Do Students Know What They Know?

This is a rather interesting research on an effect that I was never aware of till now - the Dunning-Kruger effect. This is the effect where "... low-performing students tend to overestimate their abilities, while high-performing students estimate their abilities more accurately... "

The authors in this study compared their results from a physics course and a chemistry course, and came up with roughly the same effect.

Abstract: We have conducted an investigation into how well students in introductory science classes (both physics and chemistry) are able to predict which questions they will or will not be able to answer correctly on an upcoming assessment. An examination of the data at the level of students’ overall scores reveals results consistent with the Dunning-Kruger effect, in which low-performing students tend to overestimate their abilities, while high-performing students estimate their abilities more accurately. Similar results have been widely reported in the science education literature. Breaking results out by students’ responses to individual questions, however, reveals that students of all ability levels have difficulty distinguishing questions which they are able to answer correctly from those that they are not able to answer correctly. These results have implications for the future study and reporting of students’ metacognitive abilities.

(You should be able to get the paper for free)

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DES Sky Survey

I mentioned a while ago of the Dark Energy Survey project that is trying to map our universe and possibly produce a clearer picture of the dark energy phenomenon. This week we have one of the first mapping of our universe from DES, from just 3% of the DES data.

The DES dark matter map is not the first of its kind. Several pioneering analyses have come before it, most notably the Canada-France-Hawaii Telescope Lensing Survey, which used 4 times the number of distant galaxies that DES used to map an area of similar size but at higher resolution. The two teams have reached the same conclusions, though: The luminous matter that we can see is housed within the dark matter structures that we cannot see, and this dark matter forms a cosmic web of filaments, knots, and voids. As it continues collecting and analyzing data, DES will be able to map how these dark matter structures evolve over time.

There's a lot more to be discovered here as more of the data are analyzed.

Zz.

Report From 13 TeV

So far so good!

This report briefly describes the achievement of getting to 13 TeV collision energy at the LHC.

At 10.40 a.m. on 3 June, the LHC operators declared "stable beams" for the first time at a beam energy of 6.5 TeV. It was the signal for the LHC experiments to start taking physics data for Run 2, this time at a collision energy of 13 TeV – nearly double the 7 TeV with which Run 1 began in March 2010.

So far, they haven't been swallowed by a catastrophic black hole that is supposed to destroy our world. Darn it! What's next? Sighting of supersymmetry particles? You must be joking!

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Weyl Fermions

This is a bit late, but what they hey....

Here is another triumph out of condensed matter physics experiment. This is the first reported discovery of the Weyl fermions, first predicted and now found in a Tantalum arsenide compound.

Another solution of the Dirac equation – this time for massless particles – was derived in 1929 by the German mathematician Hermann Weyl. For some time it was thought that neutrinos were Weyl fermions, but now it looks almost certain that neutrinos have mass and are therefore not Weyl particles.

Now, a group headed by Zahid Hasan at Princeton University has found evidence that Weyl fermions exist as quasiparticles – collective excitations of electrons – in the semimetal tanatalum arsenide (TaAs).

For those who are keeping score, this means that these condensed matter systems have, so far, detected Majorana fermions, and analogous signatures of magnetic monopoles.

And many people still think condensed matter physics is all "applied" and not "fundamental"?

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The Standard Model Interactive Chart

Symmetry has published a webpage of an interactive chart for the Standard Model of elementary particle. It is almost like a periodic table, but with only the most basic, necessary information. A rather useful link when you need just the basic info.

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Yoichiro Nambu

This is a bit late, but I will kick myself if I don't acknowledge the passing of Yoichiro Nambu this past week. This person, if you've never heard of his name before, is truly a GIANT in physics, and not just in elementary particle. His work transcends any field of physics, and had a significant impact in condensed matter.

I wrote an entry on his work when he won the Nobel prize a few years ago. His legacy will live on long after him.

Zz.

Pentaquark Discovery - Here We Go Again!

I read with a combination excitement and skepticism of the report that LHCb may have seen not one, but two pentaquarks. The skepticism should be justified because previous claims of the discovery of such quarks have turned out to be false. Still, this one comes with a 9sigma statistics.

The LHCb team is confident that the particles are indeed pentaquarks that comprise two up quarks, one down quark, one charm quark and one anticharm quark. "Benefitting from the large data set provided by the LHC, and the excellent precision of our detector, we have examined all possibilities for these signals, and conclude that they can only be explained by pentaquark states," explains LHCb physicist Tomasz Skwarnicki of Syracuse University in the US. 

As always, and as with any other new and important claim, time will tell as more analysis and experiments are done. The public and the media, especially, need to understand that this is still a work in progress, as with any scientific endeavor.

Zz.

Space Coffee

It's amazing how much physics and engineering go into just getting the ISS occupants to have their cup of Joe while on board the space station.



They should just open a Starbucks franchise up there. It would have been easier!

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More Physics Of Bicycles

I've already covered the topic on why a bicycle can be balanced easier when it is in motion many times in this blog. But here's another entry on this matter, this time it is a video from Minute Physics. Unfortunately, the explanation comes too rapidly for one to actually understand this simply by listening (you may have to play the video a few times).



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The Physics Of Your Vehicle Gas Mileage

While fuel prices are not as high as they were a few years ago, gas/petroleum cost is always a factor in our lives if we drive often.

This article reveals the physics of your vehicle gas mileage, and what may cause it to be better or worse than others. We can add this to another entry on this similar topic that I posted earlier.

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Don't Ask Siri To Divide 0/0

... unless you want a snarky remark about your personal life from her. You might get this response:

"Imagine that you have zero cookies and you split them evenly among zero friends. How many cookies does each person get? See? It doesn't make sense. And Cookie Monster is sad that there are no cookies, and you are sad that you have no friends."

Yowzah!

So, have you tried any other math questions with Siri and got similar amusing responses? Do share!

Zz.

100 Years Of General Theory of Relativity

This is a nice Nature Physics article summarizing the history of the General Theory of Relativity, especially on the historical verification of Einstein's idea.

If you have access to Nature Physics articles, you might also want to read the link in this paragraph:

Not everyone embraced the theory, though: in a Commentary on page 518 Milena Wazeck discusses the anti-relativist movement of the 1920s and uncovers an international network of opponents. Without any attempt at engaging in scientific argumentation, the refuters considered themselves “the last defenders of true physics”. Wazeck sees parallels with adversaries of Darwinism or anthropogenic climate change.

I suppose I shouldn't be surprised, but I continue to be amazed that human beings have such short memory, and how we continue to repeat the same things or the same mistakes that had been done before.

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4 Common Misconception About Quantum Physics

I've been critical of several physics article that have appeared in Epoch Times, many of them verging on crackpottery. But I have to admit, this one is actually quite good. It details 4 important misconception that came out of QM.

My summary of these misconceptions are:

1. Quantum entanglement transfers information faster than c.

2. Consciousness is necessary to "collapse" wave-function.

3. QM is only valid at the subatomic level.

4. Wave-particle "duality".

You may read the article to get the details, but for an article designed for the general public, it is actually quite accurate and understandable.

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Gravitational Lensing

Here's a simple intro to gravitational lensing, if you are not familiar with it.



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Quantum Superposition Destroyed By Gravitational Time Dilation?

This is another interesting take on why we see our world classically and not quantum mechanically. Gravitational time dilation is enough to destroy coherent states that maintain superposition.

With this premise, the team worked out that even the Earth's gravitational field is strong enough to cause decoherence in quite small objects across measurable timescales. The researchers calculated that an object that weighs a gram and exists in two quantum states, separated vertically by a thousandth of a millimetre, should decohere in around a millisecond. 

I think this is similar to Penrose's claim that gravity is responsible for decoherence of quantum states. It will be interesting if anyone can experimentally verify this latest theoretical finding.

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July Is The Least Popular Month For Physics

I did not know that!

The Buzz Blog at the APS Physics Central has a very interesting statistics on popularity of the word "physics" on Google search, and it showed a prominent pattern of large, yearly dip in July!

July is the least popular month for physics, marking the bottom of a decline that starts in May. This is not really surprising given that schools in the Northern Hemisphere tend to finish in May or June, and that July is the most popular month for vacations for Americans. Physics is definitely an academic term and it makes sense that its popularity aligns with students and researchers working to the academic calendar. Other academic terms such as "literature", "economics", and "math" also have minimum online interest during July. "Surfing", on the other hand, has a peak interest in July.

This means that right now, the date that this blog entry is posted, is the beginning of the downtrend. I won't blame you guys if the number of hits and read of this blog takes a strong dip starting now! :)

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How You Ask A Test Question May Impact A Student's Performance

When I first read this, I must say that I was not totally surprised by its results and conclusions.

This study was done on a group of female students at the University of Cambridge. In the study, they asked practically the same type of question, covering the same material, but in different ways. The students seem to do better when answering the questions when the "... questions are scaffolded...", i.e. it asked the students to answer one piece at a time, leading to the final answer (see the example in the paper. The paper is open access, so you should be able to get a copy of it.).

I find that one of the most common issues when students are given an entire problem in one shot is that they don't know where to start. They have all of these information swirling in their heads, and they don't know which one to use and applicable to answer the question. So having this "scaffolding", where the question asked for something obvious, and then lead the student to another level, certainly might help in guiding the student towards the final answer.

I remember my time as an undergrad at UW-Madison, taking an E&M class with Prof. Bernice Durand, that she had a unique form of assistance during her exams. She actually told us that if we got stuck, or can't answer a question, we could walk up to her during the exam, and asked for hints. Then, depending on the question, she might write something either as a hint, or something to start off. Depending on how much help she gave, the student won't get credit for knowing that part of the solution, but at least, might be able to continue and solve the rest of the problem. She told us that this way, both she and student can diagnose the source of the problem (i.e. say the student just didn't know where to start, but once that is solved, the student was able to carry out the rest of the solution),

I think this is a similar idea to this study. So as someone who benefited from this structure, I can understand how a student might do better when questions are framed like that.

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The Philosophy of the LHC

This is actually a nice article, and unlike other "confrontational" issues with regards to Physics and Philosophy, it addresses areas in which Philosophy can actually be of use in Physics, but not in the usual sense that have been tossed around.

There have been many tedious and futile discussions about the value of philosophy for modern science. I find it much more interesting and fruitful to ask if and in what way modern science can advance philosophy. The complexity, the new challenges and the new methods that arise in modern science in general - and at the LHC in particular - raise a number of questions that concern core issues of philosophy of science: what are the methods of acquiring knowledge, what is the role of models, and how does the intricate relationship between theory, computer simulations and experimental data work? The LHC has been built for fundamental physics, but it will also challenge and advance the philosophy, sociology and history of science!

We don't hear much about this aspect, mainly because it isn't "sexy". But this is a unique and useful convergence, and with physics opening up a myriad of discoveries that have changed our world view, there's nothing wrong with philosophy being guided by such discoveries.

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LHC at 13 TeV - Where Are The Crackpots Now?

I taunted the doomsday crackpots when the LHC hit 8 TeV a while back, and I'm going to taunt then again now. So where are these jokers hiding and what are their excuses for our world still had not been swallowed up by a gigantic blackhole created by the high-energy collisions?

Now granted that the last thing I want to do is hear any more nonsensical ramblings from these folks. They've take up too much oxygen already in their lifetimes. But still, I sometime wish I can come across one of them, and really, REALLY, ask them if they think that they have a huge egg on their faces. There is just not enough follow-up on things like this, and I often wonder if these people actually learned something from their silliness, or if they are still delusional and stubborn about it.

At some level, the same can be said about all those preprints and theories that came out when OPERA reported faster-than-light neutrinos. I sometime wish I could talk to these people, who I don't consider to be crackpots, but who should know better than to jump the gun. I always wanted to know why they publish their theories THAT quickly to jump on the bandwagon. Is it the idea of wanting to be the first? Is it the concept of throwing out as many darts as one can and hope that one will stick? How do they feel now that they somehow came up with a theory based on a non-existing evidence?

So many questions, and so little time to find out the answers.

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Why Do We Plot Our Data?

I stumble upon this Rhett Allain's article on Wired on the importance of plotting data, especially in experiments, and it reminded me of a similar document that had been used for quite a while at the Illinois Institute of Technology for their undergraduate physics labs.

I think both of them had the same idea and the same emphasis. Graphing and being able to know how to use it to analyze data is something that isn't normally taught in a physics class, and that is a shame, because it is an essential part of connecting experimental data to a "theory" or theoretical model. This is where the experiment and the theory meet! It is also where we can analyze how "reliable" or how much confidence we have on what we measure. This is important because when we do not have 100% certainty, we need to know when something is good enough to be accepted.

These are skills and knowledge that many are not exposed to, and it is sad that science classes, especially those involved with experiments, do not put more emphasis on such things.

Zz.