Surrey Physics Blog The blog of the Department of Physics at the University of Surrey Fri, 14 Dec 2012 20:23:34 +0000 en hourly 1 Less Ingres, more Monet Fri, 14 Dec 2012 20:09:46 +0000 Richard Sear Claude Monet The Cliffs at EtretatI have almost finished the biography of a scientific hero of mine, Pierre-Gilles de Gennes. One observation in the book has particularly struck me, and that is that de Gennes viewed his approach as more like that of the Impressionist artists, and less like the approach of the artist Jean Auguste Dominique Ingres.

Ingres, Napoleon on his Imperial throneI am no expert on 19th century art, but Impressionism was a movement in the 19th century, that include Monet, Renoir etc. According to the Wikipedia page, they emphasised the play of light on the landscape, and in contrast to earlier work, the brushstrokes are large and visible. Above is a beautiful Impressionist landscape by Monet, called The Cliffs at Etretat. By contrast, in portraits like that of Napoleon, to the right, Ingres sought to impress with rich details, such as those on Napoleon’s rather impressive get-up.

So, the idea here is that de Gennes’s approach was a broad brush approach, using only simple ingredients to describe the behaviour of a physical system. This is analagous to Impressionism, but very different to Ingres’s detail heavy approach.

I think this is a beautiful comparison. It is lovely idea that a model that tries to capture the essential physics of a system, using a few simple ingredients, is like an Impressionist painting that tries to capture the play of light on a landscape, with simple brush strokes. You can ask yourself if you think you are more of an Impressionist, or more of an Ingres.

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Science on a Harry Potter set Wed, 12 Dec 2012 21:00:16 +0000 Richard Sear King Edward's Gate, Trinity College, Cambridge - - 1057067This is the last week of semester before the Christmas break, so things are getting a little busy, and I could spend a day at Cambridge talking science with an old friend and his PhD student. The student has started from a paper I did almost ten years ago, and is extending the work. He is doing some really smart calculations, and it is a little humbling, and very flattering, to see how has taken what I have done and gone far beyond that.

My friend is a Fellow at Trinity, arguably the grandest of all Cambridge’s colleges. It is definitely the richest. Which perhaps explains the palatial nature of the room I was put up in. The Judge’s Room is the size of 2 tennis courts and comes with furnishings that would not be out of place in Downton Abbey. It is off a staircase in a tower just out of shot on the left of the picture above. It also had a good wifi signal, and a modern wet room bathroom. This is good. Century-old bed-side cabinets I am OK with, century old plumbing not so much.

But as I sat there on the overstuffed candy-striped sofa, writing emails, it did occur to me that this grandeur was not very useful. Seventeenth century architecture does not educate students or do research, and Cambridge based academics take it for granted very quickly. Universities are just people really, students and staff. Still, I was there on Tuesday night, which was very cold and foggy, and so in the dark the college really did look like a Harry Potter set, which was fun. I half expected a Dementor to float round a corner.

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Au revoir les theories, Bonjour l’action Sat, 01 Dec 2012 21:03:12 +0000 Richard Sear DE GENNES Pierre Gilles-24x30-2001I am reading a biography of Pierre-Gilles de Gennes, by Laurence Plévert. De Gennes won the Nobel prize in physics in 1991. I guess he is a scientific hero of mine. The Nobel prize was for his work on understanding polymers and liquid crystals. You are probably reading this screen with a liquid crystal display of some sort (often called just LCDs). He perhaps contributed more to understanding what liquid crystals are, than anyone else.

Reading the biography, I am conscious of how much he has influenced me. I did meet him a couple of times but never talked science with him, but his scientific papers and a book he wrote inspired me. It has also affected how I teach. De Gennes’ style was often to use simple physical arguments to obtain estimates of the order of magnitude of a physical property, as opposed to grinding through heavy maths to try and obtain a very accurate answer.

In one of this semester’s biological physics lectures, I took the students through simple geometric arguments for how as the size of an animal increases, the mass increases as size cubed, whilethe weight-bearing capacity of the bones increases more slowly, as height squared. The faster increase of mass limits the size of animals. It is why there are no 50 m giants around.

When I wrote the lecture, I was not thinking about why I was trying to explain a physical phenomenon using simple estimates of how the important physical quantities scale, in this case with animal size. I just thought the students might be interested in the fact that you can use a bit of physics, and some GCSE maths, to show why there are no 50 m tall elephants wandering around africa. I hope they were.

So, at the time, they didn’t know why, and I didn’t think about why the lecture was in this style. But I guess  the lecture was in the style of de Gennes, so although he sadly died 5 years ago, his influence is still being felt. Who knows, maybe one the students will go on to do some teaching or lecturing of their own, and they make take some inspiration from how I teach.

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Statistics without Mathematics Tue, 27 Nov 2012 21:29:30 +0000 Richard Sear I went to library to look up some statistics books this week, and my eye was caught by several copies on the shelves of Statistics without Mathematics for Psychology, by Dancey and Reidy. I did a double take. I thought statistics was a branch of mathematics. Wikipedia agrees.

But if statistics is a branch of mathematics then statistics without mathematics looks like an oxymoron, a bit like a kosher pork sausage, or vegetarian chicken breast. I took a look and the book is aimed at psychology undergraduates who don’t like maths. Fair enough. But there is a real sense in which statistics cannot function without numbers, at all. If the result of the psychology experiment is that, say 65% of people are happy, then that’s a number, and so that’s unavoidably maths. And so the title is a little misleading, a slightly more accurate title would be Statistics in which you let a computer do the Mathematics for you for Psychology.

Idea being that you put the numbers into a program, and press the button to get an answer. In terms of making stats accessible this is good. But the risk is that you don’t understand what the computer is doing. Any statistical analysis (on a computer or not) makes assumptions, and if these assumptions are wrong, so are the results. If you don’t understand the assumptions, how do you know if they are right or wrong?

So it is good to make stats accessible, but I think if I see a book called Statistics with Mathematics for Engineers, I’d worry. Not sure I like the idea of crossing a bridge designed by someone who lets the computer do all the work.

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100 million alien civilisations Sun, 25 Nov 2012 19:12:01 +0000 Richard Sear WinkAlienThis is a rough estimate of the number of alien civilisations in our galaxy, obtained from the Drake equation. Last week I went to a Institute of Physics local branch general talk, by Alok Jha. He quoted this equation. The Drake equation is clearly a bit of a guess, but it is an interesting way to think about the question of whether we are alone in the galaxy, and if we are not alone, is it likely that aliens will signal us, or even invade us.

The Drake equation assumes that the number of alien civilisations on planets in our galaxy is the product of a number of factors. It can be broken down into two bits. First, we can ask what is the rate at which planets that can support life are formed. Call that RPL. In the Drake equation this is expressed as

RPL R * fP *ne

where R is the rate at which stars form in our galaxy, fP is the fraction of these stars which have planets, and ne is the average number of planets in solar systems with planets.

Then, N, the number of civilisations that could drop us a line is

N = RPL * fL * fI * fL

where  fL is the fraction of planets where life can evolve, fI is the fraction of cases where when life evolves, that it evolves intelligence, and fC is the fraction of cases where when intelligent life evolves, that it develops the ability to emit signals (e.g., radio waves) into space. L is the length of time a communicating civillisation exists.

So we have 7 numbers, most of which we can just guess.  But guessing can be fun, and I guess the point is that R is estimated as around 7 per year. This may not sound much, but over billions of years, this adds up. Also, we now know that planets are common, over 800 exoplanets are currently in the exoplanet encyclopedia.

So our best guess at the product of all these factors is of order 100 million civilisations that could potentially drop us a line. Of course our galaxy is very large, so even if it is accurate, the nearest one would probably be a long way away. Or this estimate could be way off, but it is fun to think about these things.

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Movember is easier for some than for others Thu, 22 Nov 2012 19:56:53 +0000 Richard Sear Mona Lisa moustacheMany men are growing mustaches to raise money and awareness for prostate and testicular cancer, including a number of our students, you can see two of their taches here and here. Then I began to wonder when someone casually said that he had ‘unusually rapid hair growth’. I wondered if it was true, that indeed some people’s hair does grow faster than others, it is not just that it make look as it is growing faster if they have thicker hairs.

Well, I looked up the answer on the internet, and indeed there seems to be a range of hair growth rates from around 0.7 to 2 cm/month, at least according to work surveyed by LeBeau and coworkers. So, bad news for some, but rather better news for others. This is for head hair but I guess tache growth should be similarly variable.

It appears the rate of growth can vary from individual to individual for presumably genetic reasons. It can also change in response to hormone changes, for example hormonal changes during pregnancy can cause a speed up of hair growth. Not that this is very useful in Movember.

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David Cameron is using his brain for the purpose it evolved for, I’m not Sun, 18 Nov 2012 11:50:28 +0000 Richard Sear Capuchin monkeys sharingI don’t research on evolution any more (sadly I had to give it up as I didn’t have the time) but I still think it is pretty cool. One of the big questions in evolution is why we humans evolved such large brains. These sorts of evolutionary questions are hard to answer definitively partly because it has already happened and we can’t reurun this experiment, and partly because our brain is ferociously complex, and understanding complex things is just hard.

But one hypothesis for why we evolved such big brains is the social brain hypothesis, which basically says we evolved it to interact with other humans. Very crudely speaking, you can imagine that genes for a big brain could spread through the population if a big brained caveman used his big brain to convince a smaller brained caveman to got out on a dangerous hunt for a mammoth, and then slept with the poor sap’s wife.

Sorry for that rather misanthropic example, but evolution is a natural law, it just is, it doesn’t have to make us feel good about ourselves. A more cheery example is that a sense of fairness may, at least to some extent, be hard-wired into our brains by evolution. Indeed, not only into our brains but into the brains of other social animals, such as capuchin monkeys.

Below is a short (2 minutes) clip of the well-known Dutch anthropologist Frans de Waal introducing a short film showing a capuchin monkey acting pretty narked by unfairness

Thanks to Brian Richards for pointing it out. I feel the pain of the capuchin monkey on the left. I guess you do too, at one time or another we all are left with the boring cucumber while someone else has the tasty grapes, and it burns. It seems likely that at least some extent, the genetically programmed process that builds our brains is hard-wired to make brains that can appreciate fairness and react badly to perceived unfairness.

Our modern societies are much much larger than the social groups we lived in when our large brain was evolving. But if the social brain hypotheses is largely correct then when politicians are campaigning, and us when we are trying to judge which one to vote for, are using our brains for the purpose they evolved for. Ironically, when scientists are using their brains to try and understand evolution, they are not using them for the purpose they evolved for.

And it gets worse for me. The first number systems were developed in the first civilisations basically for tax and accountancy purposes. So when I am doing some calculations to try and understand some part of the natural world, I am using  a brain evolved for politics, and a number system developed for taxation.

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Guest post of Dr Dan Robertson: From Guildford to “The Fighting Irish”, via CERN Wed, 07 Nov 2012 20:57:59 +0000 Guest I can remember my first day at Surrey very vividly, it rained. In fact it rained everyday for 6 ½ weeks. At the time I wasn’t really sure where I wanted to be after the 4 years, but somewhere dry was at the top of my list. As it turns out the University of Surrey was actually a great place to be, not only did I enjoy my time whilst there, the contacts and collaborations of the Physics department saw me not only working at CERN for a year as part of my MPhys research, but also got me in contact with many other institutions where further positions were possible. So, after getting my MPhys degree, I found myself in the Nuclear Science Laboratory at the University of Notre Dame in the US, where after my PhD and Postdoc, I am now transitioning into a research faculty position. The University itself is a unique place, an American University founded by a French priest, with the nickname “The Fighting Irish”. However, the lab finds itself at the forefront of low-energy nuclear astrophysics research, both experimental and theoretical.

My research has covered a wide range of experimental techniques associated with the study of nuclear reaction mechanisms in stellar environments. The dry explanation would be; we measure and try to quantify the rate at which key reactions take place in stellar environments, leading to a better understanding of not only energy production, but also how the elements are created. However in my opinion, a better way to describe my day-to-day research is that I get to play with really cool equipment and experimental set-ups that I have thought-up and built for an exact purpose. This also involves the operation and manipulation of 3 accelerators up to 10 million volts. The amazing thing about research in such a hands-on environment is you get to take part in all aspects of many diverse projects. From measuring the rates of reactions that take place during explosive nucleosynthesis, to element identification of works of art thought to be fakes. I am also currently involved in a project that would see the creation of an enormous underground multi-user laboratory due to be built in an abandoned gold mine. The Deep Underground Science and Engineering Laboratory (DUSEL) project would see all fields of science and technology come together in one lab, with my particular focus on the installation of a nuclear accelerator lab about half way down the levels of the mine, in an attempt to reduce cosmic ray induced background.

It was not only the training and education I received at Surrey that was invaluable, it was also the opportunities afforded to me by the world wide recognition and connections the Physics department has. It is this basis that has made the transition possible into both new areas of research and to the forefront of modern experimental techniques.


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Would Lionel Messi’s clone end up playing for Woking? Fri, 02 Nov 2012 20:14:35 +0000 Richard Sear Lionel Messi Player of the Year 2011Over the summer I went to a couple of conferences and in one I enjoyed a talk by a Barcelona-based British scientist called Ben Lehner. It featured an interesting idea, and Lionel Messi. I guess if you work in Barcelona, Lionel Messi is your go to guy if you want to illustrate an idea; in this case, an idea about clones.

For the last century there has been much arguing over ‘nature vs. nurture‘. Very simply speaking: What determines what we are, our genes or our upbringing? In practice we now appreciate that most of the stuff about us that we care about is determined by a mixture of both. I am an OK computational physicist with some maths skills but really no coordination, while Messi is probably less good at the maths but a supremely gifted footballer. These differences are partly due to our different upbringings and partly due to our different genes.

But there is now evidence that perhaps some significant differences between us are not due to genes and not due to our unbringing, but may be just random, just due to chance. This would imply that even if you cloned Messi and gave the Messi clone exactly the same education and football training as Messi, the clone might be a very average footballer, just due to chance. I think it is quite an interesting idea that chance could have such a fundamental role in who we are.

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The Earth’s atmosphere is bigger than I thought Sat, 27 Oct 2012 11:24:34 +0000 Richard Sear Iss017e011632On Friday an atmospheric scientist I know from the University of Leeds, Ben Murray, gave a talk on his research. His research is on how ice forms in the atmosphere. It was very interesting, and one of the things I learnt is how big the atmosphere is, and how high up some clouds are. The image above is taken from the International Space Station and at the top of the image are what are called noctilucent clouds.

They can also be seen from the ground, but only at twilight. These clouds can be up to around 85 km up. Which I guess is why there is such a wide gap between the Earth’s surface and the clouds in the image above.

To give you an idea of how high up this is, the summit of Mount Everest is 8.8 km up, so these clouds are ten times higher. Felix Baumgartner’s recent record breaking jump was from around 39 km, pretty high, but less than half as high as these clouds. The International Space Station, which of course is in orbit, is only 370 km up, so these clouds are almost a quarter of the way up into the space station’s orbit. I think that’s pretty amazing.


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