Claim of matter from light

1. May 19, 2014

Ryan_m_b

Staff Emeritus
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

Last edited by a moderator: May 6, 2017
2. May 19, 2014

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.

3. May 19, 2014

Staff: Mentor

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

4. May 19, 2014

Drakkith

Staff Emeritus
As far as I understand, yes.

5. May 19, 2014

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.

6. May 19, 2014

SteamKing

Staff Emeritus
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.

7. May 19, 2014

Staff: Mentor

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.

8. May 19, 2014

brianhurren

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

9. May 20, 2014

Matterwave

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.

10. May 20, 2014

UltrafastPED

11. May 20, 2014

Ryan_m_b

Staff Emeritus
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.

12. May 20, 2014

ZapperZ

Staff Emeritus
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.