An artist's impression of SN 2006gyM, one of the brightest supernovas ever recorded. Photo: Weiss/NASA/CXC/Getty
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“Supernova in a bottle” will help create matter from light

The new process could provide a clean way of doing particle physics experiments.

In 1934, two physicists came up with a theory that described how to create matter from pure light. But they dismissed the idea of ever observing such a phenomenon in the laboratory because of the difficulties involved setting up such an experiment.

Now, Oliver Pike of Imperial College London and his colleagues have found a way to achieve this dream, 80 years after US physicists Gregory Breit and John Wheeler explained the theory. This group hopes to use high-energy lasers aimed at a specially designed gold vessel to convert photons into matter-antimatter particle pairs, recreating what happens in some exceptional stellar explosions.

Pike, who led the research published in the journal Nature Photonics, said, “The idea is that light goes in and matter comes out.” To be sure, the matter created won’t be every day-objects; instead the process will produce sub-atomic particles.

“To start with, the matter will consist of electrons and its antimatter equivalent positrons,” Pike said. “But with higher energy input in the lasers, we should be able to create heavier particles.”

Pike concedes this won’t be the first time light has been converted into matter. In 1997, US researchers at the Stanford Linear Accelerator Centre (SLAC) were able to do so, albeit in a different way.

The SLAC experiment used electrons to first create high-energy light particles, which then underwent multiple collisions to produce electrons and positrons, all within same chamber. This is called the multi-photon Breit-Wheeler process, named after the two physicists who came up with the theory in 1934.

“The key difference in the SLAC experiment and the one we propose is that our process will be more straightforward,” Pike said. In the new proposal, the laser beam will still be generated using free electrons, but it will be separated from the electrons.

Why create light using matter and then convert it back? Apart from showing that the Breit-Wheeler process can happen without the multiple photons the SLAC experiment needed, Pike thinks their process provides a clean way of doing particle physics experiments.

Current particle-physics experiments involve smashing sub-atomic particles at great speeds and sorting through the mess of new particles that are created in the explosion. This is how the Higgs boson was found in the Large Hadron Collider.

The new experimental design will be similar. Rather than involving a complicated mix of particles and photons, the laser beam will be sent into a small gold hohlraum (German for “empty room”). There, individual photons can interact with the radiation field that’s generated when the hohlraum is excited by a laser, creating the electron-positron pairs.

“While physicists have excellent methods to sift through such data, our process has the advantage that it will be easier to analyse,” Pike said. “Light will go in from one end of the hohlraum and particles created will come out from the other end.”

Pike and colleagues are now working to secure time on high-energy laser beams to carry out the experiment. The two likely candidates are Aldermaston, Berkshire in the UK or Rochester, New York in the US.

Andrei Seryi at the University of Oxford found the work interesting, but warned it is still too far away from being used in particle-physics experiments. “Theoretically, however, it would be great if we are able to create particles from only light.”

“With such high energy lasers, we may not need to build big particle colliders, such as the Large Hadron Collider, which is a 22km underground tunnel,” Seryi said.

Even if we do manage to create a photon collider, we would only be catching up with the natural world, where a specific type of supernova, called “pair instability,” involves the creation of proton-antiproton pairs. If Pike is able to achieve this phenomenon, he will essentially be creating a supernova in a bottle.

The ConversationThis article was originally published on The Conversation. Read the original article.

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How virtual reality pigs could change the justice system forever

Lawyers in Canda are aiming to defend their client by asking the judge to don a virtual reality headset and experience the life of a pig.

“These are not humans, you dumb frickin' broad.”

Those were the words truck driver Jeffrey Veldjesgraaf said to animal rights activist Anita Krajnc on 22 June 2015 as she gave water to some of the 190 pigs in his slaughterhouse-bound truck. This week, 49-year-old Kranjc appeared at the Ontario Court of Justice charged with mischief for the deed, which she argues was an act of compassion for the overheated animals. To prove this, her lawyers hope to show a virtual reality video of a slaughterhouse to the judge, David Harris. Pigs might not be humans, but humans are about to become pigs.

“The tack that we’ve taken recognises that Anita hasn’t done anything wrong,” said one of her lawyers, James Silver. Along with testimony from environmental and animal welfare experts, her defence hope the virtual reality experience, which is planned for when the trial resumes in October, will allow Harris to understand Kranjc’s point of view. Via the pigs’ point of view.

It’s safe to say that the simulated experience of being a pig in a slaughterhouse will not be a pleasant one. iAnimal, an immersive VR video about the lives of farm animals, launched earlier this year and has already changed attitudes towards meat. But whether or not Harris becomes a vegetarian after the trial is not the most pressing aspect of this case. If the lawyers get their wish to bring a VR headset into the courtroom, they will make legal history.

“Virtual reality is a logical progression from the existing ways in which technology is used to illustrate and present evidence in court,” says Graham Smith, a technology lawyer and partner at the international law firm Bird & Bird.

“Graphics, charts, visualisations, simulations and reconstructions, data-augmented video and other technology tools are already used to assist courts in understanding complex data and sequences of events.”

Researchers have already been looking into the ways VR can be used in courts, with particular focus on recreating crime scenes. In May, Staffordshire University launched a project that aims to “transport” jurors into virtual crime scenes, whilst in 2014 researchers at the Institute of Forensic Medicine in Switzerland created a 3D reconstruction of a shooting, including the trajectory of a bullet. Although this will help bring to life complex evidence that might be hard to understand or picture in context, the use of VR in this way is not without its flaws.

“Whether a particular aid should be admitted into evidence can give rise to argument, especially in criminal trials involving a jury,” says Smith. “Does the reconstruction incorporate factual assumptions or inferences that are in dispute, perhaps based on expert evidence? Does the reconstruction fairly represent the underlying materials? Is the data at all coloured by the particular way in which it is presented? 

“Would immersion aid a jury's understanding of the events or could it have a prejudicial impact? At its core, would VR in a particular case add to or detract from the court's ability objectively to assess the evidence?”

The potential for bias is worrying, especially if the VR video was constructed from witness testimony, not CCTV footage or other quantitative data. To avoid bias, feasibly both the defence and prosecution could recreate an event from different perspectives. If the jury or judge experience the life of a distressed pig on its way to be slaughtered, should they also be immersed in the life of a sweaty trucker, just trying to do his job and panicked by a protester feeding his pigs an unknown substance from a bottle?

“These are not new debates,” says Smith. “Lawyers are used to tackling these kinds of issues with the current generation of illustrative aids. Before too long they will find themselves doing so with immersive VR.”

It seems safe to trust, then, that legal professionals will readily come up with failsafe guidelines for the use of VR in order to avoid prejudice or bias. But beyond legal concerns, there is another issue: ethics.

In 2009, researchers at the University of Leicester discovered that jurors face trauma due to their exposure to harrowing evidence. “The research confirms that jury service, particularly for crimes against people, can cause significant anxiety, and for a vulnerable minority it can lead to severe clinical levels of stress or the symptoms of post traumatic stress disorder,” they wrote.

It’s easy to see how this trauma could be exacerbated by being virtually transported to a scene and watching a crime play out before your eyes. Gamers have already spoken about panic attacks as a result of VR horror games, with Denny Unger, creative director of Cloudhead Games, speculating they could cause heart attacks. A virtual reality murder, however virtual, is still real, and could easily cause similar distress.

Then there is the matter of which crimes get the VR treatment. Would courts allow the jury to be immersed in a VR rape? Despite how harrowing and farfetched that sounds, a virtual reality sexual assault was already screened at the 2015 Sundance Film Festival.

For now, legal professionals have time to consider these issues. By October, Kranjc’s lawyers may or may not have been allowed to use VR in court. If they are, they may change legal history. If they’re not, Kranjc may be found guilty, and faces six months in jail or a $5,000 fine. 

Amelia Tait is a technology and digital culture writer at the New Statesman.