TOP 100 SCIENCE SITES
| |||
|
| |||
| |||
|
| |||
| LHC becomes world's most powerful particle accelerator In the early hours of this morning the Large Hadron Collider (LHC) at Cern accelerated beams of particles to higher energies than any achieved beforeScientists at the Large Hadron Collider at Cern near Geneva are celebrating a major milestone after the machine broke energy records overnight to become the most powerful particle accelerator in the world.At 12.44am this morning, the LHC accelerated beams of subatomic particles to higher energies than any achieved before in a collider.The machine, which occupies a 27km circular tunnel that straddles the French-Swiss border, was restarted 10 days ago after being shut down for more than a year while engineers repaired damage caused by a helium leak when it was first switched on in September last year."The machine is working like a dream," Lyn Evans, project manager of the LHC, told the Guardian. "It's brilliant. By the end of the week we should be really moving."Inside the particle accelerator, two counter-rotating beams of hydrogen nuclei are whipped up to more than 99.99% the speed of light. At four points around the machine the beams are crossed, steering the particles into high-energy smash-ups. The collisions recreate in microcosm the conditions that existed moments after the big bang.According to Einstein's famous equation E = mc2, the energy released by the collisions can create matter in the form of particles that appear in the collider's detectors.Scientists hope that when they sift through the subatomic debris they will find particles that are new to physics, such as the Higgs boson, which gives mass to elementary particles, and possibly particles of dark matter, an elusive substance that clusters around galaxies and accounts for most of the mass in the universe.At 9.48pm last night, engineers at Cern accelerated one beam of particles to 1.05 trillion electronvolts. Three hours later, both beams were hurtling around the machine, each with an energy of 1.18 trillion electronvolts. The energies are greater than any achieved at what is now the second most powerful collider in the world, the Tevatron at Fermilab on the outskirts of Chicago."For me, it's not so much the energy record that matters, it's that we've got through the start of the acceleration process where things are changing rapidly," Evans said. As the beams are accelerated, eddy currents build up in the enormous superconducting magnets inside the machine and produce erratic magnetic fields that affect how the beams behave.In the next few days, Cern managers will decide whether to start colliding particles at even greater energy, or run for a short time at lower energies. Scientists will use the first collisions to calibrate their detectors, ensuring they pick up any particles that might be produced under the known laws of physics."We're about to move into a new energy regime, and when we do that, we can start to see new things," Evans said."We are still coming to terms with just how smoothly the LHC commissioning is going. It is fantastic," said Rolf Heuer, Cern's director general. "We are continuing to take it step by step, and there is still a lot to do before we start physics in 2010. I'm keeping my champagne on ice until then."Over the next week, engineers will increase the beam intensity to a level that is expected, before Christmas, to reveal new physics at work. The first extended series of high-energy collisions is expected to start in January or February next year, when each beam will be accelerated to 3.5 trillion electronvolts."I was here 20 years ago when we switched on Cern's last major particle accelerator, LEP," said Steve Myers, Cern's director of accelerators and technology, referring to the Large Electron Positron collider, which smashed electrons into their antimatter counterparts, positrons."I thought that was a great machine to operate, but this is something else. What took us days or weeks with LEP we're doing in hours with the LHC. So far, it all augurs well for a great research programme."CernParticle physicsPhysicsSwitzerlandFranceIan Sampleguardian.co.uk © Guardian News & Media Limited 2009 | Use of this content is subject to our Terms & Conditions | More Feeds guardian.co.uk |
How three wise men and a tube helped us find our place in the universe As the International Year of Astronomy draws to a close, Tim Radford nominates Seeing and Believing by Richard Panek as the definitive guide to the revolution wrought by the telescopeThe telescope changed our lives, and this book is about how it happened. Seeing and Believing tells only a fraction of a 400-year-story, and – since it was written in 1998 – it cannot even hint at the last decade of eye-opening discoveries. It is furthermore a very short book, so its scope is constrained. If you want to know how to design, fabricate and use your own telescope, this book will be no help.But Seeing and Believing is still my candidate for the best introduction to this founding instrument of the scientific revolution. The key words in the subtitle are "how we found our place in the universe", and Panek's account reminds us in short and vivid ways of the disorderly progress of scientific discovery. For instance, we learn that Galileo did not "invent" the telescope in 1609, as is popularly supposed, nor was he even the first to think of using it for scientific exploration. Roger Bacon had predicted the "wonders of refracted vision" in 1267 and, more than three decades before Galileo, at least two writers had described peering into the distance with the aid of lenses.Nor was Galileo the first to look at the heavens through a spyglass: the Englishman Thomas Harriot beat him to it by months, but failed to tell anybody. But in November 1609 Galileo began to use two lenses in a cylinder to look at the moon, Jupiter and the sun, and recognised the significance of what he saw. He saw that the moon's topography was Earth-like, that Jupiter had moons and that the sun had spots.This was all very unorthodox and heretical, and Panek offers a vivid snapshot of the medieval cosmology that Copernicus, Kepler and Galileo between them overturned: the celestial order in which an imperfect Earth was the centre of the universe, and the moon, sun and stars revolved about it, set in perfect, crystalline spheres of increasing moral excellence.The planets – the "wanderers" – required a bit of explaining, which is why the story starts with them. And if the moon had mountains and seas, like Earth, then it wasn't as "heavenly" as had been supposed. If Jupiter had moons revolving about it, then it had something in common with Earth: they were both planets. And the "wandering" of the planets made geometrical sense if the Sun was the centre of creation, rather than the Earth.Why should we believe long-dead authorities such as Aristotle and Ptolemy when our eyes tell us something different? Why rely on ancient authors when we can open the book of nature and read a different and better story?The revolution proceeded erratically, but within two generations amazing things had happened. The first telescopes presented problems of focal length, chromatic aberration, narrow field of view and so on. You could see planetary furniture that you had never seen before, but the stars remained enigmatic points of light. Galileo, with a smugness that his contemporaries must have found ever so annoying, was convinced he had discovered almost all there was to discover: "It was granted to me alone to discover all the new phenomena in the sky and nothing to anybody else."Some people, including Christopher Wren, believed him. Some people continued to believe that the naked eye was a better instrument than two lumps of glass in a tube. But the new community of lens-grinding astronomers got on with the challenge. If the sun was the centre of our world, how far away was it? If light was the agency of discovery, was it instantaneous, or did it move? If so, how fast did it move?In 1676, less than one lifetime on from Galileo, the Danish astronomer Ole Romer predicted an eclipse of a Jovian moon, and having calculated the changing orbital locations of the Earth and Jupiter at that time, boldly claimed that the eclipse would be visible 10 minutes later than expected. He was dead right, and he used the result to settle the matter: light moved, at a speed of 140,000 miles a second. Given the quality of the clocks and observing instruments of the day, that was pretty close to the true figure.To make such a calculation, he and other astronomers had to have an idea of the diameter of the Earth's orbit, and they got a good ballpark figure in the same decade. By 1728, the English astronomer James Bradley had used this value for the Earth's orbital journey to try to calculate the distance to a star by observing from two separate points. Look at something first with one eye covered, and then the other, and see how the observed object seems to move. The apparent shift in position is called the parallax, and the nearer the object the bigger will be the parallax.From his standpoint on the Earth in orbit, Bradley tried to measure the stellar distance by making observations six months and therefore (we now know) 186 million miles apart. He could detect no apparent movement, but he used this negative result to calculate that, because he could observe no parallax, therefore the nearest star (apart from the sun) must be at least 36 trillion miles away.So, in less than two lifetimes, astronomers already had a grasp of the depth of space. Heaven wasn't a "vault", it was somewhere that went on and on. They also rather gave up on the stars until the Hanoverian William Herschel came along and with the innocence of the amateur, built better telescopes and looked at the whole sky, spotted Uranus, discovered infra-red radiation and formulated in a sentence the significance of a finite value for the speed of light: "A telescope with the power of penetrating into space, has also, it may be called, a power of penetrating into time past."By 1859, someone had used a spectroscope to identify the elemental make-up of the sun; by 1888, a camera fitted to a telescope had collected enough light to discern the spiral structure of Andromeda; and within another lifetime, Edwin Hubble had confirmed that the Milky Way galaxy wasn't the beginning and the end of the universe, it was just a speck of matter in the enormity of everything.The story goes on, and Panek's version of it reminds us that such revolutionary discoveries arose from a worldwide, non-stop, free-for-all of competing, collaborating and communicating enthusiasts, who often bickered, but also generously exchanged their data, their ideas, and their techniques.We have an "exaltation" of larks and a "charm" of finches, but what's the right collective noun for a bunch of astronomers? How about a focus group?In the querulous crossfire that followed last month's book on race, IQ and dubious anthropology, @EndPseudoscience suggested that club members might look at a book by Jared Diamond which "explains this subject very well." Thanks, EP, the club will be back in February and the next book is indeed Guns, Germs, and Steel by Jared DiamondAstronomySpacePeople in scienceScience and natureTim Radfordguardian.co.uk © Guardian News & Media Limited 2009 | Use of this content is subject to our Terms & Conditions | More Feeds guardian.co.uk |
Letters: Call Me Doctor (1 Letter) To the Editor:. feeds.nytimes.com |
Australians cutting greenhouse emissions: report A new report has revealed that greenhouse gas emissions from energy use in Australia's eastern states have fallen by 1.8 per cent. abc.net.au |
Resurgence of rickets in UK Sharp rise in problem blamed on kids indoors playing computers and parents using too much sunscreenComputer-obsessed children who spend too long indoors and over-anxious parents who slap on excessive sunscreen are contributing to a sharp rise in cases of the bone disease rickets, doctors are warning.Vitamin D deficiency, which causes the condition, could be rectified by adding supplements to milk and other food, a research team at Newcastle University suggests.There are several hundred cases of the preventable condition among children in the UK every year, according to a clinical review paper in the British Medical Journal by Professor Simon Pearce and Dr Tim Cheetham."More than 50% of the adult population [in the UK] have insufficient levels of vitamin D and 16% have severe deficiency during winter and spring," they say. "The highest rates are in Scotland, Northern Ireland and northern England. People with pigmented skin are at high risk as are the elderly, obese individuals and those with malabsorption."Most vitamin D is synthesised in the body by absorption of sunlight. Some comes from foods such as fish oil. People with darker skins need more sunlight to top up their vitamin D levels.One of the main reasons for the reappearance of rickets – once considered a disease of the industrial poor in 19th-century cities – is the changing ethnic makeup of the population, Pearce explained.The most commonly affected are people of Asian or African descent who live in northern cities. He has examined cases among young Somali speakers who live in east Newcastle. But changing lifestyles are also contributing to lowering vitamin D levels in the general population."Some people are taking the safe sun message too far," Pearce said. "It's good to have 20 to 30 minutes of exposure to the sun two to three times a week, after which you can put on a hat or sunscreen."Vitamin D levels in parts of the population are precarious. The average worker nowadays is in a call centre, not out in the field. People tend to stay at home rather than going outside to kick a ball around. They stay at home on computer games."Pearce has written to the Department of Health proposing that vitamin D is added to milk. It is already added as a supplement to artificial baby milk. He has also asked the Royal College of Paediatrics to record cases of rickets but said figures were not being collected."A more robust approach to statutory food supplementation with vitamin D (for example in milk) is needed in the UK," the paper concludes.Meanwhile, figures obtained by the Tories show the number of patients leaving hospital with malnutrition has hit record levels in the last year. Those affected are primarily elderly people. The NHS figures show that last year 175,000 people were malnourished on entry to hospital but nearly 185,500 were in a similar condition on discharge, meaning more than 10,000 patients were more malnourished after medical treatment.HealthGame cultureChildrenNutritionNutritionMedical researchOwen Bowcottguardian.co.uk © Guardian News & Media Limited 2010 | Use of this content is subject to our Terms & Conditions | More Feeds guardian.co.uk |