physicsworld.com Blog
May 16, 2008
Canadian firm shelves isotope reactors
The sad saga of the MAPLE nuclear reactors may have finally come to a close with today's announcement from Atomic Energy of Canada (AECL) that the firm will no longer try to get the pair of reactors licensed to produce medical isotopes.
MAPLE was conceived in the 1980s as a replacement for AECL's ageing NRX and NRU research reactors at Chalk River, Ontario. "M" stands for "multipurpose", and the MAPLE was intended for both basic research as well as the commercial production of radioactive isotopes for medical and other applications.
Two MAPLE reactors were finally built at Chalk River in 2000, but it soon became apparent that they both suffered from serious safety problems associated with shoddy workmanship. As a result the facilities have never been granted full operational licences by the Canadian nuclear regulator.
AECL has also had safety problems with the 50-year old NRU, which had to be shutdown unexpectedly for about a month in 2007, leading to an international shortage of medical isotopes.
In the case of NRU, the Canadian government stepped in to restart the reactor — overruling its own regulator. AECL may be gambling that its move to scrap MAPLE may cause the government to pressure the regulator into approving the reactors.
The dusty cosmos
Astrophysicists have a better idea of how dust obscures the light from galaxies, according to a paper published in Astrophysical Journal Letters.
It is already well known that dust, which permeates all galaxies, attenuates the light reaching Earth from the cosmos. It absorbs light of most wavelengths and then re-emits it as a blanket of infrared radiation. Now, Simon Driver of St Andrews University in the UK and colleagues have produced the first model that accounts for this absorption.
One of the model's implications — that dust absorbs just under half the radiation produced by stars — will not be a surprise to astronomers. They already know this, having compared the average magnitude of the infrared radiation in the sky with the magnitude of the radiation from pinpoint sources like stars and galaxies. But what might be of interest is that Driver and colleagues can show how the dust affects the light output of galaxies depending on their orientation.
I spoke with Alastair Edge of Durham University, who is familiar with Driver's team's work, and he was pleased that that the researchers have managed to model the dust successfully. He followed up our conversation with an email: "The authors have made an important link between the observed properties of the galaxies we see from the light coming directly from their stars to the amount of long wavelength radiation we see coming from the dust within the galaxies. Obtaining a match between the energy absorbed and that re-radiated allows us to understand the global properties of galaxies in a more holistic fashion."
May 14, 2008
US public say yes to science debate
I'm sorry to say that, having taken a day's leave on Monday, this snippet of news (above) about ScienceDebate 2008 escaped my attention. According to a poll conducted by Harris Interactive on behalf of ScienceDebate 2008 and Research!America, 85% of US adults think agree that the presidential candidates should participate in a debate on science in the run up to the November election.
(For those of you who have missed the protests of the 37,000 signatories of ScienceDebate 2008, see my last news story on their progress.)
Shawn Otto, CEO of Science Debate 2008, gave the following statement in a press release:
"This topic has been virtually ignored by the candidates, but this poll shows that Americans of all walks know how important science and technology are to our health and way of life. We've heard a lot about lapel pins and preachers. But tackling the big science challenges is critical to our children's future — to the future of the country and the future of the planet. Americans want to know that candidates take these issues seriously, and the candidates have a responsibility to let voters know what they think."
The poll also shows that:
- 67% of adults think scientific research has contributed either "a lot" or "a great deal"
- 67% think that scientific evidence, rather than personal belief, should influence science policy
- 69% rate alternative energy as one of the most serious long-term issues
- 53% rate climate change as one of the most serious long-term issues
You can read more here.
Oh brother, where art thou?
I wonder if many other scientists under the wing of the Holy See agree with Jose Gabriel Funes, the head of the Vatican observatory, or whether he's something of a radical.
In an interview in yesterday's edition of the Vatican newspaper L'Osservatore Romano, Funes not only admits that he believes in the Big-Bang model of the universe's creation, he states that humans should be open to the possibility of alien life. "Just as there's a multiplicity of creatures on earth," he says, "there can be other beings, even intelligent, created by God."
To be clear, Funes is in no way dismissing the first two chapters of Genesis. In fact, he sees "no contrast" between the notion of aliens and the Catholic faith. The other beings might also be worshipping God, he says.
The interview is headlined "The extraterrestrial is my brother".
May 13, 2008
Nearly seeing Hawking radiation?
Astrophysicists have known for more than three decades that black holes shouldn't be totally black — they should emit a certain amount of "Hawking radiation" from the production of particle–antiparticle pairs around their event horizons. But detecting Hawking radiation has so far proved tricky, mostly because its temperature would be at least eight orders of magnitude lower than the cosmic microwave background left over from the Big Bang.
One way round this problem, as Ulf Leonhardt and colleagues from the University of St Andrews, UK, demonstrated earlier this year, might be to create systems that are analogous to black holes in the lab in which the temperature of the radiation is much higher. The researchers showed that a pulse of light travelling through a fibre can behave like a black hole, and, although they didn't actually detect Hawking radiation, they showed that in principle it should be possible.
Now, in a paper published today in the New Journal of Physics, is seems as though Leonhardt's group are one step closer. Rather than use pulses of light as an analogous system to a black hole, they have built a system of water waves. I confess that I haven't yet studied this paper carefully enough to describe with any certainty what the researchers have done, suffice it to say they claim to have observed "negative-frequency" waves, the classical analogue of anti-particles which are the hallmarks of Hawking radiation.
In a brief email conversation last week, Leonhardt told me that they are not yet sure whether this is enough to constitute an observation of a classical analogue of Hawking radiation: "Hawking's effect is a quantum phenomenon, a spontaneous quantum process, but like all spontaneous processes it can be stimulated. This is what we did, we sent in waves and saw a tiny bit of stimulated negative-frequency waves, but there are quantitative differences between experiment and theory that we do not understand yet."
Of course, if and when Leonhardt's group do find negative-frequency waves that agree with theory, there will be a debate as to whether they are "real" Hawking radiation. No doubt you will be seeing more of this on physicsworld.com soon.
May 12, 2008
Einstein's Mistakes
"Many of [Einstein's] ground-breaking discoveries were blighted by mistakes, ranging from serious misconceptions in physics to blatant errors in mathematics".
So says a promotional blurb for Einstein's Mistakes: The Human Failings of a Genius, a new book from the American physicist and author Hans C Ohanian that will be published in September by W W Norton.
Ohanian has posted an eight-page taster of his work on the arXiv preprint server, in which he presents a "critical examination" of how Einstein went about proving his most famous equation E = MC2. All of these proofs, claims Ohanian, "suffer from mistakes".
This is not the first time that Einstein's proofs have come under scrutiny, with various detractors and supporters arguing since at least 1908 — three years after the equation was first derived.
Elsewhere in the world of Einstein biography, a letter on religion written in 1954 by the physicist to the German philosopher Eric Gutkind has come up for auction in London. "The word God is for me nothing more than the expression and product of human weakness...", wrote Einstein who died the next year — and has presumably discovered whether or not this letter was a mistake.
May 9, 2008
The return of the "Science Warrior"
Plugging his new book last night in Bristol — the UK city where Physics World is based — was physicist Alan Sokal. The New York University professor rose to fame in 1996 when he published his famous hoax paper Transgressing the Boundaries: Towards a Transformative Hermeunetics of Quantum Gravity in the cultural-studies journal Social Text.
Sokal had written the paper, which was filled with scientific-sounding gibberish, to highlight what he saw as the sloppy thinking of some sociologists of science, particularly those who deem scientific knowledge to be socially constructed, rather than a matter of objective truth.
His paper sparked what became known as the Science Wars, which saw furious debate in scholarly journals and magazines, including Physics World, between physicists and sociologists. Now Sokal is back on the scene with his new book Beyond the Hoax, published by Oxford University Press.
Speaking at Bristol's Festival of Ideas, Sokal outlined the main themes of Beyond the Hoax. Post-modernist views as espoused by some sociologists still get his goat, but now that some in that camp have, as he puts it, back-tracked from their earlier, more radical stance, Sokal has extended his criticisms to other groups who he thinks also don't embrace the rational, empirical thinking that is the hallmark of all science.
That basically boils down to four main groups: religious people, pseudoscientists, proponents of homoepathic medicine, and spindoctors and others involved in PR. He saved particular anger for George Bush and Tony Blair for deciding to go to war with Iraq and then retrospectively justifying the decision based on what Sokal saw as weak evidence such as dodgy satellite photos.
Overall, it's a bigger pool of victims for Sokal's ire. But by broadening the range of targets, my concern is that his initial fury from 10 years ago has got somewhat diluted.
To his credit, Sokal responded well to the grilling given by his audience, although the majority were, I'd guess, generally supportive of his main themes. A fuller version of his lecture was previously given in London earlier this year. Meanwhile, Physics World has commissioned a review of Beyond the Hoax, to be published later this summer — so keep an eye out online and in print for an authoritative assessment of his new tome.
May 6, 2008
Who cares if it's not even wrong?
"So what would you do if string theory is wrong?" asks string theorist Moataz Emam of Clark University, US, in a paper posted on arXiv yesterday. It's obvious, you might think. String theorists would briefly mourn the 40 years of misspent speculation and leave furtively through the back door, while anti-string theorists would celebrate in light of their vindication.
Not so, says Emam — string theory will continue to prosper, and might even become its own discipline independent of physics and mathematics.
Oddly, the reason Emam gives for this prediction is precisely the same reason why many physicists despise string theory. For example, in reducing the 10 dimensions of string theory to our familiar four, string theorists have to fashion a "landscape" of at least 10500 solutions. Emam says that such a huge number of solutions — of which only one exists for our universe — may make string theory unattractive, but in studying them physicists are gaining "deep insights into how a physical theory generally works":
"So even if someone shows that the universe cannot be based on string theory, I suspect that people will continue to work on it...The theory would be studied by physicists and mathematicians who might no longer consider themselves either. They will continue to derive beautiful mathematical formulas and feed them to the mathematicians next door. They also might, every once in a while, point out interesting and important properties concerning the nature of a physical theory which might guide the physicists exploring the actual theory of everything over in the next building."
Peter Woit, author of the string-theory polemic Not Even Wrong, notes on his blog that physicists looking to pursue string theory for its beauty should "go and work in a maths department":
"The argument Emam is making reflects in somewhat extreme form a prevalent opinion among string theorists, that the failure of hopes for the theory, even if real, is not something that requires them to change what they are doing. This attitude is all too likely to lead to disaster."
May 2, 2008
Is this the youngest professor ever?
According to the Guinness Book of World Records, and what appears to be most major media outlets, Alia Sabur (pictured above) has broken the record for the world's youngest professor.
Sabur, 19, will begin teaching physics next month at the Department of Advanced Technology Fusion at Konkuk University, Korea. It will be just another entry on the teenager's laden CV, which reveals she received a bachelor's degree at 14 and a masters in materials science at 17.
Something might be awry here, though. There's nothing wrong with the media adopting the American English definition of "professor" (i.e. any university teacher) — after all, Sabur was born in New York. But it appears that the previous record holder was Scottish physicist Colin Maclaurin, who was appointed professor of mathematics at the University of Aberdeen when he was a few months over 19 in 1717.
I might have to explain to our international readers that in the UK "professor" is a more distinguished title, reserved for heads-of-departments and the like. (At least it has been as far back as any of us at Physics World can vouch for.) Sabur, I note, is yet to defend her PhD.
Does this mean the titles of Sabur and Maclaurin are being confused? Does Maclaurin, who is credited with the mathematical "Maclaurin series", deserve to keep his accolade?
Of course, science was a considerably narrower discipline back in the 18th century, and achieving a professorship might have taken a little less time than it does today (it certainly wouldn't have required a PhD). But Maclaurin can't defend his honour, and offhand I don't know enough about science in the early 1700s to cast a vote either way.
Do any of you have any thoughts? Feel free to comment below.
May 1, 2008
Nickel-based compound joins a new class of superconductor
The high Tc superconductivity community has been abuzz lately with the discovery of a growing number of iron-based materials that remain superconducting at temperatures as high as 55 K.
The first such material (fluorine-doped LaOFeAs) was reported by physicists in Japan earlier this year and has a transition temperature (Tc) of 26 K. Since then, researchers in China replaced the lanthanum (La) with samarium (Sm) and boosted Tc to 55 K. The Japanese team, meanwhile, put their material under pressure and increased Tc to 43 K.
Now, just as physicists are beginning to understand the mechanism behind these iron-based materials, scientists in Russia have come up with a new twist by replacing iron with nickel. They found that fluorine-doped LaONiBi is a superconductor with a Tc of 4K.
While this Tc is much lower than the iron-based materials, the team reports that LaONiBi has very similar structural and electronic properties as its iron-based cousins. This suggests that with a bit of fiddling with doping levels and other properties, the Tc could be boosted considerably.
April 30, 2008
LHC magnets pass test
On April 3 last year, the left-hand side of the Fermilab Today website had a graphical weather forecast depicting storm clouds. It was a fitting metaphor for the mood of the US lab, which had recently discovered that one of the "quadrupole" magnets it supplied the European lab CERN for the Large Hadron Collider (LHC) had failed a preliminary test. On the right-hand side of the website, Pier Oddone, the director of Fermilab, admitted they had taken "a pratfall on the world stage".
Indeed they had. The failure meant they had to replace all similar magnets with redesigned models and skip the low-energy test runs that were due to take place before winter. It also added to the problems that forced CERN to delay the LHC's (already repeatedly delayed) start up from May to July this year.
Now, though, everything looks to be well again. On the right-hand side of Fermilab Today, Oddone writes that the first of the replaced magnets has passed the test it failed last year. He writes that the 50 or so scientists, engineers and technicians at CERN who made the repairs deserve "a crown". And the left-hand side of the website is forecasting sunshine.
The original problem was that the magnets had inadequate support to withstand the forces produced during "quenching". This is when a magnet gets warmed up above its 1.9 K operating temperature, and could happen happen, for example, if one of the LHC's proton beams veers off course. Last Friday the replaced magnet passed the one-hour test designed to simulate quenching.
"Everyone commissioning the LHC," writes Oddone, "both accelerator and detectors, is racing excitedly towards colliding-beam operation and the great physics results that we can almost taste."
'He should seriously consider his position'
The current "crisis" in physics funding in the UK was big news this morning on BBC Radio 4's Today programme.
In an interview that ran just before the 8:00 news, physicist Brian Cox of the University of Manchester said that Keith Mason — head of UK's main funding body for physics and astronomy (the STFC) — "should seriously consider his position".
Cox was commenting on a report released today by a committee of British parliamentarians that poured criticism on recent funding decisions made by the STFC and also questioned the competency of its senior management.
Cox told the programme that the STFC has caused a great deal of anxiety in the physics community, with some researchers being told that they would have to pull out of long-standing international collaborations. He also said that morale was very low among people working at the STFC itself.
Interviewed in an earlier piece on Today was committee chairman Phil Willis MP, who said that the STFC's actions had jeopardized the UK's high international standing in physics research.
Mason declined the BBC's request for an interview.
You can listen to a repeat of the Today programme using the BBC's Listen Again service.
April 29, 2008
Computing with Playstations
With $5000 of his research grant left burning a hole in his wallet earlier this year, Frank Mueller, a computer scientist from North Carolina State University, decided to hit the shops and buy eight Playstation 3 games consoles. Not for pleasure, you understand — no, Mueller figured that with eight Playstations strapped together he could create a modestly powered supercomputer. "The cost for performance is unbeatable," he says.
Mueller's "cluster" of games consoles doesn't quite break into the TOP500 list of supercomputers. But if he had another $4m lying about, he reckons he could string together 10,000 Playstations to make the fastest supercomputer in the world.
So, could physicists use Playstations to save a few trips to Blue Gene? "Yes," says Mueller, "if they are willing to substantially rewrite their most computer-intensive code portions in a non-standard API." That's the Application Programming Interface, for those of you who don't know.
On his website, Mueller notes that he uses his Playstation cluster for "educational purposes".
April 28, 2008
Tabloid climate change
You don't need a research paper to tell you that tabloid newspapers aren't the best source of scientific information.
Or do you? Maxwell Boykoff and Maria Mansfield from the University of Oxford, UK, seem to think so. In a paper published today in Environmental Research Letters, they have surveyed nearly 1000 articles dating back seven years from the UK's most-read tabloids: the Daily Mail, the Sun, the Express and the Mirror. It seems that around a quarter of the articles have strayed from scientific consensus — that is, that anthropogenic greenhouse gases are "very likely" to be causing the observed global warming over the past half century.
This conclusion is buttressed by interviews with journalists and editors, as well as examples of dodgy environmental reporting. Here's a few to whet your appetite:
"Experts are still arguing over whether [global warming] is a natural phenomenon, or the effect of industrial societies releasing heat-trapping gases into the atmosphere..." (Ivor Key of the Express)
"It seems that the most significant global warming is caused by the hotheads who are anxious to believe their own propaganda." (Commentary in the Mail on Sunday)
"This confirms what I have been saying for years — cars do not cause global warming. Now we learn that all along it was bloody sheep and cows." (Jermey Clarkson, motoring journalist and regular aristarch of environmentalists, commentating in the Sun after learning that methane emissions from cattle are significant in global warming)
There's an interview with Boykoff on our sister website, environmentalresearchweb.
March 13, 2008
The four horsemen
This is a slide from a talk given by David Bader of Lawrence Livermore on behalf of Brian Soden of the University of Miami. It shows the four main feedback mechanisms that are believed to play a role in climate change.
They are the temperature and water content of the atmosphere; ice and snow cover; and cloud cover. Physicists are fairly certain that the first three are have a positive-feedback effect -- that is they tend to increase the rate of global warming -- but they are not so sure about clouds.
In particular, the effect of stratocumulus clouds on climate has been very difficult to understand. The problem is that these puffy clouds are very thin and turbulent, making it hard to understand the physics of how they participate in the transfer of radiation into and out of the atmosphere.
According to Bader "uncertainty of cloud feedback is the primary cause of uncertainties in climate models". That sounds like a challenge to the physics community.
Weathering the storm
"You can flood a city, but you can't drown a university", says Greg Seab, a physicist at the University of New Orleans who was speaking at a press conference on the impact of Katrina on local physics departments.
Although the university was above the high water mark when Katrina flooded much of the city in September 2005, the campus was without electricity for six months. Indeed, the power only came on three days before the campus was scheduled to reopen in 2006.
But instead of cowering in the dark, the University re-invented itself online. Just a month after the disaster, faculty were delivering lectures and course work to 7000 students. However, one third of the university's faculty eventually left after Katrina -- something that Seab blames in part on "abysmal support from the state [of Louisiana].
The Xavier University campus suffered a direct blow, with many of its lecture halls underwater. The institute managed to reopen in January 2007, extending its academic year until August. Repairs have so far cost the university $50 million according to physicist Murty Akundi. 75% of students returned that January and Akundi says that enrolment is expected to be back to 80% of pre-Katrina levels by September 2008.
On a more cheerful note, David Hoagland of the University of Mass. at Amherst explained how he received a call from a colleague at New Orleans's Tulane University asking if he could move his entire research group to Amherst. Hoagland said yes and the team were up and running in a month -- and apparently "flourished with no scientific loss".
I naturally assumed that these were theorists -- but no, these intrepid experimentalists managed to clone their Tulane lab using borrowed equipment, much of it coming from scientific equipment makers. Where there is a will, there is a way!
Glue and cuprates
One of the most sought after theories in condensed matter physics is that of high temperature superconductivity. It is hard to walk into these kind of talks and understand what is going on. If it is theory, it's next to impossible as the first slide almost jumps into a large Hamiltonian, and as I guess these Hamiltonian's have been discussed ad nauseum by now, people have started to not even describe any of the terms.
In a talk given by Doug Scalapino from the University of California at Santa Barbara, he discussed the question of a pairing 'glue' in high temperature superconductors. From what I understand this goes back to last year when Phil Anderson wrote a perspectives in science with the point that if "we have a mammoth and an elephant in our refrigerator - do we care much if there is also a mouse?"
Here the mammoth and the elephant are U, the on site repulsion and J, the exchange interaction in the Hubbard model which describes the transition between conducting and insulating systems. So Anderson says as these interactions are so large why do we need a mouse or a much smaller interaction that is the 'glue' that pairs electrons. In ordinary superconducting metals, like lead or Tin, these exchanged particles are phonons (lattice vibrations) that act like a bosonic "glue" to hold the electron pairs together. But what is the 'glue' for high temperature superconductors, like the cuprates? Anderson contends that the pairing interaction is coming from J which is instantaneous, attractive and large, so why do we need a smaller interaction to describe the bosonic glue?
Well, the glue that Scalapino was describing was not very clear to me, and it seems that was also the case with some audience members. Indeed, one person did ask at the end of the talk what is the glue and Scalapino's answer was, well, spin fluctuations. But as Anderson points out these are just a natural consequence of the exchange interaction, J.
I think the jury is still out.
A decade of the New Journal of Physics
So as not to be outdone by the APS, here's a photo of a cake baked in honour of the 10th anniversary of IOP Publishing's New Journal of Physics. The first-ever multi-discipline open access physics journal.
March 12, 2008
Happy Birthday PRL
That's some cake!
Yesterday evening my IOP Publishing colleagues and I managed to blag our way into a posh reception celebrating 50 years of the journal Physical Review Letters. I forgot to take my camera, so the photo is courtesy of James Riordon at the APS.
And yes, we did sing:
Happy birthday Physical Review Letters,
Happy birthday to you.
A new spin on silicon and graphene
At last year's March Meeting in Denver, Ian Appelbaum gave a ten-minute talk about how he had injected spin-polarized electrons into a piece of silicon, transported them micrometres and then detected a spin-polarized current at the other end. It was just one of thousands of talks given that year.
But then Appelbaum published his results in Nature and this year he has been invited back to speak for 30 minutes -- which he did today in a packed session that focused on spin injection in silicon.
The ultimate goal of Appelbaum's research is to find practical ways to make "spintronic" devices, which in principle, could use the spin of the electron to process information much more efficient ways than coventional electronics.
To make a spintronic device, you need a material through which electrons can flow without losing their spin polarization -- and it would be nice if that material was compatible with chip-making processes. Silicon fits the bill on both accounts, but is also has several drawbacks -- it is difficult to inject spin-polarized electrons into the material; and once they are there it is difficult to measure their polarization.
Working at the University of Delaware Appelbaum's team were the first to overcome these problems and you can find out how here.
I spoke with Appelbaum before his talk about how the fledgling field of silicon spin injection was shaping up. He described his breakthrough as a "clarification of the technologies that are needed", and added that at least one more year of work by his team and others was needed before it would be possible to take a broader view of where the field was going.
Also speaking at the session was Berry Jonker of the Naval Research Lab. While Appelbaum detected spin polarization electrically, Jonker has worked out ways to detect it using light -- something that is not usually possible thanks to silicon's poor optical properties. Jonker finished his talk by declaring "There is a bright future for silicon spintronics".
The future could also be bright for spintronics based on pieces of graphene -- which are tiny flakes of carbon just one atom thick. It turns out that graphene shares many of silicon's spin-friendly properties including weak spin-orbit and hyperfine interactions.
Speaking at a session on graphene, Bart van Wees of the University of Groningen, described a similar experiment to Appelbaum's -- but with graphene as the conductor. The experiment revealed that graphene is a good conductor of spin -- but nowhere as good as silicon. The Groningen team found that spin polarization decays after the electrons travelled about 2 micrometres -- a tiny distance compared to silicon. Indeed, Appelbaum told me that he hopes to transmit spins through a centimetre of silicon by the end of the year.
Van Wees described this shortcoming as a "mystery".
Graphene has earned a reputation as a "wonder material" thanks to its outstanding electrical, thermal and mechanical properties. It's comforting to know that graphene has been beaten by humble silicon when it comes to spintronics -- at least for now!