Saturday, April 10, 2021

Muon g-2 Results Signify New Physics? Maybe Not.

The big news of the week that got all the media coverage is the result that came out of Fermilab's Muon g-2 experiment that confirmed an earlier result from Brookhaven more than a dozen years ago. Fermilab even announced it like.

However, as with any scientific discovery or announcement, one has to take a deep breath and let the process works itself out before we put our stamp of validity to it. This is because there is a theoretical calculation that has also been published along with this result that basically recalculates what the Standard Model predicts as the magnetic moment of a muon, and they found that the new calculation produces a result consistent with the experiment. In other words, there is no new physics if this calculation is verified, because the old Standard Model does, in fact, predicted this new result.

One of the major difficulties in physics is that in many situations, we do not have a simple equation that we can plug-and-chug to get numbers out. In fact, this is why predicting the weather is difficult, because the non-linear differential equations that need to be solved to get the number out can only be done numerically, i.e. it has to be done via some numerical algorithm.

This is made worse when there are a gazillion interactions involved in a system. So one ends up making simplifying models or adopt calculational techniques to allow us to get to some numerical answers. We benchmark the technique to known values and known systems to make sure that it gives accurate and sensible answers, but as we push the boundary even more, there is no guarantee that that calculational technique will work all the time.

The author of the theoretical paper used a calculational technique called lattice QCD. This is a known calculational model that has been described in simple terms in the link I provided above. It appears that using this method, the Standard Model does provide a value for the muon magnetic moment that is consistent with the experiment. If this is true, then it means that the old calculation of the magnetic moment was incorrect in the first place, and that there is discrepancy between what the Standard model predicts, and what the experiment measures.

While this is good news for the Standard Model and is another evidences of why it is an amazing theory, those who are looking for new physics beyond the Standard Model will obviously not be jumping for joy. But that isn't the issue here and not what I want to highlight. Rather, it is the constant reminder that in science, and especially in such exotic areas of physics, every discovery or new ideas must not be overblown or overhyped, because those require multiple verification over a period of time. It is not a situation for instant gratification. A lot of hard work is still to come because we have seen way too many times where something that was touted turned out to not be valid.

This announcement received a lot of media coverage. I just hope that this is a valid "new physics" and not just something that turned out to be what the old theory did predict.


Monday, March 22, 2021

Getting My COVID Vaccine This Week

Being under 65 years of age, and with no major health issues (knock on wood), I was not eligible to receive the COVID vaccine in my area during the first 2 waves of its distribution.

But suddenly, it was announced by our state that starting Monday (today), higher-education workers will be included in the expanded criteria to receive the next vaccine distribution. So, after scrambling to find an appointment, I will get my first shot of the Pfizer vaccine this coming Friday, and then the second one later in April. All I can say is : PHEW!

There is certainly a push by the school to get things back to almost normal, in the sense that many of the classes are starting to be offered in person or in a blended/hybrid modality. Certainly classes that have a significant laboratory component are the ones that will probably start to be offered in person. I definitely would prefer to have the vaccine before I have to come in to the campus, so getting the vaccine now is a major peace-of-mind aspect of this whole thing.

It is certainly looking more certain that I may have to ditch my Zoom pants on most days and have to start dressing up again when I teach my classes this Fall! 😀😁


Wednesday, March 10, 2021

Tripple-Layer Mask Blocks Secondary Atomization of Cough Droplets

I had already posted several physics papers on the efficacy of masks, even single-layer ones, in reducing the airborne aerosol. Now comes another paper that deals with how cough droplets actually can break up into smaller-sized droplets that may pass through single and double-layered masks, especially when moving at such high speed from a cough.

It turns out that having a mask with 3 layers or more might be the most effective here (I wonder at how many layers will we will of suffocation? :)) The new research is to be published in Science, and you can get the paper at the link to read to your heart's content.

A review of this paper can be found here. It is fascinating to read that expertise in the study of jet engines are being leveraged in studying the dynamics of this problem. But do you think people who don't believe in wearing masks to reduce the virus transmission will buy any of this? They believe in smartphones and jet engines, don't they?


Wednesday, March 03, 2021

English And The Language Of Physics

I love reading articles like this where the history of how things become the way they are now is revealed.

This Symmetry article tells the story of how English became the language of physics and why it became dominant in the publication of physics articles and journals. It has almost nothing to do with science, but everything to do with politics, social upheaval, and world events. If Germany didn't have the Nazi coming into power, we probably would be doing physics in German, or if the Soviet Union didn't close off the interactions of non-Soviet scientists, we'd be sharing ideas in Russian as well.


Tuesday, March 02, 2021

Impact of COVID-19 Pandemic On Physicists

We, physicists, are people too (shocking, I know!). The impact of isolation, stay-at-home and work-from-home orders, and the cancellation of experimental work, in-person conferences, workshops and others do have academic, emotional, and psychological impacts on this group of people

This Physics Today article looks at such an impact on the physic community, and how they are dealing with it.

How are YOU dealing with it? Are you back on campus, in your lab, or in your office? Or are you still working from home?


Thursday, February 25, 2021

Combining The Best Of Both Worlds

This is a fascinating and important advancement in the physics of light sources. It seems that it has been shown experimentally how one can get the short, intense light pulses that one gets from a FEL source, and combine it with the repetition that one gets from a synchrotron light source.

Now a Sino-German team has shown that a pattern of pulses can be generated in a synchrotron radiation source that combines the advantages of both systems. The synchrotron source delivers short, intense microbunches of electrons that produce radiation pulses having a laser-like character (as with FELs), but which can also follow each other closely in sequence (as with synchrotron light sources). 

Another review of this work, from Nature where it was published, can be found here.

While this is an important step, it really is a proof-of-principle experiment, and it requires a bit more experimental work to show that this can be viable.

Although this paper represents a crucial step towards generating high-power, small-bandwidth light pulses in a particle accelerator, steady-state microbunching has not yet been demonstrated. Deng et al. have shown that, after one turn in the synchrotron, the microbunched beam can produce coherent radiation. The next challenge is to prove that this scheme can achieve such a feat over many turns. This will be difficult to accomplish experimentally for at least three reasons.

But if this can be demonstrated, a lot of things that are done at a FEL can be performed even more at an "ordinary" synchrotron light source, a facility that is a lot more plentiful.

An important point that I want to point out here is that, these are all "tools" that allow us to study things. Without these tools, we have no ability to experimentally detect, see, or measure things. It enables us to do things that we could not do before. So the advancement in science, technology, medicine, etc, depend on not only having these tools, but also the continual improvement of these tools. Advancement in science requires all of these things to occur to able to explore more difficult and complex ideas and scenarios.

This advancement in accelerator-based light source has nothing to do with high-energy physics. In fact, if you look at the type of applications that are being mentioned, there's nothing about particle physics at all!

.....on an accelerator that could extend the capabilities of these machines even further, potentially yielding applications in a next-generation chip-etching technology called extreme-ultraviolet lithography and an advanced imaging method known as angle-resolved photoemission spectroscopy.

So once again, this is my continuing attempt at trying to make people aware that "accelerators" do not automatically mean "particle collider" or "high energy physics". In fact, the majority of particle accelerators in this world are not involved in high energy physics experiments.


Monday, February 08, 2021

Wonders of Physics Competition

I mentioned about this more than 10 years ago in this thread. I went to UW-Madison and attended the early incarnation of this lecture-room demonstration that became a huge hit with the public. I also had Clint Sprott as an instructor in one of my courses.

Due to COVID-19, the Wonders of Physics show couldn't be held, and probably not in the near future either. To their credit, they are creating a contest instead, where you can submit a 2-minute video of an original demonstration of a physics concept.

So maybe one of you are creative enough to enter this contest. :)


Thursday, January 21, 2021

When Flipped Classroom Flopped?

I've mentioned about flipped classroom before, and that I use this format in a couple of my classes during the remote environment. This article goes the other way and pointed out when and why flipped classroom can flop and be rather ineffective.

I must say that the way this was described, it doesn't quite match what I am doing. While the students do have to watch videos and/or read something before they come to the first class of the week, they have pre-lecture quizzes that tests on whether they did watch the videos or read the material, and had a general understanding of the important ideas. These are graded and become part of their overall course grades. So there is incentive for them to go over the pre-lecture stuff.

Secondly, I don't just quickly dump them into breakout room right at the beginning. We meet twice a week and these are very long class sessions (3 hours) that often comprise of the subject matter and hands-on demos or labs (virtual labs). So I get to go over the important highlights of the subject, do a few examples, shoot off a few polls, give them a few online apps or simulations, and only then do I send them to breakout rooms to work on solving problems. In fact, in many instances, their breakout session is where they get to do their online virtual experiments and get to discuss what they are doing with one another.

I may have mentioned this before, but I did my own end-of-semester survey, and the overwhelming majority of my students liked the pre-lecture material and found them useful. So for me, the version of flipped classroom that I run appears to not be a flop.


Monday, January 11, 2021

Physics Labs At Home

I've made several posts on various virtual experiments that may be done in conjunction with the standard physics courses. While many of these are adequate, nothing beats an actual, physical experiment that requires actual observation and measurement in person.

This paper lists a few experiments that a student may be able to do at home using items that a student may find at home. Since almost everyone having smart phones, there are certainly many activities that can be done using such devices. I've asked my students to use their smartphones to install sky-viewing app to be able to track planets, stars, and other celestial bodies. We have also used various apps that made used of the accelerometer in the phone to measure acceleration. I also have an app called "Gauges" (iOS) that allows you to use your smartphone to be an altimeter, speedometer, barometer, accelerometer (of course), magnometer, and to measure sound level and luminance. I am in the middle of designing a few "in class" (and now, it is "at home") activities using these capabilities.

While virtual experiment is fine for the present unusual situation, I still believe that this is not the same as actually doing the measurement itself and physically performing the experiment. So I'm trying to find activities that a student may be able to do him/herself, or in collaboration with another student if he/she does not have all the necessary equipment. I want to incorporate this as part of the lesson rather than an actual "experiment", so that the student can see the phenomenon that they are studying or about to study.

Have you designed simple at-home physics experiments for your students?


Monday, January 04, 2021

General Physics Experiments Done Remotely

Oooh, yes please!

The problem that I have with online/remote physics courses is that we had to resort to a lot of "simulations" applications to do our "experiments". This is not what an experiment is supposed to be, because there has to be a components of errors and equipment issues that are involved in doing any physical measurement. So these simulations do not reflect reality.

The closest that I've seen so far is the one offered by Pivot Interactives, where you see a series of videos of actual experiments being done, and you get to measure what the person doing the experiment actually measure. It includes all the experimental uncertainties, quirkiness, etc. that the students have to also consider.

But here's another step further that gets the students even closer to being there and doing the actual experiment. I came across this article on UC Santa Barbara's effort to put their Sophomore-level quantum physics course online whereby the students can operate the equipment remotely and perform the actual experiments without being in the lab.

The automization of the quantum mechanical labs allows for students in the Physics 5L class to interact remotely with equipment using an online portal connected to the apparati set up in the lab, according to Fygenson. 

The online portal models the equipment setup, with buttons and knobs in the same order as where they would be on the actual equipment. Students can observe what happens in the lab using cameras aimed at the machines, Fygenson said. So far, the automated lab has been used in Summer 2020 and Fall 2020 and will be used again in Spring 2021.

That's brilliant! But that also involves a lot of money and effort to connect all of those equipment so that they can be operated remotely. Not many schools have that kind of resources and expertise.

I did a quick search and found an earlier report on this with an accompanying video. This gives you a better idea of how this is all done. It looks like from the video, the experiment being demonstrated as an example is the diffraction grating spectroscope looking at emission lines from various sources. This would be a very nice experiment to be done remotely.

Both articles indicated that they are sharing access with other schools, but did not indicate what one should do to get such access. I suppose I will have to contact one of the people listed at the end and see if I can have my students do at least that spectroscope experiment.

Anyone else have done something similar, or have used this?


Thursday, December 31, 2020

E&M Lab Manual for Virtual Classes

This appeared on arXiv on Christmas day. It is a series of lab manual for intro E&M virtual experiment suitable for online courses.

The pdf document itself contains the just the lab instruction. Most of the virtual experiments made use of the applications found in PhET. It is in the abstract that we get a bit of an explanation. The authors claim that:

Student learning outcomes (understand, apply, analyze and evaluate) were studied with detailed lab reports and end of the semester lab-based written exam which confirmed the virtual lab class was as effective as the in-person physical lab class. 

Unfortunately, they provided no evidence or data to support this, at least not in the document.

In my lessons, I try to incorporate the "experiment" as part of the lecture itself. So I had students perform one part of the virtual experiment, and then we discuss the outcome before they write down their observations. Then we move on to the next topic or examples before we come back to doing more of the simulation or measurement. So in many cases, the students encounter both the theory and the observation at almost the same time. The exception being when we did Lenz's and Faraday's law, where I actually gave the students the equipment and instruction, and let them discover for themselves the induced current and how the induced current behave with changing magnetic fields. So they observed the phenomenon first before they learned about the theory.

In any case, this set of lab instruction might be useful to be adapted to my remote classes. We'll see how that goes this coming Spring.