Table-Top Laser Ablation Unit

I was at the Chicago's Field Museum Members Night last night. Of course, there were lots of fascinating things to see, and wonderful scientists and museum staff to talk to. But inevitably, the experimentalist in me can't stop itself from geeking out over neat gadgets.

This was one such gadget. It is, believe it or not, a table-top laser ablation unit. It is no more bigger than shoe box. I was surprised when I was told what it was, and of course, I wanted to learn more. It appears that this is still a prototype, invented by the smart folks at ETH Zurich (of course!). The scientist at Field Museum uses it to do chemical analysis on trace elements in various objects in the field, where the trace elements are just too minute in quantity that x-ray fluorescence would not be effective.

Now, you have to understand that typically, laser ablation systems tend to occupy whole rooms! It's job is to shoot laser pulses at a target, causing the evaporation of that material. The vapor then typically will migrate to a substrate where it will form a thin film, or coat another object. People use this technique often to make what is known as epitaxial films, where, if suitably chosen, the new film will have the same crystal structure as the substrate, usually up to a certain thickness.

So that was why I was fascinated to see a laser ablation kit that is incredibly small. Granted, they don't need to do lots of ablating. They only need to sample the vapor enough to do elemental analysis. The laser source is commercially bought, but the unit that is in the picture directs the laser to the target, collects the vapor, and then siphon it to a mass spectrometer or something to do its analysis. The whole thing, with the laser and the analyzer, fits on a table top, making it suitable to do remote analysis on items that can't be moved.

And of course, as always, I like to tout of the fact that many of these techniques originate out of physics research, and that eventually, they trickle down to applications elsewhere. But you already know that, don't you?

Zz.

Why Does Light Bend When It Enters Glass?

Don Lincoln tackles another "everyday" phenomenon. This time, he tries to give you an "explanation" on why light changes direction when it goes from one medium to another, and why some of the more popular explanation that have been given may be either incomplete, or wrong.



Certainly, any undergraduate physics student would have already dealt with the boundary conditions using Maxwell's equations, so this should be entirely new. However, he skipped rather quickly something that I thought was not handled thoroughly.

The continuity of the parallel component of E to the boundary is fine. However, Lincoln argued that the reason why the perpendicular component of the F field is shorter in glass is due to the polarization of the material, and thus, the sum of the light's E-field and the E-field from the polarization will cause the net, resultant E-field to be shorter.

But if the material's polarization can affect the perpendicular component, why doesn't it also affect the parallel component? After all, we assume that the material is isotropic. This, he left out, and at least to me, made it sound that the parallel component is not affected. If this is so, why?

Zz.

How Beauty Leads Physics Astray

Sabine Hossenfelder is probably doing a "book tour", since this talk certainly addressed many points that she brought up in her book.



As I've said many times on here, I don't disagree with many things that she brought up. I find the trend of foundational physics to even think about discarding experimental verification to be very troubling. I'm just glad that the field that I'm in is still strongly experimental.

Zz.

First Images of a Black Hole

After a week of rumors and build-up, the news finally broke and it is what we have been expecting. It is the announcement that we finally have our first image of a black hole.

The first direct visual evidence of a black hole and its “shadow” has been revealed today by astronomers working on the Event Horizon Telescope (EHT). The image is of the supermassive black hole that lies at the centre of the huge Messier 87 galaxy, in the Virgo galaxy cluster. Located 55 million light-years from Earth, the black hole has been determined to have a mass 6.5-billion times that of the Sun, with an uncertainty of 0.7 billion solar masses.

You can actually read the papers that were published related to this announcement, so you can find a lot more details there.

Well done, folks!!

Zz.

How Do You Make Neutrino Beam?

This new Don Lincoln's video is related to the one he did previously on the PIP-II upgrade at Fermilab. This time, he tells you how they make neutrino beams at Fermilab.



Zz.

CP Violation in D Meson Decay

LHCb is reporting the first evidence of CP violation in the decay of D meson.

The D⁰ meson is made of a charm quark and an up antiquark. So far, CP violation has only been observed in particles containing a strange or a bottom quark. These observations have confirmed the pattern of CP violation described in the Standard Model by the so-called Cabibbo-Kobayashi-Maskawa (CKM) mixing matrix, which characterises how quarks of different types transform into each other via weak interactions. The deep origin of the CKM matrix, and the quest for additional sources and manifestations of CP violation, are among the big open questions of particle physics. The discovery of CP violation in the D⁰ meson is the first evidence of this asymmetry for the charm quark, adding new elements to the exploration of these questions.

If confirmed, this will be another meson that has exhibited such CP violation, and adds to the argument that such symmetry violation could be the source of our matter-antimatter asymmetry in this universe.

CP violation is an essential feature of our universe, necessary to induce the processes that, following the Big Bang, established the abundance of matter over antimatter that we observe in the present-day universe. The size of CP violation observed so far in Standard Model interactions, however, is too small to account for the present-day matter–antimatter imbalance, suggesting the existence of additional as-yet-unknown sources of CP violation.

Zz.

PIP-II Upgrade At Fermilab

Don Lincoln explains why the PIP-II upgrade at Fermilab will take the accelerator facility to the next level.



The video actually explains a bit about how particle accelerator works, and the type of improvement that is being planned for.

Zz.

Brian Greene on Science, Religion, Hawking, and Trump

I've only found this video recently, even though it is almost a year old already, but it is still interesting, and funny. And strangely enough, he shares my view on religion, especially the fact that people seem to ignore that there are so many of them, each claiming to be the "truth". They all can't be, and thus, the biggest threat and challenge against a religion is the existence of another religion.



Zz.

Why Does Light Slow Down In A Material?

Don Lincoln tackles one of those internet/online FAQs. This time, it is an explanation on why light slows down in water, or in matter in general.



Certainly, this is the explanation many of us know when we were in school. However, most of the questions that I get regarding this phenomenon came from people who want to know the explanation at the "quantum" level, i.e. if light is made up of photons, how does one explain this phenomenon in the photon picture? That is the origin of the two "wrong" explanations that he pointed out in the video, i.e. people wanting to use "photons" to explain what is going on here.

Actually, Don Lincoln could have gone a bit further with the explanation and included the fact that this explanation can account for why the speed of light (and index of refraction) inside a material is dependent on the frequency of the light entering the material.

Strangely enough, this actually reminded me of a puzzle that I had when I first encountered this explanation. If the electrons (or the electric dipoles) inside the material oscillate and create an additional EM wave, and the superposition of these two waves give rise to the final wave that appears to move slower in the material, then what stops this second EM wave from leaving the material? Is it only confined within the material? Do we detect "leakage" of this second or any additional wave due to things oscillating in the material? Because the second wave has a different wavelength, it will be refracted differently at the boundary, so it will no longer be aligned with the original wave after they leave the material, if they all leave the material.

Anyone knows?

Edit: Funny enough, and maybe because I watched this video, YouTube gave me an old MinutePhysics video that used the bouncing light particle explanation that Don Lincoln says isn't correct.



Zz.

Self-Propulsion of Inverse Leidenfrost Droplets Explained

I was not familiar at all with the Leidenfrost effect, even though I've heard the name. So when I read the article, I was fascinated by it. Unlike other people who want find the answers to the mysteries of the universe, etc... I went into physics because I was more curious about these small, little puzzles that, in the end, could have big impact and big outcome elsewhere. So thie Leidenfrost levitation phenomenon is right up my alley, and I'm kicking myself for not reading up on it sooner than this (or maybe they mentioned it in my advanced classical mechanics graduate course, and I overlooked it).

Anyhow, it appears that there is an inverse Leidenfrost self-propulsion, and a group of physicsts have managed to provide an explanation for it. the article describes both the Leidenfrost and inverse Leidenfrost propulsion, so you may read it for yourself. The research work[1], unfortunately, is currently available only via subscription. So you either need one for yourself, or log in to an organization that has site-wide access to it.

And look at the possible application for this seemingly mundane effect that grew out of a basic curiosity:

Gauthier’s team believe the effect could be used to develop efficient techniques for freezing and transporting biological materials including cells and proteins. With the help of simulations, they hope that this transport could occur with no risk of contamination or heat degradation to the materials.

Zz.

[1] A. Gauthier et al. PNAS v.116, p.1174 (2019) https://www.pnas.org/content/116/4/1174

When Condensed Matter Physics Became King

If you are one of those, or know one of those, who think Physics is only the LHC and high-energy physics, and String Theory, etc., you need to read this excellent article.

When I first read it in my hard-copy version of Physics Today, the first thing that came across my mind after I put it down is that this should be a must-read for the general public, but especially to high-school students and all of those bushy-tailed and bright-eyed incoming undergraduate student in physics. This is because the need to be introduced to a field of study in physics that has become the "king" in physics. Luckily, someone pointed out to me that this article is available online.

Reading the article, it was hard, but understandable, to imagine the resistance that was there in incorporating the "applied" side of physics into a physics professional organization. But it was at a time when physics was still seen as something esoteric with the grandiose idea of "understanding our world" in a very narrow sense.

Solid state’s odd constitution reflected changing attitudes about physics, especially with respect to applied and industrial research. A widespread notion in the physics community held that “physics” referred to natural phenomena and “physicist” to someone who deduced the rules governing them—making applied or industrial researchers nonphysicists almost by definition. But suspicion of that view grew around midcentury. Stanford University’s William Hansen, whose own applied work led to the development of the klystron (a microwave-amplifying vacuum tube), reacted to his colleague David Webster’s suggestion in 1943 that physics was defined by the pursuit of natural physical laws: “It would seem that your criterion sets the sights terribly high. How many physicists do you know who have discovered a law of nature? … It seems to me, this privilege is given only to a very few of us. Nevertheless the work of the rest is of value.”

Luckily, the APS did form the Division of Solid State Physics, and it quickly exploded from there.

By the early 1960s, the DSSP had become—and has remained since—the largest division of APS. By 1970, following a membership drive at APS meetings, the DSSP enrolled more than 10% of the society’s members. It would reach a maximum of just shy of 25% in 1989. Membership in the DSSP has regularly outstripped the division of particles and fields, the next largest every year since 1974, by factors of between 1.5 and 2.

This is a point that many people outside of physics do not realize. They, and the media, often make broad statements about physics and physicists based on what is happening in, say, elementary particle physics, or String, or many of those other fields, when in reality, those areas of physics are not even an valid representation of the field of physics because they are not the majority. Using, say, what is going on in high-energy physics to represent the whole field of physics is similar to using the city of Los Angeles as a valid representation of the United States. It is neither correct nor accurate!

This field, that has now morphed into Condensed Matter Physics, is vibrant, and encompassed such a huge variety of studies, that the amount of work coming out of it each week or each month is mindboggling. It is the only field of physics that has two separate section on Physical Review Letters, The Physical Review B comes out four (FOUR) times a month. Only Phys. Rev. D has more than one edition per month (twice a month). The APS March Meeting, where the Division of Condensed Matter Physics participatesin, continues to be the biggest giant of annual physics conference in the world.

Everything about this field of study is big, important, high-impact, wide-ranging, and fundamental. But of course, as I've said multiple times on here, it isn't sexy for most of the public and the media. So it never because the poster boy for physics, even if they make up the largest percentage of practicing physicist. Doug Natelson said it as much in commenting about condensed matter physics's image problem:

Condensed matter also faces a perceived shortfall in inherent excitement. Black holes sound like science fiction. The pursuit of the ultimate reductionist building blocks, whether through string theory, loop quantum gravity, or enormous particle accelerators, carries obvious profundity. Those topics are also connected historically to the birth of quantum mechanics and the revelation of the power of the atom, when physicists released primal forces that altered both our intellectual place in the world and the global balance of power.

Compared with this heady stuff, condensed matter can sound like weak sauce: “Sure, they study the first instants after the Big Bang, but we can tell you why copper is shiny.” The inferiority complex that this can engender leads to that old standby: claims of technological relevance (for example, “this advance will eventually let us make better computers”). A trajectory toward applications is fine, but that tends not to move the needle for most of the public, especially when many breathless media claims of technological advances don’t seem to pan out.

It doesn’t have to be this way. It is possible to present condensed-matter physics as interesting, compelling, and even inspiring. Emergence, universality, and symmetry are powerful, amazing ideas. The same essential physics that holds up a white dwarf star is a key ingredient in what makes solids solid, whether we’re talking about a diamond or a block of plastic. Individual electrons seem simple, but put many of them together with a magnetic field in the right 2D environment and presto: excitations with fractional charges. Want electrons to act like ultrarelativistic particles, or act like their own antiparticles, or act like spinning tops pointing in the direction of their motion, or pair up and act together coherently? No problem, with the right crystal lattice. This isn’t dirt physics, and it isn’t squalid.

It is why I keep harping to the historical fact of Phil Anderson's work on a condensed matter system that became the impetus for the Higgs mechanism in elementary particle, and how some of the most exotic consequences of QFT are found in complex material (Majorana fermions, magnetic monopoles, etc...etc.).

So if your view of physics has been just the String theory, the LHC, etc... well, keep them, but include its BIG and more influential brother, the condensed matter physics, that not only has quite a number of important, fundamental stuff, but also has a direct impact on your everyday lives. It truly is the "King" of physics.

Zz.

Standing Out From The Crowd In Large Collaboration

As someone who has never been involved in these huge collaborations that we see in high energy physics, I've often wondered how a graduate student or a postdoc make a name for themselves. If you are one of dozens, even hundreds, of authors in a paper, how do you get recognized?

It seems that this issue has finally been addressed by the high energy physics community, at least in Europe. A working group has been established to look into ways for students, postdocs, and early-career researches to stand out from the crowd and have their effort recognized individually.

To fully exploit the potential of large collaborations, we need to bring every single person to maximum effectiveness by motivating and stimulating individual recognition and career choices. With this in mind, in spring 2018 the European Committee for Future Accelerators (ECFA) established a working group to investigate what the community thinks about individual recognition in large collaborations. Following an initial survey addressing leaders of several CERN and CERN-recognised experiments, a community-wide survey closed on 26 October with a total of 1347 responses. 

Still, the article does not clarify on exactly how these individual recognition can be done. I'd be interested to hear how they are going to do this.

Zz.

Fermilab

Do you ever want to know about US Fermi National Accelerator Laboratory, or Fermilab?

Don Lincoln finally has made a video on everything you want to know about Fermilab, especially if you think that they don't do much anymore nowadays now that the Tevatron is long gone.



As someone who has visited there numerous times and collaborated with scientists and engineers that this facility, it is a neat place to visit if you have the chance.

Zz.

Tommaso Dorigo's "False Claims In Particle Physics"

Hey, you should read this blog post by Tommaso Dorigo. It touches upon many of the myths regarding particle physics, especially the hype surrounding the name "god particle", as if that means something.

I've touched upon some of the issues he brought up. I think many of us who are active online and deal with the media and the public tend to see and observe the same thing, the same mistakes, and misinformation that are being put in print. One can only hope that by repeatedly pointing out such myths and why they are wrong, the message will slowly seep into the public consciousness.

I just wish it is seeping through faster.

Zz.

Negative Capacitance in Ferroelectric Material Finally Found

I love this sort of reports, because it is based on a material that has been discovered for a long time and rather common, it is based on a consequence of a theory, it has both direct applications and a rich physics, and finally, it has an amazing resemblance to what many physics students have seen in textbooks.

A group of researchers have finally confirmed the existence of negative capacitance in ferroelectric material haffnium zirconium oxide Hf_0.5Zr_0.5O₂. (You may access the Nature paper here or from that news article).

Researchers led by Michael Hoffmann have now measured the double-well energy landscape in a thin layer of ferroelectric Hf_0.5Zr_0.5O₂ for the first time and so confirmed that the material indeed has negative capacitance. To do this, they first fabricated capacitors with a thin dielectric layer on top of the ferroelectric. They then applied very short voltage pulses to the electrodes of the capacitor, while measuring both the voltage and the charge on it with an oscilloscope.

“Since we already knew the capacitance of the dielectric layer from separate experiments, we were then able to calculate the polarization and electric field in the ferroelectric layer,” Hoffmann tells Physics World. “We then calculated the double-well energy landscape by integrating the electric field with respect to the polarization.”

Of course, there are plenty of potential applications for something like this.

One of the most promising applications utilising negative capacitance are electronic circuits with much lower power dissipation that could be used to build more energy efficient devices than any that are possible today, he adds. “We are working on making such devices, but it will also be very important to design further experiments to probe the negative capacitance region in the structures we made so far to help improve our understanding of the fundamental physics of ferroelectrics.”

But the most interesting part for me is that, if you look at Fig. 1 of the Nature paper, the double-well structure is something that many of us former and current physics students may have seen. I know that I remember solving this double-well problem in my graduate level QM class. Of course, we were solving it energy-versus-space dimension, instead of the energy-versus-polarization dimension as shown in the figure.

Zz.

Crisis? What Crisis?

Chad Orzel has posted a fun piece that really tries to clarified all the brouhaha in many circles about a "crisis" that many are presuming to be widespread. The crisis in question is the lack of "beyond the standard model" discovery in elementary particle physics, and the issue that many elementary particle theorists seem to think that a theory that is based on solid foundation and elegance are sufficient to be taken seriously.

I find this very frustrating, because physics as a whole is not in crisis. The "crisis" being described is real, but it affects only the subset of physics that deals with fundamental particles and fields, particularly on the theory side. (Experimental physicists in those areas aren't making dramatic discoveries, but they are generating data and pushing their experiments forward, so they're a little happier than their theoretical colleagues...)

The problems of theoretical high energy physics, though, do not greatly afflict physicists working in much of the rest of the discipline. While this might be a time of crisis for particle theorists, it's arguably never been a better time to be a physicist in most of the rest of the field. There are exciting discoveries being made, and new technologies pushing the frontiers of physics forward in a wide range of subfields.

This is a common frustration, because elementary particle physics is not even the biggest subfield of physics (condensed matter physics is), but yet, it makes a lot of noise, and the media+public seem to pay more attention to such noises. So whenever something rocks this field, people often tend to think that this permeates through the entire field of physics. This is utterly false!

Orzel has listed several outstanding and amazing discoveries and advancements in condensed matter. There are more! The study of topological insulators continues to be extremely hot and appear to be not only interesting for application, but also as a "playground" for exotic quantum field theory scenarios.

I've said it many times, and I'll say it again. Physics isn't just the Higgs or the LHC. It is also your iphone, your MRI, your WiFi, your CT scan, etc....etc.

Zz.

150 Years of the Periodic Table

Hey, I'll admit it. I wouldn't have known about this 150th birthday of the periodic table if it weren't for this news article. ScienceNews has a lot more detail on the history and background of Mendeleev, who came up with the first periodic table.

Unfortunately, there might be a chance for a bit of inaccuracy here from the Miami Herald news article.

The periodic table lists the elements in order of their atomic weights, but when Mendeleev was classifying them, no one even knew what was inside these tiny things called atoms. 

While it is true that, historically, Mendeleev originally arranged the elements with respect to each atom's atomic weight (since no one knew that was inside these atoms at that time), the periodic table that we have now lists the elements in order of their atomic number, i.e. the number of protons in the element. This is because we now know that an element of a particular atomic number may have several different isotopes (atomic weights). So the atomic weight is not a unique number for an element, but atomic number is. That is why the period table is arrange in order of the element's atomic number.

In any case, Happy 150th Year, Periodic Table!

Zz.

Rumors Emerge Following Prominent Physicist's Death

First of all, RIP Shoucheng Zhang.

It is unfortunate that my first post of the New Year is about a sad news from Dec. of 2018. Prominent Standford physicist, Shoucheng Zhang passed away in early Dec. of an apparent suicide. He was only 55, and according to his family, has been suffering from bouts of depression. But what triggers this report is the possible connection between him and US-China relation, which, btw, is purely a rumor right now.

Zhang was originally recruited in 2008 under the Thousand Talents program — a CCP effort to attract top scientists from overseas to work in China — to conduct research at Tsinghua University in Beijing. Zhang was active in helping U.S.-trained Chinese researchers return home, and expressed his desire to help “bring back the front-lines of research to China” in a recent interview with Chinese news portal Sina.  

Zhang’s venture capital firm Digital Horizon Capital (DHVC), formerly known as Danhua Capital, was recently linked to China’s “Made in China 2025” technology dominance program in a Nov. 30 U.S. Trade Representative (USTR) report. According to the report, venture capital firms like DHVC are ultimately aimed at allowing China to access vital technology from U.S. startups. Zhang’s firm lists 113 U.S. companies in its portfolio, most falling within emerging sectors that the Chinese government has identified as strategic priorities. 

The “Made in China 2025” program combines economic espionage and aggressive business acquisitions to aid China’s quest to become a tech manufacturing superpower, the USTR report continues. The program was launched in 2015 and has been cited by the Trump administration as evidence that the Chinese government is engaged in a strategic effort to steal American technological expertise. 

I have absolutely no knowledge on any of these. I can only mourn the brilliant mind that we have lost.

I first heard of "S.C. Zhang" when I was still working as a grad student in condensed matter physics, especially on the high-Tc superconductors. He published this paper in Science, authored by him alone, on the SO5 symmetry for the basis of a unified theory of superconductivity and antiferromagntism[1]. That publication created quite a shakeup in condensed matter theory world at that time.

It was a bit later that I learned that he came out of an expertise in elementary particle physics, and switched fields to go dabble into condensed matter (see, kids? I told you that various topics in physics are connected and interrelated!). Of course, his latest ground-breaking work was the initial proposal for topological insulators[2]. This was Nobel Prize-caliber work, in my opinion.

Besides that, I've often cited one of his writings when the issue of emergent phenomena comes up.[3] As someone with a training in high energy/elementary particle, he definitely had the expertise to talk about both sides of the coin: reductionism versus emergent phenomenon.

Whatever the circumstances are surrounding his death, we have lost a brilliant physicist. If topological insulators become the rich playground for physicists and engineers in the years to come, as it is expected to, I hope the world remembers his name as someone who was responsible for this advancement.

Zz.

[1] S.C. Zhang, Science v.275, p.1089 (1997).
[2] H. Zhang et al., Nature Physics v.5, p.438 (2009).
[3] https://arxiv.org/abs/hep-th/0210162

New Family of High Tc Superconductors?

We interrupt your year-end holiday to bring you this news.

It seems that there are two groups reporting the discovery of possible high-Tc superconductors in a new family of material, the hydrides. The Tc's are well above 200 K. The caveat? So far, they become superconducting at high pressures.

Researchers at the Max Planck Institute for Chemistry in Mainz, Germany say that lanthanum hydride (LaH₁₀) could be superconducting at the remarkably high temperature of 250 K (-23°C), albeit at extreme pressures of around 170 GPa. Meanwhile, another team from George Washington University in the US says that it has found evidence of superconductivity in the same material at even higher temperatures of 280 K (7°C) under 202 GPa pressures. If confirmed, the findings could be a major step towards finding room-temperature superconductors.

You may read the preprint of one of the reports here.

As usual, we need to sit back, take a deep breath, and let the process runs through. These needs to be published first, and then independent groups will have to verify the results. Only THEN can we get excited about this news. So stay tune, a lot more will be coming.

Zz.

Quantum Entanglement of 10 Billion Atoms!

Not only is the Schrodinger Cat getting fatter, but the EPR/Bell bulldog is also putting on mass.

New report out of Delft University has shown the successful demonstration of quantum entanglement of two strips of silicon resonators, consisting of roughly 10 billion atoms!

They demonstrated quantum entanglement and violations of Bell’s inequality—a canonical test of the principle that all influences on a particle are local and that particle states exist independently of the observer. They used two mechanical resonators, each containing roughly 10 billion atoms.

If you do not have access to the PRL paper, you may read the arXiv version here.

This is quite a feat, and I think that things can only get bigger, literally and figuratively.

Zz.

It Does NOT Defy 156-Year-Old Law of Physics!

Often times, popular accounts of physics and physics discoveries/advancements are dramatized and sensationalized to catch the eyes of the public. I'm all for catching their attention in this day and age, but really, many of these are highly misleading and tend to over-dramatize certain things.

This is one such example. It started off with an eye-catching title:

"Energy Efficiency Breakthrough Defies 156-Year-Old Law of Physics"

Really? Do we have a Nobel Prize already lined up for these people? After all, what could be more astounding and impactful than a discovery that "defies" an old and established law of physics?

Turns out, as I suspected, that it is a new solution to the well-known Maxwell equation that had never been discovered before. But even if you don't know anything about Maxwell equation and what the discovery is all about, if you pay attention to what they wrote, you would have noticed something contradictory to what the title claimed:

The first several efforts were unsuccessful until the team conceived of using an electrical conductor in movement. They proceeded to solve Maxwell’s equations analytically in order to demonstrate that not only could reciprocity be broken but that coupling could also be made maximally asymmetric.

Notice that they USED Maxwell's equations (i.e. the 156-year-old law of physics) and found new solutions that hadn't been thought to be possible. So how could they be defying it when they actually used it? They may have defined previous notion that there are no solutions of that type, but they did not defy Maxwell equations, not in the least bit!

Sussex University press office needs to get their act together and not go for such cheap thrills. And I'm surprised that the researchers involved in this actually let a title like that go through.

Edit 11/29/2018: THIS is how this discovery should have been reported, as done by Physics World. Notice that nowhere in there was there any claim of any laws of physics that has been violated!

Zz.

Muons And Special Relativity

For those of us who studied physics or have taken a course involving Special Relativity, this is nothing new. The case of a lot of muons being detected on the earth's surface has been used as an example of the direct result of SR's time dilation and length contraction.

Still, it bears repeating, and presenting to those who are not aware of this, and this is what this MinutePhysics video has done.



Zz.

Comparing Understanding of Graphs Between Physics and Psychology Students

I ran across this paper a while back, but didn't get to reading it carefully till now.

If you have followed this blog for any considerable period of time, you would have seen several posts where I emphasized the importance of physics education, NOT just for the physics knowledge, but also for the intangible skills that comes along with it. Skills such as analytical ability and deciding on the validity of what causes what are all skills that transcends the subject of physics. These are skills that are important no matter what the students end up doing in life.

While I had mentioned such things to my students during our first day of class each semester, it is always nice when there are EVIDENCE (remember that?) to back such claim. In this particular study, the researchers compare how students handle and understand the information that they can acquire from graphs on topics outside of their area of study.

The students involved are physics and psychology students in Zagreb, Croatia. They were tested on their understanding of the concept of slope and area under the graph, their qualitative and quantitative understanding of graphs, and comparing their understanding of graphs in the context of physics and finance. For the latter area (finance), both groups of students did not receive kind of lessons in that subject area and thus, are presumably unfamiliar with both groups.

Before we proceed, I found that in Croatia, physics is a compulsory subject in pre-college education there, which is quite heartening.

Physics is taught as a compulsory subject in the last two grades of all elementary schools and throughout four years of most of high schools in Croatia. Pupils are taught kinematics graphs at the age 15 and 16 (last grade of elementary school and first year of high school). Psychology students were not exposed to the teaching on kinematics graphs after high school, while physics students learned about kinematics graphs also in several university courses. Physics and psychology students had not encountered graphs related to prices, money, etc., in their formal education.

So the psychology students in college are already familiar with basic kinematics and graphs, but did not go further into it once they are in college, unlike physics students. I'd say that this is more than what most high school students in the US have gone through, since Physics is typically not required in high schools here.

In any case, the first part of the study wasn't too surprising, that physics students did better overall at physics questions related to the slope and area under the graph. But it was interesting that the understanding of what "area under the graph" tends to be problematic for both groups. And when we got to the graphs related to finance, it seems clear that physics students were able to extract the necessary information better than psychology students. This is especially true when it comes to the quantitative aspect of it.

You should read the in-depth analysis and discussion of the result. I'll quote part of their conclusion here:

All students solved the questions about graph slope better than the questions about the area under a graph. Psychology students had rather low scores on the questions about area under a graph, and physics students spent more time than psychology students on questions about area under a graph. These results indicate that area under a graph is quite a difficult concept that is unlikely to be developed without formal teaching and learning, and that more attention should be given to this topic in physics courses.

Physics and psychology students had comparable scores on the qualitative questions on slope which indicates that the idea of slope is rather intuitive. However, many psychology students were not able to calculate the slope, thus indicating that their idea of slope was rather vague. This suggests that the intuitive idea of slope, probably held by most students, should be further developed in physics courses and strongly linked to the mathematical concept of slope that enables students to quantify slope.

Generally, physics students solved the qualitative and the quantitative questions equally well, whereas psychology students solved qualitative questions much better than the quantitative questions. This is further evidence that learning physics helps students to develop deeper understanding of concepts and the ability to quantitatively express relationships between quantities.

The key point here is the "transfer" of knowledge that they have into an area that they are not familiar with. It is clear that physics students were able to extract the information in the area of finance better than psychology students. This is an important point that should be highlighted, because it shows how skills learned from a physics course can transfer to other areas, and that a student need not be a physics major to gain something important and relevant from a physics class.

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The Origin Of Matter's Mass

I can't believe it. I'm reporting on Ethan Siegel's article two days in a row! The last one yesterday was a doozy, wasn't it? :)

This one is a bit different and interesting. The first part of the article describes our understanding of where mass comes from for matter. I want to highlight this because it clarify one very important misconception that many people have, especially the general public. After all the brouhaha surrounding the Higgs and its discovery, a lot of people seem to think that all the masses of every particle and entity can be explained using the Higgs. This is clearly false as stated in the article.

Yet if we take a look at the proton (made of two up and one down quark) and the neutron (made of one up and two down quarks), a puzzle emerges. The three quarks within a proton or neutron, even when you add them all up, comprise less than 0.2% of the known masses of these composite particles. The gluons themselves are massless, while the electrons are less than 0.06% of a proton's mass. The whole of matter, somehow, weighs much, much more than the sum of its parts.

The Higgs may be responsible for the rest mass of these fundamental constituents of matter, but the whole of a single atom is nearly 100 times heavier than the sum of everything known to make it up. The reason has to do with a force that's very counterintuitive to us: the strong nuclear force. Instead of one type of charge (like gravity, which is always attractive) or two types (the "+" and "-" charges of electromagnetism), the strong force has three color charges (red, green and blue), where the sum of all three charges is colorless.

So while we may use the Higgs to point to the origin of  mass in, say, leptons, for hadrons/partons, this is not sufficient. The strong force itself contributes a significant amount to the origin of mass for these particles. The so-called "God Particles" are not that godly, because it can't do and explain everything.

The other interesting part of the article is that he included a "live blog" of the talk by Phiala Shanahan at occurred yesterday at the Perimeter Institute, related to this topic. So you may want to read through the transcript and see if you get anything new.

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US No Longer Attracts The Best Physics Minds

So much for making America great again.

Ethan Siegel summarizes the recent data on the severe drop in the number of international students seeking advanced physics degree in the US, and the drop in the number of applicants to US schools.

You need to read the article and the history of US advancement in physics, and science in general, to realize why this is a troubling trend. Whether you realize it or not, what you are enjoying now is the result of many such immigrants who came to the US and made extraordinary discoveries and contribution to science. This may no longer be true soon enough.

Yet, according to the American Physical Society, the past year has seen an alarming, unprecedented drop in the number of international applications to physics PhD programs in the United States. In an extremely large survey of 49 of the largest physics departments in the country, representing 41% of all enrolled physics graduate students in the United States, an overall decrease of almost 12% in the number of international applicants was observed from 2017 to 2018.

Graduate students in physics, if you are not aware of it, are the workhorse in advanced physics research. While senior researchers often think of the project, find the funding, and form the group, it is the graduate students and postdoc that often are the ones doing the actual work and executing the plan. And many of us not only rely on their skills and knowledge, but also their creativity in solving the myriads of problems that we often did not anticipate during the research work.

Without graduate students, many research programs would either come to a halt, or will be severely impacted. Period!

And the reality here is that the overwhelming majority of US institutions, both universities and US National Labs, have come to depend on a lot of international graduate students for these research projects. The ability to attract not just the best talent in the US, but also the best talent from all over the world, was a luxury that was the envy of many other countries. But that is no longer the case now, and the gloomy prediction of the beginning of the decline isn't that outrageous.

We find ourselves, today, at the very beginning of what could be the end of America's greatness in the realm of scientific research and education. Science has always been touted as the great equalizer: the scientific truths underlying our Universe know no borders and do not discriminate based on race, gender, or religion. We still have time to reverse this trend, and to welcome the brightest minds the world has to offer into our country.

But if we fail to do so, that intellectual capital will thrive elsewhere, leaving America behind. If we do not change course, "America First" will be the downfall of scientific greatness in our country.

I said as much way back in 2012 when I started noticing for the first time of many established Chinese researchers and college professors starting to migrate back to China and to Chinese institutions, something that was unheard of several years before. So now, compounding the budget constraints, we now have clear data on US no longer attracting as many international students as before.

There are no "greatness" in any of these here.

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Cerenkov Radiation

Don Lincoln tackles the origin of Cerenkov radiation this time. This is the case where a body travels faster than light in a medium.

This is not purely academic. This is how we detect certain particles, such as neutrinos. Those photodetectors in, say, SuperKamiokande, are detecting these Cerenkov radiation. In fact, if you look in a pool of water of nuclear fuel rods, the blue light is the result of Cerenkov radiation.

So here's a chance for you to learn about Cerenkov radiation.



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What Is Dark Matter And Why Does It Matter?

First of all, let me explain something If you are not in an academic institution, or a research facility, etc., you may not know that for many of us, having regular, sometime weekly, colloquium or seminars is quite common. This is where we invite experts in various topics come to our institution or department and present a talk on a particular subject. I, myself, have given such seminars. This is how we learn about many things, often topics outside of our expertise or area of studies, and we learn about these things from authorities in these various fields. It is one of the unique privileges that we enjoy being in such an environment.

In other words, we do not learn about these topics from popular media, or even from 2nd or 3rd hand sources. And this usually takes time, i.e. it can't be done in short sound bites or in a few minutes.

I'm prefacing this video with such information because this is an example of a colloquium that we typically attend, and if you are not used to it, it may appear tedious to sit through an hour of such presentation. But there is usually no other way to learn about things, especially if you wish to learn about something beyond just a superficial level.

I've mentioned about dark matter many times on here, but here's another one. It is presented in a manner that even non-scientists may understand, even if you do not understand some of the intricate details.



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Lawrence Krauss Responds To Allegations

I'm posting this here simply because I reported the original news article against Krauss. It is only fair to include his rebuttal on this issue, and I'll let you decide on your own.

As an instructor, I've gone through various Title IX and sexual harassment prevention training. And at least a couple of years ago, I've stopped having officer hours in my office. Instead, it is held in a public space, either in an open classroom or in an open lounge. I'm more weary of what I do an say, and also my surroundings in trying to make sure I do not put myself in a situation where I may get accused of something. It isn't comfortable having to always be on my toes, but that is what I have lived with.

Not sure if any of you instructors/college professors have changed the way you do your work in light of what has developed so far. But I know I certainly have.

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The Electron Remains Perfectly Point-Like

The latest and most accurate experiment to detect any hint of an electric dipole moment of an electron has revealed that there isn't any.

Now, the Advanced Cold Molecule Electron Electric Dipole Moment, or ACME, search, based at Harvard University, has probed the electron’s EDM with the most precision ever — and still found no sign of smooshing, the team reports online October 17 in Nature.

The finding improves the team’s last best measurement (SN Online: 12/19/13) by a factor of 10 to find an EDM of 10^-29 electron charge centimeters. That’s as round as if the electron were a sphere the size of the Earth, and you shaved less than two nanometers off the North Pole and pasted it onto the South Pole, says Yale University physicist David DeMille, a member of the ACME team.

This improves upon the previous measurement that I mentioned a year ago. Looks like if any theory predicts the possible structure of an electron, they have some severe constraints to overcome.

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Time Crystals

Ignoring the theatrics, Don Lincoln's video is the simplest level of explanation that you can ask for for what a "time crystal" is, after you strip away the hyperbole.



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RIP Leon Lederman

One of the most charismatic physicists that I've ever met, former Fermilab Director and Nobel Laureate Leon Lederman, has passed away at the age of 96. Most of the general public will probably not know his name, but will have heard the name "God Particle", which he coined in his book, and which he originally intended to call the "God-Damn Particle".

He had been in failing health, and suffered from dementia. It force his family to auction off his Nobel Prize medal to help with his medical cost. But his lasting legacy will be in his effort to put "Physics First" in elementary and high school. And of course, there's Fermilab.

He truly was, and still is, a giant in this field.

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2018 Nobel Prize in Physics ... FINALLY, after 55 years!

I seriously thought that I'd never see this in my lifetime, and I'm terribly happy that I was wrong!

The 2018 Nobel Prize in Physics has just been announced, and for the first time in more than 50 years, one of the winners is a woman!

The Nobel Prize in Physics 2018 was awarded “for groundbreaking inventions in the field of laser physics” with one half to Arthur Ashkin “for the optical tweezers and their application to biological systems”, the other half jointly to Gérard Mourou and Donna Strickland “for their method of generating high-intensity, ultra-short optical pulses”.

Congratulations to all, and especially to Donna Strickland.

I will admit that this wasn't something I expected. I didn't realize that the area of ultra-short laser pulses was in the Nobel Committee and nomination radar. But it is still very nice that this area of laser pulse-shaping technique is being recognized.

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Record 1200 Tesla, and then, BANG!

Hey, would you sacrifice your equipment just so you can break the record on the strongest magnetic field created in a lab? These people would.

Speaking with IEEE Spectrum, lead researcher Shojiro Takeyama explained that his team was hoping to achieve a magnetic field that reached 700 Tesla (the unit of measurement for gauging the strength of a magnetic field). At that level, the generator would likely self destruct, but when pushed to its limits the machine actually achieved a strength of 1,200 Tesla.

To put that in perspective, an MRI machine — which is the most intense indoor magnetic field most people would ever encounter — comes in at just three Tesla. Needless to say, the researchers’ machine didn’t survive the test, but it did land them in the record books.



Honestly, I don't think I can get away with doing that!

Zz.

How Fast Is The Photoelectric Effect?

Every student who studied modern physics in an undergraduate General Physics course would have encountered the photoelectric effect. It is a phenomenon that has a special place in the history of physics, and the theoretical description of this phenomenon gave Einstein his Nobel Prize.

So one would think that this is a done deal already, and we should know all there is to know about it. In some sense, we do. We know enough about it that we have expanded this phenomenon to be included in a more general phenomenon called photoemission. We use this phenomenon to study many things, including band structure of materials. So it is very well-known.

Yet, as with so many things in physics, the more we study it, the more we want to know the minute details of it. In this case, the current study is on how fast an electron is emitted from a material once light impinges upon it. In other words, from the moment a photon is absorbed, how quickly does the electron is liberated from the material?

This is not that easy to answer because, well, one can already guess at how would one determine (i) the exact time when one photon is absorbed into a material, and (ii) the exact time when an electron  is liberated due to that absorbed photon. On top of that, this may be a very fast process, so how does one measure a time scale that is almost instantaneous?

The authors of this latest paper[1] came up with a very ingenious method to determine this, and in the process, they have elucidated even more the various stages of what is involved in the photoelectric effect. But before we continue, let's get one thing very clear here.

The "photoelectric effect" that we know and love, and the one that Millikan studied, is the phenomenon whereby UV light is shown onto a metallic surface (cathode). We know now that this is an emission process of electrons coming from the metal's conduction band. This is important because, as this new study shows, this process is different than the emission from core levels (i.e. not from the continuous conduction band). Those of us who have done photoemission work using both UV and x-rays can attest to such differences.

The experiment in this report was done on a tungsten surface, or more specifically, W(110) surface. The hard UV light that was used allowed them to get photoemission from the conduction band and a core-level state.

What they found was that from the time that a photon is absorbed to the moment that an electron is emitted, the time for the process for a conduction electron is ~ 45 as, while for a core-level electron is ~100 as.

{as = attosecond = 1 x 10^(-18) second}

So the emission from core-level takes more than twice as long to occur. In their analysis, the authors stressed this conclusion:

These findings highlight that proper accounting for the initial creation, origin, transport and scattering of electrons is imperative for the proper description of the photoelectric effect.

Bill Spicer's 3-step model of photoemission process certainly highlighted the fact that it isn't a simple process. This paper not only reinforce that, but also included the effect of surface states in the influence to emission time and thus, possibly influencing other properties of the emitted photoelectron. 

There are many things in physics which we know a lot of. But these are also areas in which we continue to dig deeper to find out even more. There will never be a point where we know everything there is to know, even with established ideas and phenomena.

Zz.

[1] M. Ossiander et al., Nature 561, 374 (2018). https://www.nature.com/articles/s41586-018-0503-6
Summary of this work can be found here.

Ghost Imaging Using Relativistic Electrons

No, we're doing imaging ghosts here.

For the first time, ghost imaging using electrons have been accomplished.[1]

Optical ghost imaging using light has been previously accomplished.

Optical ghost imaging is a useful tool that can spatially resolve the characteristics of a sample using just a single-pixel detector – rather than the multipixel arrays found in digital cameras. The technique involves splitting a beam of light into a pair of correlated beams called the signal and reference beams. The signal beam strikes the sample before hitting the single-pixel detector. The reference beam goes directly to a conventional, multipixel detector. By measuring the correlation between the intensities of the beams as they hit their respective detectors, an image of the sample can be reconstructed using data from the multipixel detector, without directly imaging the sample itself.

In this new report, this technique has been accomplished using relativistic electrons. Their motivation for applying this technique using electrons is given in the text of the paper:

Potential benefits of applying ghost imaging methods to electron-based imaging systems include the possibility to minimize image acquisition time and to reduce the dose delivered to the sample and the resulting sample damage. In addition, electron ghost imaging can be useful for experimental methods (e.g. electron energy-loss spectroscopy, or cathodoluminescence) for which spatially resolved detectors either do not exist or severely increase the complexity of the setup. A special case is the growing field of time-resolved electron scattering where the use of multi-MeV, ultrashort relativistic electron sources for both imaging and diffraction has pushed temporal resolution to the ps and fs regimes. Employing structured illumination (i.e. ghost imaging) schemes on ultrashort electron beams offers the possibility to better manage the space charge effects in the electron column.

This is another opportunity for me to point out that this is a research work coming out of accelerator physics.

Zz.

[1] S. Li et al., Phys. Rev. Lett. 121, 114801 (2018). http://www.slac.stanford.edu/pubs/slacpubs/17250/slac-pub-17314.pdf

Want To Located The Accelerometer In Your Smartphone?

Rhett Allain has a simple, fun rotational physics experiment that you can perform on your smartphone to locate the position of the accelerometer in that device, all without opening it.

Your smart phone has a bunch of sensors in it. One of the most common is the accelerometer. It's basically a super tiny mass connected with springs (not actual springs). When the phone accelerates in a particular direction, some of these springs will get compressed in order to make the tiny test mass also accelerate. The accelerometer measures this spring compression and uses that to determine the acceleration of the phone. With that, it will know if it is facing up or down. It also can estimate how far you move and use this along with the camera to find out where real world objects are, using ARKit.

So, we know there is a sensor in the phone—but where is it located? I'm not going to take apart my phone; everyone knows I'll never get it back together after that. Instead, I will find out the location by moving the phone in a circular path. Yes, moving in a circle is a type of acceleration.

I'll let you read the article to know what he did, and what you can do yourself. 

Now, the only thing left is to verify the result. Someone needs to open an iPhone 7 and confirm the location of the accelerometer (do we even know what it looks like in such a device?). Any volunteers? :)

Zz.

Bismuthates Superconductors Appear To Be Conventional

A lot of people overlooked the fact that during the early days of the discovery of high-Tc superconductors, there was another "family" of superconductors beyond just the cuprates (i.e. those compounds having copper-oxide layers). These compounds are called bismuthates, where instead of having copper-oxide layers, they have bismuth-oxide layers. Otherwise, their crystal structures are similar to the cuprates.

They didn't make that much of a noise at that time because Tc for this family of material tends to be lower than the cuprates. And, even back then, there were already evidence that the bismuthates superconductors might be "boring", i.e. the results that they have produced looked like they might be a conventional superconductor. This is supported by several experiments, including a tunneling experiment[1] that showed that the phonon density of states obtained from tunneling data matches that of the density of states obtained from neutron scattering.

Now it seems that there is more evidence that the bismuthates are conventional BCS superconductors, and it comes from ARPES experiment[2]. There have been no ARPES measurement done on bismuthates before this because it had been a serious challenge to get a single-crystal of this compound large enough to perform such an experiment. But obviously, large-enough single-crystals have been synthesized.

In this latest experiment, they look at the band structure of this compound, and extract, among others, the strong electron-phonon coupling that matches the superconducting gap. This strongly indicates that phonons are the "glue" in the superconducting mechanism for this compound.

So this adds another piece of the puzzle for the whole mystery of the origin of superconductivity in the cuprates. Certainly, having similar layered crystal structure does not discount being a conventional superconductor. Yet, the cuprates have very different behavior when we perform tunneling and ARPES experiments, and they certainly have higher Tc's.

The mystery continues.

Zz.

[1] Q. Huang et al. Nature v347, p369 (1990).
[2] CHP. Wen et al. PRL  121, 117002 (2018). https://arxiv.org/abs/1802.10507

Human Eye Can Detect Cosmic Radiation

Well, not in the way you think.

I recently found this video of an appearance of astronaut Scott Kelly on The Late Show with Stephen Colbert. During this segment, he talked about the fact that when he went to sleep on the Space Station and closed his eyes, he occasionally detected flashes of light. He attributed it to the cosmic radiation  passing through his body, and his eyes in particular.

Check out the video at minute 3:30



My first inclination is to say that this is similar to how we detect neutrinos, i.e. the radiation particles interact with the medium in his yes, either the vitreous or the medium that makes up the lens, and this interaction causes the ejection of relativistic electron and subsequently, a Cerenkov radiation. The Cerenkov radiation is then detected by the eye.

Of course, there are other possibilities, such as the cosmic particle causes an excitation of an atom or molecules when they collided, and this then caused a light emission. But Scott Kelly mentioned that these flashes appeared like fireworks. So my guess here is that it is more of a very short cascade of events, and probably the Cerenkov light scenario.

This, BTW, is almost how we detect neutrinos, especially at Super Kamiokande and all the neutrino detectors around the world. Neutrinos come into the detector, and those that interact with the medium inside the detector (water, for example), cause the emission of relativistic electrons that move faster than the speed of light inside the medium. This creates the Cerenkov radiation, and typically, the light is blueish white. It's the same glow that you see if you look in a pool of fuel rods in a nuclear reactor.

So there! You can detect something with your eyes closed!

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Where Do Elementary Particle Names Come From?

In this video, Fermilab's Don Lincoln tackles less about physics, but more about history and classification of our current Standard Model of elementary particles.



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Are Math Jokes Funny?

Let's dissect!



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US National Academies Endorse Building Electron-Ion Collider

The US National Academy of Sciences, Engineering, and Medicine have endorsed the building of an electron-ion collider in the US as the top priority for the nuclear physics community. The detailed report on the building and science of such facility can be found here.

An EIC slams electrons into protons or heavier ions to investigate the quarks and gluons inside the nucleons. A collider with high energy and luminosity—a measure of the rate at which particle collisions occur—would have the fine resolution needed to answer some of the big-picture questions cited by the committee. Those include elucidating the origin of the mass and spin of nucleons, learning how gluons hold nuclei together, and determining whether emergent forms of matter made of dense gluons exist.

Beyond nuclear science, an EIC would benefit astrophysics, high-energy physics, accelerator physics, and theoretical and computational modeling, the committee writes. Further, it is the only high-energy accelerator (excluding light sources) being considered for construction in the nation, and building it would help to maintain US expertise in accelerator and collider science. “An EIC would be a unique facility in the world and would maintain US leadership in nuclear physics,” the report states. Although there is no existing EIC, China is also considering building one.

While this facility has the word "collider" attached to it, this is not a high-energy physics facility nor will it be funded out of the high-energy physics directorate of the DOE and NSF. It will be a nuclear physics facility, just like RHIC, CEBAF, and the upcoming FRIB.

Now, if only the politicians in Washington can be convinced of the need to build such a thing... y'know, make America "great" again, even though we no longer have any high-energy physics collider on US soil.

Zz.

Don't Go To The Movies With A Physicist?

OK, no one tell any of my friends that, or I'll be going to the movie alone from now on.

This article interviews professors Maxim Sukharev and Michael Dugger of the Applied Physics Lab at Arizona State University on the physics that they noticed in the movies. The article focuses on light, as in lasers, since these scientists are experts on them.

“Lightsabers? I don’t know what those are supposed to be,” said Dugger in puzzlement, as the two settled into Siskel and Ebert mode. “If that’s a laser, particles of light would never just stop abruptly like that."

“Of course, if you see somebody on the big screen with a Russian accent doing science, that person will turn out to be a bad character,” Sukharev said with a chuckle. He completed a doctorate in the Department of High-Power Lasers in the General Physics Institute of the Russian Academy of Sciences in Moscow. “But what’s really laughable to me is when a spacecraft is shown speeding through the vacuum of deep space and yet we hear, ‘Zoom, zoom.’ 

I'm not that critical of the scientific mistakes or outrageous applications of science in the movies. They are, after all, fiction. But I can suspend my disbelief only so much, and if a movie takes too many liberties and transgression against science, then the movie is not longer that credible, because one can just make things up without regards to anything.

I can't wait for Avengers 4!

Zz.

Preaching Not To The Choir

I attended a faculty meeting last week and got to chat with faculty members from various departments. This had always been a fun occasion, especially getting to know people that I've never met before.

One of the topics of conversation inevitably was on the students that we get in our classes. As a physics instructor (and I'm sure it is relevant to other subjects as well), we get a wide range of spectrum of students, especially in courses not aimed for physical sciences/engineering students. I was then asked which group of students I prefer to teach to: the physics/chemistry/engineering students, or the life sciences/biology/pre-med/non-science students?

I actually surprised myself when, without hesitation, I replied that I prefer to teach the latter, i.e. the students who are not physical science majors. In fact, if I think about it more carefully, I prefer to teach a physics class to non-science students.

We had a lively discussion on this topic, and I have boiled it down to a simple reason. Maybe I'm a glutton for punishment, but I find it to be a challenge to run a physics class for students who do not really want to take that class, and who are there because they have to.

When you teach a physics class for physics/chemistry/engineering students, you do not need to sell the importance of the material. These students, whether they like physics or not, realize that the subject matter is relevant to their major. There is a clearer connection to their area of study to the various topics that we cover in a typical General Physics course. So stressing the importance and relevance of physics to these students is preaching to the choir.

This connection is not as apparent for life science/pre-med/non-science majors. More often than not, they take the class to fill their required electives, and given a choice, they'd rather take a different class. It also does not help that, among the students, a physics class is often touted to be one of the more difficult subjects. So for these students, there are already a lot of negative vibes towards a physics class. These students are not in the choir.

My philosophy in teaching physics to these students comprises of two factors

1. I don't need to make then love, or even like, physics. However, I want to give them an appreciation of the importance of the subject matter. You do not have to like something to know that it is still important. I find the subject of Accounting to be a bore and something I can't see myself doing. However, it doesn't mean that I do not realize the importance of accountants, especially during tax time! The students to not have to like physics, but they need to be aware of its importance, and how it has affected their lives in a very significant way.
2. I appeal to things that they already know, and show them that, whether they realize it or not, they already know a lot of physics. I ask them what will happen if I toss a ball vertically up in the air; ask then which one will boil faster: a kettle with a cup of water or a kettle with a gallon of water; query them of what will happen if I take a corner too fast while driving, especially if the road is wet or icy;, etc. Inevitably, many of the students will know what will happen next, because these are all part of their everyday experience, and this is what physics is.

When I teach a physics class for non-physical science students, I very seldom start with teaching the topic. I usually begin with either a demo, or an example of an application. If this is a class for biology/pre-med students, then the example will be from biology or medicine. It is in my experience that this type of motivation and relevancy are more effective and needed for non-physical science students to get them to pay closer attention to the physics topic being presented.

For non-science students, this, and the conceptual understanding of the physics come ahead of the mathematical description. Often, these students have very weak mathematics, and a few even have math/science phobia. So I resort to using mathematics only in the latter half of the class session after the students are comfortable with the concept being presented.

But the one important reason why my preference is to teach physics to these non-physical science students is because these are group of people who make up the majority of the population, and the group of people who may be in deciding the future of science funding, the public policy on science education, scientific results, etc. This group of people should not leave school with a distaste for physics, and for science in general. They may not want to do science, but they should be aware and appreciate why science is important, and how science plays a hugely significant role in their lives.

They may not be in the choir, but they should not be neglected and not preached to.

Zz.

Another Superconductor Scandal Brewing?

I heard about this preprint and the reported result towards the end of July, and my reaction to this type of "discovery" is "wait-and-see". In the history of superconductivity, we have had MANY of such similar claims, and many of them amounted to nothing.

However, this one seems to have taken a life and a drama of its own. SciAm has a report on what has transpired so far.

I heard about the identical background noise in the data more than a week ago when Brian Skinner posted his ArXiv comment. The first thing that came to my mind was "Oh no, this is Hendrik Schon all over again!" Turns out, I'm not the only one based on what was written in the SciAm article.

The only way this will be determined is an independent verification. That is how science works, and this is how experimental discovery works. We simply do not accept something just because someone says so.

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The Quantum Form of General Relativity's Equivalence Principle?

This is an interesting approach to one of the dilemma being faced in physics, which is trying to reconcile General Relativity, or gravity in particular, with the quantum mechanical picture. We have had String Theory and Loop Quantum Gravity, etc. going through this effort. But in this paper that just got published in Nature[1], the authors tackled it in a different way, by examining the Einstein's equivalence principle and formulating the QM's version of it, which is different than the classical version.

The ArXiv version of the paper can be found here. However, I have not verified if it is identical to the published version. The ArXiv manuscript was submitted in 2015, while the version in Nature Physics has only been published recently (2018). There doesn't appear to be any updates to this version since its submission to ArXiv.

The best part about this is that the predictions are testable (gives dirty look at String Theory).

I'll let you explore this and see what you think.

Zz.

[1] Magdalena Zych, Caslav Brukner, Nature Physics, https://www.nature.com/articles/s41567-018-0197-6

MinutePhysics Special Relativity Chapter 8

If you missed Chapter 7 of this series, check it out here.

This time, the topic is on the ever-popular Twin Paradox (which really isn't a paradox since there is a logical explanation for it).



You can compare this explanation with that given by Don Lincoln a while back. I think Don's video is clearer to me, since I can comprehend the math.

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Is Online Education Just As Good And Effective?

Rhett Allain is tackling a topic that I've been dealing with for a while. It isn't about learning things online, but rather is an online education and degree just as good and effective as brick-and-mortar education? Here, he approached this from the point of view that an "education" involves more than just the subject matter. It involves human and social interaction, and learning about things that are not related to your area. He used the analogy of chocolate chips and chocolate chip cookies:

The cookie is the on-campus experience. College is not just about the chocolate chips. It's about all of that stuff that holds the chips together. College is more than a collection of classes. It's the experience of living away from home. It's the cookie dough of relationships with other humans and even faculty. College can be about clubs and other student groups. It's about studying with your peers. College is the whole cookie.
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But wait! While we are talking about learning stuff, I have one more point to make. Don't think that you should acquire all of the skills and knowledge you need for your whole career during your time at school. You will always be learning new things, and there will always be new stuff to learn (no one learned about smartphones in the '80s). In fact, a college degree is not about job training. It's not. Really, it's not about that.

Then what is the whole chocolate chip cookie about? It's about exploring who you are and learning things that might not directly relate to a particular field. College is about taking classes that might not have anything to do with work. Art history is a great class—even if you aren't going to work in a museum. Algebra should be taken by all students—even though you probably won't need it (most humans get by just fine without a solid math background). So really, the whole cookie is about becoming more mature as a human. It's about leveling up in the human race—and that is something that is difficult to do online (but surely not impossible).

I have no issue with these points. However, we can even go right down to the jugular with this one instead of invoking some esoteric plea for a well-rounded education and social skills. There are compelling evidence that online-only lessons are not as effective and efficient as in-person, in-class lessons, if the latter is done properly.

I will use the example of the effectiveness of peer-instruction method as introduced by Harvard's Eric Mazur. Here, he showed how active learning, instead of passive learning, can be significantly more effective for the students. In such cases, student-to-student interactions are a vital part of learning, with the instructor serving as a "guidance counselor".

This is not the only example where active learning is more favorable than passive learning. There have been other students that have show significant improvement in students' understanding and grasp of the material when they are actively engaged in the learning process. Active learning is something that hasn't been done and maybe can't be easily done with online lessons, and certainly not from simply watching or reading the material online.

So forget about honing your social skills or learning about art history. Even the subject matter that you wish to understand may be more difficult to comprehend when you do this by yourself in an online course. There are enough evidence to support this, and it is why you shouldn't be surprised if you struggle to understand the material that you are trying to learn by yourself.

Zz.

Loop Quantum Gravity

This is one of those still-unverified theory that tries to reconcile quantum mechanics with General Relativity. I'm not in this field, so I have no expertise in it. But I know that for many people who have read about it, they are aware of String theory and it's competition, Loop Quantum Gravity.

In this video, Fermilab's Don Lincoln tries to explain LQG to the masses.



Keep in mind that this idea is still lacking in experimental support. The gamma ray burst observation that he mentioned in the video has been highlighted here quite a while back.

Without experimental verification, both String theory and LQG continue to have issues with their credibility as a science.

Zz.

Ban Cellphone Use In Classrooms?

First of all, let me state my policy on the use of electronic devices (mobile phones, tablets, laptop computers, etc.) in my classrooms. I do not have an outright ban (other than during exams and quizzes) during class, but they can't be use in an intrusive manner that disrupts the running of the class. So no making phone calls, etc. So far, I haven't had any issues to change that policy. Many of my colleagues do have an outright ban on the use of these devices during class.

Now, a few weeks ago, I came across this paper. They studied students who used these devices for non-class related purposes during class. They found that the distraction of these devices, in the end, affects the average class grade that the student received at the end of the course (they were psychology courses). The distracted students, on average, scored half a grade lower than those that are in classes that ban the use of these devices for non-class related purposes.

But what is also surprising is that there was a collateral damage done onto students who were in the same class as these distracted students, but they themselves did not use these devices during class.

Furthermore, when the use of electronic devices was allowed in class, performance on the unit exams and final exams was poorer for students who did not use electronic devices during the class as well as for the students who did use an electronic device. This is the first-ever finding in an actual classroom of the social effect of classroom distraction on subsequent exam performance. The effect of classroom distraction on  exam performance confirms the laboratory finding of the social effect of distraction (Sana et al.,2013). 

 So this is like second-hand smoking.

The good thing about this is that, I can now tell my students that, while I allow their use in the class during lessons, there is evidence that if they choose to use them, their grades may suffer. I may even upload this paper to the Learning Management System. However, because of the collateral damage that might be done to other students who do not use these devices during class, I am seriously rethinking my policy, and am considering imposing an outright ban on the non-class related use of these devices during my lessons.

If you teach, what is your experience with this?

Zz.

APS's Don't Drink And Derive T-Shirt

I was cleaning my closet (I do that now and then) and came across this old shirt from way back when. This was bought during the 1999 APS March Meeting in Atlanta, GA, which celebrated the 100th anniversary of the APS.

When I first saw it, I said to the person at the counter that all the formulae are wrong. And then, duh, it suddenly hit me why and I got it. So of course, I had to buy it.

I haven't worn it in ages, because of a small tear on the front. But I'll probably start wearing it around the house, especially if I'm working on the yard.

This t-shirt is the opposite of the one I bought while I was at the Kennedy Space Center in Cape Canaveral, FL. That t-shirt had all the correct formulae and shows my nerdy self whenever I wear it.

😁

Zz.