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Archive for April, 2012

We’ll deal with that later…

Monday, April 30th, 2012

In my last post, I described the different LHC collision setup at LHCb this year. Today, I thought I would describe the different LHCb trigger setup.

Now what is the LHCb trigger, I hear you all ask? I actually wrote a post on the topic last year, which I invite you all to read for details, here I’m just going to explain the details I need to describe the changes.

The LHCb trigger is an online electronic system that selects which collision events will be written to disk for offline analysis. On the right here, I have a schematic of the system. It consists of two levels; the first is made up of custom electronics, called L0, while the second is a computer farm, called HLT.

We call it an online system, as it runs in real time. As fast as collision events are coming in, the L0 electronics decides whether to reject an event or send it to the HLT. The HLT gets a little more time to make a decision, but it still needs to be pretty fast. However, sometimes it can’t handle all the events that the L0 is feeding it, and we lose events as the buffers fill up.


This situation is what our new trigger setup is designed to avoid. How are we going to do this? It was noticed that the HLT computing farm sits idle when there aren’t any collisions. So somebody came up with the clever idea to buffer events locally on the farm nodes and defer processing them until after the current collision period[*]. Thus the trigger now looks something like the schematic on the left[**].

This means we can record even more data!


[*] The LHC doesn’t collide protons continuously, there’s a cycle in which protons are injected, accelerated, collided, ejected and the machine prepared for the next injection. Ideally, most of the time would be spent in collisions (in LHC speak: stable beams), but this isn’t always possible or viable.

[**] I have obviously simplified how the deferred HLT works. Like most simple ideas, it was quite complicated in practice. There were a lot of technicalities to consider, like how many events to store in the overflow, or what to do if the overflow became full, or how to avoid the scenario where we’re still processing deferred events when the next collision period starts…


Most of all, the LHC is a machine with the purpose of breaking the known laws of the Universe.

An aerial view of the Geneva region, showing the position of the LHC tunnel (Copyright CERN)

Hi All,

Us QD folks appreciate all the questions and comments we get about the Large Hadron Collider, what we do there, and how we do it. Being head-deep in physics, though, I sometimes get the rug pulled from under my feet when I am asked,

What is the Large Hadron Collider?

It is a fun question with plenty of answers. So take your pick which is your favorite answer, or add your own in the Comments Section below. Oh, and stay tuned for posts and updates! The summer conferences kick off next week with Pheno 2012 (hashtag: #Pheno2012), and from what I gather quite a few QDers will be there.

Happy Colliding,

– richard (@bravelittlemuon)

10 Answers to ‘What is the Large Hadron Collider?’

  1. It is a machine on the verge of identifying the object responsible for electrons’ massiveness and photons’ masslessness [ATLAS,CMS].
  2. It is a science experiment with the goal of replicating, on a sub-nanoscopic scale, the Big Bang in order to search for missing antimatter [LHCb,QD].
  3. It is, believe it or not, a machine that may be capable of producing microscopic black holes [ATLAS,CMS].
  4. It is an instrument being used to look for a new, higher-energy version of radioactive decay [ATLAS,CMS].
  5. It is a tool that, if it is even possible, may be able to split the quark [ATLAS,CMS].
  6. It is an instrument that may discover, and help explorenew spatial dimensions [ATLAS,CMS].
  7. It is an effort to push computing power to its limits, and beyond!, by generating over 15 million gigabytes (15 petabytes) a year and distributing it all over the world [CERN]!
  8. It is a science experiment attempting to generate the same substance (dark matter) that makes up 25% of the known Universe and is likely passing through our bodies at this very moment, but has yet to be experimentally detected [CMS].
  9. It is a machine testing for the existence of a fundamental relationship between matter (quarks and leptons) and those particles that mediate all known forces of nature (gauge bosons). [ATLAS,CMS,LHCb]
  10. It is a cleverly designed experiment to determine at what point the predictions of our current theory of particle physics, the Standard Model, deviates from experimental results.[ATLAS, CMS, QD]
  11. As a bonus: It is a demonstration of the human race’s inherent nature to work together, and evidence that we have much more in common than what we may believe [CERN, SESAME].

Domestic science

Saturday, April 28th, 2012

We physicists are a very international crowd, and proud of it! The opening slide of conference talks typically has a list of institutions and their home countries, frequently pinned on a Google map. This kind of international collaboration is imperative to advancing science. I can’t think of any scientist who would have it any other way. Is it unreasonable, then, to push for domestic science? Is it insignificant whether an experiment is based in one’s home country (i.e. the primary country in which you have a job as a scientist) or elsewhere in the world, as long as it is somewhere?

I think not.

The more we discover, the more effort it requires to uncover the next unknown. An astounding number of scientific discoveries have taken place over the last several decades. The remaining ‘known unknowns’ are hard to reach and require expensive machinery. The ‘unknown unknowns’ require even more investment. This is one reason most large experiments are international collaborations funded primarily by the governments of the host countries, with financial and scientific contributions from all their members. Scientists have access to common computing resources and data, hold meetings by video conference, and travel a few times a year to meet face to face. It works perfectly well, and I would say hardly any physicist really minds in what country their experiment is based – at least not for science reasons.

So why do I think that it is not quite enough to join foreign collaborations when a nation has the means to do science at its labs, when it can be home to an international experiment? Given the varied government structures and labor costs, it really is possible that the same science will get done for a smaller financial investment elsewhere. Private companies outsource for similar reasons, why does it make a difference in science?

Here’s why. I worked at two national labs so far. At Fermilab, not a week goes by that there isn’t a school bus parked outside Wilson Hall, the main building. Every Saturday morning we have high school students visit for that week’s installment of a lecture series. The science center is open five days a week for visitors from the public; every Wednesday morning there are guided tours. Every third Sunday afternoon we have a program where anyone from the public can come listen to a lecture, tour the facilities and ask questions of scientists over cookies and juice. I personally received additional safety training so I can take visitors to my experimental hall 300ft underground. University groups visited frequently, and as cliché as it sounds, 19-year-old physics majors’ eyes do widen when you take them on an elevator into the Earth and show them a thousand-ton neutrino detector. I’ve only been at my latest position at Brookhaven for a few months, but I’ve already received invitations to judge a science fair, guide visiting children while they walk around the synchrotron ring, and to attend an undergraduate poster session. This summer I will mentor an undergraduate intern, one of three my department will host to work on experiments both within and outside the country. These are only outreach and education programs I personally took part in; there are a plethora of others across the country at labs and universities.

Domestic science gives these young people and any interested member of the public the opportunity to visit running experiments. It lets college students build parts of state-of-the-art detectors. It connects the people to the science they are collectively funding. They get to educate their children; they get to listen to public lectures from Nobel laureate physicists. I strongly believe that the most important job we do as scientists is to train future generations and enlighten the public. We will travel and collaborate internationally to do the science, but 15-year-old high schoolers can only be inspired by seeing it in action.

Don’t get me wrong – international collaborations provide plenty of projects for students and scientists all over the world. It’s never an all-or-nothing situation. But it is clear that local students and residents will benefit the most, that local educators and scientists will have access to most of the teaching opportunities. Not every nation has the resources to build a multinational high-end science experiment within its borders. Those who do would be doing their educators, students, scientists and their public a great service by keeping domestic science active, competitive and inspiring.


The LHC sneaks along

Saturday, April 28th, 2012

Have you been paying attention to the LHC? Sure, you’ve been thinking about the scientific results being derived from last year’s data. And you are looking a few months down the road to the upcoming major conferences, now only a little more than two months away, when we might get some interesting news. But right now, the LHC has been running, and running well. Consider this: here is a plot of the integrated luminosity as a function of time for 2011:

And here is the same for 2012:

It is important to note the “preliminary” on this plot — all experiments are working to verify their luminosity calibration. But one can see that the integrated luminosity for this year at the end of April 2012, about an inverse femtobarn is about what it was for last year in the middle of June 2011. In all of 2011, we recorded “only” about five inverse femtobarns. (Dear LHC: could someone produce a plot with the integrated luminosity for both years on the same set of axes? Then I could make this point more easily.) We are recording data at a much faster pace than last year, and that can go straight into the physics bottom line. From what I have heard, the operating conditions of the LHC have been particularly good — the vacuum inside the beam pipe has been better than expected, which means that it will be easier than anticipated to increase the beam currents, and thus to increase the instantaneous luminosity more quickly.

This is important, because we’re about to hit the important big sprint of the year. The LHC has been doing machine studies and a technical stop during the past week. Regular operations for physics will restart around Monday. To be in a position to firmly observe a Higgs boson (if it exists) this year, we need to accumulate 6-7 inverse femtobarns by the “first breakpoint” in late June, under two months away. That is, we will need to accumulate as much data in the next two months as we did in all of last year’s run.

Can the LHC do it? Based on what we’ve seen so far this spring, I think we can try to be optimistic!


The evolutionary argument against naturalism

Alvin Plantinga (1932), professor emeritus of philosophy at the University of Notre Dame, is a leading theistic philosopher and opponent of evolution. He has proposed an intriguing, and specious—yet non-the-less intriguing—argument against evolution. It is intriguing for several reasons: First, because on the face of it, it is plausible. Second because it is typical of a whole class of specious arguments. Finally, because it highlights the difference between how scientists and philosophers approach a problem.

The argument runs as follows: The naturalist can be reasonably sure that the neurophysiology underlying belief formation is adaptive, but nothing follows about the truth of the beliefs depending on that neurophysiology. In fact, he’d have to hold that it is unlikely, given unguided evolution, that our cognitive faculties are reliable. It’s as likely, given unguided evolution, that we live in a sort of dream world as that we actually know something about ourselves and our world (original emphasis). In other words, if people in fact evolved, they could not trust their cognitive faculties to give them the truth and hence, do science. He goes on to argue that it is only possible to trust our cognitive faculties if people are created in God’s image.

It is amusing that unbelievers argue the opposite; namely that the existence of a God means science is impossible since he/she/it could override the rules of nature at will and there would be no reason to assume constant laws. Both are correct to this extent: Absolute knowledge is impossible,[1] independent of God’s existence.  But back to Plantinga’s argument; it hinges on the concept of truth, or equivalently, reliability. But what is truth? A profound question—or a meaningless one. The difference between profound and meaningless is often vanishingly small.

At one level, the idea of truth is simple: Does the testimony of the person on the witness stand agree with what happened? Or perhaps the simpler question: Does the testimony agree with what the person thinks happened? The second is a less stringent requirement. But from this simple concept, the grand metaphysics concept of TRUTH is generated. Whatever this grand metaphysical concept is, science is not concerned with it. Is it TRUTH ™ that colds are caused by viruses? The reductionist, at least if he believes in string theory, would say no. Colds, like all other phenomena, are caused by how strings vibrate in eleven dimensions. Viruses are just a wimpy low-energy approximation to the real TRUTH ™.

In science, we build models for how the universe works, which usually have a limited range of validity. Think of classical mechanics which is only valid for velocities much less than the speed of light.  Is classical mechanics the TRUTH ™? No, certainly no, it fails in various places. But it is certainly useful. Science is a natural extension of the model building the unconscious mind does all the time, which is necessary for us to survive in a hostile world. The surprising thing is not that beings who evolved created science, but rather, that they did not do it sooner. Plantinga’s problem is that he does not understand what science is or how it works—seeking effective models rather than the TRUTH ™, whatever that may be. He should have known better, since by the Duhem-Quine thesis, no model can be falsified.  Arguing that the current models have deficiencies is never enough. You have to provide better ones with more predicative power.

In the same manner that Plantinga’s argument relies on the grand metaphysics concept of TRUTH ™, many arguments in philosophy rely on similar word definitions. A prime example is the ontological agreement for God’s existence. First proposed by Anselm of Canterbury (1033 – 1109), the argument goes as follows: Define God as the greatest possible being we can conceive. If the greatest possible being exists in the mind, it must also exist in reality. If it only exists in the mind, a greater being is possible—one which exists in the mind and in reality. Note that his argument hinges on the definition of greatest. My daughter believes that anything, no matter how great, can be made greater by being pink. Thus the greatest being is pink. If I define non-existence as being greater than existence,[2] the ontological argument becomes an argument for God’s nonexistence. Evil is another word that is frequently made into a grand metaphysical concept, EVIL™, and used to justify various philosophical positions. The concept of actions I do not like is then taken a step further and personified in the concept of the devil.

While our concepts and word definitions may reflect reality, they do not constrain it. In the end, models founded on observation take precedence over philosophical arguments based on word definitions and phenomenologically unconstrained speculations. If such philosophical arguments disagree with scientific models, so much the worse for them. Thor showing up for Thursday afternoon tea at the Empress Hotel would make all arguments regarding his existence moot[3].  One observation is worth a thousand philosophical arguments.

Additional posts in this series will appear most Friday afternoons at 3:30 pm Vancouver time. To receive a reminder follow me on Twitter: @musquod.

[2] See Ecclesiastes chapter 4 for why this definition may be reasonable.

[3] You can tell it is Thor because he would be carrying a large hammer and one of the goats pulling his chariot would be limping.


Before I began working at TRIUMF, I knew that science communication was a thing; much in the same way that I knew that there was someone, somewhere manufacturing tissue paper. It was just something that was. Reading an article in Scientific American or, to an extent, Wired, I never paused to consider who had written the article and what made an effective piece of science writing. I simply read it and moved on. Now that I have written a few articles that discuss science—nothing too long or in-depth, mind you—I have caught a glimpse of the harrowing plight of the science communicator and it is one fraught with frustration and self-doubt, but it is not without hope.

I, along with the majority of the communications team at TRIUMF, attended a talk at UBC called, “STORYOMICS: Proof that Scientists Evolved from Humans,” presented by scientist and documentary filmmaker, Randy Olson. I won’t go into too much detail about what he talked about because, to me, it was somewhat commonsensical. (Note: This may be because I’m an English major, whose sole purpose is to be painfully familiar with the components of a story.)

After the talk, a man named Dave Ng joined us for lunch. While we were chattering away, he said something that, initially, seemed like just an insightful observation. However, It has been ricocheting around in the damp recesses of my brain ever since. The observation was this: when news broke about the faster-than-light neutrinos, everyone covered it. Everyone. Of all the people who covered it, what percentage do you think knew—without reciting the Wikipedia entry for it from memory—what a neutrino actually was? Very few, I would bet. Judging from what I had read at the time, it seemed that everyone had reposted chunks of CERN/OPERA’s press release with bits of fluff around it to make it look like an original work. The main thrust of my scattershot thought process, the philosophical question that has me wandering the desert of my psyche looking for an answer is: can you ever effectively report on/write about something that you don’t have a deep knowledge of?

I used to write for a university newspaper and, while I did write about current events and physical fitness (which, if you know me, is not my forte), I gravitated towards the Arts and Life section. I wrote about books, movies, television, and video games.  What do all of these things have in common? I know about them. When I wrote about books, I was in my natural element because I understood the underlying principles that govern narrative and I knew the significance of things that the woefully uninitiated don’t pick up on (I once wrote an entire paper on the use of en and em dashes in a play, so don’t even dispute me on this). The writing was full of verve and wit (if I do say so myself). It had a confident, singular voice behind it. Confidence is the key to communicating anything effectively, but it is rare to find someone who is confident speaking about something they are not knowledgeable of. That’s why we see this paradigm: The head of the communications department at TRIUMF, Tim Meyer, is an excellent science communicator…who has a PhD in physics. Randy Olson is an effective science communicator…who has a PhD in biology. The list goes on: Neil DeGrasse Tyson, Stephen Hawking, Carl Sagan, etc. The point is that there is no doubt that scientists can become communicators. Can communicators communicate science, though? That seems to be a point of contention for scientists and communicators alike.

Before we go any further, I should probably establish my credentials: My background in science is less than negligible. I took Physics 11 in high school and Biology 100 in university. One of my (many) problems is that I was born with the curiosity of a scientist but without any of the skills to back it up. My interest in science is what made the opportunity to work at TRIUMF so appealing. It promised the opportunity to write about science, which is something that scared me, still scares me.

I recently wrote about the controversy surrounding the CERN/OPERA faster-than-light neutrino experiment and I was nervous the entire time. The prose was shaky, too reliant on quotes, and meek. It was listless and gray, devoid of all effervescence or joie de vivre. It was a passable science article. I felt how I think many science communicators feel in the beginning: gutted. The lack of “myself” in the article called into question whether I could communicate effectively, or if I had ever done so.

Science communicators are in the enviable and rare position to be attacked from every angle: from scientists for not being thorough enough and from communicators for being boring and ineffective. Both parties are assailing disparate aspects of the work and no one is pleased. If you heard a funeral dirge in the back of your mind while reading this, prepare for the tinkling, inspirational piano number because, in my mind, there is hope. I’ve only been at TRIUMF for three months, but I already feel like I’ve learned a great deal about science communication.

1.)       Always collaborate, when possible, with someone who is deeply familiar with the science you are discussing. I know it’s easier to Google, but this is the Internet. I’m a doctor on the Internet. This way, when you cite your sources, you don’t have to cite Wikipedia, you can cite a professional, which will confer a lot of credence to whatever you wrote.

2.)       Metaphor is your new best friend. You already have a best friend? Too bad. You might not know the dictionary definition of metaphor, but humans have been using it forever (hyperbole) to communicate complex ideas to the many. The more complex the concept, the more important the metaphor becomes.

3.)       Don’t be afraid to imbue the work with a sense of style. This is what I see most often. People think that because something is about science, it needs to be antiseptic. It doesn’t. If you’re a communicator, you have a unique voice, or I hope you have, anyway.

With the modicum of experience that I have in communicating science, I realize I’m no professional—yet—and this is by no means an “answer” to the questions posed earlier. These points are, however, a jumping off point for people who may be thinking about communicating science, but are afraid it has to be the written or verbal equivalent of gruel. They are also for the people who are communicating science but it has become so mechanical for them that they can’t see themselves in their work anymore.

My time at TRIUMF lasts five more months, and the journey will, without a doubt, involve more frustration and failure in the face of this nigh-rhetorical question. Instead of gently weeping into that good night, I will use the words of Charles Kettering, an engineer I just Googled, to give me hope: “99 percent of success is built on failure.”

–Written by Jordan Pitcher (Communications Assistant)



Les baryons Ξ (Xi), comme tous les baryons, sont des particules constituées de trois quarks. Le premier baryon X  a été découvert dans les rayons cosmiques dans les années 50.  Plus récemment, les expériences du Fermilab ont découvert les particules Xb, qui contiennent un quark b ou beauté. Cette semaine, CMS a annoncé l’observation d’un nouvel état excité du baryon neutre, le Ξb*0, le premier de la famille découvert à ce jour.

Les baryons Ξb* contiennent un quark beauté (b), un quark étrange (s), et encore soit un quark up (u), ce qui donne un baryon Ξb*0 neutre, soit un quark down (d), et on obtient un Ξb* chargé. Les états fondamentaux, c’est-à-dire les baryons Ξb de plus faible masse, chargés ou neutres – ont déjà été observés précédemment. Toutefois, aucun des états excités prédits par le Modèle Standard n’avait encore été observé. L’état excité Ξb*0 que l’on vient de découvrir à CMS est une première.

Les particules qui sont dans un état excité, y compris le Ξb*0, se défont normalement rapidement  en une cascade de désintégrations, donnant plusieurs particules de faible masse, ce qui rend la reconstitution particulièrement difficile. L’observation de CMS a été faite dans un échantillon de données de collisions proton-proton fournies en 2011 par le LHC fonctionnant à une énergie dans le centre de masse de 7 TeV. Cet échantillon correspond à une luminosité intégrée de 5,3 fb-1. La masse du nouvel état excité est, d’après les mesures, de 5945,0 ± 2,8 MeV, ce qui en fait également l’état de particule le plus lourd découvert à ce jour dans la famille des Ξ.

Les résultats de CMS présentent une signification statistique de plus de 5 écarts-type (5σ) au-dessus du bruit de fond attendu. Voilà donc un élément supplémentaire qui contribue à former une image cohérente des différents états que peut prendre la matière.

En décembre dernier, l’expérience ATLAS avait elle aussi annoncer l’observation d’une nouvelle particule, le χb(3P) fait d’un quark b et d’un antiquark b.

Pour en savoir plus, consulter le site de CMS (en anglais seulement)

Un signal clair venant de particules Ξb*0 (en bleu)  au-dessus du bruit de fond (en rouge)


La matière peut être formée de différents états d’énergie. L’état le plus stable, c’est-à-dire celui qui survit le plus longtemps avant de se désintégrer, est appelé « état fondamental » ; c’est dans cet état que les particules ont l’énergie la plus basse possible. Les états présentant une énergie plus élevée sont appelés « états excités ». Ces états sont possibles d’après les lois de la nature, mais ils sont instables. Plus l’énergie de formation (autrement dit la masse) est élevée, plus ces particules sont instables.

Antonella del Rosso


CMS observes a new beauty particle

Friday, April 27th, 2012

The Ξ (Xi) baryons, like all baryons, are particles made of three quarks. The first X baryon was discovered in cosmic rays in the 50s. More recently, Fermilab experiments discovered the Ξb particles, which contain a beauty or b quark. This week, CMS has reported the observation of a new excited state of the neutral baryon, the Ξb*0, the first of the family discovered so far.

The Ξb* baryons contain one beauty (b) quark, one strange (s) quark, and either an up (u) quark, which results in a neutral Ξb*0 baryon, or a down (d) quark, which results in a charged Ξb*. The ground states, that is the lowest-mass Ξb baryons — both charged and neutral — have been previously observed. However, none of the excited states predicted by the Standard Model had ever been seen. The Ξb*0 excited state just discovered by CMS is the first one.

The excited states of particles, including the Ξb*0, are expected to break up rapidly in a cascade of decays to lower mass particles, making the particle reconstruction particularly difficult. The CMS observation was made in a data sample of proton-proton collisions delivered in 2011 by the LHC operating at a centre-of-mass energy of 7 TeV. The sample corresponds to an integrated luminosity of 5.3 fb-1. The mass of the new excited state is measured to be 5945.0 ± 2.8 MeV, which makes it also the heaviest particle state of the family discovered so far.

The CMS result comes with a statistical significance of more than 5 standard deviations (5σ) above the expected background. This is one more piece of information contributing to building up a coherent picture of the various states that matter can form.

In December, the ATLAS collaboration had also reported the first observation of a new particle called χb(3P) made of a quark b and an antiquark b.

Detailed information about the CMS result is available here.

A clear signal revealing the presence of Ξb*0 particles (blue) above the background level (red)


Matter can be formed in different energy states. The most stable one – that is, the one that survives the longest before decaying – is the so-called “ground state”, in which particles have the lowest possible energy. States with higher energy are called “excited states”. They are still allowed by Nature but they are unstable. The higher the formation energy (i.e. the mass) the more unstable they are.

Antonella del Rosso


Tetrahedral Carbon Lattice

Tuesday, April 24th, 2012

I gave you a golden ring to show you my love
You went to stick it in a printed circuit
To fix a voltage leak in your collector
You plug my feelings into your detector.

— Les Horribles Cernettes, “Collider”

But never mind gold. The material that’s really good for building particle detectors, for some applications, is diamond. This very strongly-bonded lattice of carbon is almost uniquely sturdy, with a high melting point and — more importantly — a very good ability to take radiation damage and keep working the same way. It can also act as a semiconductor, carrying charge deposited by high-energy particles in the same way that the LHC’s more “ordinary” silicon-based tracking detectors do.

Diamond is already used in both ATLAS and CMS, as part of the Beam Condition Monitors. These are very small detectors designed to detect when the LHC beams stray too far from their expected path; if this happens, they can automatically request that the LHC beam be dumped. This is necessary because the silicon pixel detectors at the center of ATLAS and CMS would be damaged if they were hit with a large number of protons. Of course, operating so close to the beam, the Beam Condition Monitors have to be able to take a lot of damage themselves, and that is why they are made of diamond. Particle physicists have also studied making entire tracking detector layers out of diamond, not so that they could take a direct hit from the LHC beam, but simply so they could last longer in the punishing environment of particles emerging from LHC collisions.

Such applications are possible because the industrial processes that make synthetic diamonds get cheaper and more efficient all the time, as well as better at making large, flat, uniform diamonds. But It turns out that you can also cut diamond gemstones from these processes. They are entirely the same as the “real” ones made underground over millions of years, unless you study them with special equipment designed to tell the difference. Of course, the diamond mining and distribution industry would like you to appreciate that it is the rarity and naturalness of diamonds that makes them special: a synthetic one simply won’t do.

I mention this because, when my fiancée and I went ring shopping this past weekend, we decided to take this argument one step further. A few centuries ago, diamonds were a lot more difficult to come by and to process, and they rarely had the “perfect” cuts and transparency that many people expect today. Diamonds on antique rings are small and cloudy, and the rings themselves are a bit weathered, so they’re surprisingly affordable. But the point we took is this: it’s not the price or appearance of the diamond that matters, it’s how unique and special it is. Like, say, the ones on this ring:

Some examples of tetrahedral carbon lattices, attached to some gold, attached in turn to my fiancée.

Of course, for building particle detectors, I’ll probably stick to the synthetics.


So if you are a reader of this blog, chances are you already have some sort of propensity towards liking the subject material in physics regardless of it the immediate impact of the subject material at hand will “build the better mouse trap,” so to speak.

However, it has been my experience that most people do not have such an interest in physics. Worse still, from my experience as a teaching assistant and tutor, people will always come back to this question:

“When am I going to use this in the real world”

When this question comes up, as it inevitably does when trying to convince someone to find the coefficient of friction for a block sliding down an incline plane, I am always left reaching for the “problem solving skills” answer more than any other answer. So you can imagine my delight when I stubled upon at article in Wired UK that showed a real life example of someone using their knowledge of physics to beat a traffic ticket that was given in error. (See article here)

Basically, by utilizing his understanding of angular and linear velocity Dmitri Krioukov of  the University of California was able to lay out the argument that because of the police officers position and difficulty we have discerning linear velocity from angular velocity when observing from a distance perpendicular to the direction of motion the police officer mistakenly thought that Dmitri failed to stop at a stop sign.

If you have been near a railroad track crossing when a train is coming you’ve likely experienced this. Often when the crossing gates come down you look down the track and see a train in the distance that appears to be approaching very slowly. As the train gets closer is seems to be speeding up until it passed directly in front of you when it seems to have reached maximum speed. Of course the truth of the matter is that the linear speed of the train is constant, while what you are observing is the angular speed which gives you the illusion that the train was moving slower and then accelerating as it comes closer.

This is in fact one of the reasons car accidents occur when cars attempt to “beat” a train across the tracks. We are really bad at estimating the actual speed of the train and thus the train appears to “speed up” and cross the tracks much quicker then we anticipate.

Using this as the building block for the argument Krioukov traces out the basis of how the police officer mistakenly thought that he failed to come to a stop. As he states in the abstract of his paper he published on the arxiv


We show that if a car stops at a stop sign, an observer, e.g., a police officer, located at a certain distance perpendicular to the car trajectory, must have an illusion that the car does not stop, if the following three conditions are satisfied: (1) the observer measures not the linear but angular speed of the car; (2) the car decelerates and subsequently accelerates relatively fast; and (3) there is a short-time obstruction of the observer’s view of the car by an external object, e.g., another car, at the moment when both cars are near the stop sign.

Taken from the paper found here: http://arxiv.org/pdf/1204.0162v1.pdf

What I found so great about this is that using little more then simple geometry and basic kinematics he convincingly argues how this easy mistaken can be made and using simple (and rather well drawn) graphs makes his compelling argument. Finally, i am left with a serious example that is easy to follow and according to the Wired UK source resulted in the defendant not having to pay the $400 ticket. So for all those non-physics people that somehow found their way onto this blog….STUDY YOUR KINEMATICS! It may just save your driving record.