Showing papers in "Physics World in 2003"
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TL;DR: Loop quantum gravity as mentioned in this paper is a quantum field theory that incorporates the notions of space and time from general relativity directly into quantum field theories to provide a precise mathematical picture of quantum space and space, and also offers a solution to long-standing problems such as the thermodynamics of black holes and the physics of the Big Bang.
Abstract: General relativity and quantum theory have profoundly changed our view of the world. Furthermore, both theories have been verified to extraordinary accuracy in the last several decades. Loop quantum gravity takes this novel view of the world seriously, by incorporating the notions of space and time from general relativity directly into quantum field theory. The theory that results is radically different from conventional quantum field theory. Not only does it provide a precise mathematical picture of quantum space and time, but it also offers a solution to long-standing problems such as the thermodynamics of black holes and the physics of the Big Bang.
128 citations
TL;DR: All living cells contain long DNA molecules that carry genetic information in their base sequences that must be read so that proteins can be made, and they must also be duplicated and separated from one another so that cells can divide.
Abstract: All living cells contain long DNA molecules that carry genetic information in their base sequences. These molecules must be read so that proteins can be made, and they must also be duplicated and separated from one another so that cells can divide. Furthermore, if a cell's DNA suffers damage, it must be repaired. These essential processes are carried out by enzymes – proteins that catalyse biochemical reactions – that "walk" along the DNA double helix. So where does physics come in?
59 citations
TL;DR: Last November OmniSonics Medical Technologies of the US started to commercialize ultrasound technology that it had developed to treat blockages in blood vessels, finding it less invasive than other current methods.
Abstract: Last November OmniSonics Medical Technologies of the US started to commercialize ultrasound technology that it had developed to treat blockages in blood vessels. European and Australian doctors are already using the method to treat patients, finding it less invasive than other current methods, and the technology is also undergoing clinical trials in the US.
30 citations
TL;DR: The remarkable properties of DNA that allow it to be used as bricks, mortar and fuel could even lead to molecular assembly lines with conveyor belts that play an active role in the construction process.
Abstract: DNA is a wonderful material with which to build. It can act as a molecular glue or as the fuel for molecular engines. It can be made into rigid girders and tiles, and can also be used to design complex structures capable of self-assembly. DNA nanostructures can act as parallel computers, as "scaffolds" in protein-crystallography experiments and may soon form support structures in 3D molecular electronic circuits. The remarkable properties of DNA that allow it to be used as bricks, mortar and fuel could even lead to molecular assembly lines with conveyor belts that play an active role in the construction process.
27 citations
TL;DR: In this paper, a beam of light cross the interface between two different materials, its path is altered depending on the difference in the refractive indices of the materials, and the greater the difference, the higher the refraction of the beam.
Abstract: One of the most fundamental phenomena in optics is refraction. When a beam of light crosses the interface between two different materials, its path is altered depending on the difference in the refractive indices of the materials. The greater the difference, the greater the refraction of the beam. For all known naturally occurring materials the refractive index assumes only positive values. But does this have to be the case?
24 citations
TL;DR: The role of water in the greenhouse effect is rarely discussed as discussed by the authors, and water barely rates a mention in the hundreds of pages of the 2001 report by the Intergovernmental Panel on Climate Change.
Abstract: Extreme variations in local weather and the seasons make it easy for people to mutter "greenhouse effect", and blame everything on carbon dioxide. Along with other man-made gases, such as methane, carbon dioxide has received a bad press for many years and is uniformly cited as the major cause of the greenhouse effect. This is simply not correct. While increases in carbon dioxide may be the source of an enhanced greenhouse effect, and therefore global warming, the role of the most vital molecule in our atmosphere – water – is rarely discussed. Indeed, water barely rates a mention in the hundreds of pages of the 2001 report by the Intergovernmental Panel on Climate Change.
17 citations
TL;DR: The double-slit interference experiment with electrons was first performed by Claus Jonsson of the University of Tubingen in 1961 as mentioned in this paper, and the next milestone was reached by Akira Tonomura and co-workers at Hitachi in 1989 when they observed the build-up of the fringe pattern with a very weak electron source and an electron biprism.
Abstract: The article "A brief history of the double-slit experiment" (September 2002 p15; correction October p17) describes how Claus Jonsson of the University of Tubingen performed the first double-slit interference experiment with electrons in 1961. It then goes on to say: "The next milestone – an experiment in which there was just one electron in the apparatus at any one time – was reached by Akira Tonomura and co-workers at Hitachi in 1989 when they observed the build-up of the fringe pattern with a very weak electron source and an electron biprism (Am. J. Phys. 57 117–120)."
17 citations
TL;DR: The Routes to scientific discovery are sometimes strange as discussed by the authors, and such stories serve a function in science, emphasizing individual psychology and the flash of inspiration from a heroic scientific genius, over the more routine and collective aspects of scientific work.
Abstract: The Routes to scientific discovery are sometimes strange. We are all familiar sometimes strange. We are all familiar with the story of Newton and the falling apple, or with Friedrich Kekule's dream of a snake biting its own tail that led to the discovery of benzene's ring-like structure. But such stories – engaging though they might be – are often mythical. They serve a function in science, emphasizing individual psychology and the flash of inspiration from a heroic scientific genius, over the more routine and collective aspects of scientific work.
17 citations
TL;DR: In this paper, a light source that emitted just one photon at a time was considered, and it was shown that the effect of one photon on the entire light spectrum can be observed directly.
Abstract: QUANTUM mechanics has gained a reputation for making counterintuitive predictions. But we rarely get the chance to witness these effects directly because, being humans, we are simply too big. Take light, for example. The light sources that are familiar to us, such as those used in lighting and imaging or in CD and DVD players, are so huge that they emit billions and billions of photons. But what if there was a light source that emitted just one photon at a time?
14 citations
TL;DR: The free-electron laser project at DESY and Stanford Linear Accelerator Center (SLAC) as discussed by the authors was the first to generate X-ray laser radiation at wavelengths that range from 10 nm down to as little as 0.1 nm.
Abstract: Imagine making movies of chemical reactions, watching surfaces melt in real time or taking photographs of individual molecules. These are just some of the ambitious goals that researchers have set for powerful new X-ray "free-electron lasers" that are currently being developed at the Deutsches Elektronen Synchrotron (DESY) laboratory in Hamburg and the Stanford Linear Accelerator Center (SLAC) in California. These facilities will generate intense X-ray laser radiation at wavelengths that range from 10 nm down to as little as 0.1 nm. With pulses lasting just 50–500 fs, the lasers will let researchers directly study how atoms change position and how chemical bonds form.
13 citations
TL;DR: The basis of temperature and thermometry is the zeroth law of thermodynamics, which states that temperature is the quantity that takes the same value in two systems that are in thermal equilibrium as discussed by the authors.
Abstract: Most physicists probably learned about the laws of thermodynamics at high school, but few of us will have been told the whole story. Although these laws are extremely good at describing thermal phenomena, such as how a cup of coffee cools, they are too abstract to explain these processes. This is particularly relevant for temperature – one of the most important, yet conceptually most difficult, variables in thermodynamics. The basis of temperature and thermometry is the zeroth law of thermodynamics, which states that temperature is the quantity that takes the same value in two systems that are in thermal equilibrium. But how does this help us to actually measure it?
TL;DR: The ULTRACOLD world has fascinated and surprised scientists since 1911, when Heike Kamerlingh Onnes discovered superconductivity in mercury at 4.2 K as discussed by the authors.
Abstract: THE ULTRACOLD world has fascinated and surprised scientists since 1911, when Heike Kamerlingh Onnes discovered superconductivity in mercury at 4.2 K. Now physicists routinely achieve temperatures millions of times colder.
TL;DR: In this article, it was shown that the superluminal effect cannot be used to transmit energy or information, while some images or patterns appeared to travel faster than light, such as the motion of a spotlight projected on a distant wall.
Abstract: Ever since Einstein stated that nothing can travel faster than light, physicists have delighted in finding exceptions. One after another, observations of such "superluminal" propagation have been made. However, while some image or pattern – such as the motion of a spotlight projected on a distant wall – might have appeared to travel faster than light, it seemed that there was no way to use the superluminal effect to transmit energy or information.
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TL;DR: The answers could lie in the new interdisciplinary science of astrobiology, which seeks to unravel the origin, evolution and destiny of life – wherever it might exist in the universe.
Abstract: HUMANKIND has been observing the night sky for thousands of years. But one question has always eluded us: does life exist beyond the Earth? Life as we know it is based on DNA, RNA and proteins, but why and how it was all initiated is not understood. The answers could lie in the new interdisciplinary science of astrobiology, which seeks to unravel the origin, evolution and destiny of life – wherever it might exist in the universe.
TL;DR: Scientists have long been eager to probe living cells in full colour over extended periods of time, believing this technique could reveal the complex processes that take place in all living organisms in unprecedented detail, such as the development of embryos.
Abstract: Biologists have long been eager to probe living cells in full colour over extended periods of time. Such a technique could reveal the complex processes that take place in all living organisms in unprecedented detail, such as the development of embryos.
TL;DR: In this paper, a young assistant professor at the University of Chicago asked a question that seemed purely academic: "What would happen to a metal if there was a phase transition at absolute zero?" The answer that John Hertz arrived at involved quantum theory, extra dimensions and a singularity that could undermine our view of the metallic state.
Abstract: IN THE mid-1970s, when the study of phase transitions was undergoing a renaissance, a young assistant professor at the University of Chicago asked a question that seemed purely academic: "What would happen to a metal if there was a phase transition at absolute zero?" The answer that John Hertz arrived at involved quantum theory, extra dimensions and a singularity that could under-mine our view of the metallic state.
TL;DR: The laws of nature as discussed by the authors are a set of divine and unchanging rules that transcend the "here and now" to apply everywhere and at all times in the universe and have been verified by experiment.
Abstract: What do we mean by "the laws of nature"? The phrase evokes a set of divine and unchanging rules that transcend the "here and now" to apply everywhere and at all times in the universe. The reality is not so grand. When we refer to the laws of nature, what we are really talking about is a particular set of ideas that are striking in their simplicity, that appear to be universal and have been verified by experiment. It is thus human beings who declare that a scientific thory is a law of nature – and human beings are quite often wrong.
TL;DR: In trying to find the origin of the universe and describe its subsequent evolution, it is not surprising that extravagant assertions are made as mentioned in this paper, and I sometimes feel that I belong to a legion of researchers suffering from delusions of grandeur.
Abstract: Cosmologists can lay claim to addressing some of the most dramatic problems that humankind has to face. In trying to find the origin of the universe and describe its subsequent evolution, it is not surprising that extravagant assertions are made. I sometimes feel that I belong to a legion of researchers suffering from delusions of grandeur. There is a firm belief that we are seeing the first instances of creation imprinted in the sky, which George Smoot famously likened to "the face of God". It has also led to claims that the universe is the "simplest possible" or, alternatively, "preposterous".
TL;DR: The first landing of a man on the Moon was made by David R Scott as mentioned in this paper with a feather in his left hand and a hammer in his right hand, and the feather was used to confirm the falling objects in gravity fields.
Abstract: Commander David R Scott (2 August 1971, lunar surface): "Well, in my left hand I have a feather; in my right hand, a hammer. And I guess one of the reasons we got here today was because of a gentleman named Galileo, a long time ago, who made a rather significant discovery about falling objects in gravity fields". And we thought: "Where would be a better place to confirm his findings than on the Moon?".
TL;DR: In physics, women are greatly underrepresented in the field of physics as discussed by the authors, and the increase in the number of women involved in physics has been particularly slow, and many bright young people do not get the chance to learn about physics and to prepare themselves for a career in physics.
Abstract: Women are greatly under-represented in physics. Of all the sciences, physics is the subject in which the increase in the number of women involved has been particularly slow. Many bright young people do not get the chance to learn about physics and to prepare themselves for a career in the field. Others are simply discouraged from studying physics altogether.
TL;DR: Einstein introduced the cosmological constant to his equations of general relativity because he believed the universe was static as mentioned in this paper, however, when it was shown that the universe is actually expanding, he decided to remove it, later referring to it as the biggest blunder of his life.
Abstract: Einstein introduced the cosmological constant to his equations of general relativity because he believed the universe was static. Faced with evidence that the universe was actually expanding, however, he decided to remove it, later referring to the cosmological constant as the biggest blunder of his life. Recent observations suggest that the expansion of the universe is accelerating, which favours a small, but non-zero, positive cosmological constant with a value of 10-120 in Planck units (see article on p3).
TL;DR: Computer components are getting smaller all the time, and no doubt they will eventually reach the nano-scale where quantum effects start to play a part, but this alone will not make them quantum computers.
Abstract: Quantum computers are a very special breed of computer that depend on the superposition and entanglement of quantum states. Computer components are getting smaller all the time, and no doubt they will eventually reach the nano-scale where quantum effects start to play a part. But this alone will not make them quantum computers. They will still work pretty much like an ordinary PC, and be able to solve the same limited kind of problems.
TL;DR: Today, the phrase "going for a scan" can refer to any one of a multitude of different medical imaging techniques that are used for diagnosis and treatment.
Abstract: Medical physics has come a long way since Wilhelm Conrad Rontgen first described a "new kind of ray" back in 1895. The discovery that X-rays could be used to display the innermost workings of the human body on a photographic plate was of immediate interest to the medical community at the time. Today, over a century later, the phrase "going for a scan" can refer to any one of a multitude of different medical imaging techniques that are used for diagnosis and treatment.
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TL;DR: The authors argued that women appear to enjoy physics, but do not select it as a university subject because of its poor image, and claimed that the girls at the school where he used to teach "opted instead for degrees that they thought would benefit them both practically and financially, and bring them esteem in the world of work".
Abstract: Christopher Bishop (August p15) argues that women appear to enjoy physics but do not select it as a university subject because of its poor image. He says that the girls at the school where he used to teach "opted instead for degrees that they thought would benefit them both practically and financially, and bring them esteem in the world of work". Girls take up physics less often than boys, he suggests, because they are more "market savvy".
TL;DR: A major focus of the hadron-therapy session at the World Congress in Medical Physics and Bioengineering, which is taking place in Sydney this month, will be on efforts to transform particle therapy into a practical and affordable treatment option.
Abstract: Until a cure for cancer is found, about one in three of us will probably have to undergo surgery, chemotherapy or radiotherapy at some point in our lives. Traditional radio-therapy uses X-rays to target cancerous tissue, but there is growing interest in using particles instead. Beams of hadrons, such as protons, neutrons and ions, offer important advantages over X-ray radiotherapy. Their clinical applications, however, are much less widespread. Most of the 25 or so hadron therapy facilities that are currently in operation around the world are sited at large particle-physics laboratories–not hospitals. A major focus of the hadron-therapy session at the World Congress in Medical Physics and Bioengineering, which is taking place in Sydney this month, will be on efforts to transform particle therapy into a practical and affordable treatment option.
TL;DR: In this article, it was shown that the interaction between the Sun's magnetic field and the plasma of which the star is composed can be modeled as a nonlinear interaction, which is called solar magnetohydrodynamics.
Abstract: Solar physics is currently enjoying a golden age, but many fundamental questions about the nature of the Sun have not yet been fully answered. What generates the Sun's magnetic field? How is its atmosphere heated? And what governs the acceleration of the solar wind? However, over the past five years there have been significant advances in our understanding of solar magneto-hydrodynamics – the subtle and intimate nonlinear interaction between the Sun's magnetic field and the plasma of which the star is composed.
TL;DR: In this article, a person raised her hand and asked, "Dr Watson, I wonder if you could comment a little bit more on Rosalind Franklin's contribution to the discovery of DNA." Whereupon some in the audience applauded.
Abstract: I once attended a series of lectures at the Brookhaven National Laboratory delivered by James Watson. In his initial talk he spoke of the historical events that surrounded the discovery of the structure of DNA. Afterwards, there was time for one question. A person raised her hand. "Dr Watson," she asked, "I wonder if you could comment a little bit more on Rosalind Franklin's contribution to the discovery of DNA." Whereupon some in the audience applauded.
TL;DR: The field of ultracold quantum gases is no longer in its infancy as discussed by the authors, and experiments on quantum gases are relevant to many different areas of physics, from atomic clocks and quantum computing to superfluidity and quantum phase transitions.
Abstract: The Field of ultracold quantum gases is no longer in its infancy. Since the first gaseous Bose–Einstein condensate was formed in 1995, physicists have made an exhaustive study of the many amazing properties of this new state of matter. Similar progress has been made with degenerate Fermigases – the quantum-mechanical cousins of Bose condensates. In addition to being fascinating in their own right, experiments on quantum gases are relevant to many different areas of physics – from atomic clocks and quantum computing to superfluidity and quantum phase transitions.
TL;DR: In 1651 a collection of Gilbert's manuscripts, which had been edited by his half brother, was posthumously published under the title De Mundo Nostro Sublunari Philosophia Nova as mentioned in this paper.
Abstract: When William Gilbert of Colchester died on 30 November 1603, England lost one of its greatest Elizabethan scientists. Three years earlier he had published a book called De Magnete, which was nothing less than the first ever work of experimental physics. Its fuller title, translated from the original Latin, was On the Magnet, Magnetic Bodies and that Great Magnet the Earth. In 1651 a collection of Gilbert's manuscripts, which had been edited by his half brother, was post-humously published. Going under the title De Mundo Nostro Sublunari Philosophia Nova, the book provided "a new philosophy of our sublunary world".
TL;DR: In 2001, the National Tourist Board of Zambia (NTB) co-ordinated the preparation of the total solar eclipse in the country as mentioned in this paper, with the goal of explaining the eclipse and safe viewing methods.
Abstract: On 21 June 2001 parts of Zambia were due to experience a total solar eclipse. The nearest thing the country has to an astronomy institution is the physics department at the University of Zambia. By virtue of being the person in the department most interested in astronomy, I became scientific consultant to the Zambia National Tourist Board, the body co-ordinating eclipse preparations. My job was to explain the eclipse and safe viewing methods to the public.