Praxis Archives – Page 160 of 183

Paul Dirac: a genius in the history of physics

cerndirac1_9-02 — Dirac as a young man in about 1925.

The year 2002 is the centennial year for Paul Dirac, who was born in Bristol on 8 August 1902. His Swiss father, Charles, was born in Monthey near Geneva in 1866 and migrated to Bristol, England, to become the French teacher at the Merchant Venturers Technical College. His mother was Florence Holten, a Cornish woman who was born in Liskeard in 1878 and became a librarian in Bristol. They married in Bristol in 1899 and had three children: two sons (of which Paul was the younger) and then a daughter. After his primary and secondary education at the technical college, Paul Dirac joined the electrical engineering department of Bristol University in 1918 to train as an electrical engineer. This choice was due to prompting from his father who was concerned about his son’s job prospects.

Dirac did well at university, but he did not find a suitable job due to post-war conditions. His desire was to go to Cambridge University to study mathematics and physics. He was accepted by St John’s College, Cambridge, in 1921, but was offered only a minor scholarship, insufficient to support him there. Fortunately, he was able to study Applied Mathematics at Bristol University for two years, paying no fees and living at home. After this, in 1923, he was awarded a major scholarship at St John’s College and a Department of Scientific and Industrial Research training grant, but even these did not cover the amount he needed to study at Cambridge. In the end he was able to go to St John’s College because extraordinary action was taken by the college. He did all his life’s work there, from postgraduate studies in 1923 to retirement from his Lucasian professorship in 1969 (excluding sabbatical leaves). Thus, it turned out that the college made a profitable investment when they gave him a modest increase to the major scholarship they had awarded him.

cerndirac2_9-02 — A reflective Dirac in later life attending a conference while still Lucasian Professor.

Paul Dirac died, aged 82, on 20 October 1984 as a Nobel Prize winner (1933) and a member of the British Order of Merit (1973). He was the outstanding theoretical physicist in Britain in the 20th century. In 1995 there was a great celebration of Dirac and his work in London. A plaque was placed in Westminster Abbey as a memorial to him and his achievements, joining similar plaques to Newton, Maxwell, Thomson, Green and other outstanding theoretical physicists. It included Dirac’s equation in a compact relativistic form (as Dirac’s full equation would not have fitted on the plaque). This was not a form that Dirac would ever have used, although later students of Dirac often used it. As part of the celebration, addresses were given on four topics related to Dirac’s work (see P Goddard 1998 in Further reading).

Monumental discoveries

Dirac established the most general theory of quantum mechanics and discovered the relativistic equation for the electron, which now bears his name. The remarkable notion of an antiparticle to each particle – i.e. the positron as antiparticle to the electron – stems from his equation. He was the first to develop quantum field theory, which underlies all theoretical work on sub-atomic or “elementary” particles today, work that is fundamental to our understanding of the forces of nature. He proposed and investigated the concept of a magnetic monopole, an object not yet known empirically, as a means of bringing even greater symmetry to Maxwell’s equations of electromagnetism. He quantized the gravitational field, and developed a general theory of quantum field theories with dynamical constraints, which forms the basis of the gauge theories and superstring theories of today. The influence and importance of his work has increased with the decades, and physicists daily use the concepts and equations that he developed.

cerndirac3_9-02 — This plaque to commemorate Paul Dirac has been placed in the floor of London’s Westminster Abbey, adjacent to Newton’s grave. It was made at Cambridge, using green slate, in Cardoso Kindersley’s workshop.

Dirac’s first step into a new quantum theory was taken late in September 1925. R H Fowler, his research supervisor, had received a proof copy of an exploratory paper by Werner Heisenberg in the framework of the old quantum theory of Bohr and Sommerfeld, which leaned heavily on Bohr’s correspondence principle but changed the equations so that they involved directly observable quantities. Fowler sent Heisenberg’s paper on to Dirac, who was on vacation in Bristol, asking him to look into this paper carefully. Dirac’s attention was drawn to a mysterious mathematical relationship, at first sight unintelligible, that Heisenberg had reached. Several weeks later, back in Cambridge, Dirac suddenly recognized that this mathematical form had the same structure as the Poisson Brackets that occur in the classical dynamics of particle motion. From this thought he quickly developed a quantum theory that was based on non-commuting dynamical variables. This led him to a more profound and significant general formulation of quantum mechanics than was achieved by any other worker in this field (see P Dirac 1925 in Further reading).

This was a major achievement that marked him out from others in the field. As a young, 25-year-old physicist he was quickly accepted by outstanding physicists. He was invited to speak at their most exclusive conferences, such as the Solvay Congress of 1927 (see Further reading), and joined in their deliberations as an equal.

cerndirac4_9-02 — Dirac lecturing at Cambridge University in 1946.

However, this general formulation allowed him to go much further. With it, he was able to develop his transformation theory, which showed explicitly (see P Dirac 1927 in Further reading) how it was possible to relate a range of different formulations of quantum mechanics, all of them equivalent in their physical consequences, such as Schrödinger’s wave equation and Heisenberg’s matrix mechanics. This was an astonishing achievement, which led to a deeper understanding of quantum mechanics and its use. This transformation theory was the pinnacle of Dirac’s development of quantum mechanics since it unified all proposed versions of quantum mechanics, as well as giving rise to a continuum of other possible versions. In later life Dirac considered this transformation theory to be his own as no other quantum mechanician had found any hint of it. Altogether, Dirac’s quantum mechanics takes a simple and beautiful form, with a structure showing elegance and economy of concept, and linked directly with the classical theory. It showed us a new aspect of our universe, both profound and perplexing in its new concepts, and certainly unexpected.

Even as an undergraduate Dirac had been deeply conscious of the importance of special relativity in physics, the theory that Einstein had put forward in 1905 and that Dirac had learned about from lectures by C D Broad, the philosophy professor at Bristol University. Most of his early papers as a postgraduate student were devoted to modifying calculations already in the literature to make them compatible with special relativity. In 1927 Dirac sought to develop a theory of the electron that satisfied this requirement and he published his relativistically invariant equation for the electron early in 1928 (see P Dirac 1928 in Further reading).

Although this goal had been in the minds of many other physicists, none had been able to find a satisfactory equation. He gave an argument, simple and of the utmost elegance, that was based on the requirement that his transformation theory should also hold for relativistic quantum mechanics – an argument that specified the general form this relativistic equation should have, an argument that all physicists have found compelling. His transformation theory requires the equation to be no more than linear in time-derivative, while relativity arguments indicate that the equation can be only linear in the space derivatives also. Dirac’s equation is certainly one of the most beautiful physics equations. Professor Sir Nevill Mott, former director of the Cavendish Laboratory, wrote recently: “This [equation] seemed, and still seems to me, the most beautiful and exciting piece of pure theoretical physics that I have seen in my lifetime – comparable with Maxwell’s deduction that the displacement current, and therefore electromagnetism, must exist.” (See B Kursunoglu and E P Wigner 1988 in Further reading.) Also, the Dirac equation for the electron implied that it should have spin 1/2, and a magnetic moment of eh/(4pm), where h is the Planck constant and m is the electron mass, correct to the accuracy of 0.1%.

Dirac’s equation and his theory of the electron have remained firm up to the present day. Its predictions have been thoroughly verified for all atomic and molecular systems. It has been demonstrated to hold for all other particles that have the same spin as the electron, such as the protons, the hyperons and all other baryons, when their induced magnetic moments are taken into account; and all known leptons, to say nothing of the fundamental building blocks of all hadrons, the quarks themselves. It is universally applicable and well known by all physicists and chemists, something nobody could deny. Indeed, in 1929 Dirac felt able to state: “The general theory of quantum mechanics is now complete… The underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known.” (See P Dirac 1929 in Further reading.)

Beautiful physics

Dirac, Pauli and Peierls — Paul Dirac, Wolfgang Pauli and Rudolf Peierls in discussion at the International Conference on Nuclear Physics, Birmingham, 1948.

Dirac soon showed that his equation had other, unexpected, implications for these particles. The equation predicted the existence of antiparticles, such as the positron and the negatively charged antiproton, objects now well known in high-energy physics laboratories. Indeed, all particles have corresponding antiparticles and almost all of them are now known empirically. The positron and antiproton are particularly well known, both being stable in a vacuum, and are now widely used in collider accelerators, with which physicists study physical phenomena at very high energies.

It is important to emphasize here the outstanding beauty of Dirac’s equation. It may be difficult to convey this quality to non-scientists, but we can be confident that no physicist would disagree with this statement. The Dirac equation is one of the most outstanding discoveries. Through this work, Dirac uncovered for us all a fundamental and satisfying principle governing our universe, which demonstrates to an unsurpassed degree the elegance of its structure. For this discovery, Dirac’s name will be known forever. It is an outstanding monument to his ability and ingenuity, leading us to comprehend at least one aspect of the fundamental forces in this remarkable universe in which we live.

Dirac’s name would be high in physics records even if quantum mechanics and transformation theory were his only contributions to knowledge. His discovery of the Dirac equation puts him far above all others – an outstanding genius in the history of physics.

Quarks and Kiwis interact in New Zealand

cernkiwi1_9-02 — A view from the Department of Physics and Astronomy at the University of Canterbury looks east over the city of Christchurch.

In June, two New Zealand universities formally applied to join the CMS experiment at CERN’s Large Hadron Collider (LHC). This marked the launch of an initiative to establish a New Zealand high-energy particle physics and instrumentation programme called NZ_CMS. The basis of this programme is the formation of an experimental particle physics and instrumentation research group within New Zealand that not only contributes directly to the CMS experimental programme, but does so in a way that also optimizes the benefits for New Zealand, its industry and its young researchers. The application was made on behalf of six staff from the universities of Auckland and Canterbury, and also includes several graduate students. In addition, NZ_CMS is receiving support from staff and university groups within the two universities in the fields of electrical engineering, computer science, medical imaging, nanotechnology and optics.

The CMS pixel system was identified as the area where NZ_CMS should contribute, as it provides the best match in terms of personnel, resources, and the focus on instrumentation development sought by Auckland, Canterbury, and the New Zealand government. Over the last year members of NZ_CMS have been working within the CMS pixel community, ensuring a smooth integration into CMS as well as establishing the connections and the technology transfer necessary for the continued development of the programme.

Pixel systems

NZ_CMS has benefited greatly from input from New Zealand, the CMS management and the CMS pixel group at the Paul Scherrer Institut (PSI) in Villigen, Switzerland. Realistic goals have been outlined for long-term benefits and contributions to CMS, whist enabling NZ_CMS to establish itself within the New Zealand academic climate, as well as allowing the shorter-term goals attractive to funding agencies to be achieved. Roland Horisberger, the CMS pixel detector project leader, and the PSI group have strongly supported NZ_CMS, facilitating pixel technology transfer to New Zealand and helping to define the scope of the NZ_CMS deliverables. At present, members of NZ_CMS are working within the PSI pixel group on the pixel control systems and services. As the NZ_CMS collaboration develops, it is expected that the New Zealand-PSI connection will be strengthened, and a training-exchange programme for students, engineers and researchers will be established.

cernkiwi3_9-02 — A delegation from CERN and the CMS collaboration visited New Zealand in January. At the Tamaki campus are (left to right) NZ_CMS team leader Alick Macpherson; David Krofcheck of the University of Auckland; Ralph Cooney, pro-vice chancellor for the Tamaki campus; and Diether Blechschmidt of CERN.

As a sign of the enthusiasm and support for NZ_CMS, the development from initial idea to application for CMS membership has taken only a year and a half, and it has already secured preliminary funding for pixel instrumentation research. The initiative was first presented at the New Zealand Institute of Physics conference in July last year, which was followed by a visit from a CMS-CERN delegation to New Zealand in January.

The week-long itinerary of the delegation, led by John Ellis (representing CERN) and Diether Blechschmidt (representing CMS), included formal meetings with the minister of research, science and technology, the Royal Society of New Zealand and the Universities of Auckland and Canterbury. The delegates also visited Industrial research Ltd (a Crown Research Institute of some 400 staff) and participated in the 18th International Workshop on Weak Interactions and Neutrinos (WIN 2002) held at Canterbury. There was also time for a public lecture by Ellis entitled “From Rutherford to Higgs” in which he described particle interactions using vocabulary from the sport of rugby.

Following the delegation’s visit, Steve Thompson, chief executive officer of the Royal Society of New Zealand, made an official information visit to CERN. Soon afterwards initial funding was obtained from the New Zealand government and it was decided to proceed with the NZ_CMS application to join CMS. It is now hoped that concurrent with the NZ_CMS application New Zealand and CERN can negotiate and sign an agreement on co-operation. This would facilitate the development of the country’s participation in the LHC.

Current programmes

In an effort to build on its strengths and resources, NZ_CMS is endeavouring to work in conjunction with the country’s existing particle physics programmes. Current areas of research in New Zealand include heavy-ion physics at Auckland, ultra-high-energy neutrino physics at Canterbury and theoretical physics at Massey University.

cernkiwi2_9-02 — This CMS pixel readout chip, measuring 8 mm x 12 mm and holding around 400,000 transistors, is to be the basis of the NZ_CMS pixel testing programme.

In addition to the University of Auckland’s taking a leading role in the NZ_CMS pixel programme with the establishment of a pixel laboratory at its Tamaki campus, Auckland’s David Krofcheck is augmenting NZ_CMS’s contribution to CMS through reaction-plane studies for the CMS Heavy Ions programme. This follows on from work done with gold-gold collisions at the E895 experiment at Brookhaven in the US. E895 used the Alternating Gradient Synchrotron (AGS) to deliver gold beams of 2, 4, 6 and 8 GeV per nucleon to measure the excitation functions of collective nuclear matter “flow”. The NZ_CMS Heavy Ions group currently consists of three researchers and is based entirely at the University of Auckland.

As far as Canterbury is concerned, its particle physics group is participating in the Radio Ice Cherenkov Experiment (RICE) in Antarctica. RICE is a neutrino telescope at the south pole using radio antennas to detect the coherent emission of radio-wavelength Cherenkov radiation from the electromagnetic shower of particles produced when an ultra-high-energy electron neutrino interacts in the ice. The Canterbury group is involved in the Monte-Carlo simulation of the shower and the subsequent detection of the Cherenkov pulse, and the investigation into other possible physics sources such as the transition radiation from air showers. The absence of any neutrino events in the data analysed to date implies upper limits for the neutrino flux comparable to the air shower experiments AGASA and Fly’s Eye over the neutrino energy range of around 10⁷-10¹² GeV.

With research into medical imaging instrumentation, digital-signal processing and nanotechnology, Canterbury is also looking to establish instrumentation applications associated with pixel systems and pixel data visualization. These would tie in with its new HITLab NZ, the annex of the Human Interface Technology Laboratory (HITLab) at the University of Washington in Seattle. The HITLab consortium is a world leader in virtual-reality technology such as remote surgery and virtual retinal display, which scans images directly into the retina of the eye.

An additional aspect to be developed is online and offline computing, with a contribution from New Zealand now being possible thanks to the installation of the high-bandwidth transpacific Southern Cross Cable, which started operation in late 2000. The cable removes the bandwidth bottleneck between Australasia and the United States, and delivers 120 Gbit/s of fully protected capacity (the equivalent of eight full-length motion pictures every second). An upgrade in early 2003 will double capacity to 240 Gbit/s. At present, the currently available bandwidth to the US from within the universities is around 100 Mbit/s. This removal of bandwidth constraints, coupled with a developing interest in GRID research within New Zealand’s IT community, has prompted discussion of possible contributions to online and offline computing within the context of NZ_CMS.

The third component of New Zealand’s existing particle physics programme is the theoretical physics group at Massey University, which focuses on nucleon-structure functions and deep inelastic scattering calculations. Their interest in NZ_CMS is ongoing, as experiments at the LHC are an excellent opportunity for studying quark and gluon distribution functions. Detailed knowledge of these distribution functions is needed for much of the physics that will be performed at the LHC, and the NZ_CMS programme will enable the Massey group to participate directly in a facility that should contribute significantly to this area of research.

Finally, the NZ_CMS initiative should be seen as part of the resurgence in New Zealand particle physics that looks to work in close collaboration with both the country’s established research groups and our international collaborators (PSI and CMS/CERN). This is a significant step towards New Zealand’s participation in the truly global “big science” projects associated with modern high-energy particle physics laboratories, and is based on access to research at the frontier of particle physics.

The NZ_CMS initiative is also a way to combat New Zealand’s perceived geographical isolation and the continued “brain drain” of young researchers who venture overseas for graduate and career opportunities – often never to return.

This brain drain is, of course, not a new phenomenon. One of the best documented cases is a young Kiwi (New Zealander) called Ernest Rutherford, who left the country in 1895 to work with J J Thompson at Cambridge University’s Cavendish Laboratory. NZ_CMS intends to reunite quarks and Kiwis in New Zealand!

Particle physics: a world without borders

cernview1_9-02 — Judy Jackson: “When it comes to communication, every laboratory is an island.”

Belorussian, Catalan, Taiwanese, Afrikaans, Japanese, Persian, Russian, Mandarin, Hebrew, Italian, Tagalog, Croatian, Malayalam, Serbian, German, Korean, Swedish, Cantonese, Turkish, Arabic, Romanian, Gujarati, Welsh, Georgian, Lëtzebuergesch…

These are just some of the more than 60 languages spoken by collaborators on Fermilab’s CDF and D0 experiments, as determined by a quick and utterly unscientific survey in mid-July. A poll of collaborations at CERN, DESY, KEK or any of the world’s particle physics laboratories would reveal a comparable population of polyglots – men and women from every corner of the world who have come together to explore the nature of matter and energy, space and time. Particle physics is truly one community, without borders.

Moreover, when it comes to advances in research at the world’s handful of particle physics laboratories, we are all in this together, for better or worse. When CERN gets a cold, Fermilab sneezes, and vice versa. At the moment, the particle physics world is watching as Fermilab struggles to fulfil the promise of Run II at the Tevatron; and CERN’s current LHC budget and schedule challenges have strong implications for the future of every physics laboratory. On a brighter note, a physics discovery at laboratory A inevitably builds upon work at laboratories B and C. It all comes together in one worldwide particle physics enterprise.

Yet while particle physics collaborations are international, particle physics communication is not. For the most part, each region and each laboratory communicates for itself, with little coordination on issues, strategies, resources and messages. Does a press release from one laboratory (my own, for example) trumpeting a new experimental result give more than a nod to the work at other laboratories that made the result possible? It’s doubtful. With difficult news to break, does one laboratory seek support from the others? Provide a clue that it’s coming? Not likely. In planning communication strategies, do communicators coordinate their efforts? Probably not. Global Communication Network? Forget it. When it comes to communication, every laboratory is an island.

Standard model of communication

It is high time particle physics communication caught up with the reality of particle physics collaboration. To achieve the kind of future that particle physicists everywhere would like for their field, the Standard Model of Physics Communication will have to change.

In December 2001, communicators from six of the world’s physics laboratories met at DESY in Hamburg to form a worldwide collaboration for physics communication. The immediate stimulus for the meeting was a message from Petra Folkerts, communication director at DESY, to Fermilab on 12 September 2001:

“I want to say that we are all with you in these days. I myself can’t find the right words to express my feelings after this terrible 11 September. From my point of view now it’s absolutely important that we outreach people around the world will meet as soon as possible, not only to figure out how to help international particle physics stay alive, but how we, in our field of activity, can set visible footprints for the significance of peaceful collaboration across all borders.”

The message gave impetus to a project that communicators at particle physics laboratories had pondered for some time, and led to the formation of an international laboratory communication council. Membership has grown to 10 laboratories from five countries.

Initial actions of the council include the development of a particle physics image bank comprising the best photographs and graphic resources from the world’s laboratories, appropriately captioned and credited – one-stop shopping for reporters, physicists, students, teachers and policy makers who need outstanding graphics to tell the particle physics story. The image bank will live on a new website – interactions.org – devoted not to the support of any one laboratory or region, but to all. Advance coordination of press releases among member laboratories has already begun, not only to enhance the recognition of discoveries wherever they occur, but also to foster the recognition of the interconnected nature of advances in particle physics throughout the world. The collaboration plans staff exchanges, workshops and panels at international physics conferences.

The time has passed when one laboratory or one sector of the particle physics field could profit at the expense of another. Progress at every laboratory and in every region depends on the success of particle physics everywhere. As the early American experimental physicist Benjamin Franklin told his colonial colleagues in 1776: “We must all hang together, or assuredly we shall hang separately.” The Quark Wars are over. The laboratory communication council represents a recognition of this reality by the world’s particle physics communicators. As Folkerts stressed in her message of September 2001, it is a collaborative endeavour.

Whether they speak Gujarati or Georgian, Swedish or Romanian, Tagalog or the Queen’s English, I hope that particle physicists everywhere will support this worldwide venture in physics communication.

Heavy Flavour Physics – Theory and Experimental Results in Heavy Quark Physics

edited by C T H Davies and S M Playfer, Institute of Physics Publishing, ISBN 0750308672, £40.00 (€ 63).

A graduate text based on lectures originally presented at the 55th Scottish Universities Summer School in Physics, held at St Andrews in 2001. The school was a NATO Advanced Study Institute.

Facing Up: Science and its Cultural Adversaries

by Steven Weinberg, Harvard University Press, ISBN 067400647X, £17.95 (€ 28).

cernbooks1_9-02 — Facing Up: Science and its Cultural Adversaries by Steven Weinberg.

These 23 essays written by Steven Weinberg from 1985 to 1999 make a nice collection around the theme of reductionism. Each is preceded by a page or so describing the context, which is often a valuable addition to the main texts of the essays. Professor Weinberg’s introduction to the set led me to believe that the book would be about facing up to the reality of a neutral universe: Tycho Brahe’s statue looking up to the sky is on the cover. The secondary title is more apt: the majority of the essays are in defence of the scientific approach to understanding our surroundings. Flaws in other approaches, especially constructionist, are pointed out.

Weinberg makes a strong case for reductionism. Phenomena can be explained in terms of others, but these explanations come in a hierarchy, which clearly points back to a theory of everything, as yet to be discovered. Physics is closest to this origin and physicists are closing in.

Not being a physicist myself, I found that many of the essays are brilliant formulations of our understanding of physics, better than anything I have read before. Apart from two more or less political statements, which I felt were out of place, the collection is very homogeneous. However, this is also its weak side: points are necessarily repeated and I will now certainly remember that the Standard Model has 18 parameters that we cannot yet calculate. From 1985 to 1999 many things happened to high-energy physics, such as the cancellation of the Superconducting Super Collider. Unless one knows the dates of these events, it is somewhat confusing to the non-physicist to follow the arguments as there is neither a synoptic nor a statement of the current state of affairs.

One thing I am not so sure of is the “emergence” argument. According to Weinberg, apart from historical accidents (initial conditions), what we observe can be understood exclusively in terms of the hierarchy of explanations, with physics at the root. However, computer simulations (for example of neuronal systems) seem to indicate that more than one underlying “physics” can indistinguishably lead to the same behaviour, by construction. Does that not mean that the mathematics governing this behaviour is independent of those physics? Then there may be independent sciences after all.

My favourite essays are the one in which Weinberg takes the humorous view that non-physicists are somewhat odd, and the 19-page overview of the history of physics in the 20th century. The latter is by far the clearest article on the fundamental ideas behind relativity and quantum mechanics that I have encountered.

The argument that science advances and that it does so independently of the cultural background is certainly in agreement with my own limited experience. Wherever in the world you walk into a university you suddenly feel this, whether lunch is eaten with chopsticks or a totalitarian regime has just been shed.

I greatly enjoyed this collection – it makes me want an entire book in which Weinberg expands on the individual views rather than repeating them in the condensed form of the essays. We need more of this eminently clear exposure of how science works.

Europe coordinates astroparticle research

cernnews3_7-02 — Italy’s Gran Sasso laboratory – the site of a diverse range of experiments in astroparticle physics. (Oxford University PPU.)

European astroparticle physics received a boost last year with the formation of the Astroparticle Physics European Coordination (APPEC), established in an agreement signed by funding agencies from France, Germany, Italy, the Netherlands and the UK. Astroparticle physics – which covers topics as diverse as cosmic rays, dark matter and gravitational radiation – falls between more traditional areas such as particle physics, nuclear physics and astronomy, and so can lose funding opportunities. Also, different countries have different ways of defining astroparticle physics. APPEC has been set up to promote co-operation within Europe’s growing astroparticle physics community, and to develop long-term strategies at the European level, in particular for funding.

APPEC’s activities are organized through two main committees: a steering committee, currently led by Jean-Jacques Aubert of the French CNRS; and a peer-review committee, chaired by Ricardo Barbieri of the Scuola Normale Superior in Pisa. The steering committee, which meets twice a year and includes representatives from the initial partners, has already met in Berlin and London. One important action has been to begin work on a bid to the EU 6th Framework for up to 720 million for an Integrated Initiative Infrastructure (I3). The committee also seeks to widen APPEC’s membership – Spain, for example, is joining, and other countries have been approached.

The peer-review committee, which also meets twice a year, aims to assess existing programmes in different areas of astroparticle physics, and to encourage future collaboration. The committee has already met twice, to review experiments in double beta decay and in dark matter. Its next meeting, in January 2003, will consider high-energy neutrino experiments.

David Wark from Sussex and RAL, who is one of the members of the steering committee, said: “I believe this is a positive step for astroparticle physics, as it can help bring some of the rigour, co-operation and international clout to astroparticle physics that organizations like CERN and DESY bring to accelerator physics. It will also help to get astroparticle physics projects judged using similar criteria in all the countries from which they require support.”

Aside from its committee meetings, APPEC will keep in touch with European astroparticle physicists throughout the year with an electronic newsletter and a website, to be launched later this year. In the meantime, to register interest in receiving the newsletter, please email sacquin@dapnia.cea.fr.

RIKEN and Brookhaven renew their vows

cernnews5_7-02 — RIKEN president Shun-ichi Kobayashi (seated left) and Brookhaven interim director Peter Paul sign the extension to the RIKEN-BNL agreement. Present at the ceremony were (left to right): Akito Arima of the Japanese House of Councillors; RBRC deputy director Nicolas Samios and director T D Lee; Isao Tanihata of RIKEN; Atsuko Toyama, Japanese minister of education, culture, sports, science and technology (MEXT); Thomas Kirk of Brookhaven; Peter Rosen of the US Department of Energy (DOE); presidential science adviser John Marburger; Tsutomu Imamura and Masaru Osanai of MEXT; Satoshi Ozaki of Brookhaven; and Denis Kovar of the DOE. (Brookhaven National Laboratory.)

At a ceremony marking the beginning of spin physics at Brookhaven National Laboratory’s Relativistic Heavy Ion Collider (RHIC), the US laboratory renewed its collaboration agreement with Japan’s Institute of Physical and Chemical Research (RIKEN) for a further 5 years. Initially established in 1995, the RIKEN-BNL agreement has been instrumental in establishing the spin-physics programme at RHIC, and led to the establishment of the RIKEN-BNL Research Center (RBRC) in 1997.

Latin American physics centre celebrates 40th anniversary

cernnews9_7-02 — José Leite Lopes, one of the founders of CLAF, between former directors Roberto Bastos da Costa (left) and Carlos Aragão de Carvalho at the centre’s 40th birthday celebrations.

The Rio de Janeiro-based Centro Latinoamericano de Física (CLAF) celebrated its 40th anniversary on 26 March. Founded under the auspices of UNESCO following the CERN model, CLAF was established to promote research in physics and provide postgraduate training to young physicists in the region. The physicists Juan José Giambiagi of Argentina, José Leite Lopes of Brazil and Marcos Moshinsky of Mexico were instrumental in its creation. Today, CLAF has 13 member states.

The celebrations took the form of a week-long international meeting in Rio that focused on CLAF’s international collaborations and looked at the long-term future of the centre. Speakers included Faheem Hussain of the International Centre for Theoretical Physics in Trieste, Italy, which has been involved in a programme of joint PhD work with Latin American institutions since 1997. Vladimir Kadyshevsky, director of the Dubna-based Joint Institute for Nuclear Research, and Pavel Bogoliubov, who is responsible for the institute’s international relations, spoke of a 4-year-old programme to train Latin American graduate students in Russia, and of the 25 MeV microtron built at Dubna to form the basis of a proposed regional laboratory in Havana, Cuba. CERN’s Juan Antonio Rubio, who is responsible for the laboratory’s education and technology transfer activity as well as links with Latin America, spoke of the agreement signed in 2001 between CERN and CLAF to organize a joint biennial school in Latin America. Staying with education, Ramón Pascual, former rector of the Universidad Autónoma in Barcelona, signed an agreement at the meeting allowing Latin American students to take part in the European Joint Universities Accelerator School.

Research was discussed by Ana María Cetto, coordinator of the Latin American Scientific Networks, who spoke of a project to foster greater Latin American use of observatories in Chile and the possibility of extending the facilities at Mount Chacaltaya in Bolivia.

Looking to the future, CLAF support for the second CERN-CLAF school to be held in Mexico in 2003 was confirmed at the meeting, and CLAF announced the creation of a biennial school in medical physics and synchrotron radiation. The centre is also promoting improvements in postgraduate education through the ICTP programme and by coordinating a regional Masters degree programme. In research, CLAF will assume a stronger role in coordinating Latin American efforts in medical physics, condensed-matter physics and optics. It will also examine the possibility of building a proton accelerator for cancer treatment. The meeting concluded with a request to the governments of Latin America to increase their percentage of GDP spending on science and technology.

Globalization, collaboration and trust

cernview1_7-02 — Albrecht Wagner, chairman of the DESY directorate.

Industry pushes economic globalization to strengthen its market position. The process is driven by the need and desire to increase efficiency and reduce costs, but also by the wish to make the best use of different competencies in different countries. Take the European aircraft industry: parts of planes, such as the wings, tail unit, body and engines are built in different regions of Europe, and finally assembled at one plant. This has enabled distributed regional industries to jointly play a major role on the international market. Yet people are afraid to be at the mercy of some anonymous pressure, and thus increasingly oppose globalization.

Large-scale facilities in science are also increasingly tackled on a global scale. Radio-astronomers around the world have united behind the idea of jointly building their next project, ALMA, a merger of the major millimetre-array projects into one global project. Particle physics has for quite some time moved in the same direction: the large experiments have always been a role model for the shared construction of large equipment. The LHC is built with components from around the world, like HERA before it.

Global challenge

To meet the challenges of the future, accelerator-based particle physics needs to become even more global than in the past. One possible concept, the Global Accelerator Network (GAN), was originally developed as a way to build a linear collider as an international collaboration, to make the best use of worldwide competence, ideas and resources, to maintain and foster the centres of excellence in accelerator physics around the world, and to root the linear collider as an international project firmly inside the national programmes (CERN Courier June 2000).

Global projects rely on collaboration. In the past, particle physicists have developed a culture of collaboration that has worked very successfully. Indeed, they had to do so to meet the scientific challenges. Collaborations function well if their leadership acknowledges the individuality and freedom of all the partners. They do not have a strong hierarchical structure, but are driven instead by a common scientific goal. They probably would not function with an industry-style management.

Therefore the question arises as to whether a model that works for experiments can be extended to accelerators. Or to put it differently: what is needed to make this model work for accelerators as well? These questions were studied by an ICFA working group in 2001, and are now being addressed within the framework of a series of workshops, the first of which, “Enabling the Global Accelerator Network”, took place in March at Cornell. This workshop dealt with technical aspects of the remote operation of facilities, which is a key ingredient of the shared operation of accelerators. No basic problems are expected here. In fact, the TESLA test facility has already been operated remotely from Italy and France.

On the other hand, it became clear at the workshop that the sociological aspects of such a joint endeavour are probably the true challenge. As the GAN concept is built on the principle of shared responsibility, the sharing of know-how and controls is also part of the concept. The laboratory at which the facility is located would therefore relinquish the project control it traditionally had to become one of the equal partners. Mutual trust is the critical element required in order for such a collaboration to be successful.

It is well known that distributed organizations need to build up and maintain trust. Sharing working time from the very beginning is a powerful agent in establishing this trust. This requires a mixture of face-to-face interactions and the use of appropriate communication and collaboration technologies. These interactions should start as early as possible, even during the planning and R&D phase. Mutual trust and interest will continue to grow during the build-up time of the project, and will have to be sustained through the transition from early commissioning to operation and scientific exploitation. Industry is developing many tools to support the full spectrum of situations, ranging from planned, structured activities (such as scheduled meetings) to unplanned interactions.

Trust and involvement of both institutions and individuals have to be maintained over a long time – the duration of the project being typically more than 20 years. Producing exciting science and meeting technological challenges will be the key ingredients for ensuring a long-term interest of all the partners. Working on the frontiers of technology creates the need for a continuous upgrade culture. This culture needs to be distributed around the world.

However, even if the necessary trust is established, we need to solve many questions of key relevance in order to guarantee the success of the project and the major investment it requires. These questions include the management structure and organizational forms. They again are closely related to trust – we cannot afford for scientists and engineers to become disenchanted and to walk away. We need to approach global collaboration on large scientific infrastructure projects with a lot of imagination and determination.

The future of particle physics is no longer determined by scientific challenges only.

The Atom in the History of Human Thought

by Bernard Pullman (late professor of Quantum Chemistry at the Sorbonne, and director, Institut de Biologie Physico-Chimique, France), Oxford University Press, ISBN 0195114477, £14.95 (€23). Translated from the original French, Editions Fayard, ISBN 2213594635, 729.3.

cernbooks1_7-02 — The Atom in the History of Human Thought by Bernard Pullman.

“This book endeavours to describe the turbulent relationship between atomic theory and philosophy and religion over a period of 25 centuries,” states the preface – a daunting task by any standards. Pullman admits that he is neither a philosopher nor a man of religion, but a chemist “having long lived side-by-side with atoms”. As such, he achieves a great deal.

The book begins with the birth of the atomic theory – the “Greek miracle” of the 7th-5th centuries BC in Pullman’s words, when a few Hellenic thinkers shed the Greek pantheon in favour of a natural philosophy. This began with theories advocating various primordial substances – water (Thales), air (Anaximenes), fire (Heraclitus) and earth (Xenophanes) – from which all things come to be. The two fundamental concepts of atomism – impenetrable, indivisible (atomos) corpuscles and void through which they travel – were formulated around 450 BC by Leucippus and Democritus, and refined a century later by Epicurus and Lucretius to a logical structure that remained essentially unchanged for the next 2000 years. The book also touches on Hindu and Buddhist atomism, which evolved independently at about the same time, but had no impact on the atomic theory of the Western world.

The book then moves on to “a few scattered revivals” during the 1st-15th centuries AD. After describing the antiatomistic position of the Church as put forward by Basil of Caesarea, St Augustine and Thomas Aquinas (among others), some mediaeval Christian atomists make an appearance. These are divided into chroniclers (such as Isidore de Seville), sympathizers and proponents. The sympathizers include Adelard of Bath (a translator of scientific Arab texts) and Thierry of Chartres (a reviver of the works of antiquity). Among the proponents are Constantine the African, a physician from Carthage who explicitly defined atoms as the fundamental constituents of substances; William of Conches; and William of Ockham.

Jewish philosophy from the 9th to the 13th centuries is discussed. This was largely opposed to atomism, although Moses Maimonides (1135-1204) described the teaching of the Arab atomists. The schismatic Jewish sect of the Karaites (founded in the 8th century) adopted the atomic theory borrowed directly from teachings of Muslim philosophers and theologians.

While Greek atomism was to free mankind from invisible powers, Arab atomism is decidedly religious in nature. The Arab atomic doctrine is expressed in the Kalam, a set of 12 propositions, one of which introduces the notion of “accidents”. These reside within atoms, and include characteristics such as life and intelligence, along with inanimate properties such as colour and odour.

Moving into the Renaissance and the age of enlightenment, Pullman describes the resurgence of atomic theory starting with Pierre Gassendi, who is counted among the Christian atomists along with the likes of Galileo, Bruno, Newton and Boyle. Gassendi criticized Aristotle and defended ancient atomists, especially Epicurus, whose teachings he tried to make acceptable to the Church. The doctrine of John Locke, who doubted any future experimental proof of the existence of these atoms, is labelled “agnostic atomism”. Pullman also discusses Maupertuis and Diderot, with their sensitive and intelligent atoms; Holbach, with his materialistic atoms; and Maxwell, who believed that atoms exist due to the action of a creator.

Christian antiatomists – philosophers or scientists who use religious arguments to reject the theory – include Descartes, who rejected the concept of void; and Leibniz with his metaphysical atoms (monads). Others mentioned are Roger Boscovitch, who tried to blend Leibniz’s monads with Newton’s laws of attraction and repulsion; George Berkeley, who rejected matter, material corpuscles and void; and Immanuel Kant, who is labelled an “atomist turned antiatomist”.

The final part of the book moves into the modern era with the advent of scientific atomism through the 19th and 20th centuries. Pullman begins with the demise of the 2000-year-old theory of four elements by the demonstration of Lavoisier that water, and of Cavendish and Priestley that air, have a compound structure. Elements came to be defined as substances that could not be decomposed. Confusion over nomenclature followed until Canizzaro formulated a distinction between atoms and molecules in 1860. Soon afterwards, Mendeleev arranged the first 63 elements in the periodic table.

Controversy, however, continued. Philosophers such as Hegel and Schopenhauer were both opposed to atomism. So were die-hard antiatomists like Berthelot, Mach and Ostwald, and a few that Pullman calls “nostalgic philosophers”, such as Nietzsche, Marx and Bergson.

Nevertheless, atomic theory was almost universally accepted by the time J J Thomson discovered the electron in 1897, bringing the hypothesis of indivisible atoms to an end.

Pullman then brings us into the quantum age in 1900 with Planck’s famous constant. He guides us through Rutherford’s 1911 conclusion that atoms are mainly vacuum with a tiny nucleus surrounded by electrons, to Bohr’s 1913 observation that Planck’s constant leads to stable orbits in the atom and to discrete spectral lines. The rest of the modern atomic picture is carefully covered, with Chadwick’s 1932 discovery of the neutron; de Broglie’s postulation of the wave-like character of matter particles, and its subsequent confirmation by Davisson and Germer; and Schrödinger’s wave mechanics leading to serious conceptual difficulties among scientists.

Chemical bonding naturally plays a large part in the book, given that its author was a chemist. Covalent bonding, where electrons are shared between atoms, leads Pullman to an interesting analogy developed in the chapter “Society of atoms: marriage”, where he concludes that “as always in life, this implies the ability and even obligation both to give and to receive”.

In a closing chapter, Pullman delves into the nanoworld. Here he describes how the scanning-tunnel microscope and the atomic-force microscope led to visualization and manipulation of single atoms interacting with bulk surfaces, and how complete isolation of single (charged) atoms surrounded by vacuum was accomplished using ion traps.

No-one can contest that the atoms conceived 2500 years ago as invisible and indivisible impenetrable philosophical constructs have today become divisible and visible objects of reality. But are they really in human thought? They are certainly in the thoughts of scientists and philosophers, but I doubt they are uppermost in the minds of most people, as Pullman suggests when he claims that “quantum physics has stoked an interest in the ‘problem of God’ among a general public”. The book is let down by its index, which is difficult to use and occasionally inaccurate. That said, however, to read this book is a fruitful learning exercise, and it has a host of informative notes.

Topics

Reset your password

Registration complete