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Cold war tourism hotspot

By Hamish Johnston

Is it cold and rainy where you are?

Then why not pack your bags for Hanford, Washington, where the forecast calls for blazing sunshine and temperatures in the mid-30s (90s in old money) for the rest of the week.

While in town you could take a guided tour of the famous “B Reactor” at Hanford, where much of the plutonium for the Manhattan project was made. Some of this material ended up in the “Fat Boy” bomb that detonated over Nagasaki.

After fuelling many a cold-war weapon, Hanford B was shut-down in 1968 — but instead of being “entombed” like its neighbours, the reactor was designated a National Historic Landmark last year.

The plan is to turn the reactor into a museum and the Department of Energy is gearing up by offering occasional guided tours of the site — and the BBC’s Rajesh Mirchandani boarded the tour bus for what was a front line in the Cold War. You can watch his report here.

But don’t bring the kids — tourists must be at least 18 — and wear sensible shoes.

Hanford guide Michelle Gerber

Remaining tours for this year are on July 25, August 8, 15, 22, and 29
and September 5, 12, 19, and 26. Hanford’s online booking system says the tours are fully booked, but suggests you check back occasionally in case anyone has dropped out.

And if Hanford B is like most defunct reactors worldwide, it will be there for a very, very long time — so you’ll get your chance to see it eventually!

Controversy bubbles over particle physics prize

The European Physical Society (EPS) has defended its handling of its 2009 prize for high-energy and particle physics, despite complaints that the awarding committee has overlooked a vital scientific contribution to the prize-winning work. The biennial CHF5000 award, presented yesterday at a conference in Kraków, Poland, went to collaborators on the Gargamelle experiment at CERN for their 1973 discovery of the weak neutral current — one of the ways in which the weak nuclear force is mediated between fundamental particles. However, the award did not formally recognize the “leptonic” evidence for neutral currents, without which some particle physicists say the discovery could not have been made.

I am amazed and appalled that the leptonic neutral-current channel will not be recognized in the EPS prize Alan Michette, King’s College London

Several Gargamelle collaborators have contacted the EPS with their objections, with Alan Michette of King’s College London and Don Perkins of Oxford University requesting that their names be removed from the prize list. “I am amazed and appalled that the leptonic neutral-current channel will not be recognized in the EPS prize,” Michette told physicsworld.com. “In my opinion this is a historical and scientific error that is being committed in the face of all expert advice to the contrary.”

Smoking gun of unification

Alan Michette

The discovery of weak neutral currents put the nascent standard model of particle physics — namely electroweak theory — on solid experimental ground. Until then, all known weak processes involved a rearrangement of electric charge (so called charged-current reactions) and historically could be described as taking place at a single point. But by the early 1970s a better theory of the weak force had emerged in which charged-current interactions are mediated by a charged particle called the W boson and a new interaction, mediated by a neutral particle called the Z boson, was predicted. The theory required that the Z particle would “mix” with the photon (the mediator of electromagnetism) such that the weak and electromagnetic forces were unified in a single theory.

The Gargamelle results allowed physicists to estimate the ratio of the masses of the W and Z particles, which were directly observed at CERN in the early 1980s and then studied in detail with the lab’s Large Electron Positron collider. That machine has since made way for the Large Hadron Collider, which should unearth the mechanism (widely expected to involve the Higgs boson) responsible for breaking the electroweak force into the two entities we perceive in the low-energy universe today.

Gargamelle, which was a bubble chamber that now stands outside on display near CERN’s main restaurant, recorded the first neutral-current event in December 1972. Filled with 12,000 litres of dense liquid in which charged particles leave trains of tiny bubbles, an electron (a type of particle called a lepton) appeared to have been kicked by an incoming neutrino, which leaves no bubble trace. Soon afterwards, the Gargamelle team had observed many more neutral-current events, this time when an incoming neutrino struck a proton (a type of particle called a hadron).

Vital confirmation

While there were many more “hadronic” events than there were “leptonic” ones, it was harder to pick them out from the bulk of background events that produced a similar signature, and it took a year for the Gargamelle results to be fully accepted. (In fact, an experiment at Fermilab in the US turned out to have already seen hadronic neutral-current events yet had put them down to neutrons). Since the electroweak theory made firmer predictions for the leptonic channel than it did the hadronic channel, largely because protons are not elementary particles, Gargamelle physicists say that the single-electron event was vital in confirming the neutral-current prediction.

Gerard ‘t Hooft of the University of Utrecht, who shared the 1999 Nobel physics prize for his theoretical work on electroweak interactions, says both the leptonic and hadronic contributions were important in the discovery of neutral currents, but that they were also rather different discoveries. “Now, of course, it’s obvious that there is a single weak interaction, but in those early days it was far from clear,” he said. “Having neutral currents among leptons doesn’t necessarily mean there are neutral currents among hadrons, and vice versa.”

Decision stands

James Pinfold

The two Gargamelle results were published in September 1973: one paper reporting the leptonic event and the other the hadronic analysis. The controversy over this year’s EPS prize stems from the decision to award it only to authors of the hadronic paper, leaving four authors of the leptonic paper — Charles Baltay of Yale University, Michel Jaffre of IN2P3-CNRS in Orsay, Jacques Lemonne of Vrije Universiteit in Brussels and James Pinfold of the University of Alberta — out in the cold.

The leptonic channel was at least as important as the hadronic channel in confirming the discovery of neutral currents with Gargamelle James Pinfold, University of Alberta

“The leptonic channel was at least as important as the hadronic channel in confirming the discovery of neutral currents with Gargamelle,” says Pinfold, who wrote to the chair of the EPS High Energy and Particle Physics Division Board, Per Osland, on behalf of all four affected authors requesting that the board amend the prize accordingly. “My request was rebuffed,” he says.

In defence of its decision, the EPS cites the titles of the two neutral-current papers. “The Gargamelle collaboration did a variety of measurements and published many papers with a variety of authors,” Osland said. “The board decided to give the prize for the ‘observation of the weak neutral current interaction’, so it was then natural to point to the ‘Observation…’ paper, where observation was actually claimed, rather than the ‘Search for…’ paper, which presented the leptonic event but did not claim observation of the neutral current.” Osland added that the EPS can not remove names from the list of winners because that would amount to tampering with the list of authors of a paper published 36 years ago.

Michette, however, puts events down to bureaucratic intransigence. “The EPS decided to ignore the voices of a number of members of the Gargamelle Collaboration,” he said. “Simply put, the committee couldn’t admit that it had made a big mistake.”

Listen to Heisenberg compare Sommerfeld, Born and Bohr

Martin Schwarzschild being interviewed in 1977

By Hamish Johnston

If you’d like to listen to Werner Heisenberg compare the physics prowess of Arnold Sommerfeld, Max Born, and Niels Bohr , just click here and you will be taken to the new online Oral Histories section at the Niels Bohr Library & Archives.

The American Institute of Physics — which runs the library — has unveiled a vast online archive of interviews with some of the 20th century’s most prominent physicists.

The archive includes pioneers of quantum theory such as Heisenberg and Max Born, Paul Dirac, Niels Bohr and Eugene Wigner.

The list of histories reads like a Who’s Who of physics. The earliest interviews were done in the 60s and the latest — including NASA’s James Hansen were done quite recently.

Most of the histories are available as written transcripts, but a few voice clips are also available — including Heisenberg, Hans Bethe, George Gamov and Steven Weinberg.

A word of warning about the site: I found that many of the links didn’t work — and I could not actually listen to Heisenberg and company (this could be a problem with my browser). But it’s worth persevering.

Is this the ‘Article of the Future’?

I can’t believe they used to print these things out!

By James Dacey

Do you relish the challenge of ploughing through online abstracts in search of the article’s “bottom line”?
Do you still print out all your papers before going at them with the fluorescent pen?
Do you still love the arcane language and the classic layout: intro – method – results – images – discussion?

Well, your habits could be about to change with the launch of a new initiative by a leading scientific publisher. The Article of the Future project by Elsevier has set out with a modest aim to “redefine how a scientific article is presented online”.

One of the key features of the new format is a kind of web-based filing system in which different aspects of the research – i.e. intro, images, discussion – can be “taken out” and viewed separately.

Intros are different – including a bulleted article highlights section and a graphical abstract. Multimedia is present throughout such as interviews with the authors. If interested, you can see a couple of prototypes of the new format here.

Elsevier say the project is intended to promote interdisciplinary scholarship and help readers identify more quickly which papers are most relevant to their interests.

So how will this new format go down in the physics community?

I reckon pretty well, though I’m sure some purists – especially the theoreticians – will argue that you can’t always reduce the subtlety of their arguments to a few bullet points.

What’s more, if this does catch on with other publishers, it will be interesting to see how the bloggers respond. Because it seems to me that a large aspect of their job at present is to trawl through the piles of paper and pick out the highlights from their field. But if the journal publishers have already done this… what then?

One outcome is that they become more critical. The bloggers will – once and for all – move away from just cheerleading for their chosen specialism. We might see a new form of blogging in which the key players start championing / laying into research with a new-found vigour.

Well, whatever happens I reckon this is another key development in an interesting transitionary period for both the publishing and media sectors.

Higgs boson spotted

Catching up on the latest physics

By Michael Banks

Sorry, not at CERN’s Large Hadron Collider near Geneva or Fermilab’s Tevatron in Batavia, Illinois, but at our office here in Bristol.

This morning, Physics World’s postbag contained our very own Higgs boson plush toy sent from Julie Peasley at Particle Zoo.

Particle Zoo, based in Los Angeles, makes plush toys of all your favourite particles including the neutron, electron as well as particles that have not yet been discovered such as the graviton.

Recently, Particle Zoo even branched out from just making particles to produce a plush toy of the cosmic microwave background and higher-dimensional “branes”.

Physics World can confirm that the mass of the Higgs is surprisingly large and that it is currently taking pride of place in the office next to the latest issue of the magazine.

‘Nanopillars’ make good photovoltaics

A new type of solar-cell module based on arrays of tiny pillars has been made by researchers in the US. According to its inventors, the module is flexible, efficient and can be made using industrial processing techniques — which means that it could offer a low-cost route to efficient and robust solar panels.

Efficient and bendy: nanopillar-based solar cell

Ali Javey and colleagues at the University of California at Berkeley grew regular arrays of cadmium sulphide (CdS) pillars on anodized aluminium-foil membranes. The pillars are identical cylinders, which are each a single crystal about 200 nm in diameter and about 500 nm tall.

To make the pillars, the team deposited a thin layer of gold seeds in the highly regular pores that form in the aluminium foil after anodization. These seeds encourage the growth of the nanopillars when exposed to a vapour-liquid-solid (VLS) process — a technique that produces ordered structures with an orientation that can be controlled.

CdS is a semiconductor and the nanopillars function as photoelectrodes, which convert light into electrical current. Previous studies have shown that such structures have a higher efficiency than flat surfaces because more photons are absorbed at greater depths in the photoelectrode.

The team then fabricated solar cells from the nanopillar arrays and achieved a conversion efficiency of about 6%. This is higher than many other thin and flexible devices, including those based on nanostructured materials. Another advantage compared with bulk solar modules is the small amount of active semiconductor used in the device, which makes them more cost-effective, says Javey.

The technique also shows commercial promise because it could be compatible with “roll-to-roll processing”, which is used to make electronic devices.

“The nanopillars we produced could be used to develop a robust technology for low-cost and lightweight photovoltaics with respectable efficiencies,” he says. “Our work could have important implications for the large-scale integration of solar modules for a wide range of applications. There are still a lot of challenges ahead of us, but the work shows the potential of our technique.”

The team, which includes researchers from the Lawrence Berkeley National Lab, now plans to further enhance light-conversion efficiencies in the devices. The first thing that they will do is optimize and/or replace the top contact material, which is currently causing a 50% loss in the optical transmission. “We will also explore other materials systems by using our device structure and fabrication approach and try to make the technology more viable for large-scale integration,” added Javey.

Nanopillars as far as the electron microscope can see

In particular, the researchers will try to replace the cadmium-based materials used in their devices, because the metal is highly toxic.

The work was reported in Nature Materials.

Apollo conspiracy theories still going strong

Apollo 11 photograph: too good to be true? (NASA).

By Hamish Johnston

Today is the 40th anniversary of Neil Armstrong’s stroll on the Moon so it’s not surprising that conspiracy theorists are one again arguing that the Apollo programme was a hoax.

This morning Marcus Allen, UK publisher of Nexus Magazine — which specializes in conspiracy theories — was interviewed on BBC radio.

He thinks the Apollo landings were hoaxes, partly because of the “high-quality” of the photos taken by crews on the moon. In particular, he claimed that it would be impossible to take such nice photos under the extreme conditions on the Moon — and even if you could, the film would be fogged by the ambient radiation experienced by the mission.

Martin Ward, Head of physics at Durham University, was on hand to debunk the debunker. He explained that the extreme temperatures are a red herring because the lack of atmosphere on the Moon means that the camera and film would take a long time to heat up or cool down once outside the lunar module. As for the effects of radiation, Ward pointed out that lots of other photos have since been taken in space and have not been fogged.

You can listen to their exchange here.

Although I have no doubt that the Apollo missions were real — it’s interesting to ask the following question:

“Would it have been much easier (and much cheaper) to fake the Apollo programme and cover it up for 40 years, than to actually put people on the Moon?”

If you apply Occam’s razor to this question, you may find yourself siding with Marcus Allen…which is what makes the the Apollo missions all the more amazing!

Migrating giants enrich asteroid belt

The Solar System underwent a violent shake-up during its teenage years slinging millions of dark primitive rocks and ice from beyond Neptune into the main asteroid belt, which lies between Mars and Jupiter. This idea contrasts with the standard picture of Solar System formation, which assumes that the entire contents of this belt originate from the same part of the Solar System. It could also yield valuable insights into how the Earth was born from a cloud of interstellar dust nearly 5 billion years ago.

The main asteroid belt in the Solar System is a narrow disc of small objects lying between the orbits of Mars and Jupiter. Images from spectroscopy along with samples gathered from rare collisions with the Earth reveal a wide variety of material from primitive ice-rock mixtures through to igneous rocks. The standard interpretation is that this diversity is a good indicator of what conditions were like in the early solar system before the planets were formed.

A violent youth

In the widely accepted view of how the Solar System evolved, the planets formed in the same orbits they occupy today, by gravitational collapse of a giant molecular cloud some 4.6 billion years ago. In this interpretation, the material in the asteroid belt has also remained in its current location throughout the history of the solar system. Meteorites are studied by geologists to get an idea of what the planet was composed of at the beginning of Earth history.

Now, Harold Levison at the NASA Lunar Science Institute and his colleagues offer a different view of the early Solar System through a simulation they have been developing since 2005. The “Nice model” has all the giant planets forming within a compact configuration between 5 and 15 AU from the Sun — 1 AU is the distance between the Earth and the Sun. Then, after roughly 600 million years, the orbits of these planets started to become unstable, resulting in Uranus and Neptune being scattered outwards into proto-planetary material, which stretches to 30 AU from the Sun.

In astronomical terms this process occurs very rapidly taking just 10,000 years for these planets to migrate to their present orbits. As a result, the arrival of these planets sends material flying in all directions including back towards the inner Solar System. A significant number of these asteroids are then captured in orbits between Mars and Jupiter, or as Trojan asteroids — sharing an orbit with Jupiter. “This is a violent process. I like to use the analogy of a bowling ball colliding with a set of pins,” explained Levison.

Levison and his team estimate that 10–20% of the material in the main asteroid belt could have arrived by this process. He told physicsworld.com that his team intend to develop their research by refining the initial conditions that existed in the proto-planetary disc. “The Nice model is undoubtedly controversial, but there are no other alternative numerical models that can explain how the solar system evolved into its current configuration,” he said.

This research was published in the latest issue of Nature.

NASA unveils aerial views of Apollo landing sites

The highest-ever resolution aerial views of the Apollo landing sites will be made publicly available by NASA today. The photos have been returned by NASA’s Lunar Reconnaissance Orbiter (LRO), launched in June to produce maps of the Moon’s surface with the highest resolution yet. The agency will release the images at noon Eastern Daylight Time and they will also be holding a teleconference at 2.00 p.m. to discuss future plans for the LRO mission.

NASA’s Lunar Reconnaissance Orbiter was launched on 19 June with the mission of gathering a variety of data on the lunar environment. It will have seven on-board instruments, including a camera that will map the Moon with a resolution of about 50 cm. NASA hope this will help them in preparing for a new generation of longer-duration manned expeditions to the moon.

LRO will spend at least a year in a low polar orbit approximately 50 km above the lunar surface, while its seven instruments find safe landing sites. Its objectives include the location of potential resources, characterization of the radiation environment, and the testing of new technology.

“Accomplishing these significant milestones moves us closer to our goals of preparing for safe human return to the moon, mapping the moon in unprecedented detail, and searching for resources,” said LRO Project Scientist Richard Vondrak of NASA’s Goddard Space Flight Center in Maryland.

Could Fermi detect dark matter within a year?

The Fermi Gamma-ray Space Telescope could detect the telltale signs of dark-matter annihilation in as little as a year, if calculations by UK and US astrophysicists prove correct.

The calculations, which are the first to take into account the relative velocities of dark-matter particles, suggest that dark-matter annihilation is many times more prevalent than has been predicted before. If this is true, the annihilations could be producing enough gamma rays to expose several clumps or “subhaloes” of dark matter in Fermi’s first year of data collection alone.

Michael Kuhlen, lead author of the research and an astrophysicist at the Institute for Advanced Study in Princeton, US, says such a detection by Fermi would be “an amazing confirmation” of the standard paradigm of structure formation in “cold” dark-matter theories. “First of all, it would show that dark matter is cold, and that it forms small clumps that populate the Milky Way,” he says. “Second of all, it would show that it is a fundamental particle, which is still not really

Confirming theory

Cold dark matter has become the most accepted explanation as to why the universe appears to have at least 80% more gravitating mass than is directly visible to telescopes. According to theory, cold dark matter is not luminous and interacts only via gravity, and exists in vast haloes around the centres of galaxies. These haloes are full of lumpy substructures called subhaloes, which would be the most likely places for dark-matter particles to collide with one another and annihilate.

Past simulations of dark matter for a galaxy like our own Milky Way have always predicted annihilations to be so rare that telescopes would barely be able to detect the resultant gamma-rays and other particles above the universe’s background. Last year, however, the European satellite PAMELA and the international balloon-borne experiment ATIC recorded excesses of positrons and electrons respectively, hinting at dark-matter annihilation.

Kuhlen, together with Piero Madau at the University of California in Santa Cruz, US, and Joseph Silk at the University of Oxford, UK, decided to see whether these observations could be explained if dark-matter annihilation rates were boosted by an effect known as the Sommerfield enhancement. In this effect, a long range force — which would manifest as either a conventional weak-force boson or a new force carrier — increases the rate of annihilations when the dark-matter particles are moving slowly. Kuhlen’s group applied several different models of Sommerfield enhancement to a simulation of the Milky Way that contained more than a billion particles to see how the gamma-ray flux would be affected.

Seeing subhaloes

For the greatest enhancement, the researchers found that more than 400 subhaloes would be detectable to the Fermi space telescope — which was launched in June 2008 — after one year, and after ten years the figure would rise to over 900. But even for the most conservative model, the researchers found that after a year five subhaloes would be visible.

The news is likely to excite astrophysicists, many of whom have spent decades searching for dark matter’s smoking gun.

“The indirect search for dark matter through its signature in gamma rays is one of the central topics in the Fermi science programme,” says Ronaldo Bellazzini, a physicist at the University of Pisa, Italy, and principal investigator of Fermi’s Italian team. Bellazzini explains that Fermi could detect gamma rays from annihilation even without effects such as the Sommerfield enhancement, but that the latter will improve the chances. “We have already started a search for a dark-matter signal in candidate subhaloes,” he says, adding: “No dark-matter [signal] has been found in the three months of data. This is not yet in contradiction with the most conservative predictions of this paper.”

This research appears in the latest edition of Science.

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Cold war tourism hotspot