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Home » Page 1500

The psychology of climate-change scepticism

By Margaret Harris

As the person who (with editor Matin Durrani) compiles letters and web comments for the “Feedback” section of Physics World, I’ve been paying close attention to the flood of comments on physicsworld.com’s various climate-change articles.

A majority of the comments have been negative, as many readers will have noticed, and the same has been true for feedback in the form of letters and emails. On the face of it, this is pretty typical, even for a good magazine: angry readers write letters, while happy readers, by and large, do not.

But I have to wonder what else might be going on that is specific to the issue of climate change. Most people who make negative comments have not read an enormous number of peer-reviewed publications on the subject; at best, they seem to have read an enormous number of websites set up by avowed climate-change sceptics. However, neither do they appear to be in the pay of the fossil-fuel industry, as some environmentalists have charged. So why is there such a huge amount of vitriol out there against the idea that the climate is changing, and humans are (at least partly) responsible?

The answer, it seems, may be partly down to human psychology — at least according to a report from the Center for Research on Environmental Decisions (CRED) at Columbia University. Liz Kalaugher, editor of environmentalresearchweb.org (one of physicsworld.com‘s sister websites within the Institute of Physics Publishing) has written a very good summary of the report here . Alternatively, you can download a guide to the CRED report here.

Quantum processor executes 160 different operations

 

Physicists in the US have used two trapped atomic ions to create the first multiple-qubit programmable quantum computer. The device can be controlled to perform at least 160 different quantum computing operations. Its inventors claim that the device is an important step towards the development of a practical “universal quantum computer” that can be set to run any program allowed by quantum mechanics.

While classical computers store and process information as “bits” that can have one of two states – “0” or “1” – a quantum computer exploits the ability of quantum particles to be in the “superposition” of two or more states at the same time. Such a device could, in principle, outperform a classical computer on some tasks. In practice, however, physicists have struggled to create even the simplest quantum computers because the fragile nature of quantum bits – or qubits – makes them very difficult to transmit, store and process.

Earlier this year researchers at the National Institute of Standards and Technology (NIST) in Colorado unveiled a quantum processor that uses two beryllium ions as a pair of qubits – each of which can store information in two quantum states. The ions are trapped on a small ultracold chip using electric and magnetic fields. Ultraviolet laser pulses are used to store data by setting the quantum state of each qubit. Electric fields are then used to move the ions between different zones in the trap. In this way, the qubits can be moved around and made to interact with each other in 15 different ways – without losing their quantum nature 94% of the time.

All possible operations

Now, the NIST researchers, led by David Hanneke, have gone a step further and combined these 15 basic operations to perform 160 different quantum computing programs. The operations were chosen at random from the infinite number of ways that two qubits can be used to perform quantum calculations – but Hanneke claims that the set of 160 is large and diverse enough to represent all possible operations. As a result, he claims that the quantum processor is “universal”.

“It’s a step toward the big goal of doing calculations with lots and lots of qubits,” says Hanneke. “The idea is you’d have lots of these processors and you’d link them together,” he explained.

The quantum-computing processes that the chip executed included the “rotation” of the value of a single qubit – changing its value from “1” to a superposition of “1” and “0”, for example. The team was also able to “entangle” the two qubits. Entanglement means that the particles can have a much closer relationship than allowed by classical physics, something that could be exploited in a wide range of applications such as the massive parallel processing of information secure transmission of quantum-encrypted information.

The programs worked about 79% of the time, averaged over 900 runs. This figure will have to be boosted much nearer to 100% before it can be used in a practical quantum computer. In addition, physicists will have to work out ways of hooking up many such systems in order to perform large calculations.

The research is described in Nature Physics.

From baguettes to bosons

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Now where did I put my sandwich? (credit: CERN)

By Michael Banks

The mystery surrounding the electrical fault last week at the Large Hadron Collider (LHC) at CERN has taken a new twist today.

Last week, a piece of baguette was found to be lying on an electrical connection in one of the eight above-ground cryoplants – used to cool the LHC to 1.9 K – that caused two of the eight sectors around the LHC’s 27 km ring to heat up to 10 K.

But in the latest issue of the CERN Bulletin, James Gillies, head of communication at CERN, claims that a bird carrying a baguette did not stall the world’s most powerful particle-physics experiment from starting up on schedule.

“Of course, no such thing happened,” says Gillies. But he did admit that engineers at CERN do not fully understand how the heating occurred in the two sectors. “To this day, we do not know what caused the power cut,” he says.

However, Gillies, who was not at CERN when the incident happened, says it is true that “feathers and bread” were actually found at the site of the mystery electrical fault.

Could it be that someone intent on sabotaging the LHC has cleverly laid a decoy of feathers and bread?

Whatever the reason, Gillies is keen for the media to now focus on the LHC and the science it will produce once low-energy collisions begin early next month.

“Soon, the headlines should be turning from birds to b-quarks, and from baguettes to bosons,” he says. Well there is hope.

Exoplanets and the 'lithium problem'

exoplanet123.jpg
Artist’s impression of a giant exoplanet. (Courtesy: Spitzer Space Telescope).

By Hamish Johnston

About a month ago we reported that astronomers might be able find Earth-like exoplanets by studying the chemical signatures of distant stars.

The idea is that the formation of rocky planets such as Earth and Mars leave their companion stars deficient in heavy elements such as aluminium, iron and nickel. The team came to this conclusion after finding that the Sun seems to have about a 15% deficit in these elements compared to similar stars.

Now another group of astronomers has looked at the lithium content of Sun-like stars, and discovered that stars with exoplanets have less lithium than those with no exoplanets. It is already well known that the Sun has 140 times less lithium on its surface than predicted by models of solar evolution.

I spoke to one of the group — Garik Israelian of the Institute of Astrophysicists in the Canary Islands — and he told me that there are two mechanisms by which planet formation could lead to low levels of lithium.

The first is related to “giant migration”, whereby the orbits of Jupiter-like planets change over time. The resulting transfer of angular momentum can leave the lithium-rich outer atmosphere of the star spinning faster relative to the core of the star. This leads to turbulence, which sends some of the lithium deeper into the star where it is hot enough for it to burn via nuclear fusion.

The second is related to the fact that much of the angular momentum in a solar system is tied up in the planets — which means that the core of a star with planets is probably rotating much slower than a similar star with no planets. However, the atmosphere of such a star still rotates rapidly, leading to turbulence and lithium burning.

Indeed, both of these effects could act in succession on the same star – really setting its lithium ablaze.

Israelian believes that exoplanets could be behind the ‘lithium problem’ — the puzzling observation that stars of the same temperature, age and metallicity have very different levels of lithium.

The discovery could also help to further accelerate the discovery of exoplanets — about 400 have been found so far — by narrowing down the field of stellar candidates.

The research is reported in Nature 462 189.

If you want to know more about exoplanets, check out this article by Alan Boss.

Scientists spy on the first stages of crystal growth

A new microscopy technique has allowed researchers in the US to make the first measurements of the earliest stages of crystallization. The technique could help scientists to gain a more complete understanding of how materials crystallize – which might eventually lead to high-speed computer memories based on crystallization.

Crystallization usually starts with the formation of nanometre-sized crystalline clumps called nuclei, which increase in size to take over the entire material. The classical theory of nucleation assumes that the tiny clumps are constantly forming and breaking apart, and it is only when they reach a critical size that they can trigger runaway crystallization.

Although the presence of these “sub-critical” nuclei had been predicted decades ago, it has been extremely difficult to observe how they evolve and affect crystallization, according to Bong-Sub Lee, a materials scientist at the University of Illinois at Urbana-Champaign, who played a leading role in this latest research.

Using fluctuation

To address these problems, the team used a modified form of transmission electron microscopy (TEM) called fluctuation TEM. This technique involves recording hundreds of electron diffraction patterns from a single sample, and then using statistics to build up a histogram showing the number of nuclei observed as a function of size.

According to Lee, an important advantage of this method over other techniques is that it can easily pick out crystalline regions 1–2 nm in size from the background noise. A conventional high-resolution TEM is limited to nuclei larger than about 4 nm

The team studied an alloy of antimony, indium, silver and tellurium called AIST, which is used to make rewritable CDs and DVDs. By heating the alloy with a laser, regions of the AIST can be switched back and forth between crystalline and amorphous forms, allowing binary data to be encoded on the disk. Heating to 250–400 °C produces the crystalline phase, whereas heating to 600 °C followed by rapid cooling produces the amorphous phase.

Super-criticality takes time

By combining fluctuation TEM with a pulsed-laser technique, the team watched these processes in action. “We observed that if a particle becomes bigger than a critical size it can keep growing to become a big crystal. But it takes time to make such a super-critical nucleus. If you have a lot of smaller sub-critical nuclei already embedded in the material, this waiting can be shortened,” Lee told physicsworld.com.

Lee’s team was able to show that it is possible to increase the number of embedded nuclei in the material – priming it for crystallization. This was done by annealing the material – heating it up and letting it cool slowly.

Their results agree with numerical simulations based on the classical theory and showed that even if two amorphous materials have the same composition, the crystallization speed may be vastly different depending on how they are prepared.

Memory potential

AIST and other “phase change” materials are currently being investigated for use in miniaturized memory chips for use in computers or mobile phones. “This technique gives new insight into the initial formation mechanisms of crystalline nuclei, so it may prove very helpful,” says Matthias Wuttig at Aachen University in Germany.

“Phase change materials have a number of exciting scientific characteristics that make them promising,” Wuttig explains. “They can very rapidly switch between amorphous and crystalline states, and there is a pronounced contrast in properties between the two.”

Lee’s team has already started looking at other materials – and because nucleation and crystallization are key processes in nature, they hope to extend the work to experimentally test other long-standing theoretical predictions in nucleation science.

The work is described in Science.

The biomedical attraction of magnetic nanoparticles

Just press “play” on the video Q&A with Kevin O’Grady, professor of physics at the University of York, UK, for an engaging overview that covers the fundamental science of magnetic nanoparticles as well as looking ahead to the delivery of real-world diagnostic and therapeutic nanoparticle technologies.

Right now magnetic nanoparticles are the focus of fast-moving R&D efforts in areas like targeted drug delivery, gene therapy, heat treatment of cancerous tumours (hyperthermia) and magnetic-particle imaging.

When it comes to the science, a recurring theme is the ability to tailor the magnetic properties of nanomaterials by reducing the length scale of certain critical dimensions – for example, particle diameter, separation distance and thickness.

Equally important is the creation of cross-disciplinary research teams. “It’s absolutely critical,” notes O’Grady. “You not only need to make the particles and to understand the physics of their magnetic properties. Then you need chemistry – because you need to separate the particles so that they can act individually to provide the functionality that you’re trying to achieve.”

To add a further level of complexity, scientists must tailor the performance of the nanoparticle so that it does exactly what it’s intended to do in vivo or in vitro.

“[For example], you possibly want the particle to attach to one type of cell but not to another,” explains O’Grady. “Therefore you need to ‘functionalize’ the nanoparticle and that takes you immediately into the realm of biochemistry.”

He concludes: “In this area, as in many areas of biomedical technology, you need the full complement of skills. There can’t be any boundaries in this kind of science.”

Distant stars shed light on the solar cycle

Sustained drops in the energy output of the Sun could be more common than modern experience suggests, according to an international team of astronomers that has studied the activity of a number of Sun-like stars. The results could mean that past changes in global temperatures are more likely to be related to variations in solar activity than previously thought, and could allow us to predict similar changes in future.

Our Sun has a well documented cycle of magnetic activity with a period of about 11 years. This cycle can be observed as a rise and a fall in the number of sunspots and a variation of about 0.15% in the power output of the Sun. Direct observations of sunspot numbers stretch back about 400 years, but the amount of carbon-14 taken up by living things drops during periods of high activity and this can be used to chart solar activity back several thousand years.

Solar laboratory

In 2006 Mark Giampapa of the National Solar Observatory, Arizona, and colleagues used the Very Large Telescope (VLT) in Chile to measure the activity levels of 60 stars in the M67 galactic cluster – nearly 3000 light-years away. “M67 is an ideal solar laboratory in the sense that it has the same age as the Sun and virtually identical chemical abundances,” Giampapa told physicsworld.com.

Sunspots cannot be observed directly on distant stars, so the team focused on certain emission lines in the spectra of light emitted by the stars. The width of these lines can be related to the level of magnetic activity in the star, allowing the team to conclude that 7–12% of the stars exhibited activity beyond a typical solar maximum and 17% were below a typical solar maximum.

Now, Giampapa and Ansgar Reiners of Germany’s George August University have made further measurements of these high-activity stars and found them to be less like the Sun than first thought. “Those stars that are more active than the Sun at the maximum of its sunspot cycle appear to be more rapidly rotating, which naturally gives rise to enhanced activity,” explained Giampapa. In some cases the stars were rotating twice as a fast as the Sun and so are unlikely to be a true representation of our star.

Atypical feature?

The low activity levels cannot be so easily explained and might represent a typical feature in the activity of a Sun-like star. One well documented example of such a period of unusual solar quiescence was the Maunder Minimum of the 17th century, when a significant drop in sunspot numbers coincided with a recorded drop in global temperatures. If Giampapa’s research rings true, it could mean that the Sun spends a significant amount of its time in a Maunder Minimum-like state – and it might reveal how likely we are to experience such periods of cooling in the future.

“This interpretation of the Sun is also supported by the terrestrial carbon-14 record showing that the abundance of this isotope is consistent with lower solar activity,” Giampapa.

However, Lyndsay Fletcher, a solar physicist at the University of Glasgow not involved in the research, suggests being a little more cautious about how to interpret the findings. She described the result as “genuinely interesting” and that “the evidence is there but it’s subtle and it’s hard to know how to relate it to the Sun.”

Not absolutely identical to the Sun

The problem might lie in the fact that the M67 stars are not absolutely identical to our Sun. “These stars are solar type but they’re not exactly the same class. They range from G2 to G6 and the Sun is a G2 star,” Fletcher explained.

“It’s very challenging research and it looks like they’ve done an extremely good job but I think there is more work that needs to be done to see whether this interesting suggestion actually bears out,” she said.

The research has been accepted for publication in Astrophysical Journal.

A lively chat about the history of radiation

By Hamish Johnston

There was more stimulating discussion about the history of physics on BBC Radio 4 this morning.

Melvyn Bragg was joined by physicists Jim Al-Khalili and Frank Close, and historian Frank James for a lively chat about the history of electromagnetic radiation.

The team began with a discussion of Newton’s particle theory of light and moved swiftly on to the early 19th century and Thomas Young’s double slit experiment – which established the wave nature of light…

…but that’s when I bumped into a colleague who was also walking to work and stopped listening!

According to the BBC website – where you can listen to the discussion on line – the trio then traced the histroy of electromagnetic radiation through the work of Michael Faraday, Henri Becquerel, Max Planck, Ernest Rutherford and others.

And if your are wondering if you can listen to other radio programmes about physics on Radio 4, just click here for a choice of 20.

Isotope study puts a chill on ancient oceans

 

A new study of stable isotopes in ancient rocks suggests that the oceans were much cooler 3.4 billion years ago than previously thought. The discovery that the ocean could have been cooler than 40 °C was made by geophysicists in the US and could change our understanding of how life evolved after first appearing in these ancient seas.

Fossils created by mats of microbes suggest that life began on Earth more than 3.5 billion years ago in the Archaean eon, when many geologists believe that our planet was covered in an ocean that was very hot (55–80 °C). The origin of life in such a hostile environment is backed up by “universal tree of life” studies of DNA, which suggest that modern life can be traced back to “thermophilic” microbes that thrive at such temperatures.

Geophysicists have a rough idea of how hot the Archaean oceans were thanks to studies of the relative abundance of oxygen isotopes in certain rocks called “cherts”. These studies are based on the fact that cherts formed in room temperature waters, for example, contain much more oxygen-18 than cherts formed in water at 80 °C.

Unknown quantity

But to estimate the temperature of Archaean oceans we need to know the relative abundance of oxygen isotopes in Archaean seawater, which most studies to date have assumed is the same as in modern seawater. However, that may not be the case. The Earth looked very different 3.5 billion years ago compared with today – with little land and an atmosphere possibly rich in hydrogen gas – and the abundance of isotopes may have been very different.

Now Michael Hren at the University of Michigan, Mike Tice of Texas A&M University and Page Chamberlain at Stanford University have devised a new way of working out Archaean temperatures – without having to make any assumptions about Archaean seawater.

Their technique is based on the fact that cherts also contain small amounts of deuterium, the abundance of which the team measured along with oxygen-18. It turns out that the abundance of oxygen-18 drops dramatically if the chert is formed at temperatures greater than about 55 °C, whereas the deuterium abundance remains relatively stable.

Lower upper limit

The team examined the deuterium and oxygen-18 abundances for about 25 chert samples from South Africa known to be about 3.42 billion years old. From their data they were able to constrain the ancient ocean composition and put an upper limit on ocean temperatures of about 40 °C.

The result suggests that Archaean life could have existed in a wider diversity of environments than previously thought. For example, life could have first emerged as thermopiles in hot water near to hydrothermal vents, but then ventured further away into cooler water, adapting to conditions there. “A cooler ocean would mean that life could be more diverse,” explained Hren.

Commenting on the research, astrobiologist Malcolm Walter of the University of New South Wales told physicsworld.com that “one of the big issues in speculation about the origin of life is whether the ancient oceans were hot”. Walter also pointed out that “there have long been doubts that…the oxygen isotopic composition has been constant” – a problem that he said is compounded by the fact there are very few known examples of Achaean cherts that can be studied.

Walter described the work of Hren and colleagues as “innovative”, but added that he will treat the results with “caution” until he could gauge the response of the wider geological community.

In the meantime, Hren and colleagues will repeat their measurements on other cherts that have been subject to different aging processes.

Elspeth Drayson: life in the fast lane

What sparked your interest in physics?

At school, my best subjects were maths and sciences, and while I was doing my degree at Imperial College London I particularly enjoyed classes in medical physics. This was partly because my father ran the medical-engineering department at Oxford University, so I had been exposed to the subject as an early age. My five sisters also studied science, so it was definitely in the blood. While I was then doing my MSc in medical physics and electronics at Bart’s Hospital, I became interested in the business side, so after finishing the MSc I did a degree in management studies at Oxford.

What did you do next?

I joined a small start-up company that was working on a system that monitored platelets prior to blood transfusion, to assess their viability. Platelets have to be stored at room temperature, not frozen, and they only last about five to seven days. At the end of their life they change from a disc shape to a sphere, and the idea was that we could measure their shape by shining light through them. The machine the company built to do this turned out to be an expensive solution, but it was a very interesting field, and I got quite involved in the marketing side. Then after I met my husband – which happened, literally, over a Bunsen burner in a lab at Oxford – we co-founded a vaccine company, PowderJect Pharmaceuticals, and developed it over a 10-year period.

How did you become involved in motor racing?

Paul went into politics after we sold PowderJect in 2003, and by that time I had already stepped down from being a director to have a family. But we had really enjoyed working together and we wanted to do something else. When he announced that he had always wanted to drive a racing car, I thought this was obviously a midlife crisis of some description. Then, after he had entered several races and started doing quite well, I recognized that it was not a temporary interest and if the children and I did not get involved, then we would hardly see him. We set up our own race team two years ago, and owing to Paul’s political commitments, I have been the one running it. My current role does not involve a lot of physics, but it does involve understanding the engineering decisions and the financial side of the business. I also love numbers, so at races I find myself concentrating on lap times and average fuel consumption. Having a numerical mind is really useful.

What are you working on now?

In this year’s American Le Mans Series, we are racing in the prototype category for the first time. One of the reasons we moved into this category is that you have much more scope to showcase new technologies. We did use biofuel made from waste wood in our previous car, but otherwise the rules really limit what you can do. With the prototype, we are looking at a whole range of things, from carbon capture to electric motors and flywheels, which may aid performance but will also be more energy efficient. One of the key reasons we got into racing was to show that you can combine green technology with a very fast race car. Also, race technology develops very quickly, so if innovations work and have applications in other areas, they can be on a fast track to integration.

Do you worry about safety when your husband is driving?

If you are just watching the cars, oddly enough it is easy to forget who is inside them. Even when you see a crash on the big screen, you just think “Oh, I hope that person’s okay”. But also the technology has improved tremendously. Back in the old days, when people had a crash at high speeds, they would break their neck from the sheer impact. Now, there is a device that attaches the helmet to the seat so that drivers’ heads are supported. That has saved many lives, and there are also fire-retardant race suits and so on. Having better technology still does not prevent all accidents; in fact, last year at Le Mans, the cars had a tendency to take off on a certain part of the track. They are like aeroplanes at that speed – not enough down force! Quite a few competitors were taking off, spinning, with parts of the car coming flying off – and then the driver would get out and walk off the track saying “I’m fine”. That reassures me that safety is pretty good.

Physics and motor racing are both very male-dominated – have you experienced any problems in either field?

At Imperial I was one of 20 women out of 200 students in my year, and at a careers evening I asked a medical physicist for advice. He said, “My advice to you – dear – is to find yourself a nice husband and not bother.” I was not disrupted by this, thankfully! There are even fewer women in motor racing than there are in physics; in fact, for a long time the only women associated with the sport were glamour models posing on the cars. But now there are a number of very good female engineers and mechanics who are not decoration – they make a contribution and excel at their jobs. I would like to think that in the future, any woman studying physics or engineering could think “Ah, perhaps a career in motor sport is for me”.

How do you think your physics background has helped you?

I think the training in physics makes you an analytical person, someone who is very precise and direct and who expects direct answers. This means you can spot people who do not know what they are talking about, even if they try to use technical language. Also, you can ask a couple of questions and soon ascertain exactly what is wrong. For example, during a race I listen to a lot of dialogue between engineers and drivers, so when someone reports smoke in the cockpit, noises or understeer, I can hear the solutions to the problems, and I know to ask about spare parts, why something was not tightened or tested, and so on.

Do you have any advice for physics students?

Pursue things that you are interested in, and dare to be different. A lot of people view science graduates as having limited options – teaching, research or finance – but it is possible to become an entrepreneur, and do something completely different that you never thought you could do. If you had asked me at aged 18 where I would be all these years later, I could never have painted the picture that now describes my life. I never thought it would be possible to have a business, a family that balances with challenging work, and the freedom to make choices without being constrained by a large institution. I really enjoyed studying physics, but I also enjoy doing things that are not necessarily related but where the physics training has been really useful.

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