Vanishing act: the Italian physicist Ettore Majorana, who disappeared in 1938. Photo: Kanijoman/Flickr
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The vanishing particle physicist and the puzzle he left behind

Ettore Majorana was an Italian physicist, the best of his generation, who disappeared in mysterious circumstances in 1938.

You probably haven’t heard of Majorana fermions. You probably haven’t heard of fermions, for that matter – nor of Ettore Majorana. Prepare yourself: it’s a story of mystery and frustration.

Let’s deal with the man first. Majorana was an Italian physicist, the best of his generation, who disappeared in mysterious circumstances in 1938. He emptied his bank account, bought a ticket for a boat ride from Palermo to Naples and left a note for his colleagues apologising for the inconvenience he was about to cause. He may have committed suicide but his body was never found. There are rumours of subsequent sightings in Buenos Aires. Some think that he abandoned physics and disappeared to live out his days in a secluded monastery.

Majorana’s specialism was quantum theory and it is tempting to think that he engineered his disappearance to reflect the subject’s strange ambiguities. A quantum particle such as an electron can be in two places at once, or simultaneously moving in two different directions; Majorana seemed to want his friends to wonder whether he could, too.

And so to his fermions. Just before his vanishing trick, Majorana predicted the existence of a particle with highly unusual properties. Although we have never seen one directly, there is every reason to think that it does exist and scientists on the 77-year-long hunt are tantalisingly close to pinning it down. This month, a group of Princeton University researchers added to the accumulating pile of evidence that the Majorana fermion is a real and fundamental building block of nature.

A fermion is one of the two types of particle that make up all matter. You have probably heard of the other one, the boson, because of all the Higgs fuss. Fermions are just as interesting. The building blocks of the atom – protons, neutrons and electrons – are all fermions. Majorana fermions have an added twist. Unlike protons, neutrons and electrons, they are their own antiparticle.

That is very odd. Matter and antimatter annihilate each other when they come into contact. Bang an electron and its antiparticle, the positron, together and they will disappear in a flash of energy. So how can a Majorana fermion be its own antiparticle?

To find out, we have to get one we can observe, hence the hunt. And in a peculiar case of life (or death) imitating art (or science), Majorana fermions are offering glimpses of their properties in materials crammed with ghostly particles that don’t actually exist.

When a solid conducts electricity, it does so because it contains negatively charged electrons that can move through the material. As they leave their usual position, the electrons leave behind a network of “holes”. Viewed from one perspective, these behave like real particles that have a charge opposite to the electron. The details get complicated but, in some materials, this can create a situation in which the moving charges and holes amount to something that behaves exactly like a Majorana fermion. That’s what the Princeton researchers have seen.

It has been very difficult to get this far. The material containing the Majorana fermion was just one atom wide and three atoms thick and had to be cooled to -272°C, one degree above the coldest temperature allowed by the laws of physics. The fermion was so small that it required a scanning-tunnelling microscope two storeys high to see it.

That said, although the observed particle is a good facsimile, it is frustratingly still more like a Majorana fermion’s shadow puppet than the real thing. Majorana’s legacy still eludes us. That note was not apologetic enough. 

Michael Brooks holds a PhD in quantum physics. He writes a weekly science column for the New Statesman, and his most recent book is At The Edge of Uncertainty: 11 Discoveries Taking Science By Surprise.

This article first appeared in the 22 October 2014 issue of the New Statesman, Why Britain and Germany aren't natural enemies

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Amazon's unlikely role in the Calais relief efforts

Campaigners are using Amazon's wishlist feature - more commonly used for weddings and birthdays - to rally supplies for the thousands camped at Calais. 

Today and yesterday, relief efforts have sprung up across the web and IRL following the publication of shocking photos of a drowned refugee child. People are collecting second hand clothes and food, telling David Cameron to offer refuge, and generally funneling support and supplies to the thousands in Calais and across Europe who have been forced from their homes by conflict in Syria and elsewhere. 

One campaign, however, stuck out in its use of technology to crowdsource supplies for the Calais camp. An Amazon wishlist page - more familiar as a way to circulate birthday lists or extravagant wedding registries - has been set up as part of the  #KentforCalais and #HelpCalais campaigns, and is collecting donations of clothes, food, toiletries, tents and sleeping supplies. 

Judging by the Twitter feed of writer and presenter Dawn O'Porter, one of the list's organisers, shoppers have come thick and fast. Earlier today, another user tweeted that there were only six items left on the list - because items had sold out, or the requested number had already been purchased - and O'Porter tweeted shortly after that another list had been made. Items ordered through the list will be delivered to organisers and than transported to Calais in a truck on 17 September. 

This, of course, is only one campaign among many, but the repurposing of an Amazon feature designed to satiate first world materialism as a method of crisis relief seems to symbolise the spirit of the efforts as a whole. Elsewhere, Change.org petitions, clothes drives organised via Facebook, and Twitter momentum (which, in this case, seems to stretch beyond the standard media echo chamber) have allowed internet users to pool their anger, funds and second-hand clothes in the space of 24 hours. It's worth noting that Amazon will profit from any purchases made through the wishlist, but that doesn't totally undermine its usefulness as a way to quickly and easily donate supplies. 

Last year, I spoke to US writer and urbanist Adam Greenfield, who was involved New York's Occupy Sandy movement (which offered relief after after hurricane Sandy hit New York in 2011) and he emphasised the centrality of technology to the relief effort in New York:

Occupy Sandy relied completely on a Googledocs spreadsheet and an Amazon wishlist.  There was a social desire that catalysed uses of technology through it and around it. And if that technology didn't exist it might not have worked the way it did. 

So it's worth remembering, even as Amazon suffers what may be the worst PR disaster in its history and Silicon Valley's working culture is revealed to be even worse than we thought, that technology, in the right hands, can help us make the world a better place. 

You can buy items on the Amazon wishlist here or see our list of other ways to help here

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.