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{jIAPS} Journal of the International Association of Physics Students

ICPS 2010 Graz

ICPS Issue 2010

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Cover photo: Clocktower, Graz, by Andrew Bossi, from Wikimedia ICPS Issue Commons 2010


In This Issue A few words from

...the Editors

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...the IAPS Executive Committee

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IAPS Activities 2009-2010: CERN Trip

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Balaton Summer School

Introducing IAPS

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The jIAPS Writing Contest

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The Loneliness of the Long-Distance Archivist, by Jim Grozier

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CERN: Black Holes and the Higgs Particle, by Mark Eaton

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Neurophysics of Vision: An Introduction to Binocular Rivalry, by Jessica Stanley

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Physicists in the Kitchen, by Anne Pawsey

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Challenges of Weightlessness, by Joshua Fuchs

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The Back Page

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Editors: Jessica Stanley Contributors: Anne Pawsey Ragnhild Schrøder Hansen Design: Jessica Stanley Contact: jiaps@iaps.info www.iaps.info/jiaps ICPS Issue 2010

Irina Cioara Joshua Fuchs Jim Grozier Ralph Lenssen Philip Seibt Jessica Stanley Milan Vrućinić Julia WIktor

{jIAPS}

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A few words from the Editors... Another year, another International Conference of Physics Students. 25 years, 21 host cities, 16 different countries, thousands of physics students over the years, and a whole lot of hard work and enthusiasm. Every ICPS is slightly different, with each organising committee bringing its own special flavour to the conference. The organisers of ICPS 2010 have been hard at work for over two years, and this issue of jIAPS is a celebration of the hard work done by all the volunteers who run ICPS and IAPS. You can read about the work done by various local and national committees of IAPS, and see pictures from the CERN trip and the Balaton Summer School. We are also carrying on the tradition of including a selection of the articles published throughout the year in the ICPS edition, and this year that covers various topics from CERN to self-heating chocolate, and an inside look at Jim Grozier’s work on the IAPS archives. We are always looking for new contributions to jIAPS, and this year there is an extra incentive in the form of a writing contest, the prize of which is a place at ICPS 2011 in Budapest, Hungary. So if you would like to get involved, or have any questions, feel free to pull one of us aside at ICPS, or you can always email us at jiaps@iaps.info. Jessica Stanley Jessica Stanley is a master student of experimental physics (specialising in neurophysics of visual perception) at Utrecht University in the Netherlands, and is from a small village called Enniskerry just south of Dublin, Ireland. She has a B.A. in Theoretical Physics from Trinity College Dublin, where she was an active member of the Mathematical Society and the Ireland branch of the Institute of Physics. Jessica was also a student representative for Nexus, the student branch of the Institute of Physics, was IAPS secretary in 2008/2009, and has attended ICPS since 2006.

Anne Pawsey is from Sheffield in the UK, and is a PhD student of ‘squishy stuff’, otherwise known as soft condensed matter, at Edinburgh University. She has an MSci from Bristol University, where for her master research project she had to make the tough choice between studying cake, chocolate or icecream. Anne has attended ICPS four times since 2006, was jIAPS editor previously in 2006/2007, IAPS secretary in 2007/2008, and was on the ICPS 2007 organising committee. She was a student representative for Nexus, the student branch of the Institute of Physics, for many years.

Ragnhild Schrøder Hansen is from Bergen, Norway. She has just finished her masters in space physics, researching Terrestrial Gamma-Ray Flashes, at the University of Bergen, where she also did her bachelor degree. Ragnhild is the former president of the Norwegian Association of Physics Students, and is an active member of Fysikkshow Bergen, doing demonstrations of experiments to teach kids about physics. She was a general member of the IAPS Executive Committee in 2008/2009, and has attended ICPS since 2007.

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...and the IAPS Executive Committee It’s that time of year again: 400 physics students have descended on the city of Graz for the 25th International Conference of Physics Students, and like in previous years the editors have produced this special issue of jIAPS that you hold in your hands, to tell you about the activities of IAPS and to share some of the articles that have been published in other jIAPS issues this year. If you have arrived at ICPS not sure what this thing called IAPS is, or what it has to do with you, then fear not, for all will be explained. The International Association of Physics Students is a network of physics students and physics associations and clubs from many different countries, and the job of the Executive Committee (EC for short) has many different levels: we maintain and update a network of contacts from different countries, and we continually try to find new contacts in countries where we have no members, or encourage individual members to start a committee in their country. We are associated with the European Physical Society, and this year we have re-established links with the International Association for the Exchange of Students for Technical Experience (IAESTE). We also organise activities for our members, such as the CERN trip earlier this year, and join forces with local associations to help them fund and promote their activities, like the Balaton Summer School which is organised by Mafihe, the national committee of Hungary. So how can you get involved? If there’s no IAPS committee in your country or region, start one yourself! On page 8 you can see a list of the national and local committees of IAPS, and in the pages after that you can read about the activities of some of these associations. Alternatively, if you have an idea for a trip of another kind of physics event, let us know so that we can help you make it happen. If writing is your thing, contact the jIAPS editors, as they are constantly looking for physics-related articles. You are also encouraged to send reports on events organised by your local association, so that the other members of IAPS can know more about what you do. Finally, there is the EC itself. A new committee will be elected at the Annual General Meeting of IAPS, which takes place during ICPS, and if working on the kind of projects we’ve just mentioned sounds good to you, come along and run for a position. We invite you to come to our workshop during ICPS, and don’t hesitate to ask us questions if you see us around: you’ll know what we look like from the picture on the right. We are looking forward to hearing your ideas.

Back: Jelmer Renema, Konrad Schwenke, Marko Banušić Middle: Sérgio Domingos, Milan Vrućinić, Istvan Szecszeni Front: Sahra Haji, Camelia Florica, Agnieszka Leyko

your EC Contact the EC: ec@iaps.info

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IAPS Activities 2009-2010:

CERN Trip

Organised by the IAPS EC

Photos by Sahra Haji

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IAPS Activities 2009-2010:

Balaton Summer School

Organised by Mafihe, NC Hungary

Photos courtesy of Mafihe

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One of the core aims of IAPS is to maintain a network of physics student all over the globe. The following is a list of the member committees of IAPS, and in the following pages you can read what seven of these committees has to say about themselves and what they do. For more information, or if you are from a country which is not represented in IAPS and would like to start a committee, see www.iaps.info or ask one of the Executive Committee members about it at ICPS. National Committees: Austria: Basisgruppe Physik an der TU Graz (our hosts for ICPS) Croatia: Student section of the Croatian Physical Society (SSHFD) Finland: Finnish Association of Physics Students Germany: Student branch of the German Physical Society (jDPG) Hungary: Hungarian Association of Physics Students (Mafihe) Italy: Italian Association of Physics Students Lithuania: Vilnius University Faculty of Physics Students’ Scientific Association (SMD) Netherlands: Dutch Physics Students Association (SPIN) Norway: Norwegian Association of Physics Students (NoFFo) Portugal: Portuguese Association of Physics Students (Physis) UK & Ireland: Nexus, student branch of the Institute of Physics USA: Society of Physics Students (SPS)

Local Committees: Bosnia & Herzegovina: University of Banja Luka Physics Students Association France: Photon, Paris Poland: Physics Student Research Association, Gdansk Physics Students’ Scientific Circle “Bozon”, AGH-UST, Krakow Physics Students’ Scientific Circle “Schrödinger’s Cat”, TU Lodz Student Scientific Society of Medical Physics, Adam Mickiewicz University, Poznań Local Committee Torun Romania: Association of Physics Students, University of Bucharest (ASF) Faculty of Applied Sciences Student Association, Bucharest Polytechnic (ASFSA) Student Association of the Faculty of Physics of Craiova Local Committee Iaşi

Serbia: Physics Students’ Club, Novi Sad Local Committee Dirac & Co., Belgrade Ukraine: Association of Physics Students of Kyiv National University

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LC Gdansk: KNSF

by Julia Wiktor

The Local Committee in Gdansk is formed by the Scientific Society of Physics Students of Gdansk University of Technology in Poland. At the moment the main activity of the society is didactics. Each year we participate in organising the Baltic Festival of Science. This event consists of various exhibitions, with the aim of explaining science to both younger and older people. We try to combine learning with fun, for example this year we demonstrated how approximately 4500 helium balloons can lift a person off the ground. During the year our members regularly visit small schools to show physics experiments to young students. Apart from didactics, we organise meetings with interesting people from different fields of physics. For example the society holds an annual “Meeting on Renewable Energy”, where everyone can come and listen to lectures held by students, scientists and experts from the industry. Our members can also propose and realise their own projects as a part of the society’s work. We are also represented at various Polish and international conferences.

Get in touch: http://www.mif.pg.gda.pl/knf/

Scenes from the Baltic Festival of Science

LC Bucharest: ASF

by Irina Cioara

The “Student Association of the Faculty of Physics” at the University of Bucharest has over 100 members and has been affiliated with IAPS since August 2004 and with the Student Association of the University of Bucharest since 1999. Our regular activities include: organising the Junior Prom, promoting and increasing the popularity of science and physics, organising sports contests and other recreational activities for the students of our University.

Our team is involved in both national and international projects organised by our association or by our partners. Our main goal is to represent and help the students in our faculty in their professional path and to solve the students’ social problems. Get in touch: http://asf.fizica.unibuc.ro

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NC USA: SPS

by Joshua Fuchs

The Society of Physics Students (SPS) is a dynamic, chapter-based professional association explicitly designed for students. Membership, through collegiate chapters, is open to anyone interested in physics. The only requirement for membership is that you be interested in physics. Our members include majors in physics, chemistry, computer science, engineering, geology, mathematics, medicine, and other fields. Within SPS is housed Sigma Pi Sigma, the United States of America’s physics honor society, which elects members on the basis of outstanding academic achievement.  This unique two-in-one society operates within the American Institute of Physics, an umbrella organization for ten other professional science societies. SPS has nearly 800 chapters on college and university campuses across the country which are housed in eighteen geographical Zones. About 5,000 students join SPS at the national level each year, and three to four times that many take part in local chapter activities and regional Zone meetings each year. The SPS national organization sponsors summer internships, scholarships, fellowships, research grants, outreach materials, conference travel grants, and awards for individuals and SPS chapters. It also helps fund regional Zone meetings.

The Angelo State University SPS Chapter, San Angelo, TX, performs an outreach demonstration to Texas school children.

Every year the SPS National Council, an elected body that includes nineteen student representatives, selects a theme to shape and develop programs and promote SPS membership and activities. The theme for 2010 is “Exciting the Imagination,” to celebrate LaserFest, marking 50 years of laser innovation. SPS produces two periodicals, The SPS Observer, the quarterly magazine of the Society of Physics Students, and the online Journal of Undergraduate Research in Physics, or JURP (http://www. jurp.org/). JURP is a peer-reviewed journal for archiving research conducted by undergraduate physicists, which publishes papers in experimental physics, theoretical physics, and educational research in physics. Every four years, the Sigma Pi Sigma honor society hosts a national congress, which is also open to members of the Society of Physics Students. This quadrennial meeting is one of the largest gatherings of undergraduate physics students of its kind. The next congress is scheduled for Fall 2012, at the Kennedy Space Center in the state of Florida.

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Get in touch: SPS National Website (http://www.spsnational.org) Facebook (http://www.facebook.com/pages/The-Society-of-Physics-Students/121425889435) Twitter (http://www.twitter.com/SPSwebster). Additionally, The Nucleus is an SPS-supported collection designed specifically to serve as an informational touchpoint and online community for undergraduate physics and astronomy students (http://www.compadre.org/student/).

LC Banja Luka

by Milan Vrućinić

Local committee (LC) Banja Luka has existed since 1999, when the Association of Physics Students of the University of Banja Luka (Udruženje Studenata Fizike Univerziteta u Banjoj Luci) was established. As the only LC of IAPS in Bosnia and Herzegovina, LC Banja Luka is trying to promote physics in our society and student research work among the physics students at our University. Despite a few breaks in its work our LC has succeeded to actively participate in the work of IAPS and to send many students from our University to ICPS. Our LC promotes students’ scientific work among our students and encourages them to participate in international student conferences where they can meet up with physics students from other countries, along with practising their English language and presentation skills. Another one of our activities is the promotion of physics to high school pupils and encouraging them to study physics, since we don’t have enough physicists in our country. In future we would like to improve the work of our LC and to try to become the student wing of the Society of Physicists of the Republic of Srpska. We also plan to make a small library for our Association where students could use second hand books from our former students and find their theses, papers and all documents that can help them in their studies. Get in touch: lc.banjaluka.iaps@gmail.com Email Aliases It is now possible to contact any of the national or local committees using the following email aliases: To email a national committee: nc-[country name]@iaps.info, e.g. nc-austria@iaps.info To email a local committee: lc-[city/region/university name]@iaps.info, e.g. lc-novisad@iaps.info The exception to the rule: NC UK & Ireland: nc-uk@iaps.info

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NC Germany: jDPG

by Philip Seibt

Five years after its foundation the German “junge Deutsche Physikalische Gesellschaft” has applied to become a national committee of IAPS. If accepted, more than one thousand German physics students will join the community of IAPS. Founded in 2005, the “jDPG” has become a national organisation within a few years, offering different kinds of activities to all 30,000 physics students in Germany. “We have three fields of activity”, explains spokesman Alexander Heinrich, who has just finished his Bachelor of Science at Bonn University. The first goal is to give all physics students in Germany insight into current research. There are more than ten different excursions every year, visiting a broad variety of research centres, industrial complexes and companies all over Germany. “We want to give people the opportunity to get out of their everyday life at uni and have a glance at what is really happening in physics at the moment”, says Anna Bakenecker, who manages the nationwide excursions of jDPG. The next big excursion will be in August, where students will be staying in the city of Dresden for one week (IAPS members are of course welcome). Enhancing the scientific program, there are different kinds of workshops offered every year. For example, in January there was a workshop for theoretical physics where advanced students had the chance to learn more about biophysics and the possible connections of physics and economics. The second field of activity is helping students to start their career after finishing university. This is especially aimed at students who are about to finish their studies. They have the possibility to meet physicists from different fields of work like consulting, journalism or research. “It is very important for us that we have small groups of people, so that students really get the opportunity to ask the questions they want to ask”, says Matthias Mader, who is responsible for the workshops. A small, but very important jDPG event is “Meet your Prof”. The idea is that a professor talks not only about his work but also about his private life. “The dialogue between different generations of physicists is our third field of activity”, explains spokesman Alexander Heinrich. Other events in this field are a breakfast with physicists and pupils or “Our institute – our research”. The founders of jDPG started the organisation from scratch. There was never any master plan, just one big aim: to be a network for physics students in Germany. Picture from jDPG website

Get in touch: www.jdpg.de info@jdpg.de

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NC Netherlands: SPIN

by Ralph Lenssen

In the Netherlands there are eleven local study associations. Depending on the university the board of these associations get a grant so they can spend more time on organising activities for their members. These activities range from full dress balls to LAN-parties and sometimes there are sports competitions. There are also excursions to interesting companies and research institutions like nuclear power plants, Philips research labs and of course beer brewers. One of the bigger tasks is the organisation of introduction weekends for the freshmen or celebrating the birthday of your association. Dutch physics associations are also often seen abroad during the study trips that they organise. These trips are sometimes long weekends to our European neighbors or even a month to China. They also often have their own book sale so they can get bigger discounts for their members and make a yearbook. The local associations often represent their members in the university management by giving advice about new rules and complaining if the quality of teaching is bad. Thanks to the free use of public transport Dutch students enjoy it is easy for them to visit each other. This helps attract students to the annual national physics quiz and physics conference. Another great advantage this brings is that the boards can visit each other’s parties. The national student association has the task of organise meetings in which best practices can be exchanged and to represent physics students at the Dutch Physical Society and in IAPS.

Right: An example of the Dutch study association tradition of marking territory with stickers (photo: Lennart Herlaar). Above: The current board of Leiden study association De Leidsche Flesch (photo: Swier Heeres)

ICPS Issue 2010

Get in touch: www.verenigingspin.nl bestuur@verenigingspin.nl

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NC UK & Ireland: Nexus

by Jessica Stanley

Nexus is the student branch of the Institute of Physics (IoP), a UK-based scientific association with the aim of communicating physics to a wide audience and also supporting working physicists and scientific research. Founded in 1992, Nexus has approximately 10,300 undergraduate and 2,150 postgraduate members, and basic membership is free to students doing their first degree in physics. Members can avail themselves of both Nexus events and services and the wider resources of the IoP, including scientific publishing, outreach opportunities, careers advice, and the monthly Physics World magazine. Nexus supports students and student physics societies on a local and (inter-)national level: affiliated societies can apply for grants to help fund their activities, and can enter the Nexus Society Awards, which are held as part of the annual Nexus Student Conference. Students from all over the UK and Ireland (and sometimes further afield) gather for this conference, which combines student talks with guest lectures and a formal dinner, where the awards, voted for at the conference based on presentations given by the societies, are presented. The 2009 Nexus Student Conference was held in November at Cambridge University, with approximately 80 attendees, and the University of Southampton physics society were awarded the first place prize by Dame Jocelyn Bell Burnell, president of the IoP and discoverer of the pulsar.

Nexus Society Award winners 2009, Southampton Physoc, with former Nexus Membership Development Officer Dr. Mischa Stocklin

Dublin physics table quiz 2009. Photos by Dr. Mischa Stocklin

There are 8 Nexus regions covering the UK and Ireland, and a total of almost 40 affiliated physics societies out of these regions combined. Student representatives from each of these regions help to make decisions about Nexus on national and regional levels, advise the IoP on the needs of students, and coordinate events and networking between the societies. Past events organised by Nexus include trips to CERN and other scientific facilities, formal dinner events, physics quizzes, and, last but not least, ICPS 2007, which was held in London. In previous years Nexus has also contributed to the cost of ICPS registration for students from the UK & Ireland. Membership is open not just to UK and Ireland residents, but to physics students worldwide. Get in touch: www.iop.org/activity/nexus member.services@iop.org

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The

{jIAPS}

writing contest

We are pleased to announce that this year jIAPS and IAPS are holding a writing contest. The idea is simple: write an article on a physics-related topic. This can be, for example, about your research, a physical phenomenon that you find fascinating, a historical piece about a physicist you admire, or a review of an activity held by your local association. The contest is open to all IAPS members (apart from the editors and the executive committee of course!), and articles should be at a level understandable by first or second year university physics students. Articles should be sent to jiaps@iaps.info by October 31st, and should be no longer than 1000 words in length. Submissions will be judged by the jIAPS editors and the IAPS executive committee, and the winner will receive a place at ICPS 2011 in Budapest with registration fee paid for. The winning article and a selection of runners up will be published in a future edition of jIAPS. To get an idea of the kind of articles that are published in jIAPS, in the following pages you can read a selection of the articles from this year’s jIAPS issues. We welcome everything (within reason!) from traditional subjects like semiconductor devices or astrophysics to fun and unusual topics like self-heating chocolate. A small archive of old issues is available at www.iaps.info/jiaps.

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The Loneliness of the Long-Distance Archivist by Jim Grozier In early 2007, as a member of the IAPS Charter Committee, I attended a meeting at the European Physical Society headquarters in Mulhouse, France. While I was there, somebody gave me a CD containing the IAPS electronic archive. I found it fascinating; but it clearly needed some work done on it – the documents it contained had obviously been hurriedly scanned and did not have meaningful titles, being catalogued simply under the default numbers allocated to them in the scanning process; and the folders into which they were divided seemed, in some cases, quite arbitrary. I offered to take on the role of IAPS archivist and go through the whole lot (about 130 megabytes), sorting the documents and giving them meaningful names so that the archive could be more easily navigated in future. As I read through the archive, the story of how a small group of physics students organised their own international conference back in 1986 and then went on to found an international, student-led organisation, in Hungary, under a communist regime which discouraged that sort of “grass roots” activity, unfolded before my eyes. As someone with a keen interest in the history of physics, including the sort of history that is quite recent and might not therefore be thought to qualify as history by some people, I wanted to re-write the story in a more readable form so that it could be discovered by others; so I started to write a historical article, and, while I continued to process the archive, the article came to take up more and more of my time, leaving less time for cataloguing. ICPS that year was in London – the first time in the UK – and I was one of the organisers. So there was a publishing opportunity for the article, which appeared, in its earliest form, a mere two and a half pages long, in the conference booklet, to mark IAPS’ 20th birthday. After ICPS, I continued to extend it as I gathered more and more material, and in 2009 I was able to submit a longer version to Europhysics News; it was published in the autumn edition of that year. However, EPN’s word limit of 1500 words did not allow me to include anything of great interest; it was merely a skeleton. I was keen to publish a longer version, although I realised that this would make it too long for most magazines, but too short for a book. There was another problem too; the article as it stood in late 2009 was mainly a collection of anecdotes – all of them interesting, but giving an inevitably “bitty” feel to the whole thing. It needed structure – a theme around which to build the story. That meant only one thing – I would have to personalise the story, by getting it first-hand from the five founders: Patroklosz Budai, Tamás Fülöp, Ákos Horváth, Péter Lévai and Péter Ván. An attempt to do this by e-mail proved fruitless – I was nominally in contact with four of them, but, while all seemed keen to help, only two had actually answered my questions. I would have to travel to Budapest and interview them face-to-face.

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The Loneliness of the Long-Distance Archivist

{jIAPS}

My visit took place in February 2010, and I was warmly received. We had a “group chat” over an extended lunch, joined by Marton Major, the 10th president of IAPS, and – probably more to the point for ICPS-goers – the inventor of the National Party. Then over the next few days I interviewed them all individually. After my return to the UK, the article grew, and a plot emerged – that IAPS had in fact resulted from a unique combination of time and place, for it became clear that the need for such an organisation was felt most strongly in the then Iron Curtain countries where budding physicists felt isolated and needed to add an international dimension to their studies, and of those countries, only Hungary, with its uniquely liberal regime born out of the tragedy of the failed 1956 revolution, could foster such an initiative, and even there, only in the mid-1980s. Because of this I added a section outlining the political and historical background. The article, or “booklet”, as it now was, stretched to over 11,000 words, and took up 40 pages by the time a few photos had been added. I am hoping to get it published, preferably in time for ICPS’s 25th anniversary in 2011, with copies being made available to ICPS attendees, although I appreciate that it is never going to be a best-seller. Meanwhile, the archiving itself has had to take a back seat. This was not just because it was less interesting than writing the article; in fact, I have found archiving to be a far from trivial task. For a start, what I found in the archive was not the sort of material one would think of as obviously worth preserving. Much of it consisted of copies of e-mails, and of the telex messages and letters that preceded them. Of conference handbooks and AGM minutes, which would be a bit more “meaty”, there was a woeful scarcity. This can be explained perhaps by the fact that the archive led a nomadic existence for the first 10 years of its life, being taken to wherever the Central Office was based each year; only after the cementing of relations with EPS in the late 1990s did it find a permanent home, and no doubt much of it got lost on the way. Then again, there have undoubtedly been years when the archive was neglected and nothing much added, just as there are years when almost everything seems to have been preserved.

The IAPS founders, the author and Marton Major, pictured in Budapest in 2010. Left to right: Péter Lévai, Péter Ván, Jim Grozier, Patroklosz Benatos, Ákos Horváth, Tamás Fülöp, Marton Major.

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The Loneliness of the Long-Distance Archivist

{jIAPS}

I actually ended up being quite grateful for this quasi-natural selection process, for, had it not taken place, the archive today would be absolutely huge, and my job would then be to cut it down somehow. This too would be far from trivial. For it is at the “microscopic” level that the archive becomes interesting; an exchange of e-mails over a particular topic, interspersed with some chatty, personal remarks, gives one a flavour of the personalities concerned, whereas minutes, while informative, are usually fairly dry and impersonal. An archivist’s job, however, is to look to the present and the future as well as the past; and here it does become seriously tricky. How does one decide which, of the huge number of documents now being produced, should go in? To say nothing of the hundreds of digital photos! (A dearth of photos from the early days is one of the disappointments I have had to face, but now, in the digital age, I have the opposite problem). I have even considered doing an archiving course, so that I can do it properly. Of course, if anyone out there gets really fired up by such things, I would willingly hand the job over… Jim Grozier is a postdoc at University College London. Besides working on the archives he was on the ICPS 2007 organising committee, the IAPS charter committee, and was elected to honorary membership of IAPS by the 2008 AGM in Krakow. His article on IAPS that is mentioned in this article was published in Europhysics News Volume 40 Issue 5 (www.europhysicsnews.org). Jim is sometimes mistaken for a certain Time Lord, but claims to be from planet Earth, not Gallifrey.

ICPS Dos and Don’ts: We all have bad ideas, and a week of physics, parties, and sleep deprivation doesn’t help anyone make good decisions. Learn from our mistakes...

“Don't wait until 30 minutes before the start of the National Party to decide what to have and end up with a bag of potato chips”

“Don’t go near the Austrians, you WILL have to down at least 1 beer” “Don’t ask mature students if they really are students”

“Don't trust Danish people when they say something doesn't have nuts in it”

“Do sample the national liquor of each nation at the National Party, but slowly”

“Don’t wear a toga to the costume party”

“If you're from Sheffield, try each liquor twice within the hour time limit...then strip” “Don’t wear a bed. Never” “Don’t be friends with the current secretary of IAPS, you may find yourself with a new position after the AGM”

“Don’t drink anything alcoholic which comes in an unlabelled plastic bottle”

“Watch out for semi-naked Finns with saunas” “Don’t go to the AGM unless you want to have an IAPS position or are bidding for ICPS” “Don't forget a costume!”

“Don’t arm wrestle with large Americans”

“If you are an organiser make sure the restaurant is open”

These wise words of advice were contributed by Alex Killeen, Daniel Machado, Scott Hilditch, Konrad Schwenke, Anne Pawsey, Robin Ravi, Nicola Fulvio Calabria, Jim Grozier, Joshua Fuchs, and Jessica Stanley.

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CERN: Black Holes and the Higgs Particle by Mark Eaton Considering that the Large Hadron Collider (LHC) at CERN in Geneva is looking at some of the smallest particles in the universe, the numbers associated with it are truly ‘astronomical’. It has never failed to amaze me how sub-atomic particles can teach us so much about the biggest issues in astronomy and cosmology such as dark matter and the Big Bang. As a mature student of astrophysics I was able to visit CERN on the IAPS trip in March 2010, and we were able to access some of the latest thinking at the world’s biggest experimental site as well as visiting some of the facilities surrounding the LHC. One immediate thing that hit me was the age of the site. CERN has been hitting the news for over 50 years and whilst most people in the world know about the search for the Higgs particle, CERN has already generated a number of Nobel prize winning discoveries and such things as World Wide Web. The site is home to around 10,000 people, including some 2,500 staff and researchers as well as students and researchers from the nations who support the facility. It is fully equipped with its own travel agency, post office and shops, and the roads are all named after famous scientists. The Large Hadron Collider itself is obviously the centrepiece of the facility, although you would

be hard pressed to spot it even at 27km long, as it is located 100m underground, with the majority of it residing in France (where it is easier to buy land). The LHC itself consists of over 9,000 magnets designed to steer two proton ‘beams’ around the 27km circuit. The beams are then converged at four experimental points called ATLAS, ALICE, CMS and LHCb, or they can be sent toward a fixed target. Each of the experiments is huge. One, the CMS (Compact Muon Solenoid) contains more metal than the Eiffel Tower and weighs 12,000 tonnes. In addition, each of the four experiments has its own control room. Protons collided in the LHC are travelling at 99.9999% of the speed of light and they impact with a combined power of 14TeV (Tera Electron Volts) (this is 14,000,000,000,000 Electron Volts where 1 Electron Volt is the kinetic energy gained by an electron when it is accelerated by 1 Volt battery). For reference, the power given to an electron in the cathode ray tubes that used to be popular in TVs is only 20,000 electron volts, so interactions within the LHC are some 700 million times more powerful. The particles in the LHC are referred to as a beam but in reality they travel around the system in ‘packets’, each containing 1011 protons. When the LHC is running it has a total of 2808 ‘pack-

ets’ of protons, each located 7.5m apart as they travel around the 27km ring. These packets are brought to four collision points within each of the four experiments producing 6.5x108 protonproton collisions every second during a run. The amount of data collected by the LHC experiments is truly vast. The CMS alone has a camera with a surface area of 220m2 and a resolution of 75 megapixels. More than that, it can take 40 million pictures per second of proton impacts when it is running, and this is more data than could ever be stored, so they have to quickly screen the image and decide whether to keep it or discard it. This reduces the number of frames taken when the machine is running to around 100 per second. Much has been written about the possibility of the LHC producing a ‘micro black hole’. They told us that this is a distinct possibility, but given that the black hole created will evaporate in one million million million millionth of a second (10-24) through ‘Hawking radiation’ it is unlikely to be a big issue. The LHC is only the end of the proton’s journey, as it first has to be accelerated by three smaller systems, raising its speed from a few metres per second to 87% of the speed of light (261,000 km/s) before injection into the LHC.

Image: Adapted from a one loop Feynman diagram of the first order correction to the Higgs mass, from Wikipedia.

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The CMS Control Room

What’s more is that the collisions going on at the LHC have been occurring naturally in the upper atmosphere at the rate of 100,000 per second for 4.5 billion years, and therefore if a serious black hole were to be created it would probably have already occurred. So no need to worry in the next few weeks! One thing that they do find regularly at CERN is antimatter. Indeed, for every million protons produced they identify one anti-proton. The team at CERN provided advice to the producers of the film ‘Angels & Demons’ (based on the Dan Brown book of the same name). Ron Howard, the director of the film, was keen to reduce many of the scientific errors that were in the book and wanted some real scientific advice. However, not all of the inaccuracies could be eliminated and in the film the Vatican is threatened by a bomb containing half a kilo of a ‘highly combustible’ material called antimatter. First of all, antimatter does not combust, it just converts normal matter into energy and in addition the time required

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to produce half a kilo of antimatter would need the LHC (working at full pelt) to be running continuously for around 10 billion years. Apart from this the CERN physicists also destroyed my faith in the availability of matter transporters and warp drives from Star Trek anytime soon (or ever!) It is a shame that we could not go down into the tunnels to see the LHC, but given that they are cooled by liquid Helium at a temperature of 1.9 Kelvin (-269 oC), and that if it warms up by only 1 or 2 degrees it will expand 800 times (meaning that anyone in the tunnels will speak with a high pitched voice for a few seconds and then drop dead), it was probably for the best. What is even more impressive is the temperatures that they can achieve in the impacts (1015 K – that’s 1,000,000,000,000,000 degrees), along with the fact that they have a vacuum that contains even fewer particles than outer space, and the ability of the LHC to recreate temperatures and energy levels not seen since one billionth of a second after the Big Bang.

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So, is all this money being used wisely? If we forget the fact that understanding how atoms work will help us to understand the universe more completely, the applications of particle physics have found their way into medical diagnostics such as PET (Positron Emission Tomography) and MRI scanners while the need to analyse data has given us the world wide web and will, they believe, in the future give us an even better system called the ‘Grid’. In terms of understanding the universe more effectively one key development they hope will come from the work at CERN is a better understanding of dark matter and dark energy. The surprising thing about all of the objects we can see in the sky is that they account for only 4% of the total mass of the universe. 26% of the rest of the mass is believed to be dark matter, which is material that does not emit electromagnetic radiation (including visible light) but that does interact gravitationally with ordinary matter. It is the halo of dark matter that is thought to enable spiral galaxies to maintain their ‘arms’ for extended periods rather than simply falling apart. The remaining 70% of the mass is in the form of dark energy, which at its simplest level is thought to be the force driving the expansion of the universe. Returning to the visible 4% of matter, what CERN is trying to understand is why the universe favours matter over anti-matter. At the Big Bang matter and antimatter particles were converted into energy as they annihilated each other, but for every one billion antimatter particles there appear to have been one billion and

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CERN: Black Holes and the Higgs Particle one particles of normal matter. This one particle per billion that was ‘left over’ actually constitutes everything we are and everything we can see. The most interesting matter to us as humans is what is termed baryonic matter. A hadron (as in Large Hadron Collider) is the generic name given to any particle made of ‘quarks’ (of which there are six types). Baryon is the name given to any particle made of three quarks, with protons being made of two up and

and gluons. Of course, discovering the Higgs Boson and the Higgs field is the priority for CERN at present. This will help us to understand more about the fundamental forces in the Universe and in particular to understand how matter has mass. To understand more about the Higgs particle and field in simple terms the physicists provided us with the briefing paper that was given to Margaret Thatcher when she was asked to help

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to discuss the rumour: this is the creation of a real particle (the Higgs Particle). Of course, the Higgs may not be real and even at best they only expect to see it once in every million million collisions, but as Rolf Landau (a leading figure in the search for the Higgs particle) said, “Not finding the Higgs will be even more exciting than finding it as it will prove that our existing model of how atoms work is wrong.”

Left: The dipole test facility; the large blue objects are dipoles, of which the there are over 2000 in the LHC, and another 9000 other magnets. Right: part of the linear accelerator, where Hydrogen atoms are ionised, and the resulting proton is passed through a further four acceleratiors before entering the LHC.

one down quark and neutrons being made of two down and one up quark. To get a feel for the size of things for those of us who had a classical education that stopped at the proton, trying to determine the size of these particles is amazing. The nucleus of an atom is actually only 1/10,000th the size of the atom and quarks are only 1/10,000th the size of a proton or neutron. The amazing thing is that quarks really don’t want to be separated from each other, which is why they need to be involved in collisions with such high energies, and in the process they give off a blast of other particles with strange names such as muons

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fund the development of it (yes, the LHC is that old) and it goes like this: 1. Imagine there is a cocktail party with a room full of people: this is the Higgs Field. 2. When someone famous enters the room people flock toward them: this is the creation of a new particle. 3. The famous person tries to cross the room but is ‘slowed down’ by people wanting autographs: this is the Higgs field giving the particle ‘inertia’. 4. A rumour starts that the personality will make a speech: this is the Higgs field becoming ‘excited’ and receiving energy. 5. Many guests clump together

Mark Eaton is based in the UK and is a mature physics student. Originally trained as an engineer he also has an MSc and MBA but has had a lifelong interest in astronomy and in 2004 decided to study a part time degree in this area split between the Open University and University of Manchester. Mark’s physics related interests are Astrobiology and Astrophysics, with a particular focus on variable stars. He is married with two children and runs a management consultancy focused on the health sector when he is not studying.

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Neurophysics of Vision: An Introduction to Binocular Rivalry by Jessica Stanley The scene of our investigation is an experiment: a person sits alone in a dark room, looking at a computer screen and pressing buttons to record what he sees. This sounds pretty normal so far, but then notice that while our supposed experimenter is pressing buttons, nothing is actually changing on screen. What he is actually looking at is some form of optical illusion, and he is, in fact, not the experimenter, but part of the experiment itself. This is an average day in the research group ‘Physics of Man’ at Utrecht University in the Netherlands, one part of which researches visual perception, often with experiments such as the one described above. Across the hall from the darkrooms where vision experiments are carried out, subjects are blindfolded for research on haptic (touch) perception. This sounds an awful lot like psychology, you might say. How can it be called physics? This kind of experimental method is called psychophysics, and along with brain imaging and computational modelling (and theory, of course!) forms the basis of a field of research known as neurophysics, which aims to crack the mysteries of the brain. This is very much an interdisciplinary research area, and that makes it difficult to categorise, in the same way that materials science and nanophysics straddle the boundary between physics and chemistry, and geophysics borders both physics and the earth sciences. It can be considered a branch of neuroscience, which in itself uses elements from biology, psychology, mathematics, physics, chemistry, computer science, and medical science (this is not an exhaustive list). Psychophysical testing has been around since the mid nineteenth century, when Gustav Fechner, a man who was both an experimental psychologist and a professor of physics, decided to formulate a mathematical description of the relation between perception and physical stimuli. Physics also has a long history of dealing with complex systems, of which the brain is a prime example, and in fact there are many areas of neuroscience that borrow methods or ideas from physics. From techniques in biomedical imaging, to neural networks analysis, to physical models of neurons (the Hodgkin-Huxley model describes the neuron as a leaky RC circuit), neurophysics itself has many sub-divisions. The Physics of Man group is a part of the larger Helmholtz Institute, which is comprised of neuroscientists, physicists, experimental psychologists, and neurobiologists who share the research aim of understanding perception and motor behaviour. The institute is named after Herman von Helmholtz, who physicists will know from his work on thermodynamics and electromagnetism, but probably not for his theories of vision and perception. In practice, where the line is drawn between neurophysics and the more psychological or physiological parts of neuroscience is unclear, and we will shelve that discussion and have a look at some of the research being done. What we will focus on is a phenomenon called binocular rivalry, which is the peculiar thing that happens when a person’s two eyes are shown conflicting images. In everyday life the horizontal offset between the two eyes’ images plays a part in depth perception. In this context, when two images are said to conflict it means that they differ to such a degree that the brain is not able to fuse

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them into one image, e.g. a horizontal line is shown to the left eye, and a vertical one to the right eye. Instead of seeing one stable image (we might expect to see the two images combined, i.e. a cross), we perceive the images one at a time, and perception switches spontaneously back and forth between the two. Since its first recorded observation in 1593 by Giambattista della Porta, an Italian polymath, binocular rivalry has been studied extensively, as it has the potential to teach us a lot about neural behaviour in the brain. In practice binocular rivalry is obtained by a number of different methods (see the box ‘Experimental methods’), but as none of these is practical for the purpose of reading this article, we will instead look at other, similar, visual stimuli, governed by the same neural process, to illustrate the ideas. Figure 1 shows two famous optical illusions, the Necker Cube and the Rubin Vase. These can both be perceived in more than one way: the Rubin Vase can be seen as a vase, or two faces; the Necker Cube can be perceived as a cube in one of two orientations. In both cases there is no information about depth. That is, there is no way to tell which part of the image should be in the foreground, and which in the background. This is the reason for the ambiguity in perception, and the brain resolves this by spontaneously switching between the two possible interpretations, in the same way that it switches between two conflicting stimuli in binocular rivalry. Figure 2 shows an example of monocular or pattern rivalry, where two superimposed patterns compete for perceptual dominance in the same way as the two percepts in Figure 1 do, but in a form that is more similar to typical images used for binocular rivalry experiments. Observe how, on extended viewing, patches, or sometimes all, of the red or green lines will disappear, and the changes take the form of a travelling wave spreading from one part of the stimulus to the other. As physicists we are not so much concerned with why perceptual switching and rivalry happens, but rather how. This means that we study the underlying neural process, and try to control it. So what is happening in the brain that a constant input results in varying perception? At this point we can make a comparison with solid state physics, in that perceptual switching is analogous to spin flipping in a magnetic system. In the brain we do not have spins, but rather nerve cells, or neurons. These are cells which receive information from the outside world, through the senses, or from other neurons, and can communicate with each other by firing an electric pulse called an action potential.

Figure 1: The Necker Cube (left) and the Rubin Vase (right) exhibit perceptual switching on prolonged viewing, though the visual input is constant. All images in this article are from Wikipedia.

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Figure 2: An example of monocular or pattern rivalry, consisting of two superimposed patterns. Fixate on the image and notice that the at different times part or all of one of the patterns will disappear.

The visual field is mapped out topographically onto neurons in the visual cortex in the brain, meaning that there is an array of neurons in the cortex where neighbouring neurons correspond approximately to neighbouring points in the visual field. We now need to know the forces acting on this system of neurons. At present there are a few competing theories describing the underlying mechanism of binocular rivalry, but the one we will describe here was formulated by researchers from the Functional Neurobiology and Physics of Man groups at Utrecht University. This model lists three main factors in the rivalry process: neural adaptation, cross-inhibition, and neural noise. Other factors include the visual input (the neural signals generated by the light from the stimulus hitting the neurons in the retina) and the overall neural activity. We have already mentioned action potentials, and the fact that a neuron can use these to excite or inhibit the activity of another neuron. Cross-inhibition is effectively when a neuron representing one percept (a horizontal line, say) sends inhibitive signals to neighbouring neurons representing the other percept (a vertical line). It is essentially a battle between the two eyes’ images, fought out locally between the groups of neurons representing the rivalling percepts. Neural adaptation is something we all experience in daily life, in many different contexts. Stick your hand under cold running water, and after a short while the water feels less cold. Look at a bright object and then close your eyes: you will see an afterimage. This occurs because the neurons in your retina respond less to a constant stimulus over time (it is as if they become tired). The level of this adaptation is dependent on the stimulus strength: if you look at the sky at midday, the glare of the sun creates a stronger afterimage than the rest of the sky does. So when you shut your eyes, the areas on your retina where the bright light was hitting are more adapted (tired) than the rest of your retina, and an afterimage will be seen for the time it takes for the adapted neurons to recover. To show how this all fits together, we can think of the rivalry process as a system with two timedependent potential wells. Keep in mind that these are not ‘real’ potential wells but simply serve as a way to visualise the process. When we ‘see’ one of the two percepts, we imagine a particle being at the bottom of one of the potential wells. As time goes on, adaptation causes the well we are in to become increasingly more shallow, whilst simultaneously causing the other well to deepen. This processes pushes our perception towards the other percept. At a certain point, due to the combined efforts of adaptation, cross-inhibition, and neural noise, we are tipped into the other potential well, corresponding to a change in percept (we now ‘see’ the other image). This process continues for as long as we view the image.

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Experimental Methods How, in practice, are binocular rivalry experiments performed? How are inputs from the two eyes separated? The easiest way of doing this is by using red-green glasses, with competing red and green stimuli. For example, the eye with the green lens views a green horizontal line, the eye with the red lens views a red vertical line at the same location. The main problem with this is that there is often some degree of leakage, i.e. a small amount of the green stimulus will be visible through the red lens. Most experiments make use of mirror stereoscopes instead. In this case the stimuli from the two eyes will be shown on two screens (or two halves of the same screen), and mirrors are used so that each eye only sees one screen (or one half of one screen), and the two images appear to be at the same location in space. So-called convergence clues are used to align the two dissimilar images and prevent drifting. A circle surrounding the image is one such clue that can help align the eyes. So that is a very rough explanation of how we think visual rivalry works, on a local scale. But as you can tell just from viewing Figure 2, there is apparently a correlation between the activity in different areas of the visual field: we do not see randomly distributed patches of red and green lines, but often almost exclusively red or green, and changes between the two percepts (the red lines vs. the green lines) appear as a wave travelling from one end of the image to the other. This is somewhat analogous to the way that when a spin flips in a magnetic system, its neighbours follow suit, in what is called a nucleation (for another example of a nucleation process see the article ‘Physicists in the Kitchen’ in this issue), and a wave propagates through the system. The neural situation is a little more complex, as neurons have additional long-range connections which link distant areas together. Nonetheless this similarity allows techniques from statistical physics to be used to model visual rivalry, though that is beyond the scope of this article. Psychophysical research generally has a more empirical focus. For example, it has been shown that if one of the images is brighter than the other, it will be more dominant (i.e. it will be seen for longer periods of time relative to the other). Furthermore, studies of travelling waves confined to one dimension have produced well-controlled waves that can just about be tracked with the eye. All in all, the different methods of research all contribute to the general understanding of neural dynamics, which is both interesting for its own sake, and for research into diseases such as epilepsy, which involves the collective behaviour of populations of neurons. But that should perhaps be left to the more medically-inclined. For now, this physics student will stick to looking at headache-inducing optical illusions in dark rooms. References: Blake, R. & N. K. Logothetis (2002). "Visual Competition." Nature Reviews: Neuroscience 3(1): 1321. Physics of Man website: http://www.phys.uu.nl/~wwwpm Noest A.J., Ee R., Nijs M.M., Wezel R.J.A. van. “Percept-choice sequences driven by interrupted ambiguous stimuli:A low-level neural model”. Journal of Vision 7(8):10, 1-14, 2007. Brascamp J.W., Ee R. van, Noest A.J., Jacobs R.H.A.H., Berg A.V. van den. “The time course of binocular rivalry reveals a fundamental role of noise”. Journal of Vision 6, 1244-1256, 2006. Naber, M., Carter, O., Verstraten, F.A.J. “Suppression wave dynamics: Visual field anisotropies and inducer strength”. Vision Research 49 (2009) 1805–1813.

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Physicists in the Kitchen By Anne Pawsey Photo by AndrĂŠ Karwath, from Wikimedia Commons.

Imagine a sweet that as you place it on your tongue feels pleasantly cool, as you chew it starts to become warm, then hot, before turning into a hard crystal which dissolves leaving your mouth cool again. This sounds like something from Charlie and the Chocolate Factory but it is in fact possible and was developed over the last academic year in the physics department of the University of Bristol. The whole idea was the brainchild of Professor Peter Barham, known to those who attended ICPS 2007 and most of Bristol as a purveyor of liquid nitrogen icecream and for being (mildly) obsessive about penguins. In addition to the icecream he has for several years been interested in the use of science to create new dishes. He has a long standing collaboration with chef Heston Blumenthal of the Fat Duck in Berkshire, England, and Noma in Copenhagen (recently voted 3rd best resturant in the world). Both of these resturants use what has become known popularly as molecular gastronomy. Every year he takes two master's level students to work on a dish or phenomenon which might be of intestest to these chefs. Last year I was lucky enough to get this opportunity and I worked with Prof. Barham and Catherine Needham to create the sweet described at the beginning of the article. The key to the temperature changes is to exploit the phase changes of a material. We used a sugar alchol, xylitol. Manufactured from the sap of birch trees, it is more commonly used in chewing gum and breath freshening sweets as it can help prevent dental cavities and produces a pleasant cooling sensation as it dissolves in saliva. It is this endothermic dissolution which produces the cooling effect in the sweet. Cooling is the easy bit, to get a heating effect a little more work is needed. When rapidly cooled from its molten state xylitol forms a glass, an amorphous solid. The xylitol molecules do not crystallise as the cooling is too rapid and they then possess too little thermal energy to rearrange themselves into a crystal. The glassy state is out of equilibrium and therefore very unstable; if glassy xylitol is heated above its glass transition temperature (-30oC) it crystallises very rapidly in an exothermic reaction. The maximum rate of this crystallisation process occurs rather conveniently at 30oC, or roughly mouth temperature. The exothermic nature of the crystallisation makes it the ideal way to produce a heating effect in a food. So far so simple, the challenge is to control the effect and also produce something that tastes nice.

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Nucleation Nucleation is the process by which a phase change proceeds. When a liquid is cooled below its freezing point it doesn't instantaneously change into a solid. The freezing process happens over time. Random fluctuations in the density create areas of the solid phase, at a critical radius Rc the system can minimise its energy by increasing the size of this area, as can be see from Fig 1. Areas of lower energy with R>Rc grow spontaneously, they are called nuclei and the process of their formation is known as nucleation. However, this is only the first step in the process, in order for the nucleus to grow molecules must be able to diffuse through the liquid to its surface. This can only happen if the temperature is sufficiently high, but higher temperatures hinder the formation of nuclei so the process of freezing is a delicate balance between these two opposing requirements. Given xylitol's naturally sweet taste, creating some form of confectionary seemed the natural option. We chose chocolate as it is the solution to everything. Food science textbooks were adamant that fat such as cocoa butter does not influence the phase behaviour of sugars. In reality it turned out to be a bit more complicated than that. First we needed to combine xylitol in its glassy phase with chocolate to produce a homogeneous mixture, and this needed to be done carefully to prevent the xylitol from crystallising. In standard chocolate making, cocoa mass, cocoa butter and sugar are heated and ground together in a process known as conching. Unfortunately the temperatures involved are exactly wrong for our system. If the materials are combined in this way the xylitol crystallises and the potential for a heating effect is lost. The solution is to use liquid nitrogen, the discerning physics chef's favourite ingredient. The ingredients can be cooled and ground together into a homogeneous powder of chocolate and glassy xylitol. Contary to popular belief, chocolate does not solve all problems. It turns out that cocoa butter impedes the crystallisation of xylitol and acts as a thermal insulator so the perceived heating effect is reduced and the sweet is much less spectacular. The powdered glass phase is also more soluble in saliva than the crystalline phase so the cooling effect kicks in too soon. This can be counteracted by adding alcohol so liqueur chocolates which self heat are an active topic of research.

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Challenges of Weightlessness by Joshua Fuchs Skyshot by Omniii at en.wikipedia.org, used under GNU Free Documentation License

Though Coulomb’s Law of Electrostatics has been around for over 200 years, an electrostatic orbit between two charged objects was not experimentally demonstrated until 2006 by a research team from Rhodes College in Memphis, Tennessee, USA. In 2008, a new research team comprised of six undergraduate physics students, including myself, and two faculty members from Rhodes College decided to expand on the previous experiment, attempting to demonstrate the first binary electrostatic orbit. Because of the small electrostatic attraction between the spheres, the experiment required a weightless environment. The team was awarded time on NASA’s Weightless Wonder aircraft through NASA’s Reduced Gravity Student Flight Opportunities Program. The weightless environment is created by flying in parabolic trajectories. Each parabola created around 25 seconds of weightlessness. Between each period of weightlessness there was a period of hypergravity as the aircraft positioned itself for the next parabola. The flight took place at NASA’s Johnson Space Center in Houston, Texas in July 2008. The program awards participants a total of sixty parabolas over two flights on consecutive days. Designing an experimental apparatus and preparing to conduct an experiment in weightlessness was a new experience for the team. We had nine months after we submitted our proposal to prepare for the flight. Having no previous experience in weightlessness, there were many issues we had to identify and address as we prepared for this unique experience. First among our concerns was the difficulty of designing an experimental apparatus. To a certain extent we were able to rely upon the previous experiment for some guidance. Since our experiment was different, though, we had to determine what information was useful to us and what needed to be modified. We carefully thought out every aspect of our apparatus. One of our chief challenges was designing part of the apparatus to accurately charge and launch a conducting sphere without the sphere discharging. We were also concerned about the electrostatic interaction the spheres would have with the rest of our apparatus. Complicating our design, we had to anticipate how everything would behave in a weightless environment. We first thought through the experimental procedure to help guide our design. We used two identical spheres for the experiment which needed to be charged first. After charging, the spheres had to be launched antiparallel to each other. The original velocity, radial separation, and charge needed to be accurately controlled and adjustable. This was necessary because our theoretical model predicted a range of each variable in which a stable orbit would be possible. Finally, we needed to move everything away from the spheres to allow them to orbit freely. With this framework in mind, we were able to begin designing an apparatus to meet our needs.

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Joshua and teammates during the zero gravity part of one of the parabolic flights

We decided to build the frame of our apparatus out of wood because it has lower electromagnetic conductivity. This limited the electrostatic interaction of the spheres with the apparatus. To launch the spheres without discharging them, the spheres had small holes drilled into them and sat on polypropylene tips prior to being launched. These tips were propelled forward using elastic bands, and then suddenly stopped by another part of the launching system. When this happened, the spheres slid off the ends of the tips and were free to float. The launching system and the entire apparatus went through many versions before we arrived at the final one. These versions allowed us to perfect every part of the apparatus and increased our chances for success during the flight. Trying to conduct the experiment in weightlessness was another challenge we faced. None of us had been weightless before, so it was a new environment that to which we had to quickly adapt. We decided to use our first two parabolas to physically acclimate to the environment. We hoped this would be long enough to become accustomed to weightlessness and be able to conduct the experiment. The aircraft dived into the first parabola, creating the hypergravity portion first. I sat against the wall of the aircraft, felt myself get heavier, and then all of a sudden lighter and lighter. When you lift off the ground, it is such a foreign environment that you do not know what to do, so you sort of flail. I grabbed onto something and was able to control myself well enough. It was an odd experience gaining a whole other degree of freedom. I quickly learned to grab whatever I could reach to control myself. My other teammate and I moved into position on the apparatus during the third parabola. We attached ourselves to the floor of the aircraft using straps provided by NASA. These helped immensely. They limited our mobility just enough to focus on conducting the experiment. The oscillation between weightlessness and hypergravity made it difficult to complete everything we wanted to in time. I was constantly changing between being barely able to move (hypergravity) and moving freely (weightlessness). As a team, we had underestimated how difficult it would be to work effectively in the weightlessness environment. Though as the flight progressed we got better at working in this environment, we were not as efficient as we had hoped. We had planned on making adjustments to the initial velocity, radial separation, and charge during this time. With the changes in the environment and limited time, it was not possible to make these adjustments. In the end, this did not adversely affect us because we got ample data for our analysis.

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This switch in effective gravity also made it difficult to determine when to launch the spheres. Too early and they would fall to the floor of the aircraft, but too late and they would not have much time to orbit. Choosing the correct launch time was complicated further by our adrenaline. We were all excited to finally be conducting the experiment and wanted to see results. We attempted to contain our excitement in order to enable us to produce useful scientific results. In the end, we succeeded. We had twenty three orbital attempts that produced data we could analyze, including ten attempts with at least one-third of an orbital revolution and three attempts with multi-revolution orbits. To see a video of one of our multi-revolution orbits, visit http://www.youtube. com/watch?v=SGvkTnQcuB4. We compared our data to a recently published theoretical paper discussing orbital stability. Fortunately for us, we solved many of the challenges we faced along the way. The uncertainty of the effect the weightless environment would have on both us and the apparatus was resolved by careful and thoughtful planning. Beyond addressing the design and function of the apparatus, our planning included significant attention to anticipating many different scenarios that could occur in the foreign weightless environment, an investment that ultimately paid off in the form of the world’s first binary electrostatic orbit.

The Rhodes College Team, from left to right: Dr. Brent Hoffmeister, Chase Sliger, Jennifer Thompson, Brad Atkins, Gavin Franks, Joshua Fuchs, and Dr. Deseree Meyer.

Joshua Fuchs is a third year physics student at Rhodes College in Memphis, Tennessee, USA. He plans to study astrophysics in graduate school.

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The Back Page

From the Archives

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Jim Grozier, IAPS’ hardworking archivist, has dug into the archives once again to retrieve this amusing email exchange from October 2003: “AMOROUS PORTUGUESE STUDENT to NANNA NICOLAISEN: I want to greet the new IAPS president, which I ashamedly didn’t do in Bodrum [venue of ICPS 1993]. Yes, shame on me, but I had a very stupid reason which is that as I’d never spoken to you before you might think I’d do it just because you’re the new IAPS president. Yes, you’d be right. Anyway, my congratulations: I bet you succeeded to be the most beautiful of all IAPS presidents. I mean, yes, you’re pretty good-looking, but anyway, all previous IAPS presidents were men … NANNA NICOLAISEN to A.P.S.: I’m glad you think the president is pretty, and I guess that Bente is too, because it is Bente and not me who is the president. I am the secretary …. A.P.S. to N.N.: Well, I sure did what in Portugal we call “to put the feet in the big hole”, I mean, I blew it. I was really thinking you were the IAPS president, but then, I must not repeat the previous compliment. I mean, now I withdraw it and restate: Not the president, but the actual secretary is quite beautiful” In the hole, and digging furiously! Moral: Always check your data, like a good physicist …

A webcomic of romance, sarcasm, math and language

ICPS Issue 2010

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{jIAPS}

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ICPS Issue 2010


jIAPS ICPS Issue 2010  

A special issue of jIAPS for the 25th International Conference of Physics Students in Graz, Austria. Featuring a selection of articles from...

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