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May 27, 2011 10:48 pm
The world’s most powerful atom smasher, the Large Hadron Collider at Cern near Geneva, has been running at full tilt for more than a year. Yet, despite rumours on the internet of exciting discoveries, the thousands of scientists working on the LHC have not yet found the elusive Higgs boson, or previously hidden dimensions of space or indeed any “new physics”.
Cern’s top scientists, gathered at the Royal Society in London last week to discuss the latest LHC results, asked the media not to expect too much too soon. They want another 18 months to find out whether the Higgs boson – the subatomic particle supposedly responsible for the fundamental property of mass – actually exists.
“I’m pretty confident that towards the end of 2012 we will have an answer to the Shakespeare question for the Higgs boson: to be or not to be?” said Rolf Heuer, Cern director-general.
If the Higgs does appear in the seething subatomic debris as the LHC smashes together protons at almost the speed of light, scientists will have put in place the last important piece in the “standard model” of physics they have built up since the mid-20th century. And Peter Higgs, the Edinburgh University theorist who proposed the particle’s existence in the 1960s, will win a Nobel Prize.
But if no trace of the Higgs boson emerges at the energy ranges predicted to generate the particle, its absence could be just as exciting – and could prompt a rethink of the framework of theoretical physics.
Discovering a subatomic particle is not a single eureka moment but a statistical process of analysing billions of collisions and terabytes of data for evidence of something new. Last month a small group of researchers at Atlas, one of the LHC’s four giant subterranean detectors, thought they had evidence for the Higgs particle and sent an e-mail to their colleagues – which then leaked to the outside world, causing great excitement on the physics blogosphere.
Sadly, the evidence evaporated on further analysis. “It was wrong,” said Fabiola Gianotti, Atlas research co-ordinator. “We see no peak and no evidence of a Higgs boson.”
Cern scientists were “not very amused” by the leak, Heuer said. “This should be a lesson to journalists not to report results they might see from blogs,” he chided. “If we do discover something and we are sure of it, we will announce it officially. Any other news is speculative.”
Heuer’s plea may be unrealistic, given the nature of the media today. Any really exciting scientific news – whether it’s the discovery of a new subatomic particle or a signal from an extraterrestrial civilisation – is likely to leak out before official confirmation.
The orphan planets without parent stars
Our galaxy may contain billions of free-floating planets, not bound to a parent star, according to an international study using telescopes in New Zealand and Chile.
The first 10 of these “orphan planets”, roughly the size of Jupiter, have been discovered by a Japanese-led team of astronomers who scanned the centre of the Milky Way galaxy. None had a star anywhere near them.
“Although free-floating planets have been predicted, they have now been detected, holding major implications for planetary formation and evolution models,” says Mario Perez, an exoplanet scientist at Nasa in Washington.
The discovery, published in the journal Nature, suggests that there are many more free-floating Jupiter-mass planets that can’t be seen. Extrapolating from their small survey, the astronomers estimate there are about twice as many independent planets as stars in the galaxy – hundreds of billions altogether.
“Our survey is like a population census,” says David Bennett of the University of Notre Dame in Indiana. “We sampled a portion of the galaxy, and, based on these data, can estimate overall numbers in the galaxy.”
The researchers say the most likely explanation for the planets’ solitary existence is that they were ejected from early, turbulent planetary systems in the process of formation, as a result of close gravitational encounters with other planets or stars. Without a star to orbit, these planets would move through the galaxy as our sun and other stars do, orbiting instead around the centre of the galaxy.
The astronomers could detect such dim and distant objects – typically 10,000 light-years away – through the phenomenon of microlensing. This takes place when light from a distant object (such as a planet) is bent and focused by a more massive object (such as a star) between it and the observer.
Why simple tattoos age best
Tattoos have become routine body adornment among young adults. Some choose a simple design, others have extremely intricate patterns inked onto their body, but few think decades ahead to how they will look in middle or old age.
To help predict the deterioration of tattoos over the years, Ian Eames, an expert in fluid mechanics at University College London, has produced what he says are the first computer models of the long-term movement of ink particles in skin. The results, published in the journal Mathematics Today, are not pretty.
“Skin type, age, size, exposure to sunlight and the type of ink used all influence how a tattoo disperses with time,” says Eames. “But broadly speaking, what my paper shows is that the small details in a tattoo are lost first, with thicker lines being less affected.
“Although finely detailed tattoos might look good when they are first done, they tend to lose their definition after 15 years – depending on how fine the lines are.”
There is no getting away from the fuzzing and fading of tattoos, because dermal cells are bound to divide and die over time, dispersing the ink particles within them.
The message of the study is that, if you want a tattoo that will look good after a lifetime, select a simple shape with large, bold lines rather than intricate details. Choose a design with blurring in mind.
Sixth sense and sensibility
Claims by a leading US psychologist, Daryl Bem of Cornell University, that he has statistically significant evidence for extrasensory perception (ESP) have caused a stir.
Not surprisingly, most mainstream scientists remain deeply sceptical about Bem’s studies, which show that volunteers are more likely to predict a future event – for example whether a picture will appear on the left or right side of a computer screen – than would be expected by chance alone.
Now Jeffrey Rouder of the University of Missouri and Richard Morey of the University of Groningen have applied a new statistical method to Bem’s work – and shown that sceptics need not change their mind. Their study appears in the Psychonomic Bulletin & Review.
Their “Bayes factor meta-analysis” combines the evidence across all nine of Bem’s experiments. They conclude that the studies do provide some evidence for ESP but not nearly enough to convince sceptics – including themselves.
Rouder and Morey say that people’s beliefs should be tilted by a factor of 40 in favour of ESP. So if you thought previously that there was just one chance in a million of ESP being genuine, you should revise that to one chance in 25,000 on the basis of Bem’s experiments.
“We remain unconvinced of the viability of ESP,” the scientists conclude. “There is no plausible mechanism for it, and it seems contradicted by well-substantiated theories in both physics and biology. Against this background, a change in odds of 40 is negligible.”
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