Elementary Particle Explorer Welcome to the Elementary Particle Explorer, designed by Garrett Lisi and Troy Gardner. Every known elementary particle is identified by its charges with respect to the electromagnetic, weak, strong, and gravitational forces. Electrons have electric charge -1, up quarks 2/3, down quarks -1/3, and neutrinos 0, with antiparticles having opposite electric charges. In the Standard Model, as you are about to see, these electric charges are a combination of the particles' hypercharge, Y, and weak charge, W. The Elementary Particle Explorer (EPE) allows you to rotate in charge space (by dragging the image), showing the charges of all known particles. These charges correspond to the geometry of Lie groups, and unified models of particle physics correspond to how the Lie groups of the Standard Model and gravity embed in larger Lie groups, up to the largest simple exceptional Lie group, E8.
Incriminating booze tests face fresh scrutiny - health - 10 February 2011 Fail an alcohol test and you could lose your job. But confidence is draining from the blood and urine tests that are supposed to show conclusively whether someone has been drinking – and the US government has decided it's time to take another look at them. Typically, the body destroys alcohol within 6 hours, so the tests are designed to pick up tiny amounts of substances such as ethyl glucuronide (EtG) and ethyl sulphate (EtS) that are formed exclusively from the breakdown of alcohol. These remain detectable in urine for almost a week. But the tests can return a positive result in people who haven't drunk any alcohol but have been exposed to minute quantities of it in alcohol-based hand-wipes and mouthwashes, alcohol-free wine, and even foods such as bananas and sauerkraut. In the US, several legal cases are under way in which doctors, nurses and other professionals who were being monitored for abstinence but tested positive are protesting their innocence. Inappropriate action
Vacuum has friction after all - space - 11 February 2011 A BALL spinning in a vacuum should never slow down, since no outside forces are acting on it. At least that's what Newton would have said. But what if the vacuum itself creates a type of friction that puts the brakes on spinning objects? The effect, which might soon be detectable, could act on interstellar dust grains. In quantum mechanics, the uncertainty principle says we can never be sure that an apparent vacuum is truly empty. Now, Alejandro Manjavacas and F. So over time, a spinning object will gradually slow down, even if equal numbers of virtual photons bombard it from all sides. The strength of the effect depends on the object's make-up and size. The rate of deceleration also depends on temperature, since the hotter it is the more virtual photons pop in and out of existence, producing the friction. Could this effect be tested in the lab? How to float above a vacuum Houdini would be proud. More From New Scientist Lip-reading computers unlock with a word (New Scientist)
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?
'Lightfoil' soars on a stream of photons - physics-math - 06 December 2010 Light has been used to generate aerodynamic-like lift for the first time. The technique, which takes advantage of the fact that light bends, or refracts, when moving from one medium to another, could be used to create solar-sail spacecraft that could steer using light itself. Photons create pressure when they bounce off objects. Solar sail prototypes are made highly reflective to maximise this push, but the effect does not allow the sails to be easily steered. He says future sails could be manoeuvred if the photons did not just rebound off the material's surface but passed through it. Swartzlander and his colleagues demonstrated the effect in the lab with semi-circular plastic rods, each just a fraction of the size of a human hair. Asymmetrical shape They put the rods in a container of water, then shined laser light on them from below. The fact that the rods' asymmetrical shape affected their movement makes them the optical equivalent of aeroplane wings, or aerofoils, says the team.
Higgs hunt may delay LHC's planned shutdown - physics-math - 13 December 2010 Physicists are considering delaying a planned shutdown of the Large Hadron Collider by a year to keep hot on the trail of the elusive Higgs particle. Located near Geneva, Switzerland, the LHC is the most powerful particle smasher ever built, designed to produce collisions at energies up to 14 trillion electron volts (TeV). It was built to look for the Higgs particle, which is thought to endow other subatomic particles, such as electrons, with mass. But the LHC's ramp-up to full energy has been slower than expected. Now the LHC's managers are considering delaying the shutdown by a year, to the end of 2012. "A discovery could be just around the corner and we want to keep up the momentum," says Ian Shipsey of Purdue University in West Lafayette, Indiana. Rival collider News about the possible change in plans comes in the wake of recommendations in September and October to extend the search for the Higgs at the Tevatron. In fact, he hopes both extensions will be approved. Promoted Stories
Less is more when measuring fragile atomic bonds - physics-math - 15 December 2010 IF YOU want to look at individual atoms, it helps to have a powerful microscope. But for delicate situations such as a lone atom on the edge of a sheet of carbon atoms, a high-energy beam can disturb the bonds that hold such atoms in place, making them difficult to study. Now, for the first time, a low-energy beam has been used to count these bonds. In the past, beams of high-energy electrons have been used to probe individual atoms. For example, such an electron beam was used to identify single atoms of so-called "rare earth" elements that were trapped inside buckyballs, round cages made of carbon atoms. Probing atoms in other situations, however, may require more delicate methods. In principle, the energy spectra of electrons scattered off an edge atom can be used to count the bonds. Suenaga and Koshino took advantage of a new electron microscope that was capable of precisely resolving the spectra of scattered electrons, even if they were of relatively low energy. More from the web
No black holes found at LHC – yet - physics-math - 17 December 2010 The Large Hadron Collider has not yet seen any of the microscopic black holes that inspired numerous scare stories in recent years. Many theorists actually hope the collider, based near Geneva, Switzerland, will create short-lived, miniature black holes. These would not pose a threat to Earth, but they would provide evidence for hypothetical extra dimensions that might lie beyond the 3D world we normally experience. If these dimensions exist, gravitons, the particles thought to transmit the force of gravity, could leak into them, providing a much-needed explanation for why gravity is much weaker than the other forces. At the high energies created inside the LHC, though, colliding protons could be affected even by gravitons in the extra dimensions, making gravity strong enough to create fleeting black holes. Inside the LHC, black holes would produce an excess of high-energy particles at right angles to the proton beam. More From New Scientist More from the web Recommended by
New Scientist Short Sharp Science Blog: Why the world WON'T end on September 10 Hurray for the European Court of Human Rights. It has rejected an emergency injunction to block the Large Hadron Collider from turning on on 10 September. It's the latest legal case brought against the LHC by scientists who fear that the world's largest particle accelerator will produce fearsome entities that could destroy the Earth. I'm thrilled that the ECHR has understood the science and has given the LHC the green light. Here's why. Instead, a lone beam of protons will make its way round with just 450 gigelectronvolts of energy. Supposing this does happen, the collision energy will be a paltry 30 gigaelectronvolts (30 GeV). OK, so we have a reprieve of a few months until physicists finish their tests and start creating collisions with 14 TeV of energy. Theorists have speculated about all manner of things popping into existence, including the infamous mini black holes. Really, I don't think so. No, for me, there is a much more compelling argument why the LHC won't destroy the world.
Tree-like giant is largest molecule ever made - physics-math - 07 January 2011 Meet PG5, the largest stable synthetic molecule ever made. With a diameter of 10 nanometres and a mass equal to 200 million hydrogen atoms, this huge molecule festooned with tree-like appendages, paves the way to sophisticated structures capable of storing drugs within their folds, or bonding to a wide variety of different substances. Complex macromolecules abound in nature and PG5 is about the same size as tobacco mosaic virus. But making such large molecules in the lab is tough, as they tend to fall apart while they are being made. "Synthetic chemistry so far was simply not capable of approaching the size range of such functional units," says Dieter Schlüter at the Swiss Federal Institute of Technology in Zürich. Previously, polystyrene was the largest stable synthetic molecule, at 40 million hydrogen masses. To create their molecular giant, Schlüter and his colleagues started with standard polymerisation, in which smaller molecules join up to form a long chain. Outrageous trick (YouTube)