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Ultrafast X-rays watch matter melt

The germanium sample was bombarded with powerful laser pulses to excite the electrons and cause thermal melting. In this process, unlike normal melting, the metallic crystal goes from a cold solid to a hot liquid state and never passes through the classical equilibrium stage of a hot solid. “The short laser pulse neutralises the glue that keeps atoms in a crystal and they are instantaneously freed,” said one of the team, Andrea Cavalleri from the University of California at San Diego (UCSD). “The initial and final state are the same as in traditional melting, but the pathway is very different.”

At the same time the laser pulses were hitting the sample, the researchers fired a series of ultra-fast X-rays at the germanium. “This is the first time that we have been able to directly see such non-thermal rearrangement of the atoms and molecules in a material,” said Craig Siders, also of UCSD. “With ultrafast x-rays we could watch this rigorously symmetric crystal lattice of germanium atoms just fall apart in an incredibly short period of time. The X-rays allowed us to see this not just at the surface but also, and importantly, inside the material too.”

UN promotes space science for developing nations

During the 1990s the UN and ESA organized a series of workshops to promote the development of small telescopes in countries such as Sri Lanka, the Philippines, Colombia and Jordan. Over 800 astronomers have attended these workshops. And although the workshops have not led to any new telescopes in Africa, they have resulted in a bilingual newsletter for the space community called African Skies. Next year the workshop will be held in Toulose, France and will look at the possibility of creating a network of robotic telescopes in Asia.

Haubold believes that the workshops have helped to bring scientists from developing countries together. He also believes that this is the only way that such nations will learn how to exploit satellite communications, remote sensing and satellite meteorology. “How can these countries benefit from such technologies without basic knowledge in astronomy?” asks Haubold.

Electron transfer made easy

Electron transfer in protein results from quantum tunnelling between reduction- oxidation (redox) centres. “There’s a widely accepted idea that electrons get from one redox centre to another in a protein by travelling down a series of molecular bonds that describe a best pathway,” said Christopher Moser, one of the team. “What we’ve found is that there is nothing special about that pathway. Instead, evolution ignores the structure of the protein medium between the two points and uses only proximity to ensure that the electron transfer rates are fast enough to satisfy the needs of biology.”

First evidence for planet orbiting a binary star

The majority of stars in the universe are believed to be in binary systems, but previously no one had produced any evidence to show that such systems could contain planets. The 20 planets that have been detected outside our solar system all orbit around single stars. “To find evidence of a planet orbiting a pair of stars means there could be more planetary systems than we previously thought,” said Morris Aizenman of the US National Science Foundation.

The two stars are relatively close to each other – just 1.8 times the Earth-Sun distance (AU) apart – while the planet is orbiting them at a distance of 7 AU. “It is entirely plausible that such a planet could exist” says Richard Nelson, an astronomer at Queen Mary & Westfield College in the UK. “But the problem of microlensing observations is that they are very difficult to verify,” he cautions.

Johannes van Paradijs dies

Storing fuel in nanotubes

Carbon nanotubes are rolled up sheets of graphite that can have lengths of about 30-100 nanometers and diameters of about a nanometer. Two years ago it was discovered that carbon nanofibres – which consist of bundles of nanotubes – could absorb hydrogen. The Chinese/US team has now synthesised extra-wide nanotubes that can store 4.2% of their weight as hydrogen gas. Some 80% of the absorbed hydrogen can be released at room temperature, and the rest can be released by heating the fibres. Moreover, the nanotubes can be “refuelled” in less than 60 minutes. Carbon nanofibres are also extremely strong, which decreases the chance of an accidental release of the gas and increases their attractiveness to car makers.

Celebrating women of talent

The difficulties faced by women in science come brilliantly to life in this hugely enjoyable book of cartoons by Jim Ottaviani. The strips include a fascinating account of Rosalind Franklin’s scandalously undervalued role in the determination of the structure of DNA. The story tells of her battle to be taken seriously as a scientist, and questions whether the discrimination she faced was due to her gender or simply her fiery, no-nonsense character.

The strangest tale is the true story of the German film star Hedy Lamarr, who fled from the clutches of her husband, an arms manufacturer in league with Hitler and Mussolini. Lamarr arrived in Hollywood, where she ended up patenting a device that could control torpedoes without enemy signals jamming the system. The device was based on the idea that secret messages can be coded as a series of random musical notes. Although the device could not be built with the technology of the 1940s, her idea of “frequency hopping” is widely used today to enable secure communication between mobile phones. The story has been included because Lamarr – like so many other women – was discouraged from pursuing her talents in science any further.

Emerging from Hawking’s shadow

Physics World is not in the habit of reviewing books by non-physicists, but when the author was married to one of the most famous physicists of the 20th century, we can make an exception. In this book, Jane Hawking – who was Stephen Hawking’s wife for 30 years – spills the beans on her life with him, in an attempt to “exorcise the strain, the tensions and ultimately the overpowering toll of unhappiness” of that life.

She recounts in painful detail the long and often difficult struggle to support her husband’s battle with motor-neurone disease. There was the daily grind to look after Hawking and their young family, and the fight to obtain medical care for him. It was also far from easy being married to someone so focused on his work. She was made to feel second-string intellectually to her husband, and his firm atheism would often clash with Jane’s Christian faith. “It seemed that Stephen had little respect for me as a person and no respect at all for my beliefs and opinions,” she protests.

The problems mushroomed following the publication of A Brief History of Time in 1988. As Hawking’s fame grew, Jane felt increasingly bitter at being sidelined by everyone from college dons to journalists, who pushed her views aside as if they were of little interest compared with those of her husband. “Outside the marriage, and apart from Stephen, I was nothing,” she says. Ironically, it was Jane who originally encouraged her husband to write a popular account of cosmology and quantum physics.

The marriage reached breaking point when Hawking began a relationship with one of his nurses, Elaine Mason, in 1989. “Many factors – fame, fortune, diverging aspirations, priorities and outlook, as well as many people – had come between Stephen and me, and they proved stronger than the pull of home and family,” she explains. “I was cast aside in favour of someone who seemed to offer more constant and devoted nursing care and travel companionship than I ever could.” Hawking eventually filed for divorce and married Mason in 1995, and Jane herself later married a long-standing musician friend, Jonathan Hellyer Jones.

Although the tone of the book is often gratingly self-important and overblown, there are many intriguing insights into the family life of a celebrity physicist. For example, we are told how a succession of cranks – including one “Mr Isaac Newton” from Japan – would phone the Hawking household in the middle of the night, claiming to have solved the riddle of the universe and demanding to speak to “The Prof” to tell him where his calculations had gone wrong.

Indeed, the author takes a rather dim view of physicists in general. They might be “quite charming, friendly and down-to-earth” as individuals, but as a group have “a natural tendency…to slip inexorably into interminable discussion and arguments, almost always about physics”.

Reflections on the life of a laser pioneer

Charles Townes has written a biography – but it is not clear if it is his own or that of the laser. The laser is now such a feature of our everyday life that the remarkable story of its birth needs to be told, and Townes does so in a clear and personal way – because he was there when it happened.

He argues that the basic ideas about the laser could have appeared decades before they did, and points out that even after the laser was invented, it took decades before the physics community got used to its beauty and basic simplicity. Although we may now find it hard to understand why even well established scientists considered a device based on induced emission an impossibility, it might be instructive to try to put ourselves in their position. Maybe our understanding is just as defective when we take the laser operation to be self-evident.

Townes introduces his account by reviewing all the roles of the laser today in both scientific endeavours and commercial enterprises. It plays our compact discs and measures the distance to the Moon; it cuts metals and heals our wounds. No longer do we remember that the laser was once dubbed a solution looking for a problem.

The author then turns to the very beginning, namely his own childhood in South Carolina, US, where his view of life was forged. His upbringing gave him the will and the strength to push forward, but it also made him a person of high integrity, honesty and modesty. As a manifestation of this, his writing makes the reader easily underestimate the remarkable progress the author made from an unpretentious Furman University, via Bell Labs, Columbia University and the Massachusetts Institute of Technology, to the University of California at Berkeley, where he has been based for over 30 years.

At each step, Townes must have stood out as a recognized and appreciated collaborator, which made him wanted and accepted wherever new science was born. His achievements in the development of lasers and masers were recognized when he shared the 1964 Nobel Prize for Physics with his Soviet competitors in the race, Nikolai Basov and Alexander Prokhorov. Townes got to know them well, and he recalls in this book those early contacts between American and Soviet researchers.

However, the book is mostly a professional biography that gives only brief glimpses of the author’s personal life, even if his family is always mentioned when a professional move is undertaken or a sabbatical leave is arranged. Townes’ life really follows the development of the laser, from its roots in the development of radar and in the birth of the maser after the Second World War.

When radar technology became available to the scientific community, it was first used to study the spectra of molecules. This, in its turn, led to a search for sources of radiation of ever shorter wavelength – and hence eventually to the laser. Throughout the story, we are reminded both of the central role played by Bell Labs and Columbia University in bringing the wartime technology into basic research, and of the remarkable scientists involved.

However, this is no book of gossip, although the personalities of many well known researchers are illustrated through their contacts with the author and are acknowledged as teachers, collaborators or friends. In fact, Townes’ favourite collaborator and close friend, the late Art Schawlow, also became his brother-in-law. Although Schawlow contributed to the idea of the laser in an essential way, he had to wait until 1981 for his Nobel prize.

A consistent theme in the book is the joy and openness offered by free basic research. Townes stresses how the essential steps in the technical development of the laser derived from scientists “playing” and exchanging ideas freely, and from fortuitous opportunities realized and put to use by open-minded researchers. No strategic planning by expert panels could have led to the development of the laser as it actually happened.

But Townes also covers the darker side of research. In particular, when there is money at stake and when commercial aspects enter the fray, solidarity and fair play are put to the test. This is exemplified by the long and tortuous story of the laser patents, which Townes retells in detail, providing a view of the more controversial side of academic life.

Another contentious issue is the author’s involvement with government planning and with weapons research. He has been an advisor to both NASA and the White House. Between 1959 and 1961 he was the vice president and director of research at the Institute for Defense Analysis in Washington, DC. Here his basic loyalty to his country and his deep humanism stood against each other. One may disagree with his choices on some of these issues, but one cannot but admire his honesty and sincerity in presenting them, and his motivations in doing so.

I highly recommend this book to everyone interested in the modern history of physics. Its terse but clear style makes it easy to read, and the reader is invited to experience the continuous excitement in one central theme of the development of post-war physics as told by one of its main contributors. As a document of what really happened, it is immensely valuable. Townes has lived through it all – from his early recognition of the importance of induced emission, to the present use of lasers to unravel the mysteries of our universe from its origins to its ultimate end.

Three cheers for 100 triumphant years

In mid-December 1900 Max Planck presented a series of papers to the Prussian Academy of Sciences in Berlin that were, eventually, to revolutionize not only physics as a discipline, but our entire conceptions of the constitution of matter and energy. It would be fair to say that the century that followed was the century of physics par excellence, just as – if one were to believe recent developments – the coming century will be that of molecular biology and the study of the mind.

Academic physics at the turn of the 20th century was a relatively new profession, one that had evolved from a broad-ranging natural philosophy into a vibrant, growing and increasingly specialized field, producing cohorts of scientists and engineers who would exponentially populate industry, research laboratories, the military and government. By the middle of the century, physics and physicists – in particular theoretical physicists – reached the zenith of popular and professional recognition, mostly as a result of the extraordinary, and frightening, harnessing of nuclear power.

For several decades after Hiroshima, the services of physicists were highly sought, their independence guaranteed by lavish funding and accolades. And even though some high-priced projects such as the Superconducting Super Collider have not succeeded, the profession is flourishing and continuing to expand. Astronomy and astrophysics, materials science, optics and telecommunications are all exploding with discoveries and inventions, and despite dire predictions to the contrary, young people all around the world seem to be eager to enter a career in science and engineering with unabated optimism.

Helge Kragh’s book Quantum Generations is geared to just such inquisitive minds. The book is an ambitious one-volume history, the first comprehensive textbook to address most of the significant aspects in the intellectual history of 20th-century physics. Kragh’s achievement as far as depth and scope are concerned is quite remarkable. Quantum Generations is a slightly old-fashioned (not pejoratively so!) “survey” book written by a very knowledgeable historian of physics. Kragh – a professor of history of science at Århus University in Denmark whose other recent books include a biography of Paul Dirac and a history of cosmological controversies – has covered most of the significant institutional, political and national aspects of physics, and has drawn on all the available scholarship in a deft and inclusive manner.

While the book examines in detail the major, well established and recognized highlights – from the work of Planck, Einstein and Bohr to quarks and string theory, from the philosophical implications of quantum mechanics, the atom bomb and the militarization of science, to “big science” projects such as CERN – some of the most interesting chapters are those that depart from traditional narratives. These include science and politics in the Weimar Republic, and physics in totalitarian regimes. Kragh is fundamentally interested in pursuing broad theoretical themes across many decades, such as the predominant role played by the electromagnetic view of nature and the pursuit of a unified theory, well into the present.

But despite what the publishers say in the book’s press release, Quantum Generations will not be easily accessible to those ignorant of physics. Although there is hardly an equation in sight, Kragh implicitly assumes much physics knowledge. Moreover, it often seems as if he expects his readers to be already committed to what we now know, as if they come with a full-blown understanding of the significance of the questions asked and the success of the answers provided by the physicists in question. Ultimately, Kragh insists on illustrating a triumphant, rational march of science towards clearly articulated progress.

And despite historians’ recent fascination with scientific practice, Kragh’s book only occasionally gives a nod to experiment, instruments and technology, or to education, the popular image of science, and the often disturbing incomprehensibility of modern physics to the general public. Nor do we get a sense that scientists ought to concern themselves with what the rest of the world thinks of them. Implicit in this book is the assumption that the achievements of modern physics justify unlimited resources and unlimited faith. It is perhaps the unproblematic approach to the history of science that is most characteristic of Kragh’s self-confident and eloquent writing style.

For historians of science such as myself, the most intriguing chapter is perhaps “Science Under Attack – Physics in Crisis?” Here Kragh rather linearly and causally links the work of J D Bernal, Herbert Marcuse, Thomas Kuhn, Paul Feyerabend and the more recent sociology of scientific knowledge and social constructivism to the growing anti-scientific climate and the alleged decline in the interest of young people in physics. And while it is true that enrollments in physics PhD programmes in the US have declined by 27% since 1992 – probably due to the end of the Cold War and the reduction in defence-related employment opportunities, rather than a few dozen academic books on the social construction of science – the total number of science and engineering PhDs awarded by US universities rose by 25% to some 26 000 in the ten years to 1995. These statistics indicate shifts in interest, rather than mere disinterest in science and engineering.

Moreover, the comprehensive bibliography in Kragh’s book shows that the history of physics is not, as many believed in the early 1980s, a closed subject. On the contrary, the last 15 years have seen the publication of an impressive number of monographs, biographies, popularized books and specialized articles that have changed and deepened quite dramatically our understanding of the history of modern and contemporary physics.

For physicists who want to “humanize” their courses, or brush up on their professional past, for those who teach the history of modern science, and for anyone fascinated with physics, I can recommend this book as an indispensable resource.

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