Physics

NASA
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Dark forces are afoot: a glimpse of dark matter?

What makes up 96% of the universe? Not rocks or dust, or even microscopic aliens. No, the universe is mostly dark. And that shouldn’t elicit a “well done Sherlock Holmes – I can see that most nights when I’m having an essay crisis in the library at three in the morning” sort of reply. When we say it’s 96% darkness, we mean it’s made up mostly of dark matter and dark energy. This is, however, another way of saying that we have just about no idea what it’s made of, because dark matter and energy are names that we have given to substances that we don’t understand. We didn’t even have much evidence – until now.

Gamma rays originating from the heart of the Milky Way have been detected by a research group using the Fermi Gamma-ray Space Telescope. At first scientists were skeptical, but the most recent analysis of the results, carried out by a team including Daniel Hooper, from the university of Chicago, has revealed that the signals are most likely due to a particle which is thought to be hiding under the shroud of dark matter – known as the WIMP. WIMP is not just an abusive name from a rather irate astronomer – it stands for Weakly Interacting Massive Particle. When these WIMPs annihilate one another, they are predicted to emit electromagnetic radiation in the gamma region, exceedingly similar to what has been observed. The team in their paper confirmed that the analysis of the results were “in good agreement with that predicted by simple annihilating dark matter models”, implying that there are now few other alternatives to the dark matter theory.

 

[caption id="attachment_52532" align="aligncenter" width="300"]Gamma-ray emissions detected, thought to be produced by annihilating WIMPs Gamma-ray emissions detected, thought to be produced by annihilating WIMPs[/caption]

 

The reason for the lack of direct evidence for dark matter is that it does not interact at all with electromagnetic radiation, i.e. visible light and the whole spectrum of waves above and below. Right, you say, but even when it’s completely dark, I can just feel my way around – I may trip over a few textbooks but I find the way to the bathroom eventually. Well, dark matter does not experience a nuclear strong force either, so not only can we not see it, it will not be held in any atoms. We can’t see it, touch it, or use any other sensory means to establish its existence. We must, therefore, rely on more indirect evidence, in this case the annihilation of WIMP particles, to infer their existence.

One force dark matter is predicted to experience is gravity. If it were found, its presence could help to explain the continued expansion of the universe, and also the behaviour of various galaxies that is not explained by the visible matter inside them. This was one of the lines of reasoning that lead to the dark matter hypothesis in the first place. Now, we may be well on the way to confirming this theory and explaining one of the great unsolved mysteries of the universe.

However, this is not the discovery of a new field of substance in our universe yet. In order to confirm the theory, research must be done into other systems which are predicted to exhibit similar behaviour, beyond our Milky Way, such as certain dwarf galaxies which orbit around us. Should similar signals be seen, this would provide further evidence for the theory of dark matter and help to confirm it. Only then will we be able to say with confidence that we are taking our first look into the darkness of the universe, and seeing what is really there…

 

PHOTO/ NASA/Goddard Space Flight Centre Scientific Visualisation Studio

If you would be interested in writing for the OxStu science team contact us on scitech.oxstu@gmail.com. We provide lots of opportunities for interviews, interesting article topics each week and are open to suggestions for article ideas.

meteorite
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Meteorite strike Russian mountains

meteoriteOn Friday 15th February, a large meteorite crashed into Russia’s Ural Mountains. Latest reports suggest 1200 people were injured by the incident with a number of people still being treated in hospital. Although there are some reports of fragments of the meteor striking the ground the vast majority of damage in the region is believed to have caused by shockwaves of the explosion, as the rock shattered into several fragments up in the upper atmosphere. The resulting shockwave blew out windows and shook buildings. Fortunately, no large fragments hit populated areas; however a 6m crater has been discovered at a frozen lake near Chebarkul, where a large fragment is thought to have impacted.

Asteroids are small bodies that, like the Earth, orbit stars. They predominantly rock and elements such as nickel and iron. Small asteroids are known as meteoroids and, if these enter the Earth’s atmosphere, they are called meteors. Many meteors break into pieces or burn up entirely as they speed through the atmosphere. Once meteors or fragments actually hit the earth, they become meteorites.

The Russian meteorite was the largest recorded object to strike Earth in more than a century. According to Russia’s Academy of Sciences the meteor weighed about 10 tonnes when it entered the Earth’s atmosphere and broke apart 30-50km (20-30 miles) above ground, releasing several kilotons of energy – the equivalent of a small atomic weapon. However, the US space agency NASA said the meteor weighed 10,000 tonnes before entering the atmosphere, and released about 500 kilotons of energy. As more research is carried out into incident more light may be shed on these conflicting reports. The Emergencies Ministry have urged calm, saying background radiation levels were normal after what it described as a “meteorite shower in the form of fireballs”.

A big rescue and clean-up operation involving more than 9,000 workers is going on in the Ural mountains following the meteor strike, Russia’s Emergencies Ministry says. Despite its massive size, the object went undetected until it reached the atmosphere. A network of telescopes watches for asteroids that might strike Earth, although it is geared towards spotting larger objects — between 100 metres and a kilometre in size. Scientists claim there is no link between the event in the Urals and 2012 DA14, an asteroid which raced past the Earth later on Friday at a distance of just 27,700km one fourteenth of the distance to the moon- the closest ever recorded for an object of that size. Despite, occurrences of meteors colliding with Earth are extremely infrequent and there are many precautions in place if an emergency does arise so don’t despair, there is no need to start planning emergency contingency plans just yet.

 

PHOTO/Navicore

science
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An off-the-record guide to Science at Oxford

[caption id="attachment_24849" align="alignright" width="300"] A Day in the Life… /Phillip Martin[/caption]

Coming up to Oxford is filled with ideals of lounging in old building, reading romantic novels, soaking up the intellect that permeates the very fabric of life, spending all day exchanging political opinions with the future leaders of the country and writing essays minutes before deadlines. If you’re a humanities student.

The life of a scientist is slightly different – but following a few simple guidelines can help you lead a life closer to that of your non-white labcoat-ed friends. 

DO: Go to lectures. For God’s sake, do. It might sound very obvious, but empty chairs fill more of the hall than filled ones by a few weeks into term – give them a chance, you’d be amazed how intelligent and knowledgeable some of those professors are. That said, sometimes a mere five minutes into the first lecture of a course can be enough to happily discover that the all-amazing hand-out covers everything and you never need to go again, in which case nurse those Park End hangovers in bed as much as possible before labs.

DON’T: Try doing the tute sheet before at least looking at the books suggested. My cohort only realised at the start of Trinity that actually reading the books our tutors had recommended contained relevant information… surprising, that.

DO: Use Wikipedia. All this school nonsense of it being ‘made up’ and ‘wrong’ – it’s not. Most of it is written by the very people who teach you. Repeat the mantra “Google and  Wikipedia are my friends” every night before bed in the weeks leading up to coming to Oxford.

DON’T: Buy the textbooks. Seriously, the core ones are helpful (but also available in the library) and all the others are useful for a week’s tutorial and then never again.  Add to your mantra ‘The library books are my friends’ – that too will set you in good stead. But, should you want your own copy, at least wait to buy them at a knock-off price from the third years who – demonstrating their superfluity – no longer need them

DON’T: Buy a lab coat, or safety specs before coming up. Some kind, rich company will pay for you all to have ones with their logo stamped firmly upon them – my year happen to be branded by BP. Save the money for textbooks or ATS* for lunch in labs.

DO: Write ups for labs ASAP. You need to pass first year – put in enough time to pass (get 40%) and not a second more (genuine words of wisdom straight from my tutors. And second years. And third years). Not doing them is just a pain; and involves more meetings and remedial action than you can imagine. Plus, if you get it wrong, they just explain it, and send you on your merry way (probably none the wiser), so it’s all fine.

*ATS: Alternative Tuck Shop – a legendary sandwich shop close to labs, to which students from all years pay homage during the free time which punctuates labs (normally when the experiments are merrily stirring away) for sandwich-y goodness to keep them going for the rest of the day.

Can the world's fastest man be duplicated through technology?/tedz01
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The science behind Bolt’s effortless sprint

Everybody has watched Usain Bolt casually breeze past the finish line in his races – a little grace, a little smile and he’s done it again, the gold dangled mercilessly in front of his fellow competitors only to adorn Bolt’s neck on the podium. A little science can help us analyse Bolt‘s technique.

One cannot be of world class standard at anything without spending huge amounts of time training and having a level of dedication most can only dream of – however, many experts will agree that a world class sprinter is born rather than made. Everything from body shape, muscle strength, tendon length and even what you wear affects your time significantly, especially where only a mere 0.3 seconds separates 7 sprinters in the 100m final. And what is viewed as the best makeup is constantly shifting. “The body shape of male sprinters seems to have changed over the past decade or so. Taller, more linear individuals are emerging as the better sprinters… we think it’s got something to do with increased stride length” said Dr Nevill of the University of Wolverhampton.

Sprinting is all to do with impulses, and in fact, the same can be said of most, if not all, sport. An impulse is the product of force acting on a body and the time it acts over. Let’s consider two 17 years olds taking turn trying to push their broken-down car. The first teenager is strong and can push the 1 ton car with a force of 500N but he can only do it for 10 seconds before getting tired and having to stop. If he does this, he has an impulse of 5,000 Ns which will make the car go at about 0.5m/s (we are ignoring all kinds of friction here). The slighter weaker friend, however, can only push at 250N, but he has a bit more stamina and he can keep pushing for 30s. This translates to an impulse of 7,500Ns and a car speed of 0.75m/s, which is 50% better than his stronger friend.

Thus, for a sprinter, there are two ways to maximise your speed – either exert a greater force or spend more time in contact with the ground. A typical champion sprinter will hit the ground with 2.5-3 times their own body weight (the average person manages about 2 times), however Usain Bolt’s feet land with up to 4,000N (400kg) for less than a tenth of a second. How great this force can be has many genetic and biological considerations, for example, the strength of your leg muscles, whether you have fast twitch muscle fibres and certain natural variants of a gene call ACTN3 that boosts the performance of these fibres. However, the body is an incredibly complex system of muscles and tendons and we do not truly understand how movements and body strength translate to running speed, and thus we cannot predict how fast a runner will run from his physique.

The other way to decrease running time is to increase the contact time. It is hard for humans to increase this dramatically and it explains why animals like cheetahs and greyhounds are so fast. Cheetahs and greyhounds have flexible backbones: as their front feet land, their spines compress and bend, giving the back legs more time in the air. Then, their spine decompresses while their hind legs are on the ground to maximise the contact time. Humans can’t do this naturally and so have tried to replicate this with technology, which has turned out to be very difficult. Running shoes have been known to increase contact time using flexible spring-like materials and air sacs at their base. However, all these systems suffer from the same problem: as they leave the ground, they have elastic rebound which decreases impact time, thus losing the extra time they provided on the way down.

There is also the concern over what to wear. Drag plays a huge part in cutting off 0.1s of sprinting time. Long gone are the days of baggy uniforms – it is now stretched tight to absolutely minimize resistance. But that isn’t the only way; the suits incorporate dimples within the design, almost impossible to see unless you are up close. These dimples are inspired from the design of golf balls, and have been shown to significantly reduce drag by creating a thin layer of turbulent air around the surface, preventing a phenomenon known as eddy currents from occurring, which increase drag dramatically.

In the end, there are a large number of factors that affect how fast man can sprint, and as we better our understanding of these things, we will continue to push the boundaries of human speed.

170px-Oxford-University-Circlet.svg
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Oxford Science Shines with Awards

Being at one of the best universities in the country, let alone the world, has its perks, and several awards to boot. The Science and Technology section would like to congratulate the following for their remarkable achievements.

[caption id="attachment_23767" align="alignright" width="300"] Professor Fraser Armstrong FRS was awarded the Davy Medal in 2012 for his pioneering protein film electrochemistry allowing exquisite thermodynamic and kinetic control of redox enzymes, exemplified by hydrogenases, key in energy technology/The Royal Society[/caption]

Oxford chemists Professor Fraser Armstrong and Professor Frances Ashcroft have been recognised by the Royal Society in this year’s Awards, Medals and Lectures. Professor Armstrong received the Davy Medal for his pioneering work with protein film electrochemistry, specifically metal centres in enzymes such as hydrogenases. This research could help the eventual development of microorganisms that can be farmed to produce hydrogen from sunlight via photosynthesis, and thus allowing it to be a much more viable resource of sustainability. Professor Frances Ashcroft, a Royal society research professor at the University of Oxford, and author of The Spark of Life has been awarded the Croonian Lecture for her work on finding the link between an increase in blood sugar level when you eat a chocolate bar to the following secretion of insulin. By unravelling the genetic mutations in a particular protein that is behind a rare genetic condition known as neonatal diabetes ( where patients develop diabetes very soon after birth), she has enabled many patients with this condition to switch to a better form a of medication.

Members of the biological physics group, with colleagues from the Centre for Mechanochemical Cell Biology at the University of Warwick, presented their research at the Royal Society Summer exhibition. The research is focused around biological Nano scale transport and spanned naturally occurring motors such as kinesin and the bacterial flagellar motor, to building synthetic motors from DNA. Their “Mini Motors” stall was well received, granting over 11,000 visitors the opportunity to use optical tweezes to trap E.coli, track cellular motor proteins, experience swimming through water as a small bacterium and play Escape the Cell. The stand will be making a reappearance in the Clarendon Laboratory on the 15th of September 2012 for the Alumni Weekend.

Dr. Yulin Chen (Department of Physics, the University of Oxford) is one of two winners of the 2012 Outstanding Young Researcher Award (Macronix Prize) of the International Organization of Chinese Physicists and Astronomers (OCPA).His research area is that of condensed matter physics and understanding the behaviour of electrons in more unconventional materials. His award came with the  following citation: “For his pioneering contribution in advancing our knowledge of topological insulators using angle-resolved photoemission spectroscopy, for the realization of the topological insulating state of Bi2Te3, and the discovery of the massive topological surface state in magnetically doped topological Bi2Se3.”
Decay of the Higgs Boson/CERN
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The Higgs Boson – fact or fiction?

 

[caption id="attachment_22999" align="alignright" width="300"] Decay of the Higgs Boson/CERN[/caption]

After $14 Billion and 800 trillion collisions, Scientists at the Large Hadron Collider (LHC) in CERN are claiming to have discovered a new particle that could potentially be the elusive Higgs Boson and thus the biggest discovery of the 21st Century.

The Higgs boson is a subatomic particle predicted by the Standard Model of Physics and is thought to be responsible for why other particles have mass, and why these masses vary from particle to particle.  The idea is that all of space is permeated with a field, known as the Higgs field, and all particles are affected, to varying degrees, as they move through it. The greater the extent of interaction between the particle and the field, the more massive it becomes – and if it doesn’t interact at all, then it has no mass, like photons.

[caption id="attachment_23023" align="alignright" width="300"] Higgs Field/Matthew Lymer[/caption]

So, where does the Higgs boson come into this? In classical physics, we think of fields as continuous, smoothly changing entities. However quantum mechanics begs to differ and in fact, rejects the notion of continuity; rather it describes fields as distributions of tiny particles where the strength of a field is merely determined by the density of the particles at that given point. So, in terms of quantum mechanics, we can describe the Higgs field as consisting of many tiny Higgs Bosons, like light being made up of photons.

At least, that’s the theory. But, the problem with just a theory is that until you have evidence that supports your theory, there are other theories which explain the same phenomenon just as well. How do you decide which theory is more accurate? Experiments, and billions of pounds worth, in the case of the LHC.  The LHC is the particle physicist’s plaything – a giant circular particle accelerator 175 metres below the ground and 27km in circumference

[caption id="attachment_23008" align="alignright" width="300"] Overview of CERN/CERN[/caption]

that allows particles to travel around it at up to 11,000 times per second. It runs two beams of these particles, normally protons, travelling in opposite directions, which are forced to collide in detectors (CMS, ALICE, ATLAS and LHCb), giving rise to the creation of new particles that can be detected.  This leads to huge amounts of data, which physicists then analyse to determine their nature.

Despite all this information, scientists are still trying to confirm that what they have discovered is the Higgs Boson. Going back to the underlying question, the importance of this particle and how it affects us – well, some of us might be sceptical about the God particle for now, but it might not be too long before we eat our own words.

 

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