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Quantum heat flow in the lab

Quantized electrical conductance was confirmed in experiments with very narrow conducting wires in the late 1980s. The electrons move through the wire along quantum channels, each of which contributes a quantum unit of 2e²/h to the conductance, where e is the charge on the electron and h is the Planck constant. As the voltage difference across the wire increases, more quantum channels open up and the current passing through the wire increases in a step-like fashion. Similar behaviour has been predicted for phonons, with the quantum of thermal conductance being given by G₀ = p²k²T/3h, where k is the Boltzmann constant and T is temperature.

Roukes and colleagues used electron beam lithography to make a narrow bridge from silicon nitride: the bridge was 60 nm thick and 200 nm wide. Niobium wires were used to connect the bridge to two pads that were attached to ultrasensitive thermometers. The group warmed one end of the bridge and measured how the thermal conductance – the rate of heating divided by the temperature difference – varied as a function of temperature. They discovered that the thermal conductance fell with temperature to about 1 Kelvin, below which it remained flat at a value consistent with thermal conductance being quantized in units of G₀.

The universe is flat – official

All the matter and radiation in the universe was created by the big bang. The radiation stopped interacting with the matter about 300,000 years later – when the universe had cooled down enough for electrons and protons to form hydrogen atoms. The fact that the CMB has a perfect black-body spectrum with a temperature of around 2.73 Kelvin is one of the key pieces of evidence for the big bang. However, since the CMB is related to the state of the universe 300,000 years after the big bang, we expect to find tiny variations in the background temperature across the sky that correspond to slight variations in the distribution of matter at the time. These irregularities later became galaxies and clusters of galaxies. The fluctuations in the CMB also contain information about the total energy density and curvature of the universe.

In 1991 the COBE satellite measured large-scale fluctuations in the CMB for the first time. The Boomerang experiment has now measured these fluctuations with a sensitivity of better than one ten thousandth of a degree. The Boomerang team has confirmed, to within 10%, that the universe is flat and should therefore expand forever. The data also confirm that the patterns caused by sound waves speeding through the early universe helped to create giant clusters of galaxies.

Boomerang is a balloon-based telescope that was launched from Antarctica on 29 December 1998. The telescope took readings at an altitude of 37 kilometres to reduce the absorption of millimetre wave radiation by water vapour in the atmosphere. Over a period of almost 11 days the experiment measured the CMB at four wavelengths — 0.75 mm, 1.25 mm, 2 mm and 3.33 mm — across about 3% of the sky. By comparing the results at different wavelengths, the Boomerang team was able to remove signals due to the instruments, dust and other sources, and then derive a “power spectrum” – a curve showing how the size of the fluctuations varied with angle. “The idea was to ignore all the other stuff and find just the contribution of the cosmic microwave background,” said Andrew Jaffe from the University of California at Berkeley.

“It is really exciting to be able to see some of the fundamental structures of the universe in their embryonic state,” said Paolo de Bernardis of the University of Rome La Sapienza. “The light we have detected has travelled across the entire universe before reaching us, and we are perfectly able to distinguish it from the light generated in our own galaxy.”

“These images represent the ultimate limit of our vision,” said Andrew Lange from the California Institute of Technology. “The enormous structures that they reveal predate the first star or galaxy in the universe. It is an incredible triumph of modern cosmology to have predicted their basic form so accurately.”

Boost for particle physics in Canada

“This renewal of funding will permit TRIUMF to become a world leader in particle physics research,” said Arthur Carty, President of National Research Council. “It will also retain and attract the leading scientific talent that is essential to build an innovative, knowledge-based economy.”

“The federal government is strongly committed to science and technology and has a key role supporting Canada’s research infrastructure,” said John Manley, the industry minister. “Investment in the advancement of knowledge is essential as Canada continues its transition to an economy built on knowledge, innovation and technology.”

Calling all cosmophysicists

Fundamental physics is a new activity for ESA, although it has ambitious plans to launch LISA, a set of three spacecraft that would detect gravitational waves. It is also considering proposals to test the equivalence of inertial mass and gravitational mass. The other main areas of overlap discussed at the meeting were cosmology, neutrinos, dark matter, cosmic rays and instrumentation.

The meeting was also intended to increase collaboration between CERN and ESA. Although the organizations exchange engineers and are collaborating on proposals for the European Grid – a new way of accessing computer power over the web – the director generals of both CERN and ESA felt that interactions between the two institutions could be increased.

Several speakers also expressed the view that Europe lagged behind the US in space-based fundamental research. On a lighter note, meeting organizer Maurice Jacob of CERN called on delegates to think of a suitable name for physicists who carry out fundamental research in space. Jacob suggested the name cosmophysicist.

Hubble prepares for the next ten years

Recently a “second decade” working group looked at the future of the billion-dollar telescope, which is funded by NASA and the European Space Agency. After ten years in orbit, what more can Hubble do? “A lot of little science has been explored with relatively short observation periods,” says Ethan Schreier, assistant director at the STScI, “but there is a lot of parameter space left if we look at large chunks of space for long periods of time. In the next decade we will try to do things with Hubble that we have not done before.”

The working group has made three main proposals: to increase infrared observations; to conduct more wide-field surveys; and to make greater use of the telescope’s archive of data. “We have so many terabytes of data in our archive that we should capitalize on that and see what new types of science we can do,” says Schreier, who is a member of the working group. Hubble will also be used more to complement observations made by other spacecraft.

The STScI has also given approval for more risky observations, such as plans to image Venus. Direct observations would melt the telescope because Venus is so close to the Sun. However, there are plans to point Hubble at Venus for no more than ten minutes during a period when the Sun is eclipsed by the Earth. “We actually have to relax some of the restrictions on pointing the telescope near the Sun for these observations,” says Melissa McGrath, who helps vet planetary observing proposals. “The approval process goes all the way to NASA headquarters.”

The ground operations related to observing “targets of opportunity” – unforeseen events such as supernova explosions – will also be revamped. In the past it took a day to reposition the telescope, which impacted on the observing schedule by as much as a week. Now the telescope can be back on the observing schedule in under a day.

However, as the number of staff working on the Next Generation Space Telescope (NGST) increases, there are worries about the impact on Hubble. “Hubble is very valuable,” says Schreier. “Targets of opportunity are very labour intensive and it would be disastrous if we made a mistake. It is a balancing act trying to match this with current cutbacks.”

But many astronomers are convinced that the telescope will survive for the whole of its extended lifetime. “I think that Hubble will do as much, if not more, in the next ten years as it has done in the past ten years,” says Livio.

The physics of a spinning coin

Moffatt became interested in the problem while looking for Christmas presents for his grandchildren. “I came across the toy in a mail order catalogue and thought it sounded interesting,” he says. After playing with the toy he became intrigued with the physics behind Euler’s disk. “The disk is continually losing energy throughout the process,” he says, “but the rattling movement goes faster.” Indeed, according to the equations describing the disk, its angular velocity should approach a ‘finite time singularity’. What, Moffatt wanted to know, stopped the angular velocity becoming infinite?

It turned out that the theory broke down when the vertical acceleration of the disk exceeded the acceleration due to gravity. Moffatt calculated that this happened when the coin was rotating at about 100 times per second. He also calculated that a commercially available Euler’s disk should spin for about 100 seconds before it stopped – which agreed with observations to within about 20%.

UK plans to sell off defence research agency

There has been speculation over the long term future of DERA and its 11 500 employees – 9 000 of whom are research scientists – since 1998 when the government’s strategic defence review recommended that the agency should be privatised. However, union officials, the House of Commons select committee on defence, and the US government – which carries out joint research projects with DERA – expressed concerns about the sell-off. Their complaints led the government to commission a further report on the future of the agency.

This report – released on Tuesday – recommends that a core staff of 3000 employees should remain with the MOD to provide “in-house impartial advice”. Research on chemical and biological weapons would also remain with the MOD. The UK’s nuclear weapons research programme is carried out at the Atomic Weapons Establishment at Aldermaston, which is not part of DERA.

Privatising NewDERA would enable it to “grow its business and diversify the wealth of knowledge it has built up,” said Geoff Hoon, the UK’s defence minister. The government would also retain a “golden share” that would prevent a foreign take-over of the company. However, union officials believe that privatisation will lead to over 3000 staff redundancies. NewDERA would also face stiff competition for MOD contracts for the first time. A final announcement, including a timetable for the privatisation, will be made before the parliamentary summer recess.

Gell-Mann from top to bottom

When Murray Gell-Mann was awarded the Nobel Prize for Physics in 1969, his colleague at the California Institute of Technology, Richard Feynman, said: “This event marks the public recognition of what we have known for a long time, that Murray Gell-Mann is the leading theoretical physicist of today. The development during the last 20 years of our knowledge of fundamental physics contains not one fruitful idea that does not carry his name.”

Gell-Mann is a well known figure in the physics community, having dominated particle physics from the 1950s to the 1970s. When he gave the opening address at the 1966 Rochester conference in Berkeley – in which he gave a sweeping overview of the field since the early 1950s – rumour has it that the organizers had originally thought of asking five or six scientists to share the task. But when Gell-Mann was identified as the best person within each field, the organizers entrusted him with the entire presentation.

Stories about Gell-Mann abound, and physicists who want to learn more about him will find that this book does a superb job in tracing his life so far. However, it does more than just that. Gell-Mann’s life is closely intertwined with the development of particle physics, and this book also provides a marvellous description of the recent history of this scientific endeavour – written for physicists and non-physicists alike. Indeed, George Johnson, who is a respected science writer, has turned what might have been just a biography into a great scientific saga. Once you grab the book it is difficult to put down.

But the author must have faced a terrific challenge. Gell-Mann is no fan of journalists, and is alleged to have once described someone – with his typically abrasive remarks about people he did not like – as “a man of impenetrable stupidity, unmatched even by science writers today”. Yet the author meets that challenge very well and the book is great to read.

This is the story of a man of many talents, who grew up in a family with strong intellectual values but much hurt and impoverished by the great Depression of the 1930s. He was admitted to Yale University at 14, went to the Massachusetts Institute of Technology (MIT) at 18 and joined the Institute for Advanced Study in Princeton after his PhD. Then, after a brief stay in Chicago, he was awarded full tenure at Caltech at the age of just 25. The Nobel prize followed when he was 40.

This is an impressive academic trajectory, which saw Gell-Mann’s many contributions to particle physics, including strangeness, the renormalization group, the vector axial (V-A), the eightfold way and quarks. The book tells all that well, but it provides more. It takes the reader to the Russian border of the Hapsburg Empire, as we trace Gell-Mann’s ancestry. It takes us to Vienna, to Jewish families in New York in the 1920s and 1930s, to wartime Yale and to MIT under the leadership of Victor Weisskopf. It takes us to Princeton with Robert Oppenheimer and his young geniuses, to Chicago with Fermi’s impressive group and then to Caltech with Gell-Mann “twisting the tail of the cosmos” with Feynman as they worked together. Later come the glittering lights of Stockholm. I leave you to read in the book how the hyphen in his name came about.

Gell-Mann was a boy-genius – and he soon realized it. The first proper words that he is alleged to have uttered were “The lights of Babylon”: he was just two at the time and was looking at the New York streetlights coming on. He had fun impressing adults with his wide knowledge, and took no offence in correcting other people’s mistakes. However, he did suffer from his constant association with bigger and stronger children, who often resented his brilliance. Since those early days, Gell-Mann has maintained an enormous span of interests, and listening to him answer any question in almost any field is like reading the pages of the Encyclopaedia Britannica. However, Gell-Mann is not expert in every field: his son once pointed out that he does not know much about baseball or football.

Gell-Mann originally wanted to go to Yale to study linguistics or archaeology and, as physicists, we should be thankful that his father directed him toward physics instead, which he only began to love when he reached MIT. However, he long felt the shadow of his overmeticulous father reading over his shoulder, and this may have induced his infamous writer’s block that once prevented him from finishing writing his Nobel lecture in time. (I am reminded of that other great physicist, Paul Dirac, who spoke very little as an adult, and as a boy had been afraid of speaking French in front of his Swiss father – even though the young Dirac could do so perfectly.)

But Gell-Mann is a marvellous lecturer, and I remember how much I learnt from his course when I spent a year at Caltech in 1959. He explained the new physics (V-A at that time) with great clarity but also in great detail, and would use many mathematical tricks that I found very helpful on other occasions.

There is indeed something special about Gell-Mann. As the book says: “He has not just discovered a series of abstract concepts that helped make sense of the subatomic realm, he has bestowed the names that anchored them in people’s minds.” These names include strangeness, the eightfold way, quarks and – most recently – quantum chromodynamics.

However, I think that Gell-Mann’s procrastination in making definitive statements about unitary symmetry and quarks is somewhat overstressed in the book. Gell-Mann is both a great formal theorist and a superb phenomenologist. In the 1960s he knew that many possibilities other than the eightfold way existed and that the experimental data were still not good enough to tell which theory was right.

The book tells us about his passion for nature’s diversity, about his wonderful first wife Margaret, who died of cancer almost 20 years ago, about his children, and about his new marriage less than a decade ago. It tells us about his many bird-watching trips and the many committees he has served on. It also tells us about the Santa Fe Institute in New Mexico, where Gell-Mann can now fulfil his dream of interdisciplinary research, and where he tries to understand – together with colleagues from many other fields – how complexity may arise from simplicity. The book also includes a good set of notes and a detailed index.

I conclude with one of the many Gell-Mann stories. This one, which does not appear in the book, illustrates how sad he always feels when people do not fully meet his cultural standards, be they linguistic, taxonomical or gastronomical. One day, so the story goes, Murray was returning with friends from a trip in the Sierra Nevada, when they decided to stop for dinner at a roadside cafe.

“What is there to eat?” Gell-Mann asked the owner.

“Not much,” replied the chef, “but I do have spaghetti.”

“Good, but are they al dente?” said Gell-Mann, putting the proper stress on both syllables of the final word.

“I don’t know what you mean,” the owner retorted, “but they’ve been cooking all day.”

Browsing back over a life on the Web

Tim Berners-Lee’s name will be familiar to most readers of Physics World as the one-time Oxford physics student who, while working at the CERN particle-physics lab in Geneva, invented the World Wide Web – a feat for which he has received numerous awards, including an OBE in 1997.

Berners-Lee first proposed the idea of the Web in 1989, as a way of helping CERN’s large physics collaborations to organize their documentation, which was until then stored in disparate formats on incompatible computers spread around the world. From the outset, however, Berners-Lee’s personal goals for the project were far more ambitious. While the original proposal sat in administrative limbo, Berners-Lee and his colleague Robert Cailliau nevertheless began working on the project under the guise of experimenting with the development environment under the then newly released NEXTSTEP operating system. After a few months’ work, they had invented the crucial ingredients of the Web, namely the hypertext transfer protocol (HTTP) and hypertext mark-up language (HTML), and soon had the world’s first Web browser and Web server running on Berners-Lee’s NeXT computer.

Berners-Lee and Cailliau then began a concerted effort to introduce the Web to as many groups of people as possible. Although progress was slow at first, the Web began to grow explosively after Mark Andreesen and his colleagues at the National Center for Supercomputing Applications in Illinois created the Mosaic browser that could display not only text but also graphics and interactive forms.

Once the Web did take off, Berners-Lee moved from being the Web’s chief evangelist to being its moral leader. While others were beginning to reap huge rewards from the commercialization of the Web, Berners-Lee steadfastly worked to ensure that it remained as one unified whole rather than being pulled in disparate directions by the many forces trying to “extend” it to their advantage.

In 1994 he moved from CERN to the Massachusetts Institute of Technology to found the World Wide Web Consortium (W3C), an international group of businesses and academic institutes charged with developing new standards and technologies for the Web. Although it seemed to many that the control of the Web had moved into the hands of corporations such as Microsoft and AOL, the consistently thorough and unbiased work of the W3C has, over time, convinced even the most competitive companies that it is in everyone’s best interest to develop standards co-operatively – as otherwise there may be no Web left to fight over.

Despite the many more lucrative opportunities that must certainly have been open to him, Berners-Lee has remained the director of the W3C, as it is here that he believes he has the best chance to influence the continued development of his brainchild. Examples of the projects he has been involved with at the W3C include PICS, a system that gives parents flexible control over Web content without the need for government intervention or censorship, and the Web accessibility guidelines, which explain to authors how to make Web content accessible to people with disabilities.

In Weaving the Web, Berners-Lee describes the thought processes that led to the invention of the Web, the history of the Web from his perspective, and the surprisingly difficult job of persuading early audiences of the utility of the project. (The first paper describing the Web was rejected by the annual Hypertext conference for, among other things, “violating the architectural principles that hypertext systems had worked on up till then”.) The book also gives interesting insights into the mind of the inventor of the Web, and his attitude to those who have the tendency to judge someone’s worth by how much money they make. One can only imagine his indignity at being asked by one American TV reporter: “So you actually invented the Web. Tell us, exactly how rich are you?”

Those of us who have worked with Berners-Lee know that his infectious enthusiasm and genuine commitment to integrity have been a major force in moulding the Web into what it is today. Unfortunately the sense of excitement surrounding the early days of the Web does not come across clearly in this book. For example, the book describes how the number of hits on the first Web server at CERN increased exponentially month after month, but it fails to put across the sense of amazement these numbers conveyed to those involved in the early days of the project. Since the explosive growth of the Web was the result of so many people working in parallel, perhaps no one person’s story can capture this exhilaration, even if that person is the inventor of the Web.

The final third of the book is more interesting, dealing instead with Berners-Lee’s hopes and dreams for the future of the Web. Despite its enormous impact during the last decade, it is clear that Berners-Lee is not entirely satisfied with the way the Web has developed so far. His original goal for the Web was that it should be used as a worldwide collaborative tool. The idea was that groups of any size would use the Web collaboratively to document ideas, while at the same time keeping a record of the discussion and reasoning that went into shaping the final document. In much the same way that the Web was invented by combining the previously disjoint worlds of the Internet and hypertext, Berners-Lee’s hope is that the Web itself will be a tool that will help to bring disjointed ideas together.

The book also describes the way that the W3C has developed XML, a document-description language that is similar to, but more flexible than, HTML. Through the increased use of XML, the consortium hopes that the semantic information currently lost when documents and databases are converted to HTML will be preserved on the Web. In this way it is hoped that computers themselves will be able to read and “understand” the Web.

Unfortunately, in the limited space devoted to these plans for the future, there is little room left for anything but a cursory discussion of the details behind these ideas. Thus it is difficult to distinguish the author’s science-fiction-like dreams of intelligent computers that can browse the Web and make logical deductions from what they find there, from his other ideas that may actually be achievable in the near future. But to sceptics Berners-Lee points out that few people believed in his last dream when they first heard about it either, a point that is hard to argue with.

In conclusion, this book will be of value to those already interested in the history of the Web, in the thought processes that led to it, and in the plans for the future of the man who led the way. For those with a more general interest in the Internet, the Web and e-life in general, there are many other books with more general appeal.

Hubble sees mystery object

There are four possible explanations for the object: a highly obscured galaxy, an old elliptical galaxy at redshift 3 or 4, a galaxy at redshift 12, or an intergalactic carbon star. However, there are problems with all of these interpretations. “It would be very strange to have found a highly obscured galaxy with colours this extreme in one very small area such as the Hubble Deep Field image,” says Dickinson. And if the object is an old elliptical galaxy, he says, the stars inside some galaxies must have formed near the beginning of the Universe. Similarly, if the object is a highly reddened carbon star, it must be well outside our galaxy.

According to Dickinson the evidence is pointing towards a normal galaxy at extreme red shift. Earlier measurements at the Kitt Peak Observatory gave a “tentative” redshift of 12.5, but Dickinson has yet to confirm these findings. “While it may or may not be correct, these estimates are usually highly accurate,” says Meg Urry from STScI.

The result has big implications for cosmology. If the object is confirmed as a galaxy, then it suggests that large-scale cosmological structures collapsed into galaxies billions of years earlier than astronomers previously believed. The galaxy would also be three times brighter than equivalent modern-day galaxies. A final answer will require new observations, but these will take some time. “Because the object is so faint, it will be very tough to nail down,” says Dickinson. “I think there’s a healthy ‘wait and see’ attitude to see how it pans out. Unfortunately this may require a long wait, although a final answer should appear when the Next Generation Space Telescope is launched in 2007.”

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