Well, not quite, but the wonderfully named Dr Mark Lewney puts on a great show not only as an axe hero extraordinaire but as a high-flying physicist who can explain why his nifty chops and runs sound the way they do. I had a quick e-chat with him the other day and we obtained permission to post his Famelab video from Channel4 on Youtube. So turn your speakers up to 11 and get ready to rock, harmonically, to the physics of heavy metal geetar!

The one thing that lets Dr Rock down is the total lack of a Justin Out of off of The Darkness jumpsuit and chest wig. Oh well, can’t have everything…

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Einstein Meets Hendrix

On this side of The Atlantic, there is growing interest this week in Jonny Wilkinson’s balls, and more to the point how he kicks them. Wilkinson’s drop goals are testament to his keen understanding of the physics of aerodynamics, fluid mechanics, and possibly even the Bernoulli effect. Perfect fodder for a physics science project I reckon, just watch…

However, it’s not all about the shape of the ball nor the swing of the leg, according to UK research published this month. The prodigious kicking success of England rugby player Johnny Wilkinson may rely more on what he does with his arms than his legs, according to a paper published in the journal Sports Biomechanics. Scientists at Bath University analysed the kicking techniques of professional and semi-professional rugby players to see which technique is most successful.

They found that players who swing their non-kicking-side arm across their chest as they make contact with the ball are the most accurate kickers, particularly over longer distances. It could be that the increased momentum produced by this arm movement helps the kicker control the amount of rotation in their bodies so that when they kick the ball their body is facing the target for longer.

Although Wilkinson’s trademark posture in lining up for the kick is well known, it is his arm movement you should watch out for in Saturday’s Rugby World Cup final, it might just signal defeat for the Springboks. Or, maybe that’s just wishful thinking on my part. Two RWC victories in a row, could it happen, could England swing it?

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Jonny Wilkinson, Physicist Extraordinaire

This effect underpins the technology that is used to read data on hard disks. It is thanks to their discovery that it has been possible to miniaturize hard disks so radically in recent years. Sensitive read-out heads are needed to be able to read data from the compact hard disks used in laptops and mp3 players, for instance.

You can read more details on the Nobel site here

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Nobel Prize for Physics 2007

There’s iron in them there bills…you might say!

So, now you’ve watched the video, you’re probably wondering, what are neodymium, or rare earth magnets and why is it so much stronger than a standard fridge magnet? Well, unlike conventional ferric or iron magnets, neodymium magnets are composed of iron, boron, and as the name would suggest, neodymium. The general chemical formula for this alloy is Nd₂Fe₁₄B which basically means for every 14 iron atoms in the material there are two neodymium atoms and one boron atom. That special blend (pardon the pun), however, means they can be up to about twenty times stronger than conventional ceramic magnets. Check out the HowStuffWorks site for a simplistic explanation of magnetism.

I asked magnetic expert (soon to be) Dr James Stephenson, who has probably forgotten more about magnets than I ever knew, why it is that the neodymium, or neo, magnets are so much stronger. The strength of a permanent magnet is down to how strong are the individual magnetic moments of the atoms from which it is composed and that’s down to how many electrons can be aligned in each atom, he explains.

Put simply, “Rare-earth magnets,
also
known as
nib magnets, are
stronger because
the individual atomic
magnetic moments are strongerRare-earth magnets, also known as nib magnets, are stronger because the individual atomic magnetic moments are stronger and that adds up to a stronger magnetic field overall,” he says. Taken individually, an isolated atom of a rare earth element, such as neodymium, has gaps in its so-called d [electron] f-shell. When Nd is alloyed with boron and iron those gaps get filled up to a maximum of 14 electrons in the f-shell of each Nd atom, this results in a very strong dipole. “In other words,” Stephenson adds, “more electrons means more current and as a result the magnetic field due to each dipole is higher.” So, there you have it.

By the way, it’s not illegal to blend a dollar bill unless you plan on trying to spend it later, but to be on the safe side bring a friend along, not only can you make sure it’s their dollar bill you blend, but you can claim it was their idea when the FBI turn up at the door too!

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There is Iron in Them There Bills

Sciencebase Exclusive - Careful experimentation and theoretical analysis of a double-slit experiment have finally quashed a controversy in fundamental physics – the complementarity-uncertainty debate.

Ever since the catflap to the quantum world was opened up to us and Schrödinger’s feline friend was idiomatically let out of the bag, to mix a metaphor or two, there have been more questions and controversies raised than conundrums solved in the world of the very, very small. How can something be both particle and wave, for instance? What allows particles of matter to tunnel through solid objects? And, how is the interference pattern destroyed in a double-slit experiment when measurements are performed on the path traversed by a particle?

What is a double slit experiment, you ask? Well, traditionally, Young’s double-slit experiment consists of shining a light through two narrow, closely spaced slits and observing the results on a screen placed beyond the slits.

Intuitively, you might think that the result would simply be two bright lines, aligned with the slits, representing where the light passes through the slits and hits the card. However, this is not seen in practice, instead, the light is diffracted by the slits and produces fringes corresponding to wave-like interference pattern. The fringes of light and dark regions correspond to where either the light waves constructively (add) and destructively (subtract) from each other. Two peaks in the light wave meet to make a brighter fringe whereas a dark fringe is formed when a peak and a trough coincide. This result seemingly settles a three-century conundrum about whether light is particle or wave, showing apparently that it is a wave.

However, a similar experiment carried out with beams of electrons or atoms fired through the slits produces a very similar interference pattern. How could that be? Particles are solid objects, surely? Well, the double-slit experiment shows that they are not. They produce an interference pattern, which suggests that the particles behave as waves.

The double-slit experiments work perfectly well and reveals interference patterns with light, electrons, and beams of other particles, but only if the experimenter does not try to find out through which slit a particular wave-particle passed before hitting the screen. Try to fire particles through the slits one at a time and as illustratd in the 5-minute video below, you will still see an interference pattern. It is as if each particle passes through both slits simultaneously, each slit individually and together and neither slit all at the same time; behaving some as waves…

As if this were not complicated enough, physicists reasoned that if they could discover which slit the individual particle really goes through each time in this experiment, they could solve the problem. So, they put a measuring device next to one slot and observed what happens as particles are fired through the slits one at a time. Astoundingly, the interference pattern disappears, simply having a measuring device present to observe the route taken by the particles somehow disturbs their wave-like nature and they revert to being tiny, solid objects and produce just two bands on the screen as if they were tiny marbles rather than wave. How could the particles know they were being watched.

This loss of interference has been explained by several of the biggest names in twentieth century physics, among them Niels Bohr and Richard Feynman. They suggested that whenever the path is measured within the double-slit, the momentum of the wave-particle is uncontrollably and irreversibly disturbed. Think about it, it has to be affected by the observer somehow because the very act of observing involves some kind of sharing of information either via photons, charge, energy or matter. This process “washes out” the interference fringes.

Most physicists simply accept this as being precisely what happens. It is a little vague and some might say “handwaving” because it does not pin down the nature of this washing out nor say anything about how the momentum is disturbed by the transaction between observer and observed. More precisely, it is simply what happens because of the back-reaction resulting from the Heisenberg uncertainty relation that says we cannot know simultaneously both the energy and position of any quantum wave or particle with absolute precision. While that kind of folds the argument into a loop, Feynman famously pointed out that, “No one has ever thought of a way around the uncertainty principle.”

But, not everyone was happy with this. In 1991, Marlan Scully, Berthold-Georg Englert, and Herbert Walther (Nature 1991, 351, 111) suggested that a microscopic pointer could be used to carry out the observation in such a way that the very act of observation would not disturb the momentum of the particle and so bypass the uncontrollable and irreversible effects suggested by Bohr that leads to interference breakdown. However, Pippa Storey, Sze Tan, Matthew Collett, and Daniel Walls (Nature, 1994, 367, 626), countered this argument, demonstrating that no matter how small the observer nor how the measurements are made, momentum is affected and the interference pattern would disappear. A long and controversial debate has raged between the two scientific factions that back either the Scully or Walls teams.

A theoretical solution was posited by Howard Wiseman and colleagues in 2003 (Phys Rev A, 2003, 311, 285) and refined in 2004 (J. Opt. B: Quant. Semiclass. Opt. 2004, 6, S506-S517). Now, in a seminal paper published today in the New Journal of Physics, Aephraim Steinberg together with Wiseman and colleagues Mir, Lundeen, Mitchell, and Garretson have applied the theory in a novel double-slit setup. Their experimental results suggest that, as is the way with all things quantum, both camps are equally correct and equally wrong. Somehow, you can have your quantum cake and eat it.

They found that by using only weak measurements, they can directly observe the momentum transfer that causes interference breakdown but equally do so without disturbing the two-slit superposition. They effectively verify both the Scully and Walls views. In terms of the Scully position, the team shows that there is no change in the mean momentum, or the mean energy, whereas with respect to the Walls work, they show that the momentum is spread, as one would expect given the uncertainty inherent in the quantum world, according to Heisenberg’s principle.

Feynman always held that the double-slit setup was central to quantum theory, but would never be fully understood. This work by Wiseman and colleagues shows that the humble double-slit experiment can still throw up new quantum mysteries to baffle us.

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Two Slits Are Better Than One

It is not so long ago, that the first thing that sprang to mind when one read the phrase ‘quantum dot’ is some rather esoteric and complicated aspect of avant garde physics. This is still partly true, there is some rather complex experimental work underway underpinned by even more complex theoretical work investigating the bizarre properties of tiny devices that can trap a single electron in zero-dimensions.

Practical applications of quantum dots have emerged recently in sensor science but US and Brazilian researchers hope to exploit them in a new kind of electronics, known as spintronics where electron charge and quantum spin add an extra dimension to electronic operations and computation. Spin currents might also be used to allow quantum communications take place “in-chip” in devices so small that light propagation is not practical. Such developments will open up quantum dots that can increase processing speed, storage capacity, and functionality of conventional electronics, communication, and computations and technologies.

Eduardo Mucciolo of the Department of Physics at the University of Central Florida, Orlando and Caio Lewenkopf of the Department of Theoretical Physics at State University of Rio de Janeiro, Brazil, are investigating lateral semiconductor quantum dots. They believe that such devices could be used as pumps to produce spin polarised currents, by exploring quantum phase coherence phenomena. The effect, called pure spin pumping, is analogous to charging a battery in conventional electronics. Such a spin pump might provide the much-needed circuit element for spin-based electronics.

Writing in the International Journal of Nanotechnology (2007, 4, 482-495), Mucciolo and Lewenkopf describe a lateral semiconductor quantum dot. In these systems, electrons within a two-dimensional gas are trapped within small puddles by the application of a voltage; applied voltages control the shape and size of these puddles. Electrodes can be used to vary the width of the point contacts between the electron puddle and the 2D gas. Controlling these point contacts allows quantum dots to be “opened” and “closed”.

Controlling these point contacts allows them to “open” and “close” the quantum dots. This effect dates back to the early 1990s, points out Mucciolo. “Closing and opening the propagation through a constriction, the point contact, can be used to detect spin-polarized currents,” he explains, “This is how Susan Watson and colleagues at Middlebury College managed to see spin currents coming out of their quantum dot pump in 2003.”

“Recently, our spin pump proposal passed its first experimental test,” say the researchers, who now hope that other teams will take up the challenge and investigate the potential of spin pump quantum dots.

“The main idea behind the spin pumping mechanism was actually published for the first time in Physical Review Letters in a paper I co-authored with Claudio Chamon (Boston University) and Charles Marcus (Harvard University),” adds Mucciolo. The main development since that earlier work presented in the current paper with Lewenkopf is that now they have carried out a much more detailed analysis to demonstrate the precise details, this was entirely missing from the PRL paper, Mucciolo told us. “In the J Nanotech paper we also develop a general formalism that could serve as a basis for the theoretical investigation of several aspects of spin pumps which, albeit important, have not yet been considered in the literature,” Mucciolo adds.

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Quantum Dots and Spin Pumps

I’m on a photography course this week, hence the leaner, meaner Sciencebase posting regime. But, I did find time to chat with technology writer Wayne Smallman on Blah Blah Tech, who pointed out this neat video showing three distinct coloured fluids (dyed corn syrup) being poured into a vessel stirred slowly and then the flow reversed.

You might suspect it is a trick, but it is not. The three coloured liquids end up separated but are not quite as perfectly aligned as they were at the start. Why does this happen? It’s laminar (non-mixing) reverse flow, is tied to the viscous nature of the corn syrup, the smooth flow of the mix and the reverse unmix. I guess the only trick might be that the three fluids are within a thin layer inside the cylinder within which is a second concentric cylinder, the stirrer, oh that and the fact that the “experimenter” cannot actually count! But the essential thing is that corn syrup has a low Reynolds number (this approximates to high viscosity).

Such effects do occur in nature at tidal river confluences where water from different flows barely mix because of differing temperatures and salt concentration. The same phenomena could underlie the seemingly stable patterns we see on Jupiter (it’s lots of viscous layers not mixing).

Anyway, here’s the video

As to what Wayne had to say about it. “Wow, well
effin’
weird, or whatWow, well effin’ weird, or what?!” were his first words. He figured my “science know-how” would do it more justice. Well, personally, I think it’s just effin’ weird too! Seriously, for a more detailed explanation check out this page on the Harvard website. The video has also been discussed on StumbleUpon here.

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Mixing and unmixing

Anyway, Barrowman took Manchester-CERN high-energy physicist, Brian Cox, along for the ride, and yes, there really are just far too many lewd puns to be made in the context of Cox, hadrons and Barrowman to be worth the effort. Actually, Cox was a ray of Sunshine, he was one of the scientific advisers on the recent sci-fi flick of that name. Barrowman, apparently, is genuinely interested in exploring the boundaries between science fact and science fiction. His fascinating response when confronted with the notion that a speeding proton in the particle accelerator experiences every second of our time as a seven thousandth of a second is illuminating to say the least - “Holey Moley”, he exclaimed. But, at least he went and donned the hard hat in the name of science.

Check out the video. Dig the groovy tune. And if you’re into that kind of thing you get to see Barrowman’s teeth, which are a miracle of modern science in themselves.

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Captain Jack and Real Science

Unfortunately, while the science is sound, no one is yet beating a path to the inventors’ door, despite NASA backing. I asked Masson why he thought this was the case and his answer provides some cutting insights into the nature of the transport industry and the manufacturers that currently underpin it.

First off he pointed out that, “Conventional jet engines (turbofans) are very reliable and can still be improved: people are still working on NOx and noise reduction (including as part of our NASA sponsored project),” he says, “Therefore, there is a lot of inertia and imposing a new and totally different technology would be very difficult.” The major advantage of using electrical power is environment preservation because the performance of an all-electric aircraft would be unchanged unless one takes into account increased controllability and decreased maintenance requirements.

Masson’s electric jet is based on using zero-resistance superconducting materials as the magnetic components of the turbo-driving motor, but he points out that these, and cryogenic support systems needed to make them work, are still very expensive thus making funding difficult to find. It is possible that mass production would reduce costs to an economically viable level, but that is probably not going to happen any time soon.

“The motor designs we proposed can exhibit impressive power densities that would unfortunately almost only benefit airborne applications, there are no other applications with critical constraints in terms of weight and volume,” he told me, “As for the car industry in which combustion engine manufacturers are putting a lot of pressure to prevent new clean technologies to take off, jet engine manufacturers would not be happy to see electrical propulsion systems becoming a new standard.”

“An all-electric aircraft prototype is feasible,” he adds, “but imposing this technology as a replacement to gas turbines would still require a lot of research and development to meet flight requirements in terms of reliability.” However, Masson asserts that the appearance of increasingly electrical airliners from both Airbus and Boeing could hint at a future of all-electric aircraft. “I am convinced that one day in a not so far future we will see small electrically powered aircraft,” he says. He concedes that, “It will be years, probably tens of years, before we can see a truly all-electrical aircraft as all the components require extensive testing and a very high reliability before being implemented in airplanes.”

Masson and his colleagues have approached several companies and aircraft manufacturers and have not yet been successful in getting funding to build a prototype of their superconducting propulsion motor for which patents are pending. “We are still hopeful and will keep looking for funding,” he says.

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Funding the All-electric Aircraft

Also under the Spotlight this month, Norwegian scientists have drawn up a league table of alternative fuels for cars based on what they call a “well-to-wheel” analysis. Their approach takes into account the energy costs in manufacturing, total energy use, and overall pollution included greenhouse gas emissions. Unsurprisingly, petrol and diesel vehicles foot the table, closely followed by hybrid vehicles. In contrast, the greenest way to power a vehicle turns out to be to use an electric fuel cell powered by hydrogen made from natural gas, methane.

Finally, in the 1950s, the atomic clock was the pinnacle of split-second time-keeping. Today, physicists use its successors based on energy transitions in rubidium atoms that gives them 100 times more accuracy. These clocks currently operate at their theoretical limit but nevertheless are accurate to one second every 50 million years. Quantum noise, the random fluctuations of atoms and ions and the grim truth of Heisenberg’s Uncertainty Principle would probably mean no improvements for the next 50 million years.

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Matrix recharged