## Archive for June, 2012

### Science and Exploring the Past

Friday, June 15th, 2012

Many years ago when I was in a grade-eight math class, I was sitting looking out the windows at the dinosaurs playing. Ok, despite what my daughter thinks, I am not quite that old. What I was looking at was planes circling around in the distance. It turns out that a plane had crashed. It was a Handley Page HPR-7 Herald 211 operated by Eastern Provincial Airlines and all eight people on board were killed.  Now, it is sometimes claimed that science cannot explain the past. It’s even argued that historical sciences like paleontology, archeology, and cosmology, somehow use different methods of discovering the past, than say, determining the reason of a plane crash and that is again different from the method for discovering the laws of nature.  In reality, the methods are all the same.

I suppose, in response to the plane crash, people could have sat around and made predictions for future plane crashes but instead they used science to try to discover the past—what had caused the plane to crash. In this case it turned out to not be so difficult. The Aviation Safety Network describes the cause thus: Failure of corroded skin area along the bottom centre line of the aircraft beneath stringer No.32 which resulted in structural failure of the fuselage and aerial disintegration. This was found out by a metallographic examination which provided clear evidence of stress corrosion in the aluminum alloy. The planes of this type that were remaining in service were repaired to prevent them from crashing as well.

The approach to understanding why the Eastern Provincial Airline’s plane had crashed followed a similar approach to any other plane crash: you analyse the debris, gather records from the black box and whatever other information is available, and construct a model for what happened. You test the model by making predictions for future observations; for example, that corrosion will be found on other planes of the same type.  This sounds very much like the standard scientific method as proposed originally by Roger Bacon (1220 – 1292) and followed by scientists ever since: observe, hypothesize, test, rehypothesize, and repeat as necessary.

The same technique is used for any reconstruction of the past, be it plane crashes, the cause of Napoleon’s death, archeology, paleontology, evolution, and cosmology. The cause of Napoleon’s death is quite interesting as an exercise in forensic science. The original cause of death was suggested to be gastric cancer. But that is too mundane a cause of death for such an august figure. So the conspiracy advocates went to work and suggested he was poisoned by arsenic. How to test? Easy look for arsenic in samples of hair. Well, that was done and arsenic was found. Case closed? Not quite. Were there other sources of arsenic than deliberate poisoning? Yes, the wall paper in his room had arsenic in it. Also further investigation revealed that he had been exposed to arsenic long before he went to St. Helena.  In support of the caner hypothesis his father also died of stomach cancer.  The current consensus is that the original diagnosis was correct. He died of stomach cancer. But notice the play of events: hypothesis—arsenic poisoning, testing—look for arsenic in hair samples, refine hypothesis—check for other sources of arsenic, etc. We can see here the classic process of science being played out in reconstructing the past.

We can continue this technique into the more distant past: When did humans evolve? Why did the dinosaurs die out? How did the earth form? How did the solar system form? What if anything preceded the big bang? All of these questions can be tackled using the standard methods of science. Observations of present tell us about the past, counting tree ring tells us when the tree started to grow.

The interplay between what might be called natural history and natural laws is very intricate. We must interpret the past in order to extract the natural laws and use the natural laws to interpret the past. All our models of science have, explicitly or implicitly, both an historical and a law component. In testing a model for how the universe works—ie to develop the laws—we conduct an experiment. Once the experiment is finished, it becomes history and interpreting it is historical science.  For example, why did the OPERA experiment claim to see faster than light propagation for neutrinos? Or is the bump seen in searches for the Higgs boson real or an artifact of the detector? Those investigations are as much forensic science as trying to decide why Napoleon died or the dinosaurs went extinct.  Thus, all science is historical and sometimes, quite explicitly. Einstein abandoned the cosmological constant based on an alternate model for the history of the universe, namely that it is expanding rather than static.

So, we have science as a unified whole, encompassing the past, present, and future; the natural laws entangled with the natural history. But what about the dinosaurs I did not see out of the math-room windows? We can be quite sure they did not exist at that time and that Fred Flintstone did not have one as a pet (a saber-toothed pussy cat is another story). The study of evolution is much like that for plane crashes. You study the debris, in the case of evolution that “debris” includes fossils and the current distribution of species.  Consider the fossil Tiktaalik roseae, a tetrapod-like fish or a fish-like tetrapod, that was found a few years ago.  One can engage in futile semantic arguments about whether it is a fish, or a tetrapod, or a missing link, or whether it is the work of the devil. However, the significant point is that a striking prediction has been confirmed by a peer-reviewed observation. Using evolution, a model of fossil formation, and a model of the earth’s geology, a prediction was made that a certain type of fossil would be found in a certain type of rock. Tiktaalik roseae dramatically fulfilled that prediction and provides information on the fish-tetrapod transition.

The cause of plane crashes, Napoleon’s death, evolution, and the extinction of dinosaurs can all be explored by using the same empirically-constrained model-building techniques as the rest of science.  There is only one scientific method.

### Art and Science: Both or Neither

Wednesday, June 13th, 2012

I don’t get it. I guess we just have different brains than them.” – two young science students, regarding a piece of art.

It’s a funny feeling, being an individual with a predominantly artistic mind working in a place dominated by science. I’m not saying I don’t have love for the sciences, but if we’re talking in terms of how my thought process lazily unfurls itself when faced with a problem, I’m definitely more of an artist than a scientist. The very fact that I have used the terms “scientist” and “artist” in a way that does nothing but reinforce the eternal dichotomy that exists between the two groups indicates that the problem is so widespread, indeed, that even the person trying to formulate an argument calling for a cessation of the “war” that exists between the two groups cannot avoid thinking of the two as incontrovertibly disparate.

A page from Leonardo da Vinci's famous notebooks. He remains one of the finest examples of an individual expanding his mind to take in both science and art.

The quote at the top is a real thing I heard. Aside from the disquieting use of “we” and “them,” the most troubling thing about the above assertion is the outright dismissal of the piece of art in question. The finality and hopelessness of the “Different Brain” argument does not seem ridiculous outright because it has been propagated by you (yes, you), me, and everyone else ever in the history of time when we don’t want to take the time to learn something new. Artists and scientists are two particular groups that use the Different Brain argument on one another all too often. In order to see the truly farcical nature that underlies the argument, picture two groups of early humans. One group has fire. The other group does not. One person from the fireless group is tasked with inventing fire for the group. The person in charge of making fire claps his hands; no fire is produced. He gives up, citing that he and his counterpart in the other group must have different brains. His group dies out because of their lack of fire.

I hope you followed the cautionary tale of our dismissive early human closely, for he is the rock I will build this post on. The reason one group died and the other thrived is quite obvious. It is not because they simply lacked fire; it is that they lacked the ability to extend their minds beyond their current knowledge in order to solve a problem. Moreover, they not only lacked the ability, they lacked the drive—a troubling trend that is becoming more pronounced as the misguided “war” between artists and scientists rages on, insofar as an intellectual war can rage.

If you were to ask a scientist what he or she would do when posed with a problem, the answer will invariably be something along the lines of, “I would wrestle it to the ground with my considerable intellect until it yields its secrets.” During my time at TRIUMF, I have noticed a deep, well-deserved pride in every scientist in their ability to solve problems. Therefore, it is truly a sad state of affairs when our scientists look at something that puzzles them and then look away. To me, that’s no scientist. That is someone who has grown too complacent, too comfortable, in the vastness of their knowledge that they begin to shy away from things that challenge them in a way they aren’t used to. What’s more is that no one (artists or scientists) sees this as a defeat. As soon as you’ve said, “Oh well, different brain,” you’ve lost.

Any person familiar with rhetoric will tell you that in order to build a strong argument and persuade people, you have to be honest. Be sneaky and fail to address something potentially damning and your credibility is shot and the argument is void. Since it works so well in politics (snark), I figure I should give is a shot here. The problem of the Different Brain argument does not just lay with the scientists; if I’ve excoriated them, it’s out of fear that soon, a generation of scientists will stop growing and thinking. The artists are guilty of invoking the Different Brain argument as well whenever faced with math, science, or anything, really, that they didn’t want to do. The only difference between the two is that I heard a scientist use the different brain argument in a place of science, in a place where knowledge is the point.

Different Brain is a spurious concept, which is obvious to anyone with more grey matter than pride, but it’s not just wrong because I say it is. It’s wrong because look around you.

I was standing in the middle of Whistler Village with my fiancé, when we spied a poster for a band called Art vs. Science (you’re doing it wrong, guys!). She immediately said, “Science would win.” No question. No pondering. No soul-searching. Gut reaction, like flinching from a feigned punch. She’s a statistics major and biology minor, so she has a “science” brain and her response didn’t necessarily surprise me. I was a little sad, though, because she wasn’t seeing the world like I was seeing it. We debated the problem for a few minutes until I told her to look around.

The shape of the buildings: Architecture

The pleasant configuration of the shrubbery: Horticulture

The signage on the buildings and lampposts: Design

The food in the bag in my hand: Cooking

The phone in her hand: Technology

I asked her to picture a world where science had “won”. What’s architecture without art? A shape. What’s horticulture without art? A forest. Design? A grid. Cooking? Paste. Technology? Sufficient. It’s a tough world to imagine. Look at the next thing you see and try to separate the science and art of it and imagine what it would look like, whether it would function at all. It’s absolutely dystopian.

It was then that my argument became clear: science and art are inextricable. There can be no dismissing, no deigning, no sighing in the face of it. There can only be and has only ever been unity between the two. The problem is that the two warring sides are too preoccupied with the connotations the words “art” and “science” seem to realize it’s not a question of either/or, but both/neither.

I was worried about whether this war of the different brains would always rage between the two sides, but three things lent me hope and I hope they will lend you hope, too.

1.)  These two quotes from Bertholt Brecht (20th century German playwright and poet, whose work I don’t much care for):

“Art and science work in quite different ways: agreed. But, bad as it may sound, I have to admit that I cannot get along as an artist without the use of one or two sciences. … In my view, the great and complicated things that go on in the world cannot be adequately recognized by people who do not use every possible aid to understanding.”

and

“Art and science coincide insofar as both aim to improve the lives of men and women.”

2.) I was feeling discouraged about my argument for this post and had taken to turning it over in my mind even when I was otherwise occupied, but when I heard Rolf Heuer, the Director-General of CERN, say, only a handful of feet from my face, “Science and Art belong together,” I felt a renewed sense of vigor course through my brain, spurring me on. If one of the foremost scientific experts of our age can see it, I wonder why many of us turn away from it, when it is clearly there.

3.) In case one thinks that I’ve gone too soft on the artists, imagine a world without science. Think of our society as a book of fiction or a painting. Unequivocal works of art. Yet, what holds the book together? How were the pages manufactured? How were the chemical composition of the paints devised? Science.

Keeping these points in mind, I am calling for the abolition of the concepts underpinning the Different Brain argument. The war between art and science is one of mutually assured destruction and will turn us into a lopsided simulacrum of a culture if we are not careful.

–Written by Jordan Pitcher (Communications Assistant)

### The Glue that Binds Us All

Wednesday, June 13th, 2012

RHIC, the Relativistic Heavy Ion Collider at Brookhaven Lab, found it first: a “perfect” liquid of strongly interacting quarks and gluons – a quark-gluon plasma (QGP) – produced by slamming heavy ions together at close to the speed of light. The fact that the QGP produced in these particle smashups was a liquid and not the expected gas, and that it flowed like a nearly frictionless fluid, took the physics world by surprise. These findings, now confirmed by heavy-ion experiments at the Large Hadron Collider (LHC) in Europe, have raised compelling new questions about the nature of matter and the strong force that holds the visible universe together.

Similarly, searches for the source of “missing” proton spin at RHIC have opened a deeper mystery: So far, it’s nowhere to be found.

To probe these and other puzzles, nuclear physicists would like to build a new machine: an electron-ion collider (EIC) designed to shine a very bright “light” on both protons and heavy ions to reveal their inner secrets. (more…)

### Auditioning for TED2013

Wednesday, June 13th, 2012

Editor’s note: Fermilab physicist Don Lincoln submitted an audition video to TED2013 on March 30. On May 22 he learned that he’d advanced to the next level of the audition process, and last Thursday, June 7, he gave his live audition in front of the TED leadership and insiders in New York City. He tells us how it went down.

Small. That was my first impression of the stage at Joe’s Pub in Greenwich Village in Manhattan. On the walls are photos of people who have performed here before, from Adele’s US debut in 2008, to Bono, to Dolly Parton, to Amy Winehouse. It was the kind of small and intimate nightclub that in another era would have had a jazz trio on the stage and been filled with stylishly dressed couples at small tables, with smoke languorously curling from their fashionable cigarettes. But, in 2012, the smoke was gone and the vibe was more bohemian, with casually dressed young twenty- and thirty-somethings assembled to watch a series of short and eclectic presentations. Following a global search for speakers, about 400 people have been invited to 14 locations around the world to audition for a coveted invitation to make a presentation at TED2013. The big TED conference has hosted newsmakers like Bill Gates and Richard Branson. This year, they have elected to build half of their program with “fresh faces.”

Well, I don’t know if my face really constitutes fresh, but here I am in New York City, one of 30 hopefuls, giving talks masterfully and wittily emceed by TED curator Chris Anderson, whose dry British humor adds a refining and cosmopolitan touch to each performer’s presentation. Each of us has between two and six minutes to make our pitch. Only about three or four of us will be going to Long Beach in February 2013. The subjects range widely, from the high school freshman who developed a test for pancreatic cancer while he was in the eighth grade to the young woman who battled depression by writing love letters to strangers and founded a movement of people who write letters to people they’ve never met to battle this increasingly lonely and isolated world. I’m the only one in the lot who does hard science. (I’m not sure the theoretical physicist and saxophonist who told how John Coltrane was his inspiration for an idea on quantum gravity counts. OK, I’m being catty. His science is good, but his talk was filled with lots of sax riffs. Come to think of it, his talk fit the venue very well.) I’ve elected to use my four minutes to tell the 200 or so people in the audience about how particle accelerators like the Tevatron and the LHC can recreate the conditions immediately after the Big Bang. I’m hoping that this will be a new idea for the audience and amaze them in the same way it amazed me when I first heard it. I don’t know. There are a lot of jaded New Yorkers in the audience, but they’re also ones who embrace new ideas. Are my ideas new enough for them?

The whole experience has been a little unsettling. While I’ve given many hundred public presentations in the past, this is the first where the organizers want to see the script and the multimedia before they’ll let me on the stage. It’s also the first where I needed to audition so I could audition. Each of us had to submit a video for evaluation before being invited to talk at the salon. While the TED people were cagey about the numbers, “many hundred” videos were submitted for the New York event and only thirty were invited. Not only did I have to audition to audition, I had to arrive a day early to rehearse in front of the organizers too. I didn’t have to jump through a hoop or juggle flaming chainsaws, but that could be next. In a way, the scrutiny is comforting, as TED performances have very high production quality, but it’s a lot to go through.

Now that the audition is over, the wait begins. In late June, videos of the 400 or so performances will be put online on the TED website and judged by the worldwide audience. The number of “likes” given to each video will be a factor in which 50 are selected to give an 18 minute-long presentation at TED2013. (In case that was too subtle, that is an invitation for you to tell all your friends, family, acquaintances, neighbors and random strangers to watch them and “like” mine. I’ll make another post when the links to the videos go live.)

Overall, it was a pretty cool experience. I got to meet some fascinating people, both the other speaker-candidates and the TED staff. It’s enjoyable talking with people who believe in the TED credo “Ideas worth spreading.”

Don Lincoln

### Why advertisers should know physics

Tuesday, June 12th, 2012

Some years ago, when I decided to start blogging, I wrote about an interesting advertisement that Ford Motor Company put up in all major magazines (it was even placed on the side of their headquarters in Dearborn, MI):

Here is what I said in that post of mine from several years ago: “What is interesting about this ad is the equations that this lady is writing — they look like the equations from the famous Peskin and Schroeder’s book on Quantum Field Theory (QFT), equations describing renormalization of phi^4 theory! How did Ford get a hold of them?

As it turns out, I happen know the answer. This ad was made by a company that is headquartered in Detroit — I have a business card of one of the authors of this ad!

What happened is that a couple of months ago I was sitting in my office at Wayne State University, looking over my QFT notes that I’m supposed to teach next Fall. A guy showed up at my door and asked to “write down a complicated-looking equation.” Now, that’s not a usual question that I get when I sit in my office during the lunchtime! He quickly explained that he works for this advertisement company (called JWT) and they were contracted by Ford to produce a series of ads that should highlight the talent of Ford engineers and at the same time appeal to young people. (He showed me a prototype of an ad with that girl sitting next to the blackboard.) So his boss sent him to the closest university (which happen to be WSU, we are located 5 min down Woodward Avenue from their office) to fish out a “complicated equation.” The rest is simple — I use Peskin and Schroeder as a main text for my graduate QFT  course, so that list of equations was indeed about renormalization of phi^4 theory… I must add that I received no monetary (or any other) compensation…

Amazing, isn’t it?”

The reason I re-post part of that old post is the following. I recently went to Florida to participate in CIPANP-2012 conference (I’ll post my impressions of this conference later this week). Now, Kennedy Space Center is on Cape Canaveral in Florida, so I rented a car and went to visit that marvelous place. The place is truly amazing! Lots of things to see. The place is still making history: I visited it just a couple of days after the historic launch of the Space X‘s Dragon capsule.

I also visited a gift shop and bought the following souvenir there:

See how many mistakes they got in there? And it’s not “rocket science”, it’s freshman physics! Quite embarrassing… Clearly, people from that JWT advertising agency in the example above take their job responsibilities much more seriously.

See that NASA seal in the upper left corner? Since I am sure that NASA scientists know physics, I take it as indication that they never visit their gift shop.

### Director Emeritus Leon Lederman departs Fermilab

Monday, June 11th, 2012

Fermilab Director Emeritus Leon Lederman sits in front of Wilson Hall. Photo: Reidar Hahn

Fermilab’s Leon Lederman is leaving the laboratory that he served for ten years as its director and for many more as an internationally renowned physicist and science education pioneer.

The directorate is hosting a farewell reception for Lederman today at 3 p.m. on the 2nd-floor crossover. He leaves Batavia, Ill. for Driggs, Idaho. His last day at the lab is Monday, June 11.

Lederman’s early award-winning research in high-energy physics brought him into national science policy circles and in 1963 he proposed the idea that became the National Accelerator Laboratory. In 1977 Lederman led the team that discovered the bottom quark at Fermilab. The following year he was named director and his administration brought Fermilab into its position of scientific prominence with the achievement of the world’s most powerful superconducting accelerator, the Tevatron. He served as director until 1989.

Lederman is the recipient of some of the highest national and international honors bestowed to a scientist. His awards include the 1965 National Medal of Science and the 1972 Elliott Cresson Medal, given by the Frankin Institute. In 1982 he received the prestigious Wolf Prize, an annual prize given by the Wolf Foundation in Israel. He received the 1988 Nobel Prize in Physics for the discovery of the muon neutrino and was honored with the Enrico Fermi Award in 1992. And just this year, he was recognized for his distinguished scientific career with the 2012 Vannevar Bush Award, given to exceptional lifelong leaders in science and technology.

Lederman advocated for math and science education and for outreach to the neighboring communities. He initiated the Saturday Morning Physics lectures and subsequently founded the Friends of Fermilab, the Illinois Mathematics and Science Academy, and the Teacher’s Academy for Mathematics and Science.

### Oscillation results from DeepCore (IceCube sub-detector)

Monday, June 11th, 2012

### What next for the Higgs?

Saturday, June 9th, 2012

There’s a good chance that there will be a Higgs discovery “just around the corner”, so it’s time to look to the future to see where to go next with Higgs analyses. At the very least, we need to know the mass of the Higgs boson so that we can manufacture the next big experiment, a TeV scale linear collider (TLC). Without knowing the mass of the Higgs boson we can’t determine the center of mass energy of such an collider and that would severely delay development. Given that, we need to have a discovery before the LHC shuts down for 2013, so we need to get moving!

The Higgs is running out of space as the LHC experiments squeeze the allowed region (CMS)

We usually require a $$5\sigma$$ observation to declare a discovery, and there are two ways to do this. We can wait until we have $$5\sigma$$ observations on both ATLAS and CMS, but this would take a long time and a lot of luminosity, or we can combine the results of ATLAS and CMS in order to get a global $$5\sigma$$ observation.

This second option is a controversial one, because once we combine results to get the final observation we can no longer use each experiment as a crosscheck for the other. (Well we can, but it gets quite subtle and we have to ask ourselves to what extent we trust the agreement between the two experiments if we’re going to combine results in this way.) To an extent the question is a moot one. Someone will combine the results from ATLAS and CMS (and CDF and D0 as well) whether we want them to or not. Even so, it’s long been a strategy and a benchmark of excellence to have two experiments for each major field of study. CDF and D0 crosscheck each other, BaBar and Belle crosscheck each other, and UA1 and UA2 crosschecked each other with the discovery of the $$W$$ and $$Z$$ bosons. If we compromise that standard then we could set a dangerous precedent for future discoveries. When
we look to other experiments when conducting our own research we run the risk of experimenter bias.

Looking beyond the discovery we also need to consider how we are going to study the properties of the Higgs boson. Assuming a mass of 125GeV we can look forward to a lot of different decay channels, including the high statistics but messy $$b\bar{b}$$ final state, the smeared out $$\tau\tau$$ and $$WW^*$$ final states, the clean but somewhat boring $$\gamma\gamma$$ final state, and the and intriguing $$ZZ^*$$ and $$Z\gamma$$ states. This huge range of final states means that there would be a very rich range of analyses.

Branching fractions of the Higgs boson at 125GeV

Perhaps the most exciting part of the available Higgs decays is that it could give us access to the quark masses. The masses of the quarks are not visible to most processes, because the quarks get tangled up in the QCD that surrounds them. The Higgs boson couples directly to the quarks, coupling to their masses. We can measure the ratio of branching fractions to quarks and muons, then with the knowledge of the muon mass and the effective color of the quarks we can get the mass of the $$b$$, $$c$$, and $$s$$ quarks. It would be an ambitious project, but a worthwhile one that would finally answer many questions about QCD.

A major part of the Higgs studies is the width of the Higgs. We measured the width of the $$Z$$ boson at LEP and this confirmed that there were only three generations of neutrinos. This goes a long way to showing that there is no fourth generation particles (and the LHC has since ruled out a fourth generation of quarks.) We can apply the same trick to the Higgs boson to see if there are any particles less than 62GeV that we have not discovered yet. For example if there is a SUSY particle at 50GeV that only couples to the Higgs boson then we would see extra invisible decays of the Higgs boson. (The largest invisible decay of the Higgs boson in the Standard Model is the process $$H\to ZZ^*\to\nu\nu\nu\nu$$ and accounts for approximately 0.08% of all Higgs decays.)

In order to perform these studies we need a different kind of collider. Producing the Higgs at the LHC is relatively straightforward: we just pump protons through the machine and smash them together. Eventually we have enough Higgs bosons to see a signal, and it’s just a matter of waiting. Unfortunately the performance of the machine is just not good enough for precision measurements. We can only see the visible decays at the LHC (so we cannot measure the width directly), we do not know the center of mass energy of the collisions so complicated states such as associated production are less accessible, and the energy scales of many objects dominate uncertainties. To see a lot of the decays of the Higgs boson we need an electron-positron collider. These give very clean working environments and a known center of mass energy. In this scenario we look for Higgstrahlung, where a $$Z$$ boson is produced which emits a Higgs boson. We can reconstruct the $$Z$$ boson and then the Higgs boson is what recoils against it to balance the momentum.

Simulation of a field inside a resonator at ILC, a contender for the next collider for Higgs physics (ILC/DESY)

If the Higgs boson is discovered at 125GeV this year then we have our work cut out of for us for the next few decades. ATLAS and CMS will continue to produce results and paper after paper. After the Phase I and Phase II upgrades the focus will change from Higgs discovery to high statistics measurements and searches for new phenomena. We’ll look towards the TLC for precision measurements and stringent constraints on the Standard Model. If all goes well with a Higgs discovery, then the next couple of decades are going to be a golden age for particles physics.

### Cause and Effect: A Cornerstone of Science or a Myth?

Friday, June 8th, 2012

Cause and effect has been central to many arguments in science, philosophy and theology down through the ages, from Aristotle’s four causes[1] down to the present time. It is has frequently been used in philosophy and Christian apologetics in the form: The law of cause and effect is one of the most fundamental in all of science. But it has it naysayers as well. For example, Bertrand Russell (1872 –1970): All philosophers, of every school, imagine that causation is one of the fundamental axioms or postulates of science, yet, oddly enough, in advanced sciences such as gravitational astronomy, the word “cause” never occurs. … The law of causality, I believe, like much that passes muster among philosophers, is a relic of a bygone age, surviving, like the monarchy, only because it is erroneously supposed to do no harm. You can accuse Russell of many things, but being mealy-mouthed is not one of them. Karl Pearson (1856 – 1936), who has been credited with inventing mathematical statistics, would have agreed with Russell. He never talked about causation, though, only correlation.

One of the people who helped elevate cause and effect to its exalted heights was David Hume (1711 -1776). He was a leading philosopher of his day and known as one of the British empiricists (in contradistinction to the continental rationalists). Hume was one of the first to realize that the developing sciences had undermined Aristotle’s ideas on cause and effect and he proposed an alternate in two parts: first, Hume defined cause as “an object, followed by another, and where all objects similar to the first are followed by objects similar to the second”. This accounts for the external impressions. His second definition, which defines a cause as “an object followed by another, and whose appearance always conveys the thought to that other”, captures the internal sensation involved. Hume believed both were needed. In thus trying to relate cause and effect directly to observations Hume started the philosophy of science down two dead ends streets: one was the idea that cause and effect was central to science and the other lead to logical positivism.

Hume’s definitions are seriously flawed. Consider night and day. Day invariably night and the two are thought of together but night does not cause day in any sense of the word. Rather, both day and night are caused by the rotation of the earth, or, if you prefer, a geocentric frame, by the sun circling the earth.  The true cause has no aspect of one thing following another or one causing thought of the other. And the cause does not have to any way resemble the effect.  One can find many other similar cases: it getting light does not cause the sun to rise despite it getting light before the sun rises; it is the sun rising that causes it to get light. Trees losing their leaves does not cause winter but rather the days getting shorter causes the trees to lose their leaves and is a harbinger of winter. The root cause being the tilt of the earth’s axis of rotation with respect to the ecliptic.

As just seen, cause and effect is much more complicated than Hume and his successor thought, but not nonexistent as it detractors maintain. In the words of the statistician: correlation does not imply causation. However, it can give a strong hint.  The cock crowing does not cause the sun to rise but the correlation does suggest that the sun rising might just motivate, if not cause, the cock to crow. Similarly, consider lung cancer and smoking. Not all people who smoke get lung cancer and not all people who get lung cancer smoke (or inhale second hand smoke).  Nevertheless, there is a correlation. It was this correlation that started people looking to see if there is a cause and effect relation. Here we have correlation giving a hint; a hint that needed to be followed up. And it was followed up. Nicotine was found to be carcinogenic and the case was made convincing. A currently controversial topic is global warming and human activities. Here, as with smoking causing cancer, we have both correlation and a mechanism (the greenhouse effect of carbon dioxide and methane).

Cause and effect went out of favor as a cornerstone of science about the time quantum mechanics was developed. Quantum mechanics is non-deterministic with events occurring randomly. Within the context of quantum mechanics, there is no reason or cause for an atom to decay at one time and not at another. The rise of quantum mechanics and the decline in the prominence of cause and effect are probably indeed cause and effect. However, even outside quantum mechanics there are problems with cause and effect. Much of physics, as Russell observed, does not explicitly use cause and effect. The equations work equally well forwards or backwards, deriving the past from present as much as the future from the past.  Indeed, the equations of physics can even propagate spatially sideways rather than temporally forwards or backwards.

In spite of all that, the idea of cause and effect is useful. To understand its limitations and successes we have to go back to one of my mantras: the meaning is in the model. Cause and effect is not something that can be immediately deduced from observation, as Hume implies, but it is not a meaningless concept as Russell said or the physics discussion above might seem to imply. Rather, when we develop our models for a particular situation the idea of causation comes out of that model, is part and parcel of the model. We believe that the post causes the shadow and not the other way around, because of our model on the nature of light and vision. Similarly, the idea that the earth’s rotation causes day and night comes out of our model for light, vision and the solar system. The first chapter of Genesis indicates that this was not always considered obvious[2]. That smoking causing lung cancer is part of the biological model for cancer. That human activities causing global warming comes out of atmospheric modeling. But arising from a model does not make cause and effect any less real nor the concept less useful. Identifying smoking as a cause of cancer has saved many lives and identifying carbon dioxide and methane as the main causes of global warming will, hopefully, help save the world. Cause and effect may not a cornerstone of science but it is still a useful concept and certainly not a relic of a bygone age.

[1] Discussed in a previous post.

[2] Day and night were created before the sun.

### Sam Zeller receives DOE award to track neutrinos

Friday, June 8th, 2012

Sam Zeller won a DOE Early Career Research Award to support her work on liquid argon neutrino dectectors. Photo: Reidar Hahn

Neutrinos are known for escaping capture. They fly through matter and their different types continuously morph into one another. That elusive, shifting behavior challenges nearly every available tool and capability scientists have to sketch their portraits.

With better tools come more detailed portraits. Last month, Fermilab scientist Geralyn “Sam” Zeller received a 2012 DOE Early Career Research Award to advance a detector technology that will capture neutrinos’ attributes with unprecedented detail. The \$2.5 million award, spread over five years, will support a proof-of-principle study towards the construction of multi-kiloton liquid-argon neutrino detectors.

“There are some really important questions we want to answer about how neutrinos behave,” Zeller said. “The best chance for answering them is to study neutrinos with this exquisite detector.”

Liquid-argon detectors are practically photographic in their ability to show what happens when a neutrino hits an argon nucleus. Tracks that the resultant particles leave behind are shown in high resolution, and it’s easy to distinguish the various particle types that arise from the interaction.

But information on how neutrinos behave in liquid-argon detectors is sparse. Most of what is known is based on simulations rather than experiment. Also, researchers have typically gathered what they need to know from event displays – pretty pictures of events that, while useful, are relatively light on quantified information.

Zeller, who has been at Fermilab since December 2009, plans to fill the gap with an abundance of new data. The DOE award will support the analysis of neutrino data recently collected by a small (less than 1 ton) liquid-argon detector prototype called ArgoNeuT. In the next few years, Zeller’s team will also generate and analyze neutrino data using Fermilab’s new MicroBooNE detector, a 170-ton liquid-argon detector. Their findings will tell them whether they can get the expected performance out of a detector of much larger scale. They’ll also characterize exactly how neutrinos behave when interacting in argon.

“There’s a big gap in our knowledge of how neutrinos interact,” Zeller said. “We want better information to inform the design of future detectors.”

Zeller’s project leverages the current ongoing U.S. neutrino program with the idea that the community could build, in manageable stages, a liquid-argon detector weighing tens of thousands of tons. Its prodigious size increases scientists’ chance of capturing a neutrino that has changed forms. Combined with its characteristic high precision, the detector would prove invaluable for the proposed Long-Baseline Neutrino Experiment, which will allow scientists to observe neutrino oscillations, as their form-changing is called. It would also be of use for the short-baseline program in looking for a fourth neutrino to add to the family of the known three.

If future neutrino experiments go well, scientists may finally have answers to basic questions surrounding the ghostly particle: which neutrino types are the lightest and heaviest, and do they behave the same as their antiparticles?

The DOE award will fund two postdocs and a dedicated team for the long-baseline program, as well as supporting technical and engineering work.

“There’s an opportunity here because we have these two detectors and the best neutrino beams in the world,” Zeller said. “Now we’re going to try to get as much information out of them as we can.”

Leah Hesla