What is the second law of thermodynamics?
Category Archive: A-Level Physics
Dec 03 2013
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Nov 29 2013
New Scientist News: Beer brewing could help make better bricks. http://google.com/producer/s/CBIw2Kfm0gM
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Nov 22 2013
IceCube detector finds first solid evidence for cosmic neutrinos
Thu 21 November 2013
Scientists have found the first solid evidence for cosmic neutrinos, ghostly particles created in violent events in the far reaches of the universe.
Neutrinos are subatomic particles that hardly ever interact with the atoms that make up stars, planets and us. Detecting them is tough: in the latest study, researchers detected 28 at the IceCube detector, built under the ice of the south pole.
“This is a huge result. It could mark the beginning of neutrino astronomy,” said Darren Grant, assistant professor of physics at the University of Alberta and one of the leaders of the IceCube Collaboration, which involves more than 250 physicists and engineers from a dozen countries.
Neutrinos are electrically uncharged particles that have a tiny mass, formed in the nuclei of atoms. Travelling at near the speed of light, they hardly interact with anything and could easily fly through a light year of lead. But there are unimaginable numbers of them in the universe: trillions of them from the sun pass through each of us every day.
Scientists know that neutrinos with even higher energy than those already observed should come from cosmic explosions, such as gamma ray bursts, black holes and active galactic nuclei, far away in the universe. Detecting these high-energy neutrinos would give scientists a way to peer inside some of the most violent processes going on at the farthest reaches of the cosmos.
Until now, scientists have used other detectors to see low-energy neutrinos created in cosmic-ray collisions in the Earth’s upper atmosphere and particles from a nearby supernova known as 1987A. The 28 neutrinos detected at IceCube are much higher energy and come from as yet unidentified sources far out in the cosmos. The results were published in the journal Science on Thursday.
“I’ll bet that 20 years from now we’ll look back and say, yeah, this was the start of neutrino astronomy,” John Learned, of the University of Hawaii, Manoa, told Science magazine.
To find the particles, scientists built a detector into a cubic kilometre of ice in Antarctica. After melting holes in the ice, they lowered 86 strings of light detectors, around 5,000 in total, to depths between 1.5km and 2.5km. Neutrinos can interact with atomic nuclei, and when that happens in the ice around a detector the collisions create an avalanche of charged light-emitting particles. That light can be measured by the detectors and, the brighter the light, the more energetic the original neutrino was.
IceCube has been on the hunt for neutrinos since 2010. Since then scientists have found evidence for 28 neutrinos with energies higher than 30 teraelectronvolts (TeV). Two of the particles had energies greater than 1,000 TeV. In comparison, the biggest particle accelerator ever made, the Large Hadron Collider at Cern, will collide particles at 14TeV when its upgrade is completed in 2015.
Since they do not interact with anything, the cosmic neutrinos found at IceCube are useful to scientists because they point in straight lines to where they came from. The few they detected are not enough to pinpoint any location in particular but, according to the project scientist Gregory Sullivan, of the University of Maryland, the IceCube team will look for further detections in coming years, “like waiting for a long exposure photograph”, to fill in their emerging picture of the faraway cosmos.
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Nov 08 2013
Physics probes ‘splashback’ problem http://www.bbc.co.uk/news/science-environment-24820279
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Oct 23 2013
The Higgs boson particle – digested
The Higgs boson particle – digested
The secret of life and the universe, explained by our science editor
An experimental result in the search for the Higgs boson particle, released by Cern.
In the aftermath of the big bang that flung the universe into existence 13.82bn years ago, the forces of nature were one. But as the universe expanded and cooled, they separated out into the four seen today. The electromagnetic force, which is carried by photons, allows you to see, and stops you falling through your chair.
The strong force holds atomic nuclei together. The weak force goes to work in the sun and helps to make it shine. Then there is gravity, which is not really a force at all, but that is for another time.
One trillionth of a second after the big bang, an invisible field that spread throughout space switched on. This Higgs field wrenched two intertwined forces apart – the weak force and the electromagnetic force. How? By making the particles that carry the weak force heavy, while leaving the photon weightless.
The weak force travels less than the width of an atom, but the electromagnetic force ranges over an infinite distance.
The Higgs field gives mass to other particles too, such as quarks and electrons, the building blocks of atoms. The Higgs boson comes with the field, a subatomic smoking gun that proves the field is there.
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Oct 18 2013
How to write a personal ucas statement for history
History is the tenth most popular subject to study at degree level in the UK, and with many universities forgoing candidate interviews, your personal statement is the most important way to make yourself stand out. The competition is fierce (the top universities require grades of A*AA), and a muddled or mediocre statement will harm your application.
So how can would-be historians impress application tutors? Dr Elizabeth Tingle, of Plymouth University, wants the statement to reflect the candidate who wrote it. She says: “When we talk about originality inpersonal statements, we really mean individuality.”
Southampton University’s Dr McHugh agrees that many applications are “too generic and vague. We want to get a sense of who you are as an individual, and what kind of student you would be.”
This individuality should not be achieved through wild or outrageous methods; your statement doesn’t need to be written in old English, or abstractly represent the consciousness of Thomas Cromwell. If you do something outrageously different, there’s probably a reason why no one’s done it before.
Instead, a personal statement should show something of you as a person, and convey your own unique engagement with history. Dr Ryrie, historian of religion at Durham says:
“The kind of personal statement that warms an admissions tutor’s heart is the kind which is honest: which describes, in genuinely personal terms, quite why the student loves the subject, and conveys something of their passion for it”.
‘Passion’, however, is a controversial word. UCL’s Dr Jason Peacey complained that “it gets a bit tiring reading hundreds of forms where the student proclaims that they have a ‘passion’ for history”.
Dr Ansari, head of history at Royal Holloway, agrees, and wants “genuine expressions of interest in history, but not in terms of ‘I am passionate about…’. Simply wanting something strongly is not enough”.
You need to convince admissions tutors that you have the intelligence and academic ability needed to successfully undertake a degree in the subject.
Dr Peacey says: “Students don’t always do enough to explain what it is about history that interests them, why this interest can only be met by undertaking more study at a higher level, and what should make me think that they have the potential and ability to study at this level”.
The same sentiments are also mentioned by Dr McGladdery, admissions officer at St Andrews. “Studying and writing about what happened in the past has little purpose if students cannot develop the skill of critical evaluation. Historiographical awareness is very important, as is the ability to present an opinion supported with evidence and cogent analysis.”
Students who show that they have considered the subject in relation to other academic avenues are likely to impress. As Dr Gadja, of Oxford university, says:
“Historians like to take insight from a huge range of perspectives, so we are always delighted when students can demonstrate how their interest and ability at foreign languages, philosophy, or political thought, literature, and so on, might intersect with their historical interests, and be of use in their development as historians”.
A clear, competent analysis of the ways in which your different subjects interact, and how this has aided your ability as a history student, can be a valuable inclusion in your personal statement.
Dr Gadja says that it is important to mention extra-curriculur interests. For Gadja, an interest in visiting museums, going to public lectures, and anything that shows an interest in history beyond the demands of one’s A-level course, would be relevant.
If you have had any relevant work experience, do mention it, but it must have had a definite impact on your approach to thinking about history. If you haven’t managed to gain experience in a historical field, though, don’t worry too much.
Gadja says: “we certainly don’t look for relevant work experience when making decisions – most applicants will not have had the fortunate opportunity to work in jobs relating to the heritage industry or similar, and that doesn’t put them at a disadvantage at all”.
Mention of non-academic areas in which you are wonderfully talented should be limited to a couple of sentences at most, and should always be linked back to the ways in which they have contributed to your academic or personal development; such as by improving time-management, or organisational skills.
Dr Simon Smith, of Oxford University, say: “Unlike some US universities or colleges, UK universities are not seeking to admit quotas of musicians, sports people, or thespians.”
It is important to write the statement in clear, concise prose, avoiding the use of formulaic words or phrases. Dr Peacey says:
“If I had a pound for every time I had been told that history is important because, as George Santayana said, those who fail to understand the mistakes of the past will merely repeat them… then I would be a rich man indeed.”
Try and avoid stilted references to the “eternal value” and “enduring fascination” of the past. Far more impressive is to explain and analyse what it is that makes you so interested in history, and specific areas in particular.
Above all, you should engage with the concepts that you are discussing, rather than just stating them. As Dr Ryrie says:
“Make us feel that you are a person of vision and imagination, for whom your outstanding A-level performance is just the beginning.”
Avoid anything bland or dull, and make the personal statement a reflection of your individual talents and interests. You want your statement to be different and engaging, otherwise it will slip through admissions tutors’ fingers without leaving a mark.
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Oct 08 2013
Blu-Ray albums target hi-fi fans http://www.bbc.co.uk/news/entertainment-arts-24441979
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Sep 23 2013
New Scientist: Leaky microwaves can power your kitchen gadgets. http://google.com/producer/s/CBIw2ZG3tQI
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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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