familiar in dealing with people from a wide variety of background. And you know what? If they continue work in such fields, the diversity carries over. Attend any physics or engineering conference, and you'll find a huge and significant international participation.

This diversity in STEM areas is often overlooked and is seldom considered as a strength in the development of students going through the program.

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Physics And Your Food Blender

I've mentioned several times on here on the effort to clearly demonstrate how physics is at work in the world of gastronomy. This is not entirely there, but certainly related to it. It is a Wired article on how the blender works, including a video that demonstrate what happens during its operation.

Question is, will it help me to make a better margarita? :)

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Measurement Of The Neutrino Oscillation Angle Theta13

This is a very good review article on neutrino oscillation and also the measurement of Theta13, which has been a very active investigation area lately. The article is aimed at "non-HEP Physicists", meaning you have to remember quite a bit of your quantum mechanics to decipher all those matrices. You get to see, quite early on, why the detection of the change in flavor of neutrinos allows not only the measurement of the mixing angle, but also implies that neutrinos must have mass.

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