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Science of Santa December 24, 2021

Posted by apetrov in Blogroll, Cool non-physics stuff, Funny, Near Physics.
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How does Santa manage to visit so many children’s homes in such a short time? While this question has been used to doubt the existence of Santa himself, different sciences might provide answers to it. Here are some of them

Astrophysics: Santa is nonluminous material that is postulated to exist in space that could take any of several forms (including the big fat guy in a red suit) that clumps in the locations of children’s houses.

Biology: Santa is a biological entity (such as Dolly the sheep) that produces multiple clones of itself once a year.

Botany: Santa is a mycelium-like vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae that propagate around most of the planet. Once a year it develops multiple fruiting bodies whose locations coincide with the locations of human children’s houses. In simpler terms, Santa is a mushroom.

Quantum Mechanics: Santa consists of multiple quantum objects in an entangled state. His existence signifies the fact that most accepted formulations of quantum mechanics are incomplete.

Cosmology: in its evolution, Santa goes through the epoch of rapid exponential superluminal expansion.

Computer science/Hollywood/sometimes even particle physics: since we all live in a computer simulation, Santa is one of the swarming bots created by the Analyst to control the inhabitants of the Matrix.

Economics: we don’t care how he does it. It positively affects the GDP of many countries.


Act to eradicate racism in academia and science! June 9, 2020

Posted by apetrov in Education, Near Physics, Particle Physics, Physics, Science.
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A lot has been said about ethnic and racial disparities in academia. As my friend and former postdoc advisor Adam Falk eloquently pointed out “the sin of silence is worse than the sin of inadequacy.” I think the sin of inaction is probably even worse. So I would like to act. I would like to see my actions, however insignificant, have immediate positive impact and lead to actual improvement of the situation.

I donated my today’s salary to the National Society of Black Physicists (NSBP). I hope that my small act will support scholarships for African American physics majors at Universities across the country. But one small act repeated many times can result in something big. Please join me and donate your today’s salary to NSBP!

Please go to https://www.nsbp.org/support-nsbp/nsbp-donations and support the organization that seeks to increase opportunities for African Americans in physics education and research. I would be very grateful if you then tell me about it in the comments!

CP-violation in charm observed at CERN March 21, 2019

Posted by apetrov in Near Physics, Particle Physics, Physics, Science.
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There is a big news that came from CERN today. It was announced at a conference called Recontres de Moriond, one of the major yearly conferences in the field of particle physics. One of the CERN’s experiments, LHCb, reported an observation — yes, observation, not an evidence for, but an observation, of CP-violation in charmed system. Why is it big news and why should you care?

You should care about this announcement because it has something to do with how our Universe looks like. As you look around, you might notice an interesting fact: everything is made of matter. So what about it? Well, one thing is missing from our everyday life: antimatter.

As it turns out, physicists believe that the amount of matter and antimatter was the same after the Universe was created. So, the $1,110,000 question is: what happened to antimatter? According to Sakharov’s criteria for baryonogenesis (a process of creating  more baryons, like protons and neutrons, than anti-baryons), one of the conditions for our Universe to be the way it is would be to have matter particles interact slightly differently from the corresponding antimatter particles. In particle physics this condition is called CP-violation. It has been observed in beauty and strange quarks, but never in charm quarks. As charm quarks are fundamentally different from both beauty and strange ones (electrical charge, mass, ways they interact, etc.), physicists hoped that New Physics, something that we have not yet seen or predicted, might be lurking nearby and can be revealed in charm decays. That is why so much attention has been paid to searches for CP-violation in charm.

Now there are indications that the search is finally over: LHCb announced that they observed CP-violation in charm. Here is their announcement (look for a news item from 21 March 2019). A technical paper can be found here, discussing how LHCb extracted CP-violating observables from time-dependent analysis of D -> KK and D-> pipi decays.

The result is generally consistent with the Standard Model expectations. However, there are theory papers (like this one) that predict the Standard Model result to be about seven times smaller with rather small uncertainty.  There are three possible interesting outcomes:

  1. Experimental result is correct but the theoretical prediction mentioned above is not. Well, theoretical calculations in charm physics are hard and often unreliable, so that theory paper underestimated the result and its uncertainties.
  2. Experimental result is incorrect but the theoretical prediction mentioned above is correct. Maybe LHCb underestimated their uncertainties?
  3. Experimental result is correct AND the theoretical prediction mentioned above is correct. This is the most interesting outcome: it implies that we see effects of New Physics.

What will it be? Time will show.


Rapid-response (non-linear) teaching: report January 25, 2018

Posted by apetrov in Blogroll, Education, Near Physics, Physics, Science.
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Some of you might remember my previous post about non-linear teaching, where I described a new teaching strategy that I came up with and was about to implement in teaching my undergraduate Classical Mechanics I class. Here I want to report on the outcomes of this experiment and share some of my impressions on teaching.

Course description

Our Classical Mechanics class is a gateway class for our physics majors. It is the first class they take after they are done with general physics lectures. So the students are already familiar with the (simpler version of the) material they are going to be taught. The goal of this class is to start molding physicists out of physics students. It is a rather small class (max allowed enrollment is 20 students; I had 22 in my class), which makes professor-student interaction rather easy.

Rapid-response (non-linear) teaching: generalities

To motivate the method that I proposed, I looked at some studies in experimental psychology, in particular in memory and learning studies. What I was curious about is how much is currently known about the process of learning and what suggestions I can take from the psychologists who know something about the way our brain works in retaining the knowledge we receive.

As it turns out, there are some studies on this subject (I have references, if you are interested). The earliest ones go back to 1880’s when German psychologist Hermann Ebbinghaus hypothesized the way our brain retains information over time. The “forgetting curve” that he introduced gives approximate representation of information retention as a function of time. His studies have been replicated with similar conclusions in recent experiments.

EbbinghausCurveThe upshot of these studies is that loss of learned information is pretty much exponential; as can be seen from the figure on the left, in about a day we only retain about 40% of what we learned.

Psychologists also learned that one of the ways to overcome the loss of information is to (meaningfully) retrieve it: this is how learning  happens. Retrieval is critical for robust, durable, and long-term learning. It appears that every time we retrieve learned information, it becomes more accessible in the future. It is, however, important how we retrieve that stored information: simple re-reading of notes or looking through the examples will not be as effective as re-working the lecture material. It is also important how often we retrieve the stored info.

So, here is what I decided to change in the way I teach my class in light of the above-mentioned information (no pun intended).

Rapid-response (non-linear) teaching: details

To counter the single-day information loss, I changed the way homework is assigned: instead of assigning homework sets with 3-4-5 problems per week, I introduced two types of homework assignments: short homeworks and projects.

Short homework assignments are single-problem assignments given after each class that must be done by the next class. They are designed such that a student needs to re-derive material that was discussed previously in class (with small new twist added). For example, if the block-down-to-incline problem was discussed in class, the short assignment asks to redo the problem with a different choice of coordinate axes. This way, instead of doing an assignment in the last minute at the end of the week, the students are forced to work out what they just learned in class every day (meaningful retrieval)!

The second type of assignments, project homework assignments are designed to develop understanding of how topics in a given chapter relate to each other. There are as many project assignments as there are chapters. Students get two weeks to complete them.

At the end, the students get to solve approximately the same number of problems over the course of the semester.

For a professor, the introduction of short homework assignments changes the way class material is presented. Depending on how students performed on the previous short homework, I adjusted the material (both speed and volume) that we discussed in class. I also designed examples for the future sections in such a way that I could repeat parts of the topic that posed some difficulties in comprehension. Overall, instead of a usual “linear” propagation of the course, we moved along something akin to helical motion, returning and spending more time on topics that students found more difficult (hence “rapid-response or non-linear” teaching).

Other things were easy to introduce: for instance, using Socrates’ method in doing examples. The lecture itself was an open discussion between the prof and students.


So, I have implemented this method in teaching Classical Mechanics I class in Fall 2017 semester. It was not an easy exercise, mostly because it was the first time I was teaching GraphNonlinearTeachingthis class and had no grader help. I would say the results confirmed my expectations: introduction of short homework assignments helps students to perform better on the exams. Now, my statistics is still limited: I only had 20 students in my class. Yet, among students there were several who decided to either largely ignore short homework assignments or did them irregularly. They were given zero points for each missed short assignment. All students generally did well on their project assignments, yet there appears some correlation (see graph above) between the total number of points acquired on short homework assignments and exam performance (measured by a total score on the Final and two midterms). This makes me thing that short assignments were beneficial for students. I plan to teach this course again next year, which will increase my statistics.

I was quite surprised that my students generally liked this way of teaching. In fact, they were disappointed that I decided not to apply this method for the Mechanics II class that I am teaching this semester. They also found that problems assigned in projects were considerably harder than the problems from the short assignments (this is how it was supposed to be).

For me, this was not an easy semester. I had to develop my set of lectures — so big thanks go to my colleagues Joern Putschke and Rob Harr who made their notes available. I spent a lot of time preparing this course, which, I think, affected my research outcome last semester. Yet, most difficulties are mainly Wayne State-specifics: Wayne State does not provide TAs for small classes, so I had to not only design all homework assignments, but also grade them (on top of developing the lectures from the ground up). During the semester, it was important to grade short assignments in the same day I received them to re-tune lectures, this did take a lot of my time. I would say TAs would certainly help to run this course — so I’ll be applying for some internal WSU educational grants to continue development of this method. I plan to employ it again next year to teach Classical Mechanics.

So, you want to go on sabbatical… February 5, 2015

Posted by apetrov in Blogroll, Near Physics, Physics, Science.
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Every seven years or so a professor in a US/Canadian University can apply for a sabbatical leave. It’s a very nice thing: your University allows you to catch up on your research, learn new techniques, write a book, etc. That is to say, you become a postdoc again. And in many cases questions arise: should I stay at my University or go somewhere else? In many cases yearlong sabbaticals are not funded by the home University, i.e. you have to find additional sources of funding to keep your salary.

I am on a year-long sabbatical this academic year. So I had to find a way to fund my sabbatical (my University only pays 60% of my salary). I spent Fall 2014 semester at Fermilab and am spending Winter 2015 semester at the University of Michigan, Ann Arbor.

Here are some helpful resources for those who are looking to fund their sabbatical next year. As you could see from the list, they are slightly tilted towards theoretical physics. Yet, there are many resources that are useful for any profession. Of course your success depends on many factors: whether or not you would like to stay in the US or go abroad, competition, etc.

  • General resources:

Guggenheim Foundation
Deadline: September

Fulbright Scholar Program
Deadline: August

  • USA/Canada:

Simons Fellowship
Deadline: September

IAS Princeton (Member/Sabbatical)
Deadline: November

Perimeter Institute:
Visiting Professors
Deadline: November

Radcliffe Institute at Harvard University
Deadline: November

URA Visiting Scholar program
Intensity Frontier Fellowships
Deadline: twice a year

  • Europe:

Alexander von Humbuldt:
Friedrich Wilhelm Bessel Research Award
Humboldt Research Award
Deadline: varies

Marie Curie International Incoming Fellowships
Deadline: varies

CERN Short Term visitors
Deadline: varies

Hans Fischer Senior Fellowship (TUM-IAS, Munchen)
Deadline: varies
Some general  info that could also be useful can be found here.

I don’t pretend to have a complete list, but those sites were useful for me. I did not apply to all of those programs — and rather unfortunately, missed a deadline for the Simons Fellowship. Many University also have separate funds for sabbatical visitors. So if there is a University one wants to visit, it’s best to ask.

On a final note, it might be useful to be prepared and figure out, if you get funded, how the money/fellowship will find a way to your University and to you. Also, in many cases “60% of the salary” paid by your University while you are on a sabbatical leave means that you would have to find not only the remaining 40% of your salary, but also fringes that your University would take from your fellowship. So the amount that you’d need to find is more than 40% of your salary. Please don’t make a mistake that I made. 🙂

Good luck!

Digital bureaucracy August 9, 2013

Posted by apetrov in Near Physics.

This post is about how digital technology of the 21st century “helps” professors (well, at least, this professor) to spend his time doing very important paper submission. Except for the fact that “paper” here refers to the receipts of the expenses that were incurred attending professional conferences. Sorry in advance for the rant that follows.

As an introduction, let me tell you how the procedure used to work at our University. Before going to a conference I had to “encumber” (“reserve”) expenses that I planed to incur – filling out one paper form, no receipts. After return from the conference, I would fill out the same form and attach receipts. Our secretary would then type the form up nicely and submit it for reimbursement. It would normally take weeks to get reimbursed, but timewise I’d spend only about 10-15 min doing the whole procedure. Including a nice cover letter to the said secretary summarizing the details and thanking her for her job. 15 min.

Enter digital age! And the age of layoffs. With great fanfare, the university rolled out a new digital system in 2012 — no paper (save the trees!), no secretary involvement (remember the age of layoffs?), maybe even quick turn-around, yahoo!!! Even MIT does not have such a system! Take that, MIT!

Except for now I have to first file the request, complete with all receipts and a conference agenda. No problem, right? So it takes about 20 min to collect all receipts, turn them into pdf files and fill out a bunch of forms electronically. Now, upon return you do the same thing. Except for now you have to

– digitize the receipts that were not digital originally (like highway tolls or gas),enter those receipts separately based on the day when the charge occurred,

– provide proof that you paid for your hotels with your own credit card — not the university one (no problem of getting the pdf file from your credit card company, blacking out your personal details and submitting, attaching it electronically to the request). Also, you’d need to itemize your hotel stay — enter how much it was per day + taxes, etc.

– you have to once again attach the same files with conference agenda.

And, of course, you have to state the business purpose of all of your lunches and dinners (not to die of hunger during the conference, I suppose?) separately for each day of the conference.

Of course, all of this is not a problem. It only takes 30-40 min to do all of this. If you know how.  So, if my math is correct (and your expense report is not returned back — so you have to fix your problems and resubmit), the whole procedure takes about 20 min+40 min = 1 hour (60 min – remember 15 min???).  Moreover, no secretary involvement, remember? I do it all myself, so the said secretary is fired.

So here is some interesting math. it takes, on average, 4 times longer for me to file the digital reports. I know now why MIT does not have such a system. I’ll take that back, MIT…. Questions remain, though. Do faculty have to do all of those reports on their own time or during the time when they are supposed to do research or write grant applications or talk to students? Does the university save money on that (hint: secretary’s salary is on average less than that of a faculty)?

So here you have it. Does it kill me to do all those things? Of course not. As it wouldn’t kill me to mop the floor in the corridor near my office or go to a supply store to buy chalk to teach my class. Hey, here is an idea for new cost-cutting measures!

Inverse superconductivity in iron telluride April 1, 2012

Posted by apetrov in Funny, Near Physics, Physics, Science, Uncategorized.
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One of the most significant advances of science in the 21st century so far is the 2008 discovery of iron-based high temperature superconductors such as LaFeAsO1-xFx. Previously, all high-temperature superconducting compounds, there so-called cuprates, were based on copper and consisted of copper oxide layers sandwiched between other substances. Much of the interest in those materials has arisen because the new compounds are very different from the cuprates and may help lead to a theory that is different from the conventional BCS theory of superconductivity, where electrons pair up in such a  way that  so coupled they can then move without resistance through the atomic lattice.

Among those new materials is the iron telluride, FeTe. This compound has the simplest crystal structure and exhibits antiferromagnetic ordering around 70 K and does not show superconductivity. It is now known that substitution of S for Te sites suppresses the antiferromagnetic order and induces superconductivity. Quite amazingly, this is not the most surprising property of those compounds. In a quite remarkable study performed by a group of Japanese physicists, it was shown that the iron-based compound FeTe0.8S0.2 exhibit superconductivity if soaked in red wine. They also performed a study of the effect with different types of wine and other alcoholic beverages, finding that a particular type of wine, 2009 Beajoulais from the French winery of Paul Beaudet, has the most profound effect.

A recent follow-up analysis, however, showed that subsequent and repeated applications of red wine and hard alcoholic beverages, such as cognac or vodka, can induce a new state in the study samples, dubbed the inverse superconductivity. The results, reported in the recent issue of Wine Spectator, clearly show steep increase of the samples’ resistivity after only five consequent applications of the liquid substance. As explained by the lead author of the study, John Piannicca, the results follow the simple model of the electron crowd. Interestingly enough, as reported by Dr. Piannicca, this model was developed by observing the change in the mean free path of a group of students visiting bars near the campus of his University.

Moreover, as was shown in a recent work of a group of scientists at the Siberian institute of Advanced Kevlar Engineering, it is also the quantity of alcohol that was responsible for the onset of inverse superconductivity. While this is also consistent with the already mentioned model of electron crowd, the samples obtained in the Siberian lab required much larger quantities of alcohol to achieve the same effect than those obtained in the American or Japanese labs, which could probably be explained by the specifics of liquid utilization. As was shown, the best effect was achieved with a brand of vodka “Imperia” commonly “recognized for it superbly smooth spirit and pure taste,” as advocated by its producers. It would be interesting to see how other brands would fare in such a study, which is on-going.

Why do physicists go to Aspen? September 1, 2011

Posted by apetrov in Near Physics, Particle Physics, Physics, Science.
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While the most obvious answer to this question is “to ski”, it is, nonetheless, not the correct one. Yes, skiing is great here in the winter (and hiking is great in the summer), but most of the time physicists come here to work. The reason is Aspen Center for Physics. I write “here” because I’m currently participating in one of the programs organized by the Center (the program is called “Flavor Origins” — it brought together theorists working on the problems of neutrinos, heavy and light quarks, CP-violation, etc.). The Center, which exists here since 1961, organizes workshops and conferences. But the main reason that theorists (and occasional experimentalists) come here is to talk to other theorists. In short, it is as if you are visiting a huge theory group — you can work individually or with your colleagues, but you can always knock on an office door and bounce your ideas off someone else visiting the Center, etc. It is great to have such a concentration of theorists of different trades. And it leads to breakthroughs and simply good papers. As it is said on the Center’s website:

“Many seminal papers have been written in Aspen, which has grown to be the largest center for theoretical physics in the world during its summer sessions. Among many other subjects, the theories of superstrings, chaos, evolution of stars and galaxies, and high temperature superconductivity have all made large strides in recent Aspen seasons.”

There is almost always someone with an expertise in a subject that you have a question about. And that makes this Center great. And, of course, hiking and skiing is also good. The only “downside” (note the quotes) is that you can meet a real bear (even at the Center) or other wildlife. Today a snake came to check out a lecture on conformal field theories…

P.S. Also check out my blog on Quantum Diaries

Congratulations Dr. Yeghiyan! July 26, 2011

Posted by apetrov in Near Physics, Particle Physics, Physics, Science, Uncategorized.
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Today my third graduate student at WSU, Gagik Yeghiyan, defended his Ph.D. thesis. Congratulations Dr. Yeghiyan! Good luck to you in your new life as an Assistant Professor at Grand Valley State University!

Update on the situation at Japan’s Fukushima nuclear plant March 15, 2011

Posted by apetrov in Near Physics, Physics, Science, Uncategorized.

The situation at Japan’s Fukushima nuclear plant remains fluid, but it makes sense to do an update. It turns out that the situation is more challenging then I originally thought. To recreate what is happening (based mainly on TEPCo’s press releases and Japan’s Nuclear and Industrial Safety Agency (NISA) press releases), let us take a look at the Mark 1 BWR reactor (for a short description of physics of the nuclear power generation and schematics, please see my earlier post):

This picture was modified (by me) from the materials provided by Department of Energy’s Nuclear Regulatory Comission’s (NRC) website. It is Mark-1 BWR-type nuclear power reactor supplied by General Electric.

The Fukushima Daiichi plant operates six reactors, Units 1, 2 and 6 are supplied by General Electric (Unit 1 is the oldest, built in the 70’s — I’ve heard it was supposed to be decommissioned this Spring), while Units 3-5 are supplied by Toshiba and Hitachi. So, what is happening there?

As you already know, the magnitude 9.0 on Richter’s scale earthquake hit Japan. The reactors at the Fukushima plant were designed to withstand the 8.2 magnitude quake. Nevertheless, the structures held (note that the Richter scale is logarithmic, meaning that 9.0 earthquake releases 10 times energy than 8.0). Since Japan is located in seismically-active zone, there exist provisions on what to do in case of one, especially for the nuclear power stations.Reactors 1-3 were operational at the time of the earthquake, while reactors 4-6 were in a shutdown mode.

So, first and foremost, control rods (containing boron, neutron-absorbing material) were automatically inserted. According to  TEPCo’s press release, this was done successfully at all three units that were in operation. There was an alarm on Unit 1 that one of the rods was not fully inserted. The alarm then went away. It is now believed that all control rods were fully inserted and chain reaction in fuel assemblies was stopped. Even after this, one must keep circulating water in order to continue cooling fuel assemblies due to the heat produced by decays of nuclear reaction products in the fuel rods. It needs to be done for several days.

It appears that over the course of three days reactor cooling systems kept failing, which resulted in increasing steam pressure in the reactor pressure vessel (see the picture above). In this case you really don’t want to keep the pressure rising, as it eventually would simply blow up the containment vessel and you’d get pretty much what happened in Chernobyl. So, the idea is to gradually release pressure by disposing the (slightly radioactive) steam through the vent line (see above picture). The steam is only slightly radioactive because one is using purified water, which does not get activated by the radiation from the fuel assemblies. This was done at all three units. You have to still keep cooling the core, which was done at Units 1 and 3 with injection of seawater into the Primary Containment Vessel and at Unit 2 with seawater injection into the Reactor Pressure Vessel. Injecting seawater is a desperate move, as it contains salt and other staff that can get activated. Which means that the reactor will be decommissioned regardless of whether there is a meltdown or not. Along with seawater, they injected boric acid to capture neutrons.

Now, if the cooling is ineffective (as it appears is at Fukushima) and you keep disposing steam, you lose the amount of water you have in your reactor (think of a boiling teapot). This leads to water levels in the reactor dropping to the point that the fuel assemblies get exposed to steam. This is what happened at Fukushima. This is bad, because this drops cooling efficiency and fuel rods start to heat up (recall the decays of radioactive decay products that are still going on). At some point, zirconium in the ziralloy (the alloy of zirconium and tin that makes up the fuel rod casings) starts react with water vapor. Here is the chemical reaction:

2 H20 + Zr = 2 H2 + Zr O2 + energy

which means that you start producing hydrogen (H2), some of which will escape into the reactor building. Most likely, escaped hydrogen exploded in units 1-3, blowing off the roofs of the reactor building hosting Unit 1, 2, and 3, like this:

This picture is done by the local TV station and posted on Wikipedia. According to the power station owners, the containment vessels are still intact, which is precisely what they are designed to do. Let’s hope that this is an accurate assessment.

Now, if there is a meltdown (fuel rods are damaged), some of the reaction products might get into the atmosphere (the troubling news is that the monitoring stations did detect small amounts of iodine nearby the reactor). The most immediate concern are radioactive Iodine (half-life of 8 days) and Cesium (half-life is 30 years). Iodine can accumulate in human’s thyroid gland – so the first line of defense is to saturate the gland with non-radioactive Iodine. This is why the population around the station is given iodine tablets as a precaution. The detected amounts of iodine are not of a concern for the US West Coast (too far).

In the case of a serious meltdown, the melted fuel will likely remain in the reactor containment below the rector pressure vessel. This would be bad, but still nowhere near Chernobyl’s explosion. BTW, I was on a school trip in Kiev when the Chernobyl power station blew up. I had to bury my shoes because the radioactivity levels on them were too high (dust)…

To add to the problem, rector unit 4 (which was not operational at the time of an earthquake) developed problems of its own. In particular, it appears that the personnel missed that the water level in the spent fuel pool came down. This exposed spent fuel rods that contain more long-lived radioactive isotopes. You want to keep spent fuel rods in the water to cool them, as the decays still produce heat. In this case, usual convection cooling (warm water is rising and is replaced by cooler water) is sufficient to keep them cool. That is, if there is water! There was report of a fire at the spent fuel pond. This might indicated that the water level in the pool went down and spent fuel caught on fire. This might be bad, as this would release radioactive material in the air. Japanese scientists monitor the situation.

I’ll try to keep you posted as well.