Topologist Predicts New Form of Matter Back in 1970, a young physicist working in the Soviet Union made a counterintutive prediction. Vitaly Efimov, now at the University of Washington in the US, showed that quantum objects that cannot form into pairs could nevertheless form into triplets. In 2006, a group in Austria found the first example of such a so-called Efimov state in a cold gas of cesium atoms. That’s puzzling. Surely the bonds that hold triplets together are the same as those that bind pairs. Actually, no! Today, Nils Baas at the Norwegian University of Science and Technology makes another startling prediction. Behind this strange result is a branch of mathematics called topology, the study of shape. A useful example to consider is the famous Borromean ring shown above left. A key point here is that the circles in a flat 2 dimensional plane cannot form a Borromean ring. It turns out that there is formal mathematical analogy between the Borromean ring and the strange triplets of cesium that Efimov predicted.
untitled Perpetual Futility A short history of the search for perpetual motion. by Donald E. Simanek Popular histories too often present perpetual motion machines as "freaks and curiosities" of engineering without telling us just how they were understood at the time. They also fail to inform us that even in the earliest history of science and engineering, many persons were able to see the futility and folly of attempts to achieve perpetual motion. Sometimes a particular device comes to us with a label, such as "Bishop Wilkins' magnetic perpetual motion machine." Popular articles leave the impression that the inventor believed it was a perpetual motion machine. Bhaskara's Wheels. Villard de Honnecourt was born in the late 12th century and probably lived and worked in the north of France from 1225 to 1250. The most celebrated of his machine designs was for a perpetual motion wheel. Villard's diagram shows seven hammers, and he insisted on an odd (uneven) number of hammers, explaining 56. That's it.
Delayed choice quantum eraser A delayed choice quantum eraser, first performed by Yoon-Ho Kim, R. Yu, S.P. Kulik, Y.H. Shih and Marlan O. The delayed choice quantum eraser experiment investigates a paradox. Delayed choice experiments have uniformly confirmed the seeming ability of measurements made on photons in the present to alter events occurring in the past. Introduction[edit] In the basic double slit experiment, a beam of light (usually from a laser) is directed perpendicularly towards a wall pierced by two parallel slit apertures. Which-path information and the visibility of interference fringes are hence complementary quantities. However, in 1982, Scully and Drühl found a loophole around this interpretation.[11] They proposed a "quantum eraser" to obtain which-path information without scattering the particles or otherwise introducing uncontrolled phase factors to them. A simple quantum eraser experiment[edit] Figure 1. In the bottom diagram, a second beam splitter is introduced at the top right. Figure 2.
Personal and Historical Perspectives of Hans Bethe How to create temperatures below absolute zero - physics-math - 01 December 2010 ABSOLUTE zero sounds like an unbreachable limit beyond which it is impossible to explore. In fact there is a weird realm of negative temperatures that not only exists in theory, but has also proved accessible in practice. An improved way of getting there, outlined last week, could reveal new states of matter. Temperature is defined by how the addition or removal of energy affects the amount of disorder, or entropy, in a system. For systems at familiar, positive temperatures, adding energy increases disorder: heating up an ice crystal makes it melt into a more disordered liquid, for example. Negative-temperature systems have the opposite behaviour. Creating negative-temperature systems to see what other "bizarro world" properties they might have is tricky. This has already been done in experiments in which atomic nuclei were placed in a magnetic field, where they act like tiny bar magnets and line up with the field. More From New Scientist Promoted Stories What is 64-Bit Mobile Computing?
An Essay by Einstein -- The World As I See It "How strange is the lot of us mortals! Each of us is here for a brief sojourn; for what purpose he knows not, though he sometimes thinks he senses it. But without deeper reflection one knows from daily life that one exists for other people -- first of all for those upon whose smiles and well-being our own happiness is wholly dependent, and then for the many, unknown to us, to whose destinies we are bound by the ties of sympathy. "I have never looked upon ease and happiness as ends in themselves -- this critical basis I call the ideal of a pigsty. "My passionate sense of social justice and social responsibility has always contrasted oddly with my pronounced lack of need for direct contact with other human beings and human communities. "My political ideal is democracy. "This topic brings me to that worst outcrop of herd life, the military system, which I abhor... "The most beautiful experience we can have is the mysterious. See also Einstein's Third Paradise, an essay by Gerald Holton
Quantum time travel: Black hole not required - physics-math - 22 November 2010 You don't need to set the universe in a spin to see time travel in action – so what happened when a photon with a quantum gun went back to kill itself? CHATTING about time travel in a room overlooking a verdant quadrangle at the Massachusetts Institute of Technology seems strangely appropriate. The building dates from 1916 and looks its age: the high ceilings, echoing corridors and musty offices with heavy wooden doors have changed little in that time. If it weren't for a computer screen in the corner, the room's interior could almost date from that time. The office belongs to Seth Lloyd, one of the world's leading theorists on quantum mechanics. We are talking about a paper he and his colleagues circulated a month or so earlier describing a subtle new twist on time travel.
Einstein for Everyone Einstein for Everyone Nullarbor Press 2007revisions 2008, 2010, 2011, 2012, 2013 Copyright 2007, 2008, 2010, 2011, 2012, 2013 John D. All Rights Reserved John D. An advanced sequel is planned in this series:Einstein for Almost Everyone 2 4 6 8 9 7 5 3 1 ePrinted in the United States of America no trees were harmed web*bookTM This book is a continuing work in progress. January 1, 2015. Preface For over a decade I have taught an introductory, undergraduate class, "Einstein for Everyone," at the University of Pittsburgh to anyone interested enough to walk through door. With each new offering of the course, I had the chance to find out what content worked and which of my ever so clever pedagogical inventions were failures. At the same time, my lecture notes have evolved. Its content reflects the fact that my interest lies in history and philosophy of science and that I teach in a Department of History and Philosophy of Science. This text owes a lot to many. i i i
How Quantum Suicide Works" A man sits down before a gun, which is pointed at his head. This is no ordinary gun; it's rigged to a machine that measures the spin of a quantum particle. Each time the trigger is pulled, the spin of the quantum particle -- or quark -- is measured. Depending on the measurement, the gun will either fire, or it won't. If the quantum particle is measured as spinning in a clockwise motion, the gun will fire. If the quark is spinning counterclockwise, the gun won't go off. Nervously, the man takes a breath and pulls the trigger. Go back in time to the beginning of the experiment. But, wait. This thought experiment is called quantum suicide.
Einstein's sceptics: Who were the relativity deniers? - physics-math - 18 November 2010 When people don't like what science tells them, they resort to conspiracy theories, mud-slinging and plausible pseudoscience – as Einstein discovered "THIS world is a strange madhouse," remarked Albert Einstein in 1920 in a letter to his close friend, the mathematician Marcel Grossmann. "Every coachman and every waiter is debating whether relativity theory is correct. Einstein's general theory of relativity, published in 1915, received an overwhelming public response - not all of it positive. Many of today's physicists and astronomers (not to mention science journalists) continue to receive this kind of mail.