New Scientist: Leaky microwaves can power your kitchen gadgets. http://google.com/producer/s/CBIw2ZG3tQI
Category: A-Level Physics
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Sep 19 2013
T2K neutrino experiment reports new oscillation results
Ben Still, who works on the T2K neutrino experiment in Japan, describes the new result they have reported today at the European Physical Society meeting in Stockholm..
For the first time ever the ghosts of the particle world, neutrinos, have been explicitly seen to actively change personality. Results presented today by the Tokai to Kamioka (T2K) experiment fills in previously unseen parts of the picture of how our universe works at the smallest scales, but it also raises some interesting questions.
Neutrino particles are ghostly, difficult to see, particles that have real personality issues. They come in three types, known as flavours: electron (νe), muon (νμ) and tau (ντ) neutrinos. The first neutrino experiments used naturally occurring sources of the particles, such as the Sun (electron neutrinos) and cosmic ray particle showers (muon neutrinos), to understand more about how they interacted with the world around them. They seemed to be misbehaving according to either experiment or theory as fewer neutrinos were seen than were predicted. For years neutrinos in nature seemed to be disappearing between being created and then detected in many various experiments that looked for them. After almost 30 years of experimentation all was finally resolved. It was proven that naturally occurring neutrinos were not disappearing, but instead were changing into other types of neutrino which could not be seen, due to having too low an energy.
Beams have now been engineered to further investigate this bizarre characteristic now known as oscillation. These beams are specifically muon-type neutrinos because physicists copied cosmic ray particle showers in nature. Experiments saw the muon-type neutrinos disappearing as expected from natural observation. Because of the disappearance they were assumed to be changing into tau-type neutrinos, which did not have enough energy to produce a tau particle and be directly seen.
For the first time neutrinos have actively been seen to change from one flavour to another rather than just viewing a disappearance. The T2K experiment has seen muon neutrinos change character to become electron neutrinos after a journey of 295km across Japan. The certainty of this measurement is quoted as 7.5 standard deviations from zero or to put in terms of percentage over 99.9999999999936% sure that the appearance is occurring.
History has shown us that the more we understand about neutrinos the more secrets of nature they uncover. The observation made by T2K opens up a whole new way of observing neutrinos. As we continue to piece together the character of the neutrinos we hope to continue uncovering more bizarre secrets; they may even be the key to how the raw material for the Universe was first created.
Ben Still is a particle physicist at Queen Mary, University of London
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Sep 19 2013
French physicist Léon Foucault celebrated in Google doodle
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Sep 14 2013
Nuclear plants’ no cancer risk
Children living near nuclear power plants do not have an increased risk of developing leukaemia, a study says.
Experts looked at data on 10,000 children diagnosed under five between 1962 and 2007, and where they lived.
The British Journal of Cancer study is not the first to rule out a link – but previous studies’ methods were challenged.
Cancer Research UK said the results were “heartening” but added monitoring should continue.
Leukaemia is the twelfth most common cancer in the UK, but accounts for a third of all cancers diagnosed in children.
Around 500 new cases were diagnosed in children under the age of 15 in 2010 in the UK.
Concern over a link between nuclear power plants and childhood cancers was triggered in the early 1980s when a TV investigation reported a higher number of cases among children living near the Sellafield plant in Cumbria.
Since then, there have been conflicting reports from studies in the UK and the rest of Europe as to whether there is a link.
Some anti-nuclear groups have criticised the way previous studies have been carried out.
They point to a German study which suggested there could be a link.
In this latest study, carried out using the same method as the German one, experts from the Childhood Cancer Research Group in Oxford looked at data on almost 10,000 children who were diagnosed with leukaemia or similar cancers in Britain between 1962 and 2007 when aged five or under.
“The incidence of childhood leukaemia near nuclear installations in Great Britain has been a concern ever since the 1980s” Dr John Bithell,Childhood Cancer Research Group
The data was taken from the National Registry of Childhood Tumours, which has kept records on nearly all children diagnosed with cancer since 1962 and which is linked to birth records for children born in Britain.
They looked at where these children were born and where they lived when they were diagnosed.
They also compared the information with data on more than 16,000 children with different cancers.
The study found there was no apparent increased risk of developing childhood leukaemia or non-Hodgkin lymphoma among children living near nuclear power plants.
Dr John Bithell, honorary research fellow at the Childhood Cancer Research Group who led the study, said: “The incidence of childhood leukaemia near nuclear installations in Great Britain has been a concern ever since the 1980s when an excess of cancer in young people near Sellafield was reported in a television programme.
“Since then, there have been conflicting reports in the UK and Europe as to whether there is an increased incidence of childhood cancer near nuclear power plants.
“Our case-control study has considered the birth records for nearly every case of childhood leukaemia born in Britain and, reassuringly, has found no such correlation with proximity to nuclear power plants.”
Cancer Research UK said the study did support previous findings, but said its small numbers and the fact it did not look at plants which carried out other work such as fuel processing – plus the finding of an increased risk in the German study – meant more work was needed.
Hazel Nunn, head of health information, said: “It’s heartening that this study supports the findings of the Committee on Medical Aspects of Radiation in the Environment (COMARE), that being born or living near a nuclear power station doesn’t lead to more cases of leukaemia and similar cancers in children under five in the UK.
“But these results can’t rule out any possible risk, so it’s still important that we continue to monitor both radiation levels near nuclear power plants and rates of cancer among people who live close by.
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Aug 07 2013
‘Critical phase’ for fusion dream http://www.bbc.co.uk/news/science-environment-23408073
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Jul 26 2013
Secret of Bolt’s speed unveiled http://www.bbc.co.uk/news/science-environment-23462815
Secret of Usain Bolt’s speed unveiled
By Melissa HogenboomScience reporter, BBC News
Scientists say they can explain Usain Bolt’s extraordinary speed with a mathematical model.
His 100m time of 9.58 seconds during the 2009 World Championships in Berlin is the current world record.
They say their model explains the power and energy he had to expend to overcome drag caused by air resistance, made stronger by his frame of 6ft 5in.
Writing in the European Journal of Physics, the team hope to discover what makes extraordinary athletes so fast.
According to the mathematical model proposed, Bolt’s time of 9.58 seconds in Berlin was achieved by reaching a speed of 12.2 metres per second, equivalent to about 27mph.
The team calculated that Bolt’s maximum power occurred when he was less than one second into the race and was only at half his maximum speed. This demonstrates the near immediate effect of drag, which is where air resistance slows moving objects.
They also discovered less than 8% of the energy his muscles produced was used for motion, with the rest absorbed by drag.
When comparing Bolt’s body mass, the altitude of the track and the air temperature, they found out that his drag coefficient – which is a measure of the drag per unit area of mass – was actually less aerodynamic than that of the average man.
Jorge Hernandez of the the National Autonomous University of Mexico said: “Our calculated drag coefficient highlights the outstanding ability of Bolt. He has been able to break several records despite not being as aerodynamic as a human can be.
“The enormous amount of work that Bolt developed in 2009, and the amount that was absorbed by drag, is truly extraordinary.
“It is so hard to break records nowadays, even by hundredths of a second, as the runners must act very powerfully against a tremendous force which increases massively with each bit of additional speed they are able to develop.
“This is all because of the ‘physical barrier’ imposed by the conditions on Earth. Of course, if Bolt were to run on a planet with a much less dense atmosphere, he could achieve records of fantastic proportions.
“The accurate recording of Bolt’s position and speed during the race provided a splendid opportunity for us to study the effects of drag on a sprinter.
“If more data become available in the future, it would be interesting to see what distinguishes one athlete from another,” added Mr Hernandez.
Bolt’s time in Berlin was the biggest increase in the record since electronic timing was introduced in 1968.
John Barrow at Cambridge University who has previously analysed how Bolt could become even faster, explained that his speed came in part due his “extraordinary large stride length”, despite having such an initial slow reaction time to the starting gun.
“He has lots of fast twitch muscle fibres that can respond quickly, coupled with his fast stride is what gives him such an extraordinary fast time.”
He said Bolt has lots of scope to break his record if he responded faster at the start, ran with a slightly stronger tail-wind and at a higher altitude, where there was less drag.
Bolt’s Berlin record was won with a tail wind of only 0.9m per second, which didn’t give him “the advantage of helpful wind assistance”, he added.
“You’re allowed to have a wind no greater than 2m per second to count for record purposes, so without becoming any faster he has huge scope to improve,” Prof Barrow told BBC News.
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Jul 21 2013
Neutrino ‘flavour’ flip confirmed http://www.bbc.co.uk/news/science-environment-23366318
An important new discovery has been made in Japan about neutrinos. These are the ghostly particles that flood the cosmos but which are extremely hard to detect and study. Experiments have now established that one particular type, known as the muon “flavour”, can flip to the electron type during flight. The observation is noteworthy because it allows for the possibility that neutrinos and their anti-particle versions might behave differently. If that is the case, it could be an explanation for why there is so much more matter than antimatter in the Universe. Theorists say the counterparts would have been created in equal amounts at the Big Bang, and should have annihilated each other unless there was some significant element of asymmetry in play.
“The fact that we have matter in the Universe means there have to be laws of physics that aren’t in our Standard Model, and neutrinos are one place they might be,” Prof Dave Wark, of the UK’s Science and Technology Facilities Council (STFC) and Oxford University, told BBC News. The confirmation that muon flavour neutrinos can flip, or oscillate, to the electron variety comes from T2K, an international collaboration involving some 500 scientists. The team works on a huge experimental set-up that is split across two sites separated by almost 300km. At one end is the Japan Proton Accelerator Research Centre (J-Parc) located on the country’s east coast.
The ‘ghostly’ neutrino particle
- Second most abundant particle in the Universe, after photons of light
- Means ‘small neutral one’ in Italian; was first proposed by Wolfgang Pauli in 1930
- Uncharged, and created in nuclear reactions and some radioactive decay chains
- Shown to have a tiny mass, but hardly interacts with other particles of matter
- Comes in three flavours, or types, referred to as muon, tau and electron
- These flavours are able to oscillate – flip from one type to another – during flight
- Could be a Majorana particle – that is a particle that is equal to its anti-particle
It generates a beam of muon neutrinos that it fires under the ground towards the Super-Kamiokande facility on the west coast. The Super-K, as it is sometimes called, is a tank of 50,000 tonnes of ultra-pure water surrounded by sensitive optical detectors. These photomultiplier tubes pick up the very rare, very faint flashes of light emitted when passing neutrinos interact with the water.
In experiments in early 2011, the team saw an excess of electron neutrinos turning up at Super-K, suggesting the muon types had indeed changed flavour en route. But just as the collaboration was about to verify its findings, the Great Tohoku Earthquake damaged key pieces of equipment and took T2K offline. Months of repairs followed before the project was able then to gather more statistics and show the muon-electron oscillation to be a formal discovery. Details are being reported on Friday at the European Physical Society Conference on High Energy Physics in Stockholm, Sweden.
“Up until now the oscillations have always been measured by watching the types disappear and then deducing that they had turned into another type. But in this instance, we observe muon neutrinos disappearing and we observe electron neutrinos arriving – and that’s a first,” said Prof Alfons Weber, another British collaborator on T2K from the STFC and Oxford.
Neutrino oscillations are governed by a matrix of three angles that can be thought of as the three axes of rotation in an aeroplane – roll, pitch and yaw. Other research has already shown two of the matrix angles to have non-zero values. T2K’s work confirms that the third angle – referred to as theta-one-three – also has to have a non-zero value.
This is critical because it allows for the oscillations of normal neutrinos and their anti-particles, anti-neutrinos, to be different – that they can have enough degrees of freedom to display an asymmetrical behaviour called charge parity (CP) violation. CP-violation has already been observed in quarks, the elementary building blocks of the protons and neutrons that make up atoms, but it is a very small effect – too small to have driven the preference for matter over anti-matter after the Big Bang. However, if neutrinos can also display the asymmetry – and especially if it was evident in the very massive neutrinos thought to have existed in the early Universe – this might help explain the matter-antimatter conundrum. The scientists must now go and look for it. It is likely, though, that much more powerful neutrino laboratories than even T2K will be needed to investigate the issue.
“We have the idea for a Hyper-Kamiokande which will require an upgrade of the accelerator complex,” Prof Weber told BBC News.
“And in America there’s something called the LBNE, which again would have bigger detectors, more sensitive detectors and more intense beams, as well as a longer baseline to allow the neutrinos to travel further.”
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