Saturday, April 22, 2017

Earth Day 2017 - March For Science Day

Today is the March for Science day to coincide with Earth Day 2017.

Unfortunately, I will not be participating in it, because I'm flying off to start my vacation. However, I have the March for Science t-shirt, and will be wearing it all day. So I may not be with all of you who will be participating it in today, but I'll be there in spirit.

And yes, I have written to my elected officials in Washington DC to let them know how devastating the Trump budget proposal is to science and the economic future of this country. Unfortunately, I may be preaching to the choir, because all 3 of them (2 Senators and 1 Representative of my district) are all Democrats who I expect to oppose the Trump budget as it is anyway.

Anyhow, to those of you who will be marching, YOU GO, BOYS AND GIRLS!


Friday, April 21, 2017

"Physics For Poets" And "Poetry For Physicists"?

Chad Orzel has a very interesting and thought-provoking article that you should read.

What he is arguing is that scientists should learn the mindset of the arts and literature, while those in the humanities and the arts should learn the mindset of science. College courses should not be tailored in such a way that the mindset of the home department is lost, and that a course in math, let's say, has been devolved into something palatable to an arts major.

I especially like his summary at the end:

One of the few good reasons is that a mindset that embraces ambiguity is something useful for scientists to see and explore a bit. By the same token, though, the more rigorous and abstract scientific mindset is something that is equally worthy of being experienced and explored by the more literarily inclined. A world in which physics majors are more comfortable embracing divergent perspectives, and English majors are more comfortable with systematic problem solving would be a better world for everyone.

I think we need to differentiate between changing the mindset versus tailoring a course for a specific need. I've taught a physics class for mainly life science majors. The topics that we covered is almost identical to that offered to engineering/physics majors, with the exception that they do not contain any calculus. But other than that, it has the same rigor and coverage. The thing that made it specific to the group of students is that many of the examples that I used came out of biology and medicine. These were what I used to keep the students' interest, and to show them the relevance of what they were studying to their major area. But the systematic and analytical approach to the subject are still there. In fact, I consciously emphasized the technique and skills in analyzing and solving a problem, and made them as important as the material itself. In other words, this is the "mindset" that Chad Orzel was referring to that we should not lose when the subject is being taught to non-STEM majors.


Wednesday, April 19, 2017

The Mystery Of The Proton Spin

If you are not familiar with the issues surrounding the origin of the proton's spin quantum number, then this article might help.

It explains the reason why we don't believe that the proton spin is due just to the 3 quarks that make up the proton, and in the process, you get an idea how complicated things can be inside a proton.

There are three good reasons that these three components might not add up so simply.
  1. The quarks aren't free, but are bound together inside a small structure: the proton. Confining an object can shift its spin, and all three quarks are very much confined.
  2. There are gluons inside, and gluons spin, too. The gluon spin can effectively "screen" the quark spin over the span of the proton, reducing its effects.
  3. And finally, there are quantum effects that delocalize the quarks, preventing them from being in exactly one place like particles and requiring a more wave-like analysis. These effects can also reduce or alter the proton's overall spin.
Expect the same with a neutron.


Tuesday, April 18, 2017

Testing For The Unruh Effect

A new paper that is to appear in Phys. Rev. Lett. is already getting quite a bit of advanced publicity. In it, the authors proposed a rather simple way to test for the existence of the long-proposed Unruh effect.

Things get even weirder if one observer accelerates. Any observer traveling at a constant speed will measure the temperature of empty space as absolute zero. But an accelerated observer will find the vacuum hotter. At least that's what William Unruh, a theorist at the University British Columbia in Vancouver, Canada, argued in 1976. To a nonaccelerating observer, the vacuum is devoid of particles—so that if he holds a particle detector it will register no clicks. In contrast, Unruh argued, an accelerated observer will detect a fog of photons and other particles, as the number of quantum particles flitting about depends on an observer's motion. The greater the acceleration, the higher the temperature of that fog or "bath."

So obviously, this is a very difficult effect to detect, which explains why we haven't had any evidence for it since it was first proposed in 1976. That is why this new paper is causing heads to turn, because the authors are proposing a test using our existing technology. You may read the two links above to see what they are proposing using our current particle accelerators.

But what is a bit amusing is that there are already skeptics about this methodology of testing, but each camp is arguing it for different reasons.

Skeptics say the experiment won’t work, but they disagree on why. If the situation isproperly analyzed, there is no fog of photons in the accelerated frame, says Detlev Buchholz, a theorist at the University of Göttingen in Germany. "The Unruh gas does not exist!" he says. Nevertheless, Buchholz says, the vacuum will appear hot to an accelerated observer, but because of a kind of friction that arises through the interplay of quantum uncertainty and acceleration. So,the experiment might show the desired effect, but that wouldn't reveal the supposed fog of photons in the accelerating frame.

In contrast, Robert O'Connell, a theorist at Louisiana State University in Baton Rouge, insists that in the accelerated frame there is a fog of photons. However, he contends, it is not possible to draw energy out of that fog to produce extra radiation in the lab frame. O'Connell cites a basic bit of physics called the fluctuation-dissipation theorem, which states that a particle interacting with a heat bath will pump as much energy into the bath as it pulls out. Thus, he argues, Unruh's fog of photons exists, but the experiment should not produce the supposed signal anyway.

If there's one thing that experimenters like, it is to prove theorists wrong! :) So which ever way an experiment on this turns out, it will bound to disprove one group of theorists or another. It's a win-win situation! :)


Monday, April 17, 2017

Hot Atoms Interferometer

This work will not catch media attention because it isn't "sexy", but damn, it is astonishing nevertheless.

Quantum behavior are clearly seen at the macroscopic level because of the problem in maintaining coherence over a substantial length and time scales. One of the ways one can extend such scales is by cooling things down to extremely low temperatures so that decoherence due to thermal scattering is minimized.

So it is with great interest that I read this new paper on atoms interferometer that has been accomplished with "warm" atomic vapor[1]! You also have access to the actual paper from that link.

While the sensitivity of this technique is significantly and unsurprisingly low when compared to cold atoms, it has 2 major advantages:

However, sensitivity is not the only parameter of relevance for applications, and the new scheme offers two important advantages over cold schemes. The first is that it can acquire data at a rate of 10 kHz, in contrast to the typical 1-Hz rate of cold-atom LPAIs. The second advantage is the broader range of accelerations that can be measured with the same setup. This vapor-cell sensor remains operational over an acceleration range of 88g, several times larger than the typical range of cold LPAIs.

The large bandwidth and dynamic range of the instrument built by Biedermann and co-workers may enable applications like inertial navigation in highly vibrating environments, such as spacecraft or airplanes. What’s more, the new scheme, like all LPAIs, has an important advantage over devices like laser or electromechanical gyroscopes: it delivers acceleration measurements that are absolute, without requiring a reference signal. This opens new possibilities for drift-free inertial navigation devices that work even when signals provided by global satellite positioning systems are not available, such as in underwater navigation.

And again, let me highlight the direct and clear application of something that started out as simply appearing to be a purely academic and knowledge-driven curiosity. This really is an application of the principle of superposition in quantum mechanics, i.e. the Schrodinger Cat.

This is an amazing experimental accomplishment.


[1] G. W. Biedermann et al., Phys. Rev. Lett. 118, 163601 (2017).

Sunday, April 16, 2017

Why Is The Weak Force Weak?

Fermilab's Don Lincoln has another fun and informative video on our elementary particles and interactions.


Saturday, April 15, 2017

To Draw Or Not To Draw?

OK, this is a rather lengthy paper, and I thought I would have gotten through it by now, but I just don't have the time. So instead, I'm just going to mention it here and let you people read for yourself.

This paper seems to argue that in cases of supporting diagram that accompanies a physics question (not diagram that actually is essential to the question), this diagram can often be useless, or even a hindrance to the students' ability to solve the problem.

This isn't the same as the student having to draw a diagram in solving a problem. That is not the subject of the paper here. I'm still trying to understand what is actually categorized as "supporting diagram" that accompanies a physics question. Maybe once I have a hang of that, the rest of the paper might be more relevant.

Still, if you're bored, you might have a go at it first ahead of me.


Tuesday, April 11, 2017

Dark Energy Is Not An Illusion

This is a good intro to Dark Energy if you want to know more about it. Even if you don't buy into Ethan Siegel's argument, you at least have a good description of what we know of about Dark Energy at the moment, and why certain explanations for what have been observed have been ruled out.


Monday, April 10, 2017

"Genuine" 3-Photon Interference

I continue to be amazed at the creativity and capability of many of these experiments. This is one such example, and there were two groups that achieved this independently.

Two papers in PRL this week are reporting the first genuine observation of 3-photon interference. This is a purely quantum mechanical effect and not explained by any classical light wave description. In case you are not familiar with the background info that is needed here, the "interference" phenomenon that we are familiar with are really single-photon interference, i.e. one photon capable of making multiple paths and taking multiple slits to produce the interference pattern that we know and love. 2-photon interference has been done and is not that commonly observed. 3-photon interference is even more difficult. That is why this is such a spectacular result coming from 2 different groups.

BTW, this is another experiment that can only be described using the photon picture.


Saturday, April 08, 2017

The Search For Neutrinoless Double Beta Decay

This is a nice and simple article on why we are searching for the neutrinoless double-beta decay.

In this new study, physicists are seeking so-called neutrinoless double-beta decay. Normally, some radioactive atoms' unstable nuclei will lose a neutron via beta decay — the neutron transforms into a proton by releasing an electron and a tiny particle called an electron antineutrino. A mirror image can also occur, in which a proton turns into a neutron, releasing a positron and an electron neutrino — the normal-matter counterpart to the antineutrino. Double-beta decay happens when two electrons and two antineutrinos (the antimatter counterparts of neutrinos) are released: basically, the beta decay happens twice. Scientists have long theorized a neutrinoless version of this process — something that would suggest that the two neutrinos annihilated each other before being released from the atom. Essentially, the neutrino behaves as its own antimatter sibling.

A large portion of high-energy physics experiments around the world are done using neutrinos (Daya Bay, MINOS, NOvA, SuperK, etc...).  It won't surprise me one bit that the another major discovery will be made with these particles.


Thursday, April 06, 2017

Developing Skills Versus Developing Concepts In Undergraduate Physics Labs

This is something that is dear to my heart.

If you have followed this blog for any considerable period of time, you might have encountered a project that I started on my own years ago on here titled "Revamping Intro Physics Lab". In a series of posts (there were 7 posts and one follow-up in total), I made suggestions on the type of lab exercises that I would like to do for students in such a class. The lab experiments are more "free form" and more of a discovery-type exercises, where the students make their own self-discovery without the baggage of knowing the underlying physics before hand.

I explained the rational for wanting to do this, and the most important aspect of it is the "skill" that one might develop in trying to systematically discover the connection and correlation between two different quantities. It is the beginning of finding first the correlations, and then proceed to finding the causation. I consider such skill to be of utmost importance, even more important than trying to make the students understand the underlying physics.

Therefore, it was a pleasant bonus when I read this paper. In it, the authors studied the E-CLASS assessment of students who went through a physics lab that (i) focused on developing lab skills; (ii) focused on developing physics concepts; and (iii) focused on both. What they discovered was that the students that went through a physics lab that focused on developing lab skills ".... showed more expert-like postinstruction responses and more favorable shifts than students in either concepts-focused or both-focused course...." And what is even more interesting is the finding that ".... the
ANCOVA demonstrated that the increase in score associated with skills-focused courses was larger for women than for men, and the difference was large enough to eliminate or even reverse the typical gender gap..... "

Of course, while this is very encouraging, I won't jump up and down (yet) because one has to read their caution at the end of the paper. As with anything, this needs to be looked at and studied a lot more to see if there is a true cause-and-effect factor here, especially on why a focus on lab skills could produce such an effect.

As for me, I'm all for this. In a class where the majority of students are not physics majors, or even in a class of non-science majors, having them understand that our knowledge of the physical universe is based on how we know about the relationship between two separate quantities is very important. That is how we make sense of our world. It is why uncorrelated events, such as how one arranges one's furniture in a room somehow affects one's prosperity doesn't make much sense. None science majors do not have a lot of opportunity for a guided study of the physical world. When we get them, we need to impart as much as we can in the most effective manner. A lab when they learn how to find out how one variable affects another, and the skills the employ to do that, can be the most valuable thing they learn in a physics lesson.


Thursday, March 30, 2017

RIP Alexei Abrikosov

A Nobel Laureate and a giant in the field of theoretical condensed matter physics, Alexei Abrikosov passed away yesterday at the age of 88.

If you have been lucky enough to have met him, you'll see that this was a very gentle man who loved to sit down and chat with you about anything and everything. Once he has met you or have seen you, he never failed to acknowledge you or say hi even if he barely remembered who you are.


Wednesday, March 29, 2017

Oh, The Hypocrisy!

I just came across a bill in the US House of Representative which asked "Do EPA Regulations and Assessments Need to be Based Only on Science That's Publicly Available?" This was introduced by Rep. Lamar Smith who isn't really someone who can't be proud of his anti-science stance in many instances.

The bill passed the House with 228 Yea and 194 Nay.

On the surface, it appears to be something sound. After all, why wouldn't you base something like this on valid science?

But it turns out that it is not that simple. The EPA cannot prevent the introduction of something without any data that are available publicly that it isn't safe.

However, what is very laughable is that this very same people who voted for this bill somehow switch the rules and are the same ones who will dismiss the issue of global warming and the human cause of it, DESPITE all the available data and peer-reviewed science. So why do they accept scientific data in one, but not the other?

Thus, the hypocrisy.


Saturday, March 25, 2017

Experimental Evidence of Indefinite Causal Order

So not only do we have a superposition of observables, we also have a superposition of causality, in which the order of events happening is also in a quantum superposition.

This evidence has been experimentally observed in a new paper published in Science Advances this past week[1]. See the press release here.

What they appear to have developed is this more robust "causal witness" that allows them to sample the superposition without destroying the coherence of the system.

Now, despite the headlines of the press release and the so-called implications, this isn't a result that destroys causality. What I seem to gather here is that, in the case where there is an uncertainty on which event occurs first, i.e. the causal order itself is in a superposition, then it is only upon a measurement will we get to know which comes first, the chicken or the egg. After that, things follows as usual. This experiment shows evidence that, yes, chicken followed by egg, and egg followed by chicken, are both there before a measurement.


[1] G. Rubino et al., Sci. Adv., 3, e1602589 (2017).

Saturday, March 18, 2017

Minutephysics's "How To Teleport Schrodinger's Cat"

It used to be that Minute Physics videos are roughly.... a minute long. But that is no longer true. Here, he tackles quantum entanglement via trying an illustration of teleporting the infamous Schrodinger's Cat.

I'm sorry, but how many of you managed to follow this?

I think I'll stick to my "Quantum Entanglement for Dummies". :)


Thursday, March 16, 2017

DOE's Office Of Science Faces Disastrous Cuts

The first Trump budget proposal presents a major disaster for scientific funding and especially to DOE Office of Science budget.

President Donald Trump's first budget request to Congress, to be released at 7 a.m. Thursday, will call for cutting the 2018 budget of the National Institutes of Health (NIH) by $6 billion, or nearly 20%, according to sources familiar with the proposal. The Department of Energy's (DOE's) Office of Science would lose $900 million, or nearly 20% of its $5 billion budget. The proposal also calls for deep cuts to the research programs at the Environmental Protection Agency (EPA) and the National Oceanic and Atmospheric Administration (NOAA), and a 5% cut to NASA's earth science budget. And it would eliminate DOE's roughly $300 million Advanced Research Projects Agency-Energy.

I don't know in what sense this will make America "great again". It is certainly not in science, that's for sure.


Born Rule Confirmed To An Even Tighter Bound

I must say that I might have missed this paper if Chad Orzel didn't mention it in his article. Here, he highlighted a paper by Kauten et al. from New Journal of Physics (open access) that performed 5-slit interference test with the purpose of detecting any higher-order interference beyond that predicted by the Born rule. They found none, and imposed a tighter bound on any higher-order effects.

As Orzel reported:

That's what the NJP paper linked above is about. One of the ways you might get the Born rule from some deeper principle would be to have it be merely an approximation to some more fundamental structure. That, in turn, might very well involve a procedure other than "squaring" the wavefunction to get the probability of various measurement outcomes. In which case, you would expect to see some higher-order contributions to the probability-- the wavefunction cubed, say, or to the fourth power.
Sadly, for fans of variant models of quantum probability, what they actually do is the latter. They don't see any deviation from the ordinary Born rule, and can say with confidence that all the higher-order contributions are zero, to something like a hundredth of a percent.

Of course, this won't stop the continuation of the search, because that is what we do. But it is amazing that QM has withstood numerous challenges throughout its history.


Sunday, March 12, 2017

The Weak Nuclear Force

I'm going to highlight this latest video by Fermilab's Don Lincoln for a number of reasons. First, the video:

Second, this is one video packed with a number of very important and illuminating stuff. First he explains about the concept of "spin" in both the classical and quantum picture. This is important because to many people who do not study physics, the word "spin" conjures up a certain idea that is not correct when applied to quantum mechanics. So this video hopefully will enlighten the idea a bit.

But what is more fascinating here is his brief historical overview of the first proposal of the connection between the weak interaction and spin, and how Chien Shiung Wu should have received the Nobel Prize for this with Yang and Lee. This might be another case of gender bias that prevented a brilliant Chinese female physicist from a deserving prize. Considering the time that she lived in and the societal and cultural obstacles that she had to overcome, she simply had to be just too outstanding to be able to get to where she was.

So this is one terrific video all around, and you get to learn a bit about the weak interaction to boot!


Friday, March 10, 2017

APS Endorses March Of Science

The American Physical Society has unanimously endorsed the upcoming March for Science.

I'll be flying out of town on that exact day of the March, so I had decided a while back to simply contribute to it. I get the sentiment and the mission. However, I'm skeptical on the degree of impact that it will make. It will get publicity, and maybe focuses some of the issues, especially funding in the physical sciences, to the public.

But for it to take hold, it can't simply be a one-day event, and as much as I've involved myself in many outreach programs, I still see a lot of misinformation and ignorance among the public about science, and physics in particular.

Here's something I've always wanted to do, but never followed through and lack the resources to do it. How about we do something similar to a family tree genealogy. But instead of tracing human ancestors, we focus on technology "family tree". I've always wanted to start with the iPhone capacitive touch screen. Trace back up the technology and scientific roots of this component. I bet you there were a lot of various material science, engineering, and physics that were part of various patents, published papers, etc. that eventually gave birth to this touch screen.

What it will do is show the public that what they have so gotten used to came out of very basic research in physics and engineering. We can even list out all the funding agencies that were part of the direct line of "descendants" of the device and show them how money spent on basic science actually became a major component of our economy.

By doing this, you don't beat around the bush. You TELL the public what they can actually get out of an investment in science with a concrete example. And it may come out of areas that they never made connection before.


Thursday, March 09, 2017

Time Crystal

This is quite an astonishing feat. It was only back in 2012 that Frank Wilczek proposed the possibility of a "time crystal", where a certain symmetry repeats in time, rather than in space. This was followed soon enough by a formal proposal for such a crystal. And now, we appear to have two experimental evidence.[1,2]

Potter is part of the team led by researchers at the University of Maryland who successfully created the first time crystal from ions, or electrically charged atoms, of the element ytterbium. By applying just the right electrical field, the researchers levitated 10 of these ions above a surface like a magician’s assistant. Next, they whacked the atoms with a laser pulse, causing them to flip head over heels. Then they hit them again and again in a regular rhythm. That set up a pattern of flips that repeated in time.

Crucially, Potter noted, the pattern of atom flips repeated only half as fast as the laser pulses. This would be like pounding on a bunch of piano keys twice a second and notes coming out only once a second. This weird quantum behavior was a signature that he and his colleagues predicted, and helped confirm that the result was indeed a time crystal.

Like I said, this is quite a feat to come up with a scheme to be able to create and test this.


[1] J. Zhang et al., Nature 543, 217 (2017).
[2] S. Choi et al., Nature 543, 221 (2017).

Monday, March 06, 2017

The Race To Make Quantum Computers

We still don't quite have a truly-accepted working model, even from D-Wave. So it is interesting to see this latest news of both Google and IBM launching projects to produce and eventually sell these quantum computers.

The folks from Google's Quantum AI Laboratory wrote a comment in Nature, while IBM's intention is reported in the news.

With the Chinese company Alibaba collaborating with the Chinese Academy of Sciences to also go into this area, the next several years will be fascinating to watch.


Sunday, March 05, 2017

Raman Spectroscopy Used To Detect Skin Cancer

I found this piece of news while reading the Flash Physics section on Physics World. And if you've followed this blog for a while, you know that I will highlight this without any shame.

Chalk this up to another important application of something that came out of physics research and subsequently finds a usefulness in medical diagnostics. Many of us in Material Science/Condensed Matter Physics/Chemistry are aware of Raman spectroscopy techniques in the study of molecules and materials. It has been a common technique in these areas of study for many, many years since its first proposal in.... get this.... 1929![1]

So already it is a very useful technique in chemistry and material science. But now it has found another application, in medical diagnostics. It turns out that this same technique can be used to find hard-to-detect skin cancer.[2]

Abstract: Melanoma is the most deadly form of skin cancer with a yearly global incidence over 232,000 patients. Individuals with fair skin and red hair exhibit the highest risk for developing melanoma, with evidence suggesting the red/blond pigment known as pheomelanin may elevate melanoma risk through both UV radiation-dependent and -independent mechanisms. Although the ability to identify, characterize, and monitor pheomelanin within skin is vital for improving our understanding of the underlying biology of these lesions, no tools exist for real-time, in vivo detection of the pigment. Here we show that the distribution of pheomelanin in cells and tissues can be visually characterized non-destructively and noninvasively in vivo with coherent anti-Stokes Raman scattering (CARS) microscopy, a label-free vibrational imaging technique. We validated our CARS imaging strategy in vitro to in vivo with synthetic pheomelanin, isolated melanocytes, and the Mc1re/e, red-haired mouse model. Nests of pheomelanotic melanocytes were observed in the red-haired animals, but not in the genetically matched Mc1re/e; Tyrc/c (“albino-red-haired”) mice. Importantly, samples from human amelanotic melanomas subjected to CARS imaging exhibited strong pheomelanotic signals. This is the first time, to our knowledge, that pheomelanin has been visualized and spatially localized in melanocytes, skin, and human amelanotic melanomas.

This is another example where experimental technique in physics EVENTUALLY finds applications elsewhere. I've highlighted other examples of this, with this being the most recent one before this post. Also note the "gestation" period between when this method was first proposed, and then when it became common in physics, to when it found other applications outside of its original main use. This is not new. Look at how long between when NMR became a common technique to when it evolved into MRI. Medical technology would not have evolved and advanced without a much earlier advancement in physics and physics experiments!

What I'm trying to emphasize here is that you may not feel the pain NOW when you cut funding to basic science research. But the pain WILL be felt later, by your children and grandchildren, because it takes years for what we work on now to become a useful technique elsewhere. That physics that we used to detect some esoteric particles that you don't care about may just one day be the diagnostic tool that saves someone's life!


[1]C.V. Raman and K.S. Krishnan, The optical analog of the Compton effect, Nature 121, 711 (1928); G. Landsberg and L. Mandelstam, A novel effect of light scattering in crystals, Naturwissenschaften 16, 557 (1928); C.V. Raman and K.S. Khrishnan, The production of new radiations by light scattering, Proc. Roy. Soc. (London) 122, 23, (1929).
[2] H. Wang et al., Scientific Reports 6, Article number: 37986 (2016). Paper is open access.

Friday, March 03, 2017

The Laws Of Life

Physics Today has made the article "The Laws of Life" from the March 2017 issue available for free. In the article, astrobiologist Charles Cockell describes how the fundamental laws of physics influences the forms of life on Earth.


Thursday, March 02, 2017

Online Homework Assignment - Are They Effective?

I read this news with a bit of interest. It appears that a student at Brooklyn College is gathering petition signatures to end the use of something called "Expert TA". This sounds like an online HW assignment that has been used by the physics department at that school.

Each homework assignment has about 15 to 20 questions, but each question has multiple parts. The number of questions, attempts, and credit reductions for wrong answers is dependent on the instructor. The instructor has the option to deduct points when a student accesses hints, and feedbacks. Expert TA consists of two types of feedback: Direct and Socratic. Direct feedback let’s a student know exactly what they did wrong, while a Socratic feedback poses a question such as “Have you considered the following?” Though this may sound quite useful, students feel otherwise.

It would be a bit more informative, and more persuasive, if a specific example on how this online tool is ineffective. For example, the best complaint that I can read from the report said this:

“The problem doesn’t lie in the concepts,” said Manasherov. “It’s more like how can we navigate this website and give the right answer—the right answer meaning what the website is looking for.”
“The hints aren’t always helpful and the feedback isn’t always clear either,” said sophomore Melissa Beagle. “And they only give you a limited number of tries, which doesn’t really help.”

There types of comments are not really that informative. It is similar to you telling your doctor "I just don't feel right" without giving any specific description of what is wrong.

I have a bit of experience in dealing with such online HW assignment. I've written about it in an earlier blog post on here. In fact, I will also add that I actually worked though the online HW assignment that my students would be facing, and I can see and experience what they will have to go through. I can see good points and bad points about it. But as I've said in that earlier blog post, the biggest issue I have about online anything is the question on whether the student doing it had any external help. But that is an issue that would be present in the traditional, written HW assignment as well since the student can easily copy or had help in completing the assignment. Except for one major difference.

You see, traditional written HW assignment requires that the student show work in arriving at an answer. You normally do not see that with online assignment. From what I can gather when chatting with students, all they care about is getting the right answer to type into those answer boxes. Often time, their "work" in deriving the answer is either done haphazardly, or not as complete and clear as one that would be required in a written HW assignment that is being submitted for grading. So in some instances, these students really could not recall what they did right and what they did wrong.

I'm still divided on my opinion regarding this type of HW assignment. I see some value in it. It certainly makes the job of an instructor a bit easier. But I also see how this can make the student being lazy to really learn what is needed in solving a particular problem.

If you have gone through such online HW assignment, or if you're an instructor whose course use such a thing, I'd like to hear from you.


Wednesday, March 01, 2017

Lenz's Law Is A "Quirk" Of Physics?

I've never heard of "fidget toys" before till after I read this piece. This one is describing a fidget toy that supposedly has "antigravity" effects that simulates the low gravitational field of the moon and Mars, making the object falls slower. The toy is called Moondrop.

Based around the principle of Lenz’s law — which *deep breath* states that the current induced in a circuit due to a change or motion in a magnetic field will create a field that opposes the charge that produced it — Moondrop is a gravity-defying fidget desk toy that imitates the differential gravitational free fall on Mars and the Moon.

OK, so immediately, there are two issues here:

1. Lenz's law is not a "quirk" of physics, as stated in the title of this report. In fact, it is quite a central phenomenon in physics that is responsible for power generators to create our household electricity! So how is that a "quirk"?

2. Any physics undergraduate can spot the error in the definition given for Lenz's law. Lenz's law is the effect whereby a magnetic field is generated to oppose the CHANGE in the external magnetic field. Maybe there is a typo in the definition given, that it should have been "change" instead of "charge". That one word (or in this case, one letter) change results in an astounding difference in the physics.

If I recall correctly, there are magnetic breaks that use the same principle. I remember reading something on roller coaster rides that made use of such magnetic breaks, so that it ensure that the vehicle can still be safely stopped even when the power goes off.

So the application of Lenz's law is neither that highly unusual, nor is it a quirk of physics.

Or maybe the writer meant a "quark" of physics?


Monday, February 27, 2017

Mildred Dresselhaus In GE Commercial

So, if you did watch the 2017 Academy Awards last night and didn't run away during the commercials (at least here in the US), you may have seen the GE commercial to celebrate women in science that featured the late Millie Dresselhaus. She, of course, passed away on Feb 20, so this commercial has become a tribute to her and left a legacy to encourage women to enter science, and physics in particular.

In the commercial, GE asks what it would be like if we treated women scientists like celebrities and deserving of the accolades and recognition like any pop celebrities.

If you missed it, here's the commercial once again:


Friday, February 24, 2017

SRF Technology For Particle Accelerator

Here's a brief video on the superconducting radiofrequency (SRF) cavity for particle accelerators.

I wouldn't call it "better particle accelerator" as in the video, because SRF cavity with Nb currently have a limit of 20-30 MV/m gradient, whereas normal conducting cavity can reach 100 MV/m or even higher at 1.3 GHz.

Still, these SRF cavities have properties that are "better" in other characteristics, especially in the Q-value. And in a number of applications, these cavities are the most efficient accelerating structures.

The technology for SRF is still evolving, especially in whether there is a need for superconducting photocathode sources for SRF guns. So there's a lot more to do in this field of study, both in terms of the physics, and in engineering.


Wednesday, February 22, 2017

Dark Energy - What Is It?

I've posted many articles on Dark Energy. But here's another one aimed at the general public that actually is quite instructive. It describes not only why we think there is dark energy, but also the puzzling phenomenon of the apparent "switching" between one regime to another.

Please take note that, while it seems that this idea has been floating around for a while, the study of Dark Energy is very much still in its infancy. The general public may find it hard to understand, but we really do need a lot more experimental observations on this, and that is easier said than done. Detection of this is not easy and requires years of design and work, and not to mention, funding!


Mildred Dresselhaus

An absolute giant in physics, and especially on condensed matter physics, Mildred Dresselhaus passed away recently at the age of 86.

Besides all of her accomplishments in physics, she was truly a trail-blazer for women in science, and in physics in particular with all of her "firsts". She, along with Vera Rubin and Deborah Jin, were the strongest candidates to break the drought of women winning the Nobel Prize in physics. Now we have lost all three.


Monday, February 20, 2017

Will SMASH Be A Smash?

Here comes a new extension to the Standard Model!

A new theoretical paper in PRL has extended the Standard Model of elementary particles to include new particles, and tries to mash different ideas and theories into this new standard model called SMASH - Standard Model Axion See-saw Higgs portal inflation (yeah, it's a mouthful).

SMASH adds six new particles to the seventeen fundamental particles of the standard model. The particles are three heavy right-handed neutrinos, a color triplet fermion, a particle called rho that both gives mass to the right-handed neutrinos and drives cosmic inflation together with the Higgs boson, and an axion, which is a promising dark matter candidate. With these six particles, SMASH does five things: produces the matter–antimatter imbalance in the Universe; creates the mysterious tiny masses of the known left-handed neutrinos; explains an unusual symmetry of the strong interaction that binds quarks in nuclei; accounts for the origin of dark matter; and explains inflation.

Of course, with ANY theoretical ideas, which often has long gestation period, a lot of patient waiting and testing will have to be done to verify many of its predictions. But this seems to create quite an excitement in revamping the Standard Model.


Friday, February 10, 2017

Politics And How It Affects US Physics Research

This is a very poignant article on how politics have impacted Physics research in the US for the past decade or so. Reading this can be very disheartening, so be forewarned!

The one impact that I had mentioned a few years ago is also mentioned here, and that had to do with not only the impact of budget cuts, but also the devastating impact of a budget cut AFTER several months of continuing resolution of the US budget.

I remember one year on December first, we had a faculty meeting where we heard funding levels would be up 10% across the board — a miraculous state of affairs after multiple years of flat-flat budgets (meaning no budgetary increases for cost of living adjustments — which ultimately means it’s a 3% cut). At our next faculty meeting on December fifteenth, we heard that it was going to be a flat-flat year — par for the course. On December nineteenth, we hear the news that there was a 30% cut in funding levels.

Now losing 30% of your budget is very bad in all circumstances, but you have to remember that the fiscal year begins on October first. The only thing you can do is fire people since all the funding is salaries and to do that legally takes about six weeks and with the holiday shutdown, that meant that this was a 50% cut in that year’s funding. There was some carry-forward and other budgetary manipulations, but 30% of the lab was lost, about three or four hundred if I recall. The lab tried to shield career scientists and engineers, but still many dozens were let go.

In a post from a few years ago, I showed the simple mathematics on why this effect is devastating for science research.

Unfortunately, I don't see this changing anytime soon. As the author of this article wrote, science in general does not have a "constituent". No politician pays a political price for not funding science, or wanting funding for science to be cut, unlike cutting funding for social programs, military, or other entitlements.

Regardless of who is in office or who is in control of the US Congress, it is business as usual.


Wednesday, February 08, 2017

Gamma-Ray Imaging At Fukushima Plant

I mentioned earlier of the muon tomography imaging that was done at the damaged reactor at Fukushima, and tried to highlight this as an example of an application that came out of high energy physics. This time a gamma-ray imaging spectroscopy was performed at the same location to pin-point contamination sites.

But as with the muon tomography case, I want to highlight an important fact that many people might miss.

To address these issues of existing methods and visualize the Cs contamination, we have developed and employed an Electron-Tracking Compton Camera (ETCC). ETCCs were originally developed to observe nuclear gammas from celestial objects in MeV astronomy, but have been applied in wider  fields, including medical imaging and environmental monitoring.

So now we have an example of a device that was first developed for astronomical observation, but has found applications elsewhere.

This is extremely important to keep in mind. Experimental physics often pushes the boundaries of technology. We need better detectors, more sensitive devices, better handling of huge amount of data very quickly, etc...etc. Hardware have to be developed to do all this, and the technology from these scientific experiments often trickle down other applications. Look at all of medical technology, which practically owes everything to physics.

This impact from physics must be repeated over and over again to the public, because a significant majority of them are ignorant of it. It is why I will continue to pick out application like this and highlight it in case it is missed.


Tuesday, February 07, 2017

Being Slowly Eaten For A Decade

This is the definition of the ultimate torture.

It appears that this black hole has been slowly feasting on this dead star for at least a decade. Ouch!

"We have witnessed a star's spectacular and prolonged demise," said Dacheng Lin, a research scientist at UNH's Space Science Center and the study's lead author. "Dozens of these so-called tidal disruption events have been detected since the 1990s, but none that remained bright for nearly as long as this one."

The arXiv version of this paper can be found here.

Moral of the story: Never piss off a black hole!


Monday, February 06, 2017

Photons Steal Momentum From Sun's Surface?

We all know that photons carry momentum. But who knew that photons leaving the sun's surface actually may cause the varying rotation of the sun with its radius?

This new paper from PRL makes the confirmation that the sun's surface has a greater drag and a slower angular rotation than the deeper part of the sun. But not only that, it also proposes that this slowdown is due to the loss of momentum when photons are emitted from the plasma on the surface.
Kuhn and his colleagues also developed a model to explain their data. Photons are created in the Sun’s dense core, where the plasma behaves nearly like a solid. As they diffuse outward, they experience plasma that is less dense, faster flowing, and subject to turbulent convection. As the photons interact with the moving plasma, they exchange angular momentum with it. Inside the Sun, the photons scatter so frequently that they lose as much angular momentum as they gain. But in the photosphere, where photons escape the Sun, the plasma-photon momentum transfer results in a net loss of the plasma’s angular momentum, as photons radiate away. The effect on the plasma is a mild braking force, which slows its overall rotation. This braking is most effective at the outer edge of the Sun, where the plasma density is at its lowest.
Those photons! They can create havoc!


Thursday, February 02, 2017

The Emperor Has No Clothes

The impact of the Trump's executive order on the admission of citizens from the 7 countries continues to be felt and the topic of conversation in many college campuses, science labs, and conferences. But something triggered in my head when I read this Washington Post news article on how this ban would not have prevented the attacks in the US since Sept. 11. When I read this, I immediately remembered a similar scenario, and this is where I connect it to the theme of this blog.

Back in, oh, I forget exactly when, probably mid-2000s, there was a laser accident at a lab (I'm not gonna name names). I'm going to rely on my memory based on what I read as the official report on the accident, and from what I heard from a friend who happened to know the person involved.

To set up the scenario, most, if not the majority, of laser accident occurred when the laser is running and the safety mode is bypassed. The most frequent reason for doing this is that the laser is either being worked on, being repaired, being serviced, or the most common occurrence, it is being aligned. People who are authorized to do this are usually trained, and had to undergo safety classes to ensure that they know what they are doing.

What happened in this accident, from what I remember, is that this person, along with at least one other person, was doing a typical laser alignment. He was wearing a pair of safety glasses as required, which protected his eyes in case there were stray beam hitting his face. Unfortunately, while in the middle of doing this work (which was part of the standard operating procedure of the facility), he had an itch around his eyes. In a moment where instinct took over, before he had time to think about it, he reached inside his safety glasses with his hand to rub his eyes, causing the safety glasses to be lifted off his face. Unfortunately, without realizing it, a beam of the laserwas, at that time, pointing straight at him. It only happened probably less than a second, but it was enough that the laser hit his eyes and sufficient to cause damage.

I'm not going to go into detail of what happened immediately afterwards, because it isn't relevant to this story. So of course, after this incident is reported, the lab issued a lab-wide stand-down, and all operations of Class 2b laser and higher had to stop. We were told to evaluate our laser operations and safety procedure, and we had to get reauthorized before we can continue work. At the same time, all personnel that are involved in any laser work had to attend a safety seminar.

So I sat through this safety seminar where they described the accident, emphasize the need for us to work safely, re-enforce the requirements for safety procedure... etc...etc. But at the same time, in response to the accident, they produced a whole new set of policy and procedures for all laser facilities. We had to have yearly inspection, yearly authorization, and new documentation of our procedure and safety analysis. In other words, new set of administrative controls were introduced.

Of course, as you can guess, there were groans in the audience, because it meant that there would be more bureaucratic paperwork and administrative hoops that we had to go through. During the Q&A session, several people asked questions, and one could tell that a lot of people in the audience weren't too pleased by this. Finally, and this is where I came, in, I raised my hand, and asked something like this:

"So how would any of the new procedures that were introduced prevented this accident?"

Now, looking back on it afterwards, I would describe the audience reaction to my question as what I imagined would happen when someone finally yelled that the Emperor had no clothes. In this case, the Emperor truly had no clothes. It was an unfortunate accident, but no amount of training, regulation, safety briefing, paperwork, review, etc. would have prevented it, because that was something instinctual. The new administrative policy that was put in place didn't make any of us who work with these lasers any safer. I certainly didn't feel any safer than before. Yet, this was imposed upon us. It wasn't to make us any safer or to prevent any accident. It is simply to placate the higher-ups, the stakeholders, the policy makers, the regulators, the administrators, and finally and ultimately, the politicians (if they decided to look into this). They can say that they implemented this and that after the accident to make them look good. The rest of us who are actually doing the work get saddled with more paperwork and more hoops to jump through.

I'm certain that this isn't new, and that many people have gone through such similar situations where what is being done in the name of something really isn't effective and may miss the mark. Often times, we simply go along just to make the administration happy so that we can move on and continue with our work. But it still means that the Emperor has no clothes, and sometime, someone really needs to stand up and points out this ridiculousness.


Tuesday, January 31, 2017

Fermilab's Greatest Hits

Highlights from the first 50 years at the historic Fermi National Accelerator Laboratory.


Monday, January 30, 2017

Presidential Executive Order and US Conferences

With the two big conferences looming this year, the APS March and April Meetings, it will be interesting to hear how the recent presidential executive order banning entry by visitors from 7 predominantly-Muslim countries will have affect. Citizens from countries such as Iran already had a long and arduous process in gaining a visitor visa to come to the US, so much so that many won't even bother to try.

So now, with the entry ban, looks like this will have an impact on visiting scientists from these affected countries. Unfortunately, this will create an even bigger ramification, because international organizations will be less inclined to hold major conferences in the US where some of its members will not be allowed to attend. This should have both scientific and economic impacts.

So far, there has been no official word from the APS on this matter.


Friday, January 27, 2017

3 Things Everyone Should Know About Physics

This is an exceptionally good answer to the question: "What do physicists wish the average person knew about physics?" The answer was written by Inna Vishik, Assistant Professor of Physics at the University of California, Davis.
  • Physics makes predictive models about the natural world based on empirical observations (experiments), mathematics, and numerical simulations. These models are called ‘theories’, but this does not mean they are speculative; physics theories explain past behavior and predict future behavior. When a previously-validated theory fails to explain the behavior in a new physical system, it doesn’t mean the theory is suddenly ‘wrong’ altogether, it means that it is inapplicable in a certain regime. It is very exciting for physicists when these exceptions are found, and it is in these holes in our models that we propel our understanding of the physical world forward.
  • The domain of physics is vast. Some physicists study the existing universe around us. Some study the smallest constituent particles and forces of matter in this universe. Some manipulate clusters of atoms, and some manipulate light. Some study crystalline solids and the myriad properties they can have when quadrillions of atoms and electrons are arranged in slightly different ways. Others study biological systems. This is not a full list of the many subfields in physics, but what they all have in common is they combine classical (including continuum) mechanics, quantum mechanics, statistical mechanics, general relativity, and electricity and magnetism in various configurations to explain the physical and engineered world around us.
  • Research in physics and other fundamental sciences play three crucial roles in an advanced society; they cement our cultural legacy by exploring one aspect of the human condition (the universe we occupy), similar to the role of the arts; they educate a portion of the work force in solving difficult, open ended problems beyond the limits of prior human innovation; they provide the seeds for future technological developments, which is often realized decades in the future in an unpredictable manner (i.e. not amenable to quarterly earnings reports). At the time of their inception, electromagnetic waves (late 19th century), quantum mechanics (early 20th century) and lasers (mid 20th century) were viewed even by their progenitors as esoteric curiosities; now they permeate our life, technology, and medicine so deeply that no one would question their practical importance. In the modern physics research era, there are newer ideas that might have an equally important impact 50 years from now, but they will never be realized without continued investment in the public good known as fundamental science.


Metallic Hydrogen?

The big news so far this week is the publication on the possible (key word) creation of solid metallic hydrogen.

If this is true, then this is a significant discovery and confirmation of a prediction from many years ago. Understandably, with the press releases on this work, the popular media have been going ga-ga over this.

However, upon trolling all the various news reports, only the Independent so far has an update on the news story about doubts about this discovery.

This is taken from a news report published in Nature:

As with ANYTHING in Science, we have to give this a period of gestation before we all jump onto the bandwagon. It needs to be independently verified, and even the authors admit that this needs to be refined even more to produce a conclusive evidence of metallic hydrogen.


Wednesday, January 25, 2017

The Technology Of Detecting Gravitational Wave

The biggest physics news of 2016 was certainly the detection (finally!) of gravitational wave by LIGO.

In this CERN Courier article, the physics and methodology of making such a difficult detection is described. As you read this article, keep in mind that at each step of the development and evolution of the facility, there had to be advances and improvements in the detection method, which by itself, is significant. The technology and engineering involved in many this detection, and in many other science experiments, often drives the development of the technology that eventually finds applications in the rest of the population.


Thursday, January 19, 2017

Rick Perry Backtracks On DOE

During his confirmation hearing today, Rick Perry changed his mind about wanting to shut down the US Dept. of Energy.

I have learned a great deal about the important work being done every day by the outstanding men and women of the Department of Energy. I have spoken several times to Secretary Moniz about the operation. I have spoken to his predecessors. And if confirmed, my desire is to lead this agency in a thoughtful manner surrounding myself with the expertise on the core function of the department. My past statements made over five years ago about abolishing the Department of Energy do not reflect my current thinking. In fact, after being briefed on some of the vital functions of the Department of Energy, I regret recommending its elimination.

While it is good of him to chance his mind once he learned a bit more of what he's talking about, it doesn't diminish the fact that he and many other politicians are in a habit of going public with ideas and policies out of IGNORANCE. For some odd reason, many of them do not care that they make up their minds AND going public with such decision BEFORE they actually gather proper information about these things.

And if you think this is an isolated incident, you'd be wrong. I've highlighted several rather DUMB AND STUPID actions or comments made in public by these elected officials, all out of ignorance (read this and this, for example). I think that this is a common, standard-operating-procedure by many elected officials, that they really didn't do their homework in many decisions that they make.


Monday, January 16, 2017

Fermions and Bosons

Fermilab's Don Lincoln describes what bosons and fermions are, for those who don't know.


Thursday, January 12, 2017

Imaging Fukushima Reactor Core Using Muons

If you are in the US, did you see the NOVA episode on PBS last night titled "The Nuclear Option"? If you did, did you miss, or not miss, the technique of imaging the Fukushima reactor core using the muon tomography developed at Los Alamos?

You see, whenever I see something like this, I want to shout out loud to the public on another example where our knowledge from high energy physics/elementary particle physics can produce a direct practical benefit. A lot of people still question whether our efforts in these so-called esoteric areas are worth funding. So whenever I see something like this, there should be a conscious and precise effort to point out that:

1. We had to first understand the physics of muons from our knowledge of the Standard Model of elementary particle.

2. Then those who do understand this often will start to figure out, often with collaboration of those in other areas of physics, of what could possibly be done with such knowledge.

3. And finally, they come up with a practical application of that knowledge, which originated out of an area that often produces no immediate and obvious application.

Things like this must be pointed out in SIMPLE TERMS to both the public and the politicians, because that is the only level that they can comprehend. I've pointed out previously many examples of the benefits that we get, directly or indirectly, from such field of study. It should be a requirement that any practical application should present a short "knowledge genealogy" of where the idea came from. It will be an eye-opener to many people.


Monday, January 09, 2017

Mpemba Effect Is Still Hot After All These Years

OK, maybe not hot, but it is certainly at least lukewarm.

If you don't know anything about this, I've made several posts on the Mpemba effect before (read here, here, here, and here). Briefly, this is the effect where hot water is seen to freeze faster than cold water. Even after its purported discovery many years ago, the validity of this effect, and the possible explanation for it are still being debated.

Add this report to the body of discussion. It seems that there are new papers that are using molecular bonds in water as the possible explanation for this effect.

Now researchers from the Southern Methodist University in Dallas and Nanjing University in China think they might have a solution - strange properties of bonds formed between hydrogen and oxygen atoms in water molecules could be the key to explaining the elusive Mpemba effect.

Simulations of water molecule clusters revealed that the strength of hydrogen bonds (H-bonds) in a given water molecule depends on the arrangements of neighbouring water molecules.

"As water is heated, weaker bonds break, and groups of molecules form into fragments that can realign to form the crystalline structure of ice, serving as a starting point for the freezing process," Emily Conover reports for Science News.

"For cold water to rearrange in this way, weak hydrogen bonds first have to be broken."
I'm sure this will not be the last time we hear about this.


Friday, January 06, 2017

The Brachistochrone Problem

There are many sources that describes this problem. Mary Boas also devoted a substantial portion of it in her classic text "Mathematical Methods in the Physical Sciences". Here, Rhett Allain describes it once more in his Wired article.

Laymen might find it fascinating just to know the shape of the path, while physics students might find it useful especially if you're just about to take class in Least Action principle.


Thursday, January 05, 2017

Happy New Year!

A belated Happy New Year to everyone. I hope you all had a great holiday season.

Those of us in the US are facing a rather uncertain next few months. With the new administration taking office and the issue of science and science funding being trivialized during this last presidential election, no one knows where things are going. With Rick Perry slated to be nominated as the Secretary for the Dept. of Energy, it is like having the wolf looking after the sheep, since he had stated on more than one occasion of abolishing this part of the US govt. Sorry, but I don't think he has a clue what the DOE actually does.

This is not the first time someone who has no expertise in STEM is heading a dept. that deals with STEM. I've always wondered about the logic and rational of doing that. You never seen someone who is not an expert in finance or economics heading, say, the Treasury! So why is the DOE, which has been a significant engine in research, science, and technology, and which is the area that has been attributed to be responsible for the significant growth in our economy, being relegated as an ugly stepchild? Is it because STEM and STEM funding does not have a built-in constituent that will make public and political noise?

At this point, I have very low expectations for a lot of things during these next few years.