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Countdown to the Nobel prize

01 Oct 2000

The Nobel Foundation celebrates its 100th birthday this year. Peter Rodgers looks at how the winners are selected and some of the discoveries that might be recognized this year

1999 Nobel Prize

On the 10th of this month a physicist – or possibly two or three – will receive a telephone call from Stockholm that will change their life. The Royal Swedish Academy of Sciences will be ringing with the news that they have been awarded the most prestigious accolade that any physicist can receive – the Nobel Prize for Physics. This year’s prize will be worth SwKr 9m (about £660 000).

Some 159 physicists have received this honour so far, dating back to Wilhelm Conrad Röntgen, who received the first prize in 1901. Indeed, the founding of the prize coincided with the revolution in physics that started around the turn of the century. Röntgen’s discovery of X-rays in 1895 was quickly followed by the discovery of radioactivity in 1896 – for which Henri Becquerel shared the 1903 prize with Marie and Pierre Curie – and the discovery of the electron in 1897, for which J J Thomson received the prize in 1906.

In the early years of the prize most of the winners were from Europe, but in recent decades American physicists have been more successful (see box below).

The 2000 prize

The selection process for this year’s prize began last September when the Swedish Academy of Sciences sent letters to more than 2000 physicists, inviting them to nominate candidates for the prize. Invitations were sent to Swedish and foreign members of the Academy, previous Nobel-prize winners, permanent and assistant professors in Scandinavia, and various heads of department and senior physicists all over the world. The response rate to the letters of invitation is typically about 15% according to Anders Bárány, professor of physics at Stockholm University and secretary to the Nobel Committee for Physics.

The 300 or so nominations that had been received by the deadline of the end of January were whittled down to between about 10 and 15 proposals by the Nobel committee, which is chaired by Tord Claeson, head of the applied solid-state physics group at Chalmers University of Technology in Gothenburg, Sweden. The other members of this year’s committee are: Per Carlson, an experimental particle physicist at the Royal Institute of Technology in Stockholm; Cecilia Jarlskog, a theoretical particle physicist at Lund University; Mats Jonson, a theoretical condensed matter physicist at Chalmers; and Sune Svanberg, an experimental laser physicist at Lund.

The committee asks the physicists whom they have consulted not to make their nominations public. However, Claeson says it is clear that in the past there have been organized campaigns in the US for particular nominations. He points out that the committee does not count the number of nominations, or discriminate against campaigns.

Each proposal selected by the Nobel committee was sent to one or two experts in the relevant field for review. The committee then studied the reviewers’ reports and made its recommendation for who should win this year’s prize in the form of a memorandum that was sent to the 40 or so members of the “physics class” of the Swedish Academy of Sciences. This year the memo was sent on 19 September and was discussed by the physics class on 26 September, with a further discussion on 2 October.

Early this month the physics class will forward the memorandum, along with its comments, to the full Academy, which includes 350 Swedish members and 164 foreign members from all areas of science. Based on past experience, says Bárány, the comments of the physics class can be minor (e.g. suggested changes to the wording of the citation) or major – they can, for example, suggest a different winner for the prize.

The full Academy is due to have a closed vote on the physics prize on the morning of 10 October and the outcome will be announced around midday.

All the proposals and material related to this year’s prize will remain a closely guarded secret for 50 years, after which time they will be made available to historians of science. In the meantime, a completely unscientific poll of physicists and Physics World staff has resulted in a list of major discoveries in physics that have not yet been rewarded with the prize.

Particles mean prizes

Since 1950 the prize has been dominated by particle physics (18 prizes) and condensed-matter physics (16). There have been eight prizes for atomic, molecular and optical physics during this period and, surprisingly, only five for astrophysics. The last prize for nuclear physics was awarded in 1975 and plasma physics received its only prize in 1970. The Nobel statutes state that the prize should be awarded for the “most important discovery or invention within the field of physics”, but only a handful of prizes since 1950 have been awarded for inventions: for example the transistor (1956), the laser (1964) and the hologram (1971).

The 1950 prize, which was awarded to Cecil Powell, marked a turning point in the history of the prize. Working on the boundary of cosmic rays and particle physics, Powell discovered the pion in a series of balloon flights that exposed photographic emulsions high in the atmosphere. Since then all the particle prizes have been awarded for theory, discoveries made at accelerators, or advances in accelerator or detector technology.

However, the development of neutrino astronomy, which started with the pioneering work of Ray Davis in the late 1960s, and the subsequent observation of neutrino oscillations by Masatoshi Koshiba and co-workers at the SuperKamiokande experiment in 1998, could result in another prize for non-accelerator particle physics. Indeed, Davis and Koshiba shared the Wolf Prize – which four of the 1990s Nobelists had previously won – earlier this year.

Particles that have been discovered but not rewarded include the gluon and the top quark. However, rewarding either discovery will pose problems for the committee. The discovery of the gluon at the DESY laboratory in Hamburg, Germany, in 1979 has already been the subject of controversy (see “Gluon prize revives discovery debate” in Physics World September 1995 p5). And it will be difficult to single out no more than three names among the 850 or so physicists who collaborated on the CDF and D0 experiments that discovered the top quark at Fermilab in the US in 1995.

Anders Bárány says that the Nobel regulations allow for the prize to be awarded to an organization, and cites the example of the 1995 peace prize, which was shared by the Pugwash movement and the physicist Joseph Rotblat. Tord Claeson confirms that this possibility has been discussed, but adds that “the committee is not close to recommending that the prize should be awarded to an organization”.

In particle theory the inventors of quantum chromodynamics (QCD) – the theory that is used to describe the strong nuclear force in the Standard Model of particle physics – could be in the running, although QCD does not enjoy the same level of acceptance as quantum electrodynamics (QED), its electromagnetic counterpart. The names most commonly associated with demonstrating asymptotic freedom in certain types of gauge theories – the crucial step on the road to QCD – are David Gross, David Politzer, Frank Wilczek and Gerard ‘t Hooft (who shared the prize last year for other contributions to the Standard Model).

The inventors of the CKM matrix – Nicola Cabibbo, Makoto Kobayashi and Toshikide Maskawa – are also contenders. The CKM matrix is used to describe mixing between the different families of quarks. Other theoretical architects of the Standard Model who might be honoured include: Yoichiro Nambu, who made many theoretical contributions to symmetry breaking and QCD, and shared the Wolf prize in 1994/95; Jeffrey Goldstone for his work on symmetry breaking; and Chen Ning Yang, who shared the prize in 1957, and Robert Mills for Yang-Mills theory. Confirmation of the discovery of the Higgs boson will almost certainly bring a prize for the experimentalists who confirm it, and for Peter Higgs and the other theorists who developed the mechanism for generating mass in field theories.

Beyond the Standard Model

The committee has no policy on the relative merits of theoretical or experimental discoveries, but in general theorists only receive the prize when their work has been verified experimentally. “Stephen Hawking is a good example,” says Anders Bárány. “I am often asked why Hawking has not won the prize. He has done fabulous work but we are not yet sure that it really applies to nature.”

Claeson adds that many theorists work over a broad range of problems, building up a “good integral”, whereas experimental discoveries are often “delta functions”. The fact that the prize is given for a discovery or an invention, rather than a lifetime’s work, may explain why more experimental physicists seem to win the prize.

There is also a wide range of discoveries outside particle physics that might be recognized by the committee. The results from the COBE satellite in 1992 – which showed that the cosmic background radiation has a perfect black-body spectrum and that there are tiny fluctuations in the background temperature across the sky – could be recognized. And if evidence that the expansion of the universe is accelerating can be confirmed beyond doubt, that would be another contender.

Astronomy is not covered by the physics prize, but Claeson points out that recent developments in instrumentation mean that more and more of astronomy is becoming astrophysics, and he expects to see a lot of discoveries in the future that will be eligible for the prize.

The creation of a Bose-Einstein condensate in a dilute atomic gas, a “new state of matter” in which all the atoms are in the same quantum ground state, in 1995 and the subsequent demonstration of an atom laser are also contenders. Other areas of atomic and optical physics that could be recognized include photonic band-gap materials and ultrashort (femtosecond) laser pulses. Within quantum physics, experimental tests of Bell’s inequalities and the prediction of various quantum and geometric phases (for which Yakir Aharonov and Michael Berry shared the 1998 Wolf Prize) might also be recognized.

In condensed-matter physics, the discovery of giant magnetoresistance in the mid-1980s has stimulated much further research and has had a major commercial impact in the multibillion-dollar magnetic-recording industry. Other areas of condensed-matter physics in the running will include quasicrystals (for which Dan Shechtman received the 1999 Wolf Prize), colossal magnetoresistance, pseudopotential theories for electrons, valence-level photoemission experiments, low-dimensional semiconductor devices that control single electrons, and the broad areas of correlated-electron systems and mesoscopic physics.

Semiconductor lasers continue to be an area of intense research activity and immense commercial importance, but their discovery has yet to be recognized with the prize. Synchrotron radiation is another physics discovery that is used in a vast range of experiments in all areas of science, but has not been acknowledged with a Nobel prize.

Who will win this year’s prize?

As is almost always the case, the field for the prize is wide open. Predictions are easy to make, but just as experiment is the final arbiter in physics, so will the Swedish Academy decide the fate of the first Nobel prize of the new century.

Prize spreads

Some 55 US-born physicists have won the prize. Germany comes second in this list (26 winners), followed by the UK (20), France (10), the Netherlands (9) and Russia (7). The last British-born prize-winner was Nevill Mott in 1977.

Alfred Nobel’s will was clear that nationality should not be a consideration in the selection of the winner: “It is my express wish that… the most worthy shall receive the prize, whether he be a Scandinavian or not.” And while successive Nobel committees have awarded the prize to just seven Scandinavians, a mere two women have received the physics prize: Marie Curie in 1903 and the nuclear physicist Maria Goeppert-Mayer, who shared the 1963 prize. It is widely believed that Lise Meitner deserved to share the prize with Otto Hahn for her work on nuclear fission.

Hahn actually won the prize for chemistry. Indeed there is a tradition of physicists winning the chemistry prize that stretches all the way from Ernest Rutherford in 1908 to Walter Kohn, the condensed-matter theorist, in 1998. Marie Curie also won the 1911 chemistry prize outright for the discovery of radium and polonium. Only one person has received the physics prize twice – John Bardeen shared the 1956 prize for the invention of the transistor and the 1972 prize for his work on the Bardeen-Cooper-Schrieffer theory of superconductivity.

In the early years the prizes were dominated by experimental discoveries, but that is no longer the case. Max Planck was the first theorist to win the prize alone, in 1918, followed by Albert Einstein (1921), and Niels Bohr (1922). In a masterful understatement Einstein received the prize “for his services to Theoretical Physics and especially for his discovery of the law of the photoelectric effect”.

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