Showing papers in "Physics World in 1999"
TL;DR: The universe itself is thought to have passed through several phase transitions as the high-temperature plasma formed by the big bang cooled to form the world as we know it today as mentioned in this paper.
Abstract: Nature abounds with phase transitions. The boiling and freezing of water are everyday examples of phase transitions, as are more exotic processes such as superconductivity and superfluidity. The universe itself is thought to have passed through several phase transitions as the high-temperature plasma formed by the big bang cooled to form the world as we know it today.
3,749 citations
TL;DR: In this article, the authors discuss the effect of roadworks on the physics of traffic jams and show that traffic jams are a fact of life for many car drivers, who blame other drivers, increasing volumes of traffic and, inevitably, roadworks.
Abstract: Traffic jams are a fact of life for many car drivers. Every morning millions of drivers around the world sit motionless in their vehicles for long periods of time as they try to get to work, and then repeat the experience on their journeys home in the evening. The same thing often happens when they are driving to the coast for the weekend or to the airport to go on their holidays. They blame other drivers, increasing volumes of traffic and, inevitably, roadworks. So what has any of this got to do with physics?
778 citations
TL;DR: Semiconductor lasers are widely used in modern life as discussed by the authors, typically a few microns in cross-section and a few hundred microns long, they are an integral part of the modern world.
Abstract: Semiconductor lasers are widely used in modern life. In telecommunications they send signals for thousands of kilometres along optical fibres. In consumer electronics, semiconductor lasers are used to read the data on compact disks and CD-ROMs. Other applications include laser printers and laser pointers. Although they are just the size of a grain of salt, typically a few microns in cross-section and a few hundred microns long, semiconductor lasers are an integral part of the modern world.
139 citations
TL;DR: In this paper, Gunther et al. published an article in Physics World on quantum tunnelling in magnetic particles that are a few nanometres in diameter and emphasized both the fundamental challenges and the technological obstacles to controlling and exploiting quantum coherent tunning in nanoscopic devices.
Abstract: In 1990 one of us (LG) published an article in Physics World on quantum tunnelling in magnetic particles that are a few nanometres in diameter. The article emphasized both the fundamental challenges – for instance understanding the nature of the transition region between quantum and classical regimes – as well as the technological obstacles to controlling and exploiting quantum coherent tunnelling in nanoscopic devices. The subject of quantum tunnelling of magnetization (QTM) was in its infancy. Since then, however, many experimentalists and theorists have contributed to this rich field. In 1994, for instance, the first workshop on the subject was held in Chichilianne, France (see Gunther and Barbara in further reading), and interest in quantum phenomena in magnetic molecules continues to grow.
79 citations
TL;DR: The Moon is our closest neighbour in space and holds the key to unlocking the secrets of the inner solar system as discussed by the authors, and 30 years ago provided the scene for what is arguably mankind's greatest achievement: our first steps on an extraterrestrial body.
Abstract: The Moon is our closest neighbour in space and holds the key to unlocking the secrets of the inner solar system. It is the most studied planetary body other than the Earth, and 30 years ago provided the scene for what is arguably mankind's greatest achievement: our first steps on an extraterrestrial body.
60 citations
TL;DR: A small number of physicists have always worked on the financial markets as mentioned in this paper, and these so-called "rocket scientists" have been valued for their mathematical and computational skills, and their ability to analyse extremely complex problems.
Abstract: A small number of physicists have always worked on the financial markets. Employed by banks and other financial institutions, these so-called "rocket scientists" have been valued for their mathematical and computational skills, and their ability to analyse extremely complex problems. And as international finance has become even more complicated, the demand for rocket scientists – most of whom have PhDs – has increased, as have their famously high salaries.
36 citations
TL;DR: A few months before Isidor Isaac Rabi died in early 1988, his doctors watched as he was gently moved into the bore of a magnetic-resonance-imaging machine as mentioned in this paper.
Abstract: A few months before Isidor Isaac Rabi died in early 1988, his doctors watched as he was gently moved into the bore of a magnetic-resonance-imaging machine. Once inside the machine, Rabi saw a distorted image of his face in the cylindrical surface surrounding him. "It was eerie," Rabi said. "I saw myself in that machine. I never thought my work would come to this." An eerie moment? Certainly – since Rabi's physical research led directly to magnetic resonance imaging, a technique that is widely used in hospitals today.
32 citations
TL;DR: In this paper, the authors discuss the role of proteins in the structure and functioning of all forms of life and how they catalyse the reactions within living systems and are responsible for signalling and communication within cells.
Abstract: Proteins play a vital role in the structure and functioning of all forms of life. They catalyse the reactions within living systems and are responsible for signalling and communication within cells.
31 citations
TL;DR: Wegh et al. as discussed by the authors discovered a phosphor material that emits almost twice as many photons as it absorbs, which may lead to a new generation of highly efficient fluorescent lights and plasma displays that are also environmentally safe.
Abstract: A phosphor material that emits almost twice as many photons as it absorbs has been discovered by researchers at Utrecht University in the Netherlands (R Wegh et al. 1999 Science 283 663). The discovery may lead to a new generation of highly efficient fluorescent lights and plasma displays that are also environmentally safe.
26 citations
TL;DR: What is the ultimate speed limit in the authors' world?
Abstract: Perhaps the most defining characteristic of modern society is its ever-increasing pace. New technological capabilities, such as computing and telecommunications, are making people more efficient. While these advances increase our standard of living, they also place new demands on our lives and make it all the more important that we maintain the pace of technological change. Of course, we sometimes wonder whether this rate of change will slow down. More specifically, what is the ultimate speed limit in our world? At what point will our computers and communications devices reach fundamental physical limits? And how close is our technology to reaching this ultimate speed limit?
26 citations
TL;DR: In this article, the authors describe a scene where the Sun is replaced by a black disc, surrounded by what seems like a ghostly veil of white smoke or steam, and they look up in terror and see that the Sun has been replaced by the disc.
Abstract: Imagine that we are in the middle of a field, thousands of years ago. It is a beautiful summer's day: blue sky, no clouds, no wind. At noon, it feels quite hot. Then we sense the temperature falling, and the light fading, but it is still a beautiful day – blue sky, no clouds, no wind. Soon the air turns much cooler and the sky much darker. There are still no clouds, but a gentle, cool breeze has picked up. The Sun is still too bright to look at, but it is fading away, and near to it we can see bright planets, as we would at night. The western horizon turns a dark shade of blue-grey, and then, in just a few short seconds, darkness invades the landscape. We look up in terror and see that the Sun has been replaced by a black disc, surrounded by what seems like a ghostly veil of white smoke or steam. The Sun – the most important thing in the sky, our source of light and heat, our clock and calendar – is no longer there.
TL;DR: The 20th century has been a period of scientific revolution, unmatched in scope by anything that has come before, save perhaps the Copernican revolution in the 16th century as discussed by the authors.
Abstract: The 20th century has been a period of scientific revolution, unmatched in scope by anything that has come before, save perhaps the Copernican revolution in the 16th century. Ever since Newtonian physics was overthrown at the beginning of this century we have been living through a period of transition, during which the new theory that will replace Newtonian physics as a unified framework for the description of everything in nature has been steadily coming into focus. Big pieces of this theory have been discovered, such as relativity quantum theory the Standard Model of particle physics, and the standard big-bang cosmology But it is very clear that we do not yet have the full theory, because that must be based on a single theoretical framework, and such a framework is still lacking. Thus, as humanity emerges into a new century, the completion of the new theory that will finally replace Newtonian physics remains the primary goal of theoretical physics.
TL;DR: Research on the prevention, detection, diagnosis and treatment of disease and disability from the rarest genetic disorder to the common cold, as well as research on the basic principles of biology are supported.
Abstract: The aim of most biomedical research is to uncover new knowledge that will lead to better health. At the National Institutes of Health (NIH) in the US we do this by supporting research on the prevention, detection, diagnosis and treatment of disease and disability from the rarest genetic disorder to the common cold, as well as research on the basic principles of biology.
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TL;DR: The light influences the way we live today in ways that could never have been imagined just a few decades ago as mentioned in this paper. But light has had a less obvious but equally profound impact.
Abstract: Light influences the way we live today in ways that could never have been imagined just a few decades ago. The invention of the laser has led to fibre-optic communications, compact disks for data storage and laser surgery. Other developments in optics have had a less obvious but equally profound impact. Examples include the optical lithography techniques used to make computer chips, high-resolution microscopes, infrared sensors and highly efficient lighting sources.
TL;DR: In a complex system, the whole turns out to be much more than the sum of its parts as discussed by the authors, and the self-organization of these parts gives rise to novel macroscopic or "emergent" properties.
Abstract: There is growing recognition that progress in many scientific disciplines depends on an understanding of complexity Complex systems play an important role in molecular biology neurobiology and ecology as well as geology engineering and economics. These systems consist of a large number of mutually interacting parts, often open to their environment, and the self-organization of these parts gives rise to novel macroscopic, or "emergent", properties. Put another way, in a complex system the whole turns out to be much more than the sum of its parts.
TL;DR: This research highlights how easy it was for an unauthorized party to gain control of a satellite system, and motivated researchers to find new ways of ensuring that messages transmitted to and from satellites remain secret.
Abstract: Cryptography has had a long and distinguished history of military and diplomatic use dating back to the ancient Greeks. But secure communications are becoming increasingly important for commercial applications as well. In 1986, for instance, a satellite television broadcast in the US was interrupted by a message from a hacker known as "Captain Midnight". The incident highlighted how easy it was for an unauthorized party to gain control of a satellite system, and sparked a massive criminal investigation. It also motivated researchers to find new ways of ensuring that messages transmitted to and from satellites remain secret.
TL;DR: This paper focuses on the part of biological cells that are interested in the collective behaviour of individual components and the role that these components have in the structure of the cell.
Abstract: Biological cells, molecules and organisms are complex systems that are increasingly capturing the imagination of physicists. Unlike many objects in the physical domain, biological systems cannot simply be described by the collective behaviour of individual components. The difference is that biological cells are living systems – a property that has less to do with the number of components they contain and more to do with the way these various components are arranged. Many physicists recognize that understanding this complexity is a fundamental challenge of biology.
TL;DR: In contrast to the behaviour observed when the crystalline form of a material is heated: it will always melt at the same temperature as discussed by the authors, glass does not melt abruptly, as a crystal does, but gradually over a range of temperatures.
Abstract: Glass is a commonplace word. One immediately thinks of windows or bottles and of properties like brittleness or transparency. However, for a glass blower another feature is more important: glass does not melt abruptly, as a crystal does, but gradually over a range of temperatures. This means that he or she can alter the temperature at which glass solidifies or becomes a liquid by changing the rate at which it is cooled or heated. This is in stark contrast to the behaviour observed when the crystalline form of a material is heated: it will always melt at the same temperature.
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TL;DR: In contrast, the inner solar system seems to be much more densely populated than the outer solar system as mentioned in this paper, with a number of long-period comets passing through on their way to the distant Oort Cloud (see box on page 38).
Abstract: Until recently the most distant parts of the solar system were thought to be very empty. The outer solar system is principally occupied by the giant gas planets – Jupiter, Saturn, Uranus and Neptune – and tiny Pluto, with a number of long-period comets passing through on their way to the distant Oort Cloud (see box on page 38). In contrast, the inner solar system seems to be much more densely populated. It is home to the terrestrial planets, many tens of thousands of asteroids in a belt between Mars and Jupiter, and a thousand short-period comets with orbits largely controlled by Jupiter. The inner solar system also contains debris ranging from micron-sized particles of interplanetary dust to kilometre-sized asteroids, the impact of which could threaten life on Earth.
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TL;DR: In this article, it is widely accepted that innovation is essential for companies to remain competitive as business and industry become increasingly international, and that innovation can help small companies to grow and large companies to maintain or increase their market share.
Abstract: It is widely accepted that innovation is essential for companies to remain competitive as business and industry become increasingly international. Innovation can help small companies to grow and large companies to maintain or increase their market share. Research and development is an important element of technological innovation because it helps to generate the superior products, processes and services that can give a company a competitive edge. But R&D alone is not enough for innovation.
TL;DR: In this article, it was shown that the true orientation of the magnetic moment is determined by the interplay of many different and competing energies, and that the magnetic moments in neighbouring domains point in different directions.
Abstract: It might seem that the state of a magnet can be fully specified by labelling its poles as north and south. However, the true orientation of the magnetic moment is determined by the interplay of many different and competing energies. This generally ensures that the magnetization breaks up into a complicated pattern of regions, called domains, and that the magnetic moments in neighbouring domains point in different directions.
TL;DR: The self-winding wristwatch was demonstrated in this paper, where the slightest movement of the wearer's wrist causes a metal weight attached to the winding mechanism to pivot freely, winding the spring that powers the mechanical watch.
Abstract: Is it possible to extract energy from random fluctuations and put it to use? This challenging question has provoked discussion ever since the early days of Brownian-motion theory. For large-scale or macroscopic fluctuations, the answer is "yes" – the principle is demonstrated in several mechanical and electrical devices in everyday use, such as the self-winding wristwatch. In this case, the slightest movement of the wearer's wrist causes a metal weight attached to the winding mechanism to pivot freely, winding the spring that powers the mechanical watch.
TL;DR: Together the human nervous system and brain form what is undoubtedly the most powerful, complex, and least understood, signal-processing network in the universe.
Abstract: The nervous system of humans, like that of all other animals, relies on electrical signals that flow along nerve cells. These electrical impulses travel to and from the brain, allowing us to respond to stimuli of all types, ranging from heat and light to articles in Physics World. Together the human nervous system and brain form what is undoubtedly the most powerful, complex, and least understood, signal-processing network in the universe.
TL;DR: In this article, it was shown that sound waves can cause an air bubble trapped in water to emit light, with short flashes of light being emitted the instant the bubble reaches its minimum radius.
Abstract: Ever since it was discovered that sound waves can cause an air bubble trapped in water to emit light, physicists and chemists have puzzled over the phenomenon of sonoluminescence. The sound waves cause the bubble to expand and contract, with short flashes of light being emitted the instant the bubble reaches its minimum radius. Single-bubble sonoluminescence was first observed in 1989 by the author as part of his PhD research at the University of Mississippi (see, for example, Physics World May 1998 p38).
TL;DR: In this article, the authors describe quantum mechanics as a way of making sense of the host of observations at the level of single electrons, atoms or molecules that could not be explained in terms of Newtonian mechanics and Maxwell an electrodynamics.
Abstract: Quantum mechanics is a great deal more than a theory; it is a whole new way of looking at the world. When it was developed in the l920s, quantum mechanics was viewed primarily as a way of making sense of the host of observations at the level of single electrons, atoms or molecules that could not be explained in terms of Newtonian mechanics and Maxwell an electrodynamics. Needless to say, it has been spectacularly successful in this task.
TL;DR: In the mid-l7th century, Galileo Galilei dropped two metal balls from the Leaning Tower of Pisa and showed that they fall at the same rate despite their different masses as discussed by the authors.
Abstract: In the mid-l7th century Galileo Galilei dropped two metal balls from the Leaning Tower of Pisa and showed that they fall at the same rate despite their different masses. In a later version of the experiment, astronaut David Scott dropped a hammer and a feather on the Moon and saw that they hit the surface at the same time. Why did Galileo not choose this more dramatic combination of objects to drop from the Leaning Tower?
TL;DR: Pons and Fleischmann as discussed by the authors demonstrated controlled nuclear fusion in a glass jar and the excess heat measured in the experiment offered the promise of a new power source for the planet, as well as huge financial rewards.
Abstract: Most physicists can probably remember where they were when they first heard of Stanley Pons and Martin Fleischmann. On 23 March 1989 the two electrochemists grabbed the world's attention by announcing at a press conference in Salt Lake City, Utah, that they had observed controlled nuclear fusion in a glass jar. The excess heat measured in the experiment offered the promise of a new power source for the planet, as well as huge financial rewards.
CERN1
TL;DR: In this paper, it was shown that collisions between high-energy particles at accelerators may reveal the presence of extra space time dimensions, and the question of how many dimensions are we living in remains unresolved.
Abstract: How many dimensions are we living in? This question is fundamental and yet, astonishingly, it remains unresolved. Of course, on the everyday level it appears that we are living in four dimensions – three space plus one time dimension. But in recent months theoretical physicists have discovered that collisions between high-energy particles at accelerators may reveal the presence of extra space time dimensions.
TL;DR: Bonnor as discussed by the authors investigated the influence of the expanding universe on the size of the hydrogen atom and found that it is positively correlated with the number of stars in the observable universe, and that the universe is not expanding.
Abstract: In Woody Allen's masterpiece Annie Hall the main character is worried about the expansion of the universe. Indeed, during a childhood visit to his psychiatrist, his mother admonishes him: "You're here in Brooklyn! Brooklyn is not expanding!" But is that really true? Relativists have attacked this naive question many times and have arrived at different answers. New light has now been thrown on the subject by William Bonnor from Queen Mary and Westfield College in London by considering the influence of the expanding universe on the size of the hydrogen atom (Class. Quantum Grav. 1999 16 1313).
TL;DR: In this article, it was argued that if different finite systems show critical behaviour, then it should be possible to find universal features that are independent of both the size of the system and the details of the forces involved.
Abstract: Phase transitions in substances – for example, water changing to water vapour – have been investigated for over a century. These studies have tended to concentrate on macroscopic systems containing a large, and essentially infinite, number of particles. In recent years, interest in phase transitions infinite systems – such as nuclei and metallic clusters – has increased rapidly. From a theoretical standpoint, phase transitions and other critical phenomena have been predicted to occur in these systems by assuming that they contain an infinite number of constituents. A few years ago, Jurgen Schulte and I argued that if different finite systems show critical behaviour, then it should be possible to find universal features that are independent of both the size of the system and the details of the forces involved. The challenge for experimentalists has been to show unambiguous evidence for critical behaviour infinite systems.