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Daily Archives: September 14, 2008

The CERN atom-smasher: A factfile

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Here is a snapshot of the world's biggest atom-smasher, due to start operations on Wednesday at CERN (the European Organisation for Nuclear Research) near Geneva:

— The Large Hadron Collider (LHC) will accelerate hydrogen protons or lead ions to more than 99.9999 percent of the speed of light. The experiments will take place in a ring-shaped tunnel 27 kilometres (16.9 miles) long and up to 175 metres (568 feet) below the ground. The tunnel stretches out from Swiss territory and into France, looping back into Switzerland.

— The beams run in parallel in opposite directions. Powerful superconducting magnets then "bend" the beams so that streams of particles collide within four large chambers. The smashups will fleetingly generate temperatures 100,000 hotter than the Sun, replicating the conditions that prevailed just after the "Big Bang" that created the Universe 13.7 billion years ago.

— Swathing the chambers are detectors which will give a 3-D image of the traces of sub-atomic particles hurled out from the protons' destruction. These traces are then closely analysed in the search for movements, properties or novel particles that could advance our understanding of matter.

— In top gear, the LHC will generate nearly a billion collisions per second. Above ground, a farm of 3,000 computers, one of the largest in the world, will instantly crunch this number down to about 100 collisions that are of the most interest. The data will then be sent out to a grid of institutions and universities around the world for analysis — a sort of mini-World Wide Web of its own.

— The tunnel is the world's largest fridge. The super-magnets are chilled to a temperature as low as -271 degrees Celsius (-456.25 degrees Fahrenheit), which is colder than deep outer space, to help them overcome resistance.

— The collision chambers are herculean in scale. The biggest, called ATLAS, is 46 metres (149.5 feet) long and 25 metres (81.25 feet) high, or about half the size of the Notre Dame Catheral in Paris. At 7,000 tonnes, ATLAS weighs almost as much as the Eiffel Tower, and has 3,000 kilometres (1,875 miles) of cabling. Nearly 300,000 tonnes of rock were dug to house ATLAS and 50,000 tonnes of concrete were poured. In one year, ATLAS will generate 3,200 terabytes of raw data, equivalent to 160 times the three billion books in the US Library of Congress.

— In the course of a 10-hour experiment, a beam might travel more than 10 billion kilometres (six billion miles), enough to get to Neptune and back. At full intensity, each beam will have the equivalent energy of a car travelling at 1,600 kilometres (1,000 miles) per hour. The LHC will use up 120 megawatts of power, equal to all the households in the Geneva area.

— LHC collisions will generate 14 teraelectron volts (TeV), amounting to a high concentration of energy but only at an extraordinarily tiny scale. One TeV is the equivalent energy of motion of a flying mosquito. There is no safety risk, says CERN.

— The LHC cost 6.03 billion Swiss francs (5.46 billion dollars, 3.9 3.76 billion euros) to build.

Old forests help curb global warming too

Old-growth forests remove carbon dioxide (CO2) from the atmosphere, helping to curb the greenhouse gases that drive global warming, according to a study published last week.
Many environmental policies are based on the assumption that only younger forests, mainly in the tropics, absorb significantly more CO2 than they release.
Partly as a result, primary forests in temperate and subarctic regions of the northern hemisphere are not protected by international treaties, and do not figure in climate change negotiations seeking ways to reward countries that protect carbon-absorbing woodlands within their borders.
Some 30 percent of global forest area — half old-growth — is unmanaged primary forest.
"Old-growth forests can continue to accumulate carbon, contrary to the long-standing view that they are carbon neutral," lead researcher Sebastiaan Luyssaert, a professor at the University of Antwerp in Belgium, said.
An international team led by Luyssaert analysed scores of databases set up to monitor the flow of carbon into and out of the world's vegetal ecosystems.
They calculated that primary forests in Canada, Russia and Alaska alone absorb about 1.3 gigatonnes of carbon per year, about ten percent of the net global carbon exchange between the ecosystem and the atmosphere.
These forests need to be protected not just because they help to absorb carbon dioxide, but also because destroying them could release huge stores of greenhouse gases.
"Old-growth forests accumulate carbon for centuries and contain large quantities of it," Luyssaert said. If these pools of CO2 "are disturbed, much of this CO2 will move back into the atmosphere," he added.
The new study, published in the London-based science journal Nature, suggests that UN climate change negotiations underway should also include incentives for northern hemisphere countries to protect their forests.
"The discussions should be expanded to include boreal and temperate forests in Canada and Russia," Luyssaert said.