Friday, October 12, 2018

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.



Zz.

Friday, October 05, 2018

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.

Zz.

Tuesday, October 02, 2018

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.

Zz.

Saturday, September 29, 2018

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.

Wednesday, September 26, 2018

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.

Tuesday, September 25, 2018

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

Sunday, September 16, 2018

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.

Friday, September 14, 2018

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

Thursday, September 13, 2018

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!

Zz.

Thursday, August 30, 2018

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.



Zz.

Wednesday, August 29, 2018

Monday, August 27, 2018

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.

Saturday, August 25, 2018

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.

Tuesday, August 21, 2018

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.

Monday, August 20, 2018

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.

Zz.

Friday, August 17, 2018

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

Tuesday, August 14, 2018

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.

Zz.

Thursday, August 09, 2018

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.

Wednesday, August 08, 2018

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.

Tuesday, August 07, 2018

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.

Sunday, August 05, 2018

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.

Sunday, July 29, 2018

Looking for Psychics To Teach Physics

I know, I know, this is trivial, but it is so hysterically funny!

Someone pointed this out to me and I couldn't stop giggling. So of course I have to share it with all of you! This is a jobs ad from Kennedy-King College, one of the City Colleges of Chicago. They are looking for someone to be an adjunct physics faculty member to, presumably, teach physics.

I'm doing a screen capture here, because I expect someone there will see this and make corrections to it soon... or maybe not!


I am guessing that two different people did this, because the category for the job is correct (circled in green), and the required qualification is also spelled correctly, but then it goes hysterically wrong in the job description. It says:

ADJUNCT FACULTY PSYCHICS/ PART-TIME
CITY COLLEGES OF CHICAGO, KENNEDY-KING COLLEGE

Kennedy-King College is currently seeking a part-time Faculty to teach Psychics during the Fall  2018 semester. 

Well of course they're looking for Psychics. This is because they want a part-time Faculty to teach it during this upcoming Fall semester!

Dear Kennedy-King College, you may want to have someone proof-read your ad. The spell-check would not have flagged you for this hilarious error. And for an academic institution, this is an embarrassing boo-boo. Having psychics to teach physics is like having heretics coming in to teach Sunday School.

Zz.

Friday, July 27, 2018

Gravitational Red Shift Shows That Einstein Is Right Once More!

Albert Einstein's General Relativity is 3-for-3 this year so far! We already had GR passing its first galactic-scale test, and then we had the verification of the strong equivalence principle. This time, observation of light from a star in our Milky Way passing near a supermassive black hole has shown the predicted gravitational red shift. Holy Cow, Batman!

The team compared the position and velocity measurements from GRAVITY and SINFONI respectively, along with previous observations of S2 using other instruments, with the predictions of Newtonian gravity, general relativity and other theories of gravity. The new results are inconsistent with Newtonian predictions and in excellent agreement with the predictions of general relativity.
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The new measurements clearly reveal an effect called gravitational redshift. Light from the star is stretched to longer wavelengths by the very strong gravitational field of the black hole. And the change in the wavelength of light from S2 agrees precisely with that predicted by Einstein’s theory of general relativity. This is the first time that this deviation from the predictions of the simpler Newtonian theory of gravity has been observed in the motion of a star around a supermassive black hole.

A copy of the paper (or maybe a preprint) can be found here.

It bears repeating: the more they test it, the more convincing it becomes!

Zz.

Thursday, July 26, 2018

The Physics Of Baking Pizza

For those who are purist and prefer the thin-crust, Neopolitano-style pizza, this one might be right up your alley.

This preprint on ArXiv tackles the question on whether baking such pizza is better done in a stone over rather than the standard metal ovens. Which one do you think will win?

Stone ovens heat up to very high temperatures, higher than typical home ovens. But ceramic or stone surface also has low thermal conductivity while having a high specific heat. It means that it retains heat longer and does not cause the dough to burn. It is why this is also the preferred way to bake rustic, crusty bread.

I guess we all just have to build a brick pizza oven in our backyards! :)

Zz.

Saturday, July 21, 2018

University Research Made Your Smartphone

A lot of people are ignorant of the fact that a smartphone, or any device, for that matter, is a result of research work done by many people and organization and over a very long time. The iPhone was not solely the work of Apple. Apple benefited from all the scientific and technological progress and accumulation of knowledge to be able to produce such a device. These knowledge and progress are often done many years ago by researchers who work on a particular topic that eventually found an application in a smartphone.

I found this interesting website that highlights how research that originated out of universities under various funding agencies, resulted in the smartphone that we currently have. It lists one aspect of each of the major component of a smartphone that had it initial incubation in university research. A lot of these research work is physics-related. It is why I continue to say that physics isn't just the LHC or the Higgs or the blackhole. It is also your MRI, your iPhone, your GPS, etc...

If you need more background info on this, check out this page.

Zz.

Friday, July 20, 2018

Feynman's Lost Lecture

If you didn't buy the book or didn't read about it, here's a take on Feynman's Lost Lecture, presented by a guest on Minute Physics video.



Zz.

Burton Richter Dies at 87

Another giant in our field, especially in elementary  particle physics, has passed away. Burton Richter, Nobel Laureate in physics, died on July 18, 2018.

Richter’s Nobel Prize-winning discovery of the J/psi subatomic particle, shared with MIT’s Samuel Ting, confirmed the existence of the charm quark. That discovery upended existing theories and forced a recalibration in theoretical physics that reverberated for years. It became known as the “November Revolution.” One Nobel committee member at the time described it as “the greatest discovery ever in the field of elementary particles.”

He would be shortchanged if all the public ever remembers him is for his Nobel Prize discovery, because he did a whole lot more in his lifetime.

Zz.

Thursday, July 19, 2018

MinutePhysics Special Relativity Chapter 7

If you missed Chapter 6 of this series, check it out here.

In this chapter, the concept of spacetime intervals is presented. This is where we have "proper time" and "proper length".



Zz.

Wednesday, July 18, 2018

Khan Academy's Photoelectric Effect Video Lesson

A lot of people use Khan Academy's video lessons. I know that they are quite popular, and I often time get asked about some of the material in the video, both by my students and also in online discussions. Generally, I have no problems with their videos, but I often wonder who exactly design the content of the videos, because I often find subtle issues and problems. It is not unusual for me to find that they were inaccurate in some things, and these are usually not the type of errors that say, an expert in such subjects would make.

I was asked about this photoelectric effect lesson by someone about a month ago. I've seen it before but never paid much attention to it till now. And now I think I should have looked at it closer, because there are a couple of misleading and inaccurate information about this.

Here is the video:



First, let's tackled the title here, because it is perpetuating a misconception.

Photoelectric effect | Electronic structure of atoms
First of all, the photoelectric effect doesn't have anything to do with "structure of atoms". It has, however, something to do with the structure of the solid metal! The work function, for example, is not part of an atom's energy level. Rather, it is due to the combination of all the atoms of the metal, forming this BANDS of energy. Such bands do not occur in individual atoms. This is why metals have conduction band and atoms do not.

We need to get people to understand that solid state physics is not identical to atomic/molecular physics. When many atoms get together to form a solid, their behavior as a conglomerate is different than their behavior as individual atoms. For many practical purpose, the atoms lose their individuality and instead, form a collective property. This is the most important message that you can learn from this.

And now, the content of the video. I guess the video is trying to tackle a very narrow topic on how to use Einstein's equation, but they are very sloppy on the language that they use. First of all, if you don't know anything else, from the video, you'd get the impression that a photon is an ordinary type of "particle", much like an electron. The illustration of a photon reinforced this erroneous picture. So let's be clear here. A "photon" is not a typical "particle" that we think of. It isn't defined by its "size" or shape. Rather, it is an entity that carries a specific amount of energy and momentum (and angular momentum). That's almost all that we can say without getting into further complications of QED.

But the most serious inaccuracy in the video is when it tackled the energy needed to liberate an electron from the metal. This energy was labelled as E_0. This was then equate to the work function of the metal.

E_0 is equal to the work function of the metal ONLY for the most energetic photoelectrons. It is not the work function for all the other photoelectrons. Photoelectrons are emitted with a range of energies. This is because they came from conduction electrons that are at the Fermi energy or below it. If they came from the Fermi energy, then they only have to overcome the work function. These will correspond to the most energetic photoelectrons. However, if they come from below the Fermi energy, then they have to overcome not only the work function, but also the binding energy. So the kinetic energy of these photoelectrons are not as high as the most energetic ones. So their "E_0" is NOT equal to the work function.

This is why when we have students do the photoelectric effect experiments in General Physics courses, we ask them to find the stopping potential, which is the potential that will stop the most energetic photoelectrons from reaching the anode. Only the info given by these most energetic photoelectrons will give you directly the work function.

Certainly, I don't think that this will affect the viewers ability to use the Einstein equation, which was probably the main purpose of the video. But there is an opportunity here to not mislead the viewers and make the video tighter and more accurate. It also might save many of us from having to explain to other people when they tried to go into this deeper (especially students of physics). For a video that is viewed by such a wide audience, this is not the type of inaccuracies that I expect for them to have missed.

Zz.

Multiverse

In this article, Ethan Siegel valiantly tried to explain, in simple language, what "multiverse" is within the astrophysical/cosmological context:

Inflation doesn't end everywhere at once, but rather in select, disconnected locations at any given time, while the space between those locations continues to inflate. There should be multiple, enormous regions of space where inflation ends and a hot Big Bang begins, but they can never encounter one another, as they're separated by regions of inflating space. Wherever inflation begins, it is all but guaranteed to continue for an eternity, at least in places.

Where inflation ends for us, we get a hot Big Bang. The part of the Universe we observe is just one part of this region where inflation ended, with more unobservable Universe beyond that. But there are countlessly many regions, all disconnected from one another, with the same exact story.

Unfortunately, as is the problem with String theory, none of these have testable prediction that can push it out of the realm of speculation and into being a true science.

Zz.

Tuesday, July 17, 2018

94 Aluminum Pie Pans On A Van de Graaf

What happens when you put 94 aluminum pie pans on a Van de Graaf? Sometime you do things just because it is darn fun!



Now let's see if you can offer your own explanation for this silly thing! :) Happy 10th Anniversary on YouTube, Frostbite Theater!

Zz.

Monday, July 16, 2018

Neutrinos Come Knocking For Astronomy

I feel as if these are the golden years for astronomy and astrophysics.

First there was the discovery of gravitational waves. Then a major astronomical event occurred, and we were able to detect it using the "old" standard technique via EM radiation, and via the detection of gravitational waves from it. So now astronomy has two different types of "messengers" to tell us about such events.

Well now, make way for a third messenger, and that is ubiquitous neutrinos. Two papers published in Science last week detected neutrinos (along with the accompanying EM radiation) from a "blazer". The neutrino detection part was made predominantly at IceCube detector located in the Antarctica.

Both papers are available as open access here and here. A summary of this discovery can be found at PhysicsWorld (may require free registration).

Zz.

Friday, July 13, 2018

The Most Significant Genius

No, not Einstein, or Feynman, or Newton. Fermilab's Don Lincoln celebrates the hugely-important contribution of Emmy Noether.



I have highlighted this genius previously, especially in connection to her insight relating symmetry to conservation laws (read here, here, and here).

Zz.

Wednesday, July 11, 2018

First Human Scanned By Spectral X-Ray Scanner

Chalk this up to an application of high-energy physics in the medical diagnostic field. The first human has been scanned by a new type of x-ray scanner (registration required to read article at this moment).

The MARS scanner uses Medipix3 technology developed at CERN to produce multi-energy images with high spatial resolution and low noise. Medipix is a family of read-out chips originally developed for the Large Hadron Collider and modified for medical applications.

The Medipix3 detector measures the energy of each X-ray photon as it is detected. This spectral information is used to produce 3D images that show the individual constituents of the imaged tissue, providing significantly improved diagnostic information.

I'll repeat this, maybe to those not in the choir, that many of the esoteric experiments that you think have no relevance to your everyday lives, may turn out to be the ones that might save your lives, or the lives of your loved ones, down the road. So think about this when you talk to your elected political representatives when it comes to funding basic science.

Zz.

Thursday, July 05, 2018

Einstein Is Right Again!

... or rather, General Relativity passed another test.

This is on the heels of the first ever verification of GR at the galactic scale. This time it is a test of GR's strong equivalence principle involving a neutron star and two white dwarfs (no, not the kind from that Snow White movie).[1]

Archibald and colleagues’ study breaks new ground because the gravitational energy inside a neutron star can account for as much as 20% of the body’s mass. The authors’ results therefore imply that the accelerations of gravitational energy and matter differ by no more than a few parts per 105 — a tenfold improvement over the bound from lunar laser ranging.

More importantly, the authors have provided what is known as a strong-field test of general relativity. Unlike the Solar System, for which Einstein’s theory predicts only small deviations from Newton’s theory of gravity, the motion of a neutron star in a gravitational field invokes full general relativity in all its complex glory. Einstein’s theory passes this strong-field test with flying colours.

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

Zz.

[1] A.M. Archibald et al., Nature, 559p73 (2018).

Tuesday, July 03, 2018

What Type of Physicist Are You?

... leader, successor, or toiler?

A new bibliometric study has found that authors can be roughly grouped into three categories: lead scientists who are already prominent in their fields, successors who are early career scientists, and toilers, which are those who do a lot of the dirty work but aren't going anywhere.

When looking at the citation data for mathematicians, psychologists and physicists, the authors identified three broad clusters that are “loosely based” on how the citations per year changes over time. Leaders tend to be experienced scientists who are widely recognized in their fields, which results in an annual citation increase. The successors tend to be early-career scientists who have had a surge in their citations in recent years. Toilers, meanwhile, may have a high citation count, but this stays mostly constant and may even drop slightly.

Not sure of the significance of this study, but hey, it's another criteria to classify people!

Zz.

Saturday, June 23, 2018

Super Kamiokande and Extremly Pure Water

This is a rather nice overview of Super Kamiokande, a neutrino detector in Japan. It has produced numerous ground-breaking discoveries, including the confirmation of neutrino oscillation many years ago. Unfortunately, the article omitted an important incident at Super-K several years ago when there was a massive implosion of the phototubes.

The article has an interesting information that many people might not know about extremely pure water, the type that is used to fill up the detector tank.

In order for the light from these shockwaves to reach the sensors, the water has to be cleaner than you can possibly imagine. Super-K is constantly filtering and re-purifying it, and even blasts it with UV light to kill off any bacteria.

Which actually makes it pretty creepy.

"Water that's ultra-pure is waiting to dissolve stuff into it," said Dr Uchida. "Pure water is very, very nasty stuff. It has the features of an acid and an alkaline."
.
.
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Another tale comes from Dr Wascko, who heard that in 2000 when the tank had been fully drained, researchers found the outline of a wrench at the bottom of it. "Apparently somebody had left a wrench there when they filled it in 1995," he said. "When they drained it in 2000 the wrench had dissolved." 

In other words, such pure, deionized water is not something that you want to drink.

And this leads me to comment on this silly commercial of PUR drinking water filter. It showed an ignorant public complaining about lead in the drinking water, even though he was told that the amount is below the safety level.



A drinking water contains a lot of other dissolved minerals, any one of which, above a certain limit, can be dangerous. Even that PUR commercial can only claim that it can REDUCE the amount of lead in the drinking water, not completely removed it. It will not be zero. So that guy should continue complaining about lead even with PUR filter.

If this person in the commercial is representing the general public, then the general public needs to be told that (i) you'll never be able to get rid completely of all contaminants in drinking water and (ii) pure water will dissolve your guts! This is why we set safety levels in many things (360 mrem of radiation per year, for example, is our acceptable, normal background radiation that we receive).

Zz.

Friday, June 22, 2018

General Relativity Passes Its First Galactic Test

Ethan Siegel is reporting the latest result of a test of General Relativity at the galactic scale.[1]

This effect of gravitational lensing, which occurs in both strong and weak variants, represents the greatest hope we have of testing General Relativity on scales larger than the Solar System. For the first time, a team of scientists led by Tom Collett performed a precise extragalactic test of General Relativity, and Einstein's theory passed with flying colors.

This new result also puts a strong damper on alternative theories of gravity, such as MOND.

For the first time, we've been able to perform a direct test of General Relativity outside of our Solar System and get solid, informative results. The ratio of the Newtonian potential to the curvature potential, which relativity demands be equal to one but where alternatives differ, confirms what General Relativity predicts. Large deviations from Einstein's gravity, therefore, cannot happen on scales smaller than a few thousand light years, or for masses the scale of an individual galaxy. If you want to explain the accelerated expansion of the Universe, you can't simply say you don't like dark energy and throw Einstein's gravity away. For the first time, if we want to modify Einstein's gravity on galactic-or-larger scales, we have an important constraint to reckon with.

This is definitely a big deal of a result.

Zz.

[1] T.E. Collett et al., Science v.360, p.1342 (2018).

Friday, June 15, 2018

Is Theoretical Physics Wasting Our Best Minds?

Before you continue reading this, let me be very clear right off the bat that there are TWO separate issues here that I will be discussing, and they are thinly connected simply by the over-general reference of "theoretical physics" made by the author of the article that I will be citing.

In this Forbes article, Ethan Siegel highlights the main point made by Sabine Hossenfelder in her book "Lost In Math". Siegel not only pointed this out, but also did an in-depth description leading up to the "naturalness" philosophy that is prevalent in the esoteric fields of physics such as string, etc.

If you are a theoretical particle physicist, a string theorist, or a phenomenologist — particularly if you suffer from cognitive dissonance — you will not like this book. If you are a true believer in naturalness as the guiding light of theoretical physics, this book will irritate you tremendously. But if you're someone who isn't afraid to ask that big question of "are we doing it all wrong," the answer might be a big, uncomfortable "yes." Those of us who are intellectually honest physicists have been living with this discomfort for many decades now. In Sabine's book, Lost In Math, this discomfort is now made accessible to the rest of us.

Certainly this is thought-provoking, and it isn't something I disagree about. For science to give up on empirical evidence, and simply pursue something that looks "natural" or "beautiful" is dangerous and verging on being a religion. So my feelings are consistent with what has been said in the article.

Now comes the other part of the issue. It has always been my pet peeve when someone over-generalize physics as being predominantly being "high-energy physics, astrophysics, string theory, etc...", i.e. the esoteric fields of study. In this case, "theoretical physics" certainly is NOT dominated by those fields. There are theoretical studies in condensed matter physics, atomic/molecular physics, medical physics, accelerator physics, etc... etc., i.e. fields of studies that are certainly not esoteric, have lots of practical applications, etc.

In fact, I would argue that the esoteric fields of physics represents the MINORITY in terms of the number of practicing physicists that we have around the world. As a zeroth-order approximation of this claim, I decided to look at the members of the APS. The APS Divisions correspond to the number of members who declared themselves to be in a certain field within physics. Note that not all members made the declaration, and it is also not uncommon for a member to declare more than one division.


First of all, 79% of APS members are accounted for in this chart for the 2018 membership. Now, what is the percentage of members within the so-called esoteric fields of Astrophysics, Gravitation, and Particles and Fields? 14.9%. Even if you include Nuclear Physics into this, it will come up to 19.8%

Now, forget about theoretical or experimental. Can 19.8% represents ALL of physics? The fields of studies that a lot of people associate physics with are done by ONLY 19.8% of physicists! Using them, one will get a severely inaccurate representation of physics and physicists.

In fact, if you look at the fields more commonly associated with the physics of materials (condensed matter physics and Materials Physics), we get 18.2%, almost as big as Astrophysics, Gravitation, Particles and Fields, and Nuclear Physics combined! Condensed matter physics alone dwarfs other fields, being almost twice as big as the next division, which is Particles and Fields.

But what is more important here is that outside of the 19.8% of physicists in these esoteric fields, an overwhelming percentage of physicists (59.2%) are in fields of studies that are associated with practical applications of physics. So if you were to bump randomly into a physicist, chances are, you will find someone who works in a field related to something of practical importance and NOT a high-energy physicist, a nuclear physicist, etc.

This is my round-about way of complaining that Ethan Siegel article should not be a damnation of "theoretical physics" in general, because the overwhelming percentage of theoretical physics is NOT about these esoteric topics that have been mentioned in his article. Rather, theories in other parts of physics rely very heavily on empirical observations and verification, i.e. the good and tested way of doing science. In those areas, we are definitely NOT wasting our best minds!

A while back, I said that physics is not just the LHC. It is also your iPhone. Even that requires modification. We should say that physics is predominantly your iPhone, with only a smidgen of LHC added as garnishing. That is a more accurate representation of the field as a whole.

Zz.

Wednesday, June 13, 2018

MinutePhysics Special Relativity Chapter 6

If you missed Chapter 5 of this series, check it out here.

Here's Chapter 6 of the Minute Physics series on Special Relativity. This time, they are tackling a topic that I see being asked numerous times : velocity addition. ("If I'm traveling close to the speed of light and I turn on my flashlight.....").

I know that this topic has been covered here many times, but it is worth repeating, especially since someone may have missed the earlier ones.



Zz.

Tuesday, June 12, 2018

Work Begins On FACET II at SLAC

The upgrade to FACET facility at SLAC promises to improve the beam electron beam quality at the accelerator facility. One of the direct benefits of this upgrade is further advancement in the plasma wakefield accelerator technique. This technique has previously shown to be capable of producing very high accelerating gradient and thus, has the potential to produce accelerating structures that can accelerate charged particles to higher energies over shorter distances.

Now, when you read the press release that I linked above, make sure you are very clear on what it said. The FACET II facility is NOT a facility that operates using this "plasma wakefield" technique. It is a facility that produces an improved electron beam quality, both in energy and emittance, among other things. This electron beam (which is produced via conventional means) is THEN will be used in the study of this wakefield accelerator technique.

The project is an upgrade to the Facility for Advanced Accelerator Experimental Tests (FACET), a DOE Office of Science user facility that operated from 2011 to 2016. FACET-II will produce beams of highly energetic electrons like its predecessor, but with even better quality. These beams will primarily be used to develop plasma acceleration techniques, which could lead to next-generation particle colliders that enhance our understanding of nature’s fundamental particles and forces and novel X-ray lasers that provide us with unparalleled views of ultrafast processes in the atomic world around us.

So read carefully the "sequence of events" here and not get too highly distracted by thinking that FACET II is a "novel X-ray laser, etc..." facility. It isn't. It is a facility, an important facility, to develop the machines that will give us more knowledge to make all these other capabilities.

Consider this as my public service to you to clarify a press release! :)

Zz.

Wednesday, May 30, 2018

What Is A Plasma?

I love the Chicago's Museum of Science and Industry (MSI). In fact, I am a member and a donor to the museum. So let's get that out of the way first.

Secondly, I know how difficult it is to explain scientific concepts to the public. The need to use simple words and terminology, AND, make it accurate can be a daunting task.

Still, I can't help but be a bit disappointed by this sign that I saw at MSI this past week. Granted, this was in the gift store, but still, for an institution promoting science, this falls a bit short.

The sign accompanies one of those "plasma arc ball" thingy that they were selling:

Here's what the sign says:

A plasma is a gas that has been heated to extremely high temperatures. At these high temperatures, the atoms are moving so fast that they lose their electrons, creating ionized particles. The electrons and ionized particles jump from one place to another to try and get as far away from each other as possible, creating a "lightening" effect.

There are problems with this description.

1. A plasma need NOT be only a gas that has been heated to high temperatures. I can create a plasma by blasting gas atoms with energetic electrons. In fact, when you have an electrical discharge, that is essentially what happens. The gas has not been heated by any means. So there are other means of creating a plasma beyond just heating. So a plasma is NOT defined as ".... a gas that has been heated to high temperatures...."

2. At high temperatures, the atoms lose their electrons not because they are moving "so fast". They lose their electrons because when they move "so fast", they also collide harder against other atoms, and collide more frequently. This tend to give each atom the energy to knock off one or more electrons, thus causing it to be ionized. Atoms do not lose electrons simply because they are moving "so fast".

3. The description that "... The electrons and ionized particles jump from one place to another to try and get as far away from each other as possible, creating a "lightening" effect.... " is extremely puzzling and, frankly, irrelevant to the description of what a plasma is. In fact, if you think about it, when an atom is ionized, it has a net positive charge. An electron, having a negative charge, would tend to want to go back to the positively-charged ion. So why would they want to "... get as far way from each other as possible..."?

4. The last part is trying to describe the creation of an electric discharge or an arc. This is superfluous, and is not part of the definition of a plasma. An electric discharge is a form of a plasma, but a plasma is not JUST an electrical discharge.

So what is a plasma? If, say, someone at MSI who isn't a physicist needed to make this sign, and Googled it, he/she will see several definitions. I'll pick one (the bold is mine).

Plasma is the fourth state of matter. Many places teach that there are three states of matter; solid, liquid and gas, but there are actually four. The fourth is plasma. To put it very simply, a plasma is an ionized gas, a gas into which sufficient energy is provided to free electrons from atoms or molecules and to allow both species, ions and electrons, to coexist. The funny thing about that is, that as far as we know, plasmas are the most common state of matter in the universe. They are even common here on earth. A plasma is a gas that has been energized to the point that some of the electrons break free from, but travel with, their nucleus. Gases can become plasmas in several ways, but all include pumping the gas with energy. A spark in a gas will create a plasma. A hot gas passing through a big spark will turn the gas stream into a plasma that can be useful. Plasma torches like that are used in industry to cut metals. The biggest chunk of plasma you will see is that dear friend to all of us, the sun. The sun's enormous heat rips electrons off the hydrogen and helium molecules that make up the sun. Essentially, the sun, like most stars, is a great big ball of plasma.

The bold sentence, to me, is a sufficient definition of a plasma to be given to the general public. An ionized gas can be made up of equal parts of positive ions and electrons, unequal parts of positive ions and electrons, all ions, or all electrons, i.e. there are free charges floating around at a given time. This, to me, is a more accurate definition than what the MSI sign says.

I'm not sure how many of MSI guests paid attention to the sign or learned what a plasma is from that sign. But I hope those responsible for such signs pay closer attention to the accuracy of the info that they put out.

Zz.

Tuesday, May 29, 2018

MinutePhysics Special Relativity Chapter 5

If you missed Chapter 4 of this series, check it out here.

In this chapter, the topic of "time dilation" and "length contraction" is tackled.



Zz.

Wednesday, May 23, 2018

That Impossible EM Drive Might Be ..... Impossible After All!

Crackpots were just having a field day when NASA announced several years ago of an EM propulsion that somehow violates momentum conservation laws. Now comes a more careful experiment from a group that tried to reproduce this result, and the outcome is rather hysterical.

The team built their EM drive with the same dimensions as the one that NASA tested, and placed it in a vacuum chamber. Then, they piped microwaves into the cavity and measured its tiny movements using lasers. As in previous tests, they found it produced thrust, as measured by a spring. But when positioned so that the microwaves could not possibly produce thrust in the direction of the spring, the drive seemed to push just as hard.

And, when the team cut the power by half, it barely affected the thrust. So, it seems there’s something else at work. The researchers say the thrust may be produced by an interaction between Earth’s magnetic field and the cables that power the microwave amplifier.

So far, this has only been reported in a conference proceeding, which is linked in the New Scientist article (you will need ResearchGate access).

I'm sure there will be many more tests of this thing soon, but I can't help but chuckle at the apparent conclusion here.

Zz.

Monday, May 21, 2018

Graphene Might Could Kill Off Cancer Cells

Here's another example of how something that came out of physics is now finding an application in other fields, namely the medical field. Graphene, which was discovered quite a while back and won its two discoverers the Nobel Prize in Physics, has now found a possible application at fighting cancer.

It began with a theory -- scientists at the University of California knew graphene could convert light into electricity, and wondered whether that electricity had the capacity to stimulate human cells. Graphene is extremely sensitive to light (1,000 times more than traditional digital cameras and smartphones) and after experimenting with different light intensities, Alex Savchenko and his team discovered that cells could indeed be stimulated via optical graphene stimulation."

I was looking at the microscope's computer screen and I'm turning the knob for light intensity and I see the cells start beating faster," he said. "I showed that to our grad students and they were yelling and jumping and asking if they could turn the knob. We had never seen this possibility of controlling cell contraction."

The source paper can be found here, and it is open-access.

Again, this is why it is vital that funding in basic physics continues at a healthy pace. Even if you do not see the immediate application or benefit from many of these seemingly esoteric research, you just never know when any of the discovery and knowledge that are gained from such areas will turn into something that could save people's lives. We have seen such examples NUMEROUS times throughout history. Unfortunately, people are often ignorant at the origin of many of the benefits that they now take for granted.

Zz.

Thursday, May 17, 2018

Noether Theorem And Symmetries

This is not something new that I'm highlighting on this blog. I've mentioned a link to Emmy Noether theorem before in this post, and also highlighted a history of her work here. However, I think that there is no such thing as too much publicity on Emmy Noether, because she deserves to be remembered and admired through eternity for her accomplishments and insights.

This video tries to explain the significance of her work connecting conservation laws with symmetry principles.



However, I think that if I were a layperson, I'd miss the important point in this video. So here is the takeaway message if you want one:

Everything that we see and every behavior of our universe can be traced to some conservation laws. Each conservation law is a manifestation of some underlying symmetry of our universe.

This is the insight, and a very important insight, that Noether brought to the table, and it was revolutionary to physics. These symmetries are what we currently have as the most fundamental description of the universe that we live in.

Watch this video, and read the links that I gave above, several times if you must, because you owe it to yourself to know about this person and her immense effect on our understanding of our world.

Zz.

Relativistic Velocity Addition

If I get $1 for every time someone asks me "If I'm moving in a spaceship and I turn on my flash light...."

Here's Don Lincoln's lesson on relativistic velocity addition:



Zz.

Wednesday, May 16, 2018

RIP David Pines

This is another one of the physicist who is a giant in his field, but relatively unknown to the general public.

Renowned condensed matter theorist David Pines passed away on May 3, 2018 at the age of 93. I practically read his text (co-authored by Nozieres) on Fermi Liquid from cover to cover while I was a graduate student. In fact, he was on the cusp of a Nobel Prize when he was working with John Bardeen at UIUC. They published a paper on the electron-phonon interaction in superconductors in 1955, a paper that many thought was the precursor to the subsequent BCS Theory paper in 1957. Unfortunately, he left UIUC, and Bob Schrieffer took over his work on this, which ultimately led to the BCS theory and the Nobel prize.

This did not diminished his body of work throughout his life. He certainly was a main figure during the High-Tc superconductivity craze of the late 80's and 90's. His 1991 PRL paper with Monthoux and Balatsky and the 1992 PRL paper with Monthoux, both on the spin-fluctuation effect as the possible "glue" in the cuprate superconductors, where ground-breaking and highly cited.

His contribution to this body of knowledge will have a lasting impact.

Zz.

Monday, May 14, 2018

Dark Energy Levels Not Too Constrained For Star Formation

I've always had a bit of a problem with the anthropic scenario of our universe, i.e. the idea that we are living in a universe JUST fined-tuned to allow us to exist. My problem isn't with the observations so far, but rather how much people are already thinking that this must be true, the data are set, and that we can run away with it. Certainly many people outside of cosmology have tried to spin this into whatever directions that they want.

So when news like this comes along, I just want to yell "I told you so!". It is not that I agree or disagree with the conclusion, but it is to point out that in our attempt to understand all of this, our knowledge is still in its infancy, and that we really don't know enough yet to be able to say things one way or the other on many of the big issues. We do have a fuzzy idea on what direction it is going, but in a number of things and observations, more is required to understand things even better.

The new studies ran the simulation on the star formation of our universe against the amount of dark energy in our universe. They can, to put it crudely, dial in various level of dark energy in their simulations. They found that there is a wider range than initially expected for our present universe to form, i.e. it is not in a very narrow range that was thought of. So keeping everything relatively the same, we could see this present universe that we're in for a large range of dark energy.

The simulations allowed the researchers to adjust the amount of dark energy in the universe and watch what happened.

The results were a surprise. The research revealed that the amount of dark energy could be increased a couple of hundred times – or reduced equally drastically – without substantially affecting anything else.

So for dark energy, the parameter is not as "fine tuned" as one expected.

Zz.

https://academic.oup.com/mnras/advance-article-abstract/doi/10.1093/mnras/sty846/4963750?redirectedFrom=fulltext

https://academic.oup.com/mnras/advance-article-abstract/doi/10.1093/mnras/sty879/4966995?redirectedFrom=fulltext

Friday, May 11, 2018

Not Insignificant Blunder on John Bardeen by UK's "Express"

OK, so to commemorate Feynman's 100th birthday, the UK's Daily Express decided to do a "Top 10" about physics. I thought this was going to be a fun read when I encountered #8 on the list:


It said "8. The only double winner is John Bardeen: 1956 (transistors) and 1972 (MRI images)"

Nope! The 1972 Nobel Prize in physics to Bardeen was for the theory of superconductivity. He is the "B" in BCS theory!

The Nobel Prize for MRI imaging was given in 2003 to Paul Lauterbur and Peter Mansfield.

How come news organizations don't do fact checking anymore nowadays?

Zz.

Happy 100th Birthday, Richard Feynman!

Today, May 11, 2018, is the 100th birthday of physicist and Nobel Laureate Richard Feynman. He was born on May 11, 1918.

This article covers the important commemoration of Feynman's birthday, ranging from the event at CalTech all the way to Tuva in remote Russia.

Zz.

Thursday, May 10, 2018

The Big Bell Test

Hey, I'm missing all the fun here!

A new paper to be published in Nature appears to have closed the "freedom-of-choice" loophole in the standard Bell-type experiment.

The BIG Bell Test asked human volunteers, known as Bellsters, to choose the measurements, in order to close the so-called "freedom-of-choice loophole" -- the possibility that the particles themselves influence the choice of measurement. Such influence, if it existed, would invalidate the test; it would be like allowing students to write their own exam questions. This loophole cannot be closed by choosing with dice or random number generators, because there is always the possibility that these physical systems are coordinated with the entangled particles. Human choices introduce the element of free will, by which people can choose independently of whatever the particles might be doing.
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Participants contributed with more than 90 million bits, making possible a strong test of local realism, as well as other experiments on realism in quantum mechanics. The obtained results strongly disagree Einstein's worldview, close the freedom-of-choice loophole for the first time, and demonstrate several new methods in the study of entanglement and local realism.

I have not read the actual paper yet, so if you have, I'd like to hear about it.

From my personal point of view, I no longer consider that the loopholes of Bell tests are anything significant anymore. This is due to the NUMEROUS consistent and non-contradictory results that we have obtained so far. In terms of the physics, Mother Nature seems to already let us know what she really is in this regards.

But I guess, until all of the loopholes are closed, we will always have to find a way to close them.

Zz.

Sunday, May 06, 2018

Alternative Theories of Gravity In Deep Doo-Doo

This is a rather nice article on the troubled times facing many alternative theories to Einstein's General Relativity due to the recent results from the colliding neutron stars. It should be especially useful to laymen to read and understand the methodology and the scrutiny that every theory goes through in physics to be considered to be valid. The one "take-home-lesson" that you should see is that my often-repeated manta here is more true than ever:

"Physics just doesn't say what goes up, must come down. It must also say when and where it comes down" - Warren Siegel.

The quantitative aspect is what is able to separate theories from being wrong to being right. One can't just say "oh, gravity gets weaker as we go farther away". It must say how much weaker, how it behaves with distance, etc.. etc.. and make precise predictions (i.e. to what level of uncertainty). These are "numbers" that we can compare with experiments, if there are already results or if new ones are collected.

This was exactly what happened with the merging neutron stars result, where our verification of the speed of gravity matches that to such precision with the speed of light, that a number of alternative gravitational theories died instantly.

The moral of the story here is that you should not fall in such deep love with any theory yet to have substantial verification, and you should not jump too quickly when new theories appear. I still point out to the OPERA debacle a few years ago when the OPERA project thought they measured superluminal neutrinos. As soon as they published their results, a bunch of theoretical explanations appeared on the e-print arXiv website, proposing theories of superluminal neutrinos, without waiting for independent verification of the validity of the result.

Not surprisingly, they all died of a horrible death when the result was attributed to bad optical cable connection! The history of physics is littered with theories that died and disappeared into obscurity when they could not match the experimental results or observations. Any beliefs or ideology, no matter how beautiful, satisfying, or popular, will crumble at the hands of Mother Nature if she says so.

Zz.

Wednesday, May 02, 2018

Hawking's Final Paper Is Published

The late Stephen Hawking's final paper written while he was alive, has been published. You can get the full version of it at that link.

If you missed it, read Ethan Siegel's earlier explanation of the paper.

Zz.

Friday, April 27, 2018

Quantum Entanglement Just Got "Big"

The "big" news of the week so far is the two papers published in nature that increased the size of entities that can be in an quantum entanglement.

It looks like we've approached the size of a human hair, which, by any quantum mechanical standards, is humongous.

This is beginning to approach the the scale size of the Schrodinger Cat. Well, not quite, but it is in the right direction. The Schrodinger Cat-type states, which is more of a demonstration of quantum superposition (and a vital ingredient in quantum entanglement), is also getting to be huge.

Zz.

Thursday, April 26, 2018

MinutePhysics Special Relativity Chapter 4

If you missed Chapter 3, check it out here.

Here's the next chapter in MinutePhysics lessons in Special Relativity.



Zz.