Can we create matter from light?

[Ryan_m_b]

A bunch of news sources are reporting that a group from the UK is working on a way to produce matter from light. As far as I was aware this was impossible so I assume that the news is getting it wrong again and/or sensationalising. But even in the abstract of the paper it's claimed that producing matter from light is possible. Am I misunderstanding something here? I'm wondering if the source of my confusion is that maybe it is possible to technically make matter from light but that doesn't mean that hypothetically you could have a technology that takes light in one end and spits atoms out the other.

News article: http://www.theguardian.com/science/2014/may/18/matter-light-photons-electrons-positrons?CMP=fb_gu

Paper: http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2014.95.html

A photon–photon collider in a vacuum hohlraum
O. J. Pike, F. Mackenroth, E. G. Hill & S. J. Rose

The ability to create matter from light is amongst the most striking predictions of quantum electrodynamics. Experimental signatures of this have been reported in the scattering of ultra-relativistic electron beams with laser beams, intense laser–plasma interactions and laser-driven solid target scattering. However, all such routes involve massive particles. The simplest mechanism by which pure light can be transformed into matter, Breit–Wheeler pair production (γγ′ e+e−), has never been observed in the laboratory. Here, we present the design of a new class of photon–photon collider in which a gamma-ray beam is fired into the high-temperature radiation field of a laser-heated hohlraum. Matching experimental parameters to current-generation facilities, Monte Carlo simulations suggest that this scheme is capable of producing of the order of 10⁵ Breit–Wheeler pairs in a single shot. This would provide the first realization of a pure photon–photon collider, representing the advent of a new type of high-energy physics experiment.

 

[Matterwave]

Why is it impossible to produce matter from light? After-all the reaction $e^+ e^-\rightarrow \gamma\gamma$ is simple enough, producing matter from light is just running this reaction backwards.

 

[Borek]

Isn't it what happened at some point during Big-Bang?

 

[Drakkith]

Isn't it what happened at some point during Big-Bang?

As far as I understand, yes.

 

[AlephZero]

Creating equal numbers of electrons and positrons is not quite the same as "taking light in at one end and spitting atoms out at the other".

From what little I have seen about this proposal, it seems like an engineering challenge to make the experiment work, rather than a theoretical leap in the dark. After all, QED is probably the most accurately verified theory in physics, with predictions agreeing with experiment to the order of 1 part in 10⁹.

 

[SteamKing]

Why is it impossible to produce matter from light? After-all the reaction $e^+ e^-\rightarrow \gamma\gamma$ is simple enough, producing matter from light is just running this reaction backwards.

A lot of reactions run easily in one direction, but the reverse reaction is often much harder to accomplish.

A uranium nucleus can fission if it is struck by a neutron of the right energy, but you can't recombine the fission products into a uranium nucleus without expending much more energy than the original fission released.

 

[Dale]

Why is it impossible to produce matter from light? After-all the reaction $e^+ e^-\rightarrow \gamma\gamma$ is simple enough, producing matter from light is just running this reaction backwards.

This is correct. It is sometimes called two-photon physics.

You need very high frequencies because you have to have a lot of energy in each photon, and you need very high luminosity because the "cross section" for this interaction is very small. But it can and does happen.

 

[brianhurren]

I think the 'impossible' lable put on it is to do with trying to achieve the extremely high energy levels nedded to convert light into matter. given the extremely high frequencies of eletrons and positrons. difficult to achieve in labratories...until now!

 

[Matterwave]

A lot of reactions run easily in one direction, but the reverse reaction is often much harder to accomplish.

A uranium nucleus can fission if it is struck by a neutron of the right energy, but you can't recombine the fission products into a uranium nucleus without expending much more energy than the original fission released.

I wasn't suggesting that this was easy to do practically speaking, only that theoretically a process which occurs should be able to occur backwards as well.

 

[UltrafastPED]

Some history: "Photon-Photon Collisions - Past and Future":
http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-11581.pdf

 

[Ryan_m_b]

Thanks everyone, seems I was mistaken. Couple of follow on questions: as this results in an electron and positron do they instantly annihilate or can they be separated and contained? In other words could this be a novel way of producing antimatter from light? Also is there any scope for producing hadrons as well and essentially making atoms from light? I suspect the answer is either no or yes but the technology/energy requirements are huge.

 

[ZapperZ]

Thanks everyone, seems I was mistaken. Couple of follow on questions: as this results in an electron and positron do they instantly annihilate or can they be separated and contained? In other words could this be a novel way of producing antimatter from light? Also is there any scope for producing hadrons as well and essentially making atoms from light? I suspect the answer is either no or yes but the technology/energy requirements are huge.

This is the technique of producing positrons for a lot of high-energy colliders. So it is a known process. The e-p pairs are often produced using gamma rays, and so each member of the pair tends to have a large kinetic energy when they are created and often moves with high velocity in the opposite direction to each other. One can improve the separate by subjecting the region to high fields.

Zz.