Jon Cartwright: August 2008 Archives

By Jon Cartwright

The debate as to whether the DAMA/LIBRA team has detected dark matter, as it claimed in April, will no doubt persist until fresh data can say either way. But in the meantime, Robert Foot, a physicist from the University of Melbourne, suggests an alternative interpretation: “mirror matter”.

I’ll take a step back for a moment in case you aren’t familiar with the story. (Alternatively, you can see Physics World’s feature.) DAMA/LIBRA is an underground experiment based at the Gran Sasso laboratory in Italy. It looks for dark-matter particles known as WIMPs (weakly interacting massive particles) — a class favoured by theorists for the mysterious substance — by monitoring for flashes that occur when the particles collide with nuclei in 250 kg of sodium-iodide detectors. The idea is that the frequency of flashes should modulate over the year as the Earth changes its speed through our galaxy’s “halo” of dark matter: in June, when the Earth’s orbit takes us faster through the halo, one would expect to see more flashes; in December, when we are moving slower, one would expect to see fewer.

(Credit: Olaf Behrendt)

By Jon Cartwright

Could it be — touch wood — that the Large Hadron Collider (LHC) will make it to the official 10 September start-up date without any further hiccups?

On Friday scientists at the European laboratory CERN were able to tick off two more items on the accelerator’s commissioning list. First, they managed to feed a bunch of protons from the transfer line of the Super Proton Synchrotron (SPS) into the LHC and then steer it some three kilometres round the beam pipe in a counter-clockwise direction. Second, a detector at LHCb — one of the four main experiments at the LHC — got the first taste of collision debris.

(Credit: Chris Lavers)

(Credit: Chris Lavers)

By Jon Cartwright

At first glance these images look like snapshots from that classic eighties sci-fi flick Predator.

It turns out, though, that the pre-eminent being responsible for them is not a brawny, gun-toting alien, but Chris Lavers, a technology lecturer at Britannia Royal Navy College in Dartmouth, UK. The images are infrared portraits of various animals dwelling at Paignton Zoo in Devon.

“I have been involved in thermal imagery for about 10 years now, and thermal imagery of wildlife with Paignton Zoo since 2002,” writes Lavers in an email. “My interest is concerned with highlighting the plight of endangered species under pressure from both man and climate change, deteriorating environments, etc.”

Lavers explains that thermal images can be used to observe animals without stressing them. “It enables a healthy baseline assessment of animals to be established and thereby aids veterinarian diagnosis,” he writes.

Aside from giving giraffes, tortoises and other creatures a once-over, Lavers is also interested in using thermal imaging to copy some of nature’s designs, such as iridescent butterfly wings. These could be employed in future stealth devices, he says.

If you want to see more of Lavers’s images — and are out and about in the south-west of the UK — you can visit his exhibition. It starts on 15 September at Paignton Zoo, and moves onto the Living Coasts zoo in Torquay until the third week of October.

By Jon Cartwright

Has a European satellite detected dark matter? That’s the question on many people’s lips who attended the recent International Conference on High-Energy Physics (ICHEP) in Philadelphia, US.

Several physicists who attended the conference have told me that Mirko Boezio, a representative of the PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) mission, briefly showed data depicting an excess of high-energy positrons in the ionosphere. If true, it would seem to be evidence of annihilation dark matter — an elusive substance thought to make up some five-sixths of all matter in the universe.

Unfortunately, neither Mirko Boezio nor the principal investigator of PAMELA, Piergiorgio Picozza, wants to comment on their data. They told me this was because they are planning to publish in either Nature or Science, and are therefore prohibited from talking to journalists because of those journals’ embargo policies. (Another little birdie told me that the PAMELA team is specifically aiming to submit to Nature by September, so if they fast-track it we might get to see the paper before Christmas.)

I’m going to tell you all I know about this, because frankly it’s not that much at the moment. The slides available from the ICHEP website only show positron data up to about 6 GeV, which doesn’t show much. Slightly better is this slide below from another PAMELA team member, Elena Vannucinni, who gave a presentation at the recent SLAC Summer Institute.

The Green Man festival. (Credit: Stinco di Porco)

By James Dacey

If you read my colleague Michael Banks’s blog entry on Tuesday, you will have heard that Queen guitarist — cum doctor of astrophysics — Brian May is poised to unleash his PhD on popular bookstores from September.

Being a geophysicist — cum amateur guitarist — I am in no position to critique the quality of his astrophysics (nor his ear for a guitar riff!). But I am intrigued by May’s activities.

It remains to be seen whether “A Survey of Radial Velocities in the Zodiacal Dust Cloud” will fly off the shelves. Even less guaranteed is the number that will be bought, read AND understood by non physicists. But leaving aside these concerns for May and his publishers, the point is that a rock star status can provide a platform to encourage non-physicists to take an interest in the subject.

Another public engagement project with a musical stage is “Physics in the Field” and it plays its next gig at the Green Man festival next weekend (14–17 August).

Let me explain.

During the widely-celebrated International Year of Physics in 2005, the Institute of Physics (IOP) sent a small group of volunteers to brave the Somerset mud and host a workshop called “Einstein at Glastonbury”. The idea was to try and spark public interest in physics by dragging demonstrations from the laboratories and plonking them in the more informal setting of a music festival. Being something of an Einstein tribute act, demonstrations linked the physicist’s ideas to music including the inner workings of Rolf Harris’s didgeridoo.