Scientists discover how to turn light into matter after 80-year quest

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Physicists have discovered how to create matter from light — a feat thought impossible when the idea was first theorized 80 years ago. In just one day over several cups of coffee in a tiny office, three physicists worked out a relatively simple way to physically prove a theory first devised by scientists Breit and Wheeler in 1934. Breit and Wheeler suggested that it should be possible to turn light into matter by smashing together only two particles of light (photons), to create an electron and a positron — the simplest method of turning light into matter ever predicted. The calculation was found to be theoretically sound, but Breit and Wheeler said that they never expected anybody to physically demonstrate their prediction.

Imperial College London physicists have discovered how to create matter from light — a feat thought impossible when the idea was first theorised 80 years ago.

In just one day over several cups of coffee in a tiny office in Imperial's Blackett Physics Laboratory, three physicists worked out a relatively simple way to physically prove a theory first devised by scientists Breit and Wheeler in 1934.

Breit and Wheeler suggested that it should be possible to turn light into matter by smashing together only two particles of light (photons), to create an electron and a positron — the simplest method of turning light into matter ever predicted. The calculation was found to be theoretically sound but Breit and Wheeler said that they never expected anybody to physically demonstrate their prediction. It has never been observed in the laboratory and past experiments to test it have required the addition of massive high-energy particles.

The new research, published in Nature Photonics, shows for the first time how Breit and Wheeler's theory could be proven in practice. This 'photon-photon collider', which would convert light directly into matter using technology that is already available, would be a new type of high-energy physics experiment. This experiment would recreate a process that was important in the first 100 seconds of the universe and that is also seen in gamma ray bursts, which are the biggest explosions in the universe and one of physics' greatest unsolved mysteries.

The scientists had been investigating unrelated problems in fusion energy when they realised what they were working on could be applied to the Breit-Wheeler theory. The breakthrough was achieved in collaboration with a fellow theoretical physicist from the Max Planck Institute for Nuclear Physics, who happened to be visiting Imperial.

Demonstrating the Breit-Wheeler theory would provide the final jigsaw piece of a physics puzzle which describes the simplest ways in which light and matter interact (see image in notes to editors). The six other pieces in that puzzle, including Dirac's 1930 theory on the annihilation of electrons and positrons and Einstein's 1905 theory on the photoelectric effect, are all associated with Nobel Prize-winning research (see image).

Written By: Science Daily
continue to source article at sciencedaily.com

28 COMMENTS

  1. I know I am revealing my ignorance here, but couldn’t they have approached it from the botanical standpoint rather than nuclear-physics?
    Plants photosynthesize all the time and surely the chemical process could be duplicated in the laboratory. Or is there some advantage to smashing atoms around to do the same thing? Sorry, babe in the physics woods here, but I was just wondering….

    • In reply to #1 by justinesaracen:

      I know I am revealing my ignorance here, but couldn’t they have approached it from the botanical standpoint rather than nuclear-physics?

      I’m no expert either, but perhaps the point is to create matter from light alone.

    • In reply to #1 by justinesaracen:

      I know I am revealing my ignorance here, but couldn’t they have approached it from the botanical standpoint rather than nuclear-physics?
      Plants photosynthesize all the time and surely the chemical process could be duplicated in the laboratory. Or is there some advantage to smashing atoms around to d…

      I don’t think plants actually CONVERT photons into matter. They convert water and carbon dioxide —> sugars + glocose. The photons provide the energy to do this. So the photons are not actually converted into matter per se. If my understanding is correct!

    • In reply to #1 by justinesaracen:

      I know I am revealing my ignorance here, but couldn’t they have approached it from the botanical standpoint rather than nuclear-physics?
      Plants photosynthesize all the time and surely the chemical process could be duplicated in the laboratory. Or is there some advantage to smashing atoms around to d…

      photosynthesis is a chemical reaction. exactly the same amount of both mass and energy exist before and after the reaction. This is the creation of mass from energy. not something any life has evolved to do yet…

      This is converting energy into mass, the opposite of a nuclear rection (NB the total mass-energy of the universe is not changed so it’s perfectly acceptable within the laws of thermodynamics)

  2. @justine I think the point is to demonstrate a purely light-light interaction. We see light-matter interactions all the time. But we don’t see light scattering off of other light, or light colliding with light and producing something new.

  3. Zarniwoop is right, justinesaracen; the total numbers of protons, neutrons, electrons and positrons – indeed, or carbon, hydrogen and oxygen atoms – are conserved in photosynthesis. What these scientists have done is use photons to produce an electron that never previously existed and a positron that also never previously existed. Destroying a pre-existing electron and positron to produce 2 photons is a much more familiar process, called electron-positron annihilation. The new achievement, an example of pair production, is what is technically known as the time reversal of such an annihilation. Time reversals of possible subatomic processes are always also possible, but there was a feasibility issue in that photons aren’t charged. Electrons and positrons are electrically charged, so can be steered with electromagnetic fields. Photons are electrically neutral, and the over-coffee breakthrough to which the article eludes was about how to arrange photon collisions despite this key difference.

    • In reply to #6 by Jos Gibbons:

      Electrons and positrons are electrically charged, so can be steered with electromagnetic fields. Photons are electrically neutral, and the over-coffee breakthrough to which the article eludes was about how to arrange photon collisions despite this key difference.

      alludes (sorry to be pedantic)

      Edit.

  4. The mass gained by plants is not energy-to-mass conversion, but simply the storing of energy in high-energy chemical bonds (in the form of glucose) using water and carbon dioxide as reactants. Oxygen is a waste product in this reaction (thanks, plants!), and mass is conserved.

  5. The Breit-Wheeler theory has yet to be demonstrated.

    Drinking all that coffee ONLY created more theorizing. Nothing has been physically demonstrated. Apparently, according to the source article, there is some kind of race going on to be the first to physically demonstrate the Breit-Wheeler theory. As such, this article is NOT true and is extremely misleading.

    • In reply to #11 by John Gohde:

      You’re right that the headline is wrong. However, the consequences are not “more theorizing” but the design of and planning for an experiment that can be carried out.

      In reply to #1 by justinesaracen:

      Photosynthesis is more like the top middle Feynman diagram, with a photon interacting with an electron and the result being an electron in a higher energy state (if I’ve understood it correctly: I’ve not studied them thoroughly, and I’m not sure what the “nucleus” bit means). The electron is what the plant uses to alter the chemical structure– (“organic”) chemical bonds are electrons shared between atoms. Though the route by which it does so is long and complicated.

    • In reply to #13 by Dog Almighty:

      So when will the first 3D-printer be created that converts sunlight into matter? Goodbye to a future in which humanity runs out of resources.

      But Hello Transporter, Replictor, and Holodeck! Sometimes seems like a lot of luddites for a site devoted to science.

    • In reply to #13 by Dog Almighty:

      So when will the first 3D-printer be created that converts sunlight into matter? Goodbye to a future in which humanity runs out of resources.

      thing is, there is no shortage of matter. we have a planetload of matter to play with already and converting light into matter would still require a nuclear fusion reactor to create heavier elements. If we had such a thing there’d be no need for more resources. The most important resources the planet needs right now are energy, which we have an abundance of in sunlight, and water which we have an abundance of in the oceans.

      That said this experiment would create electrons and positrons. I’m really not sure how you get from there to actual usable matter.

  6. So it’s not exactly light. It’s more beams of high-energy photons created by slamming high-energy electrons into a gold slab (why gold?) being directed into a glowing-hot gold can (why gold?). If it were just photons hitting one another then surely the experiment has been running for nearly fourteen milliard years. Perhaps somebody could look for the positron-electron annihilations that would be occurring all around us after the positrons had been created. Would you get the same result by pointing laser beams at each other?

    • In reply to #18 by Vanity Unfair:

      So it’s not exactly light.

      Not visible light, no; but that’s just a matter of how much energy the photons have. Two equally energetic photons that form an electron and a positron have to have a minimum energy of m c-squared each, where m is the electron mass. And that’s hundreds of thousands of times too energetic for human eyes to see.

      But arbitrarily declaring invisible electromagnetic radiation as fundamentally different from the visible kind, rather than just having a different wavelength, misses their common particulate nature. Indeed, the reason we evolved to see certain wavelengths is because their energies are typically formed when electrons change atomic energy levels, and such photons were always going to have energies much smaller than the rest-energy of the electron. The only way for that to not be so is if the physical constants were different so that electrons would always be moving close to the speed of light in an atom.

      Incidentally, if the photons used had different energies, one could be “visible” or invisible depending on your reference frame, thanks to relativity.

      photons created by slamming high-energy electrons into a gold slab (why gold?) being directed into a glowing-hot gold can (why gold?)

      A good material needs large nuclei that barely recoil, many nuclei per unit volume to give many collision opportunities in the experiment, and a high “cross-section” (this is a measure of how readily the collision happens, expressed as the nuclear cross-sectional area weighted by the collision probability). Such materials are invariably very expensive, and in practice they factor in that too; there’s only so big you can make the equipment with a given material, and that constrains how many particles you can work with. When you crunch the numbers, gold is the best option. (Few things are denser than gold, and those that are tend to be more expensive, e.g. platinum.) In fact, it’s been used for about 100 years; gold was used by Rutherford to prove an atom’s positive charge, and most of its mass, is in a central nucleus.

      If it were just photons hitting one another then surely the experiment has been running for nearly fourteen milliard years. Perhaps somebody could look for the positron-electron annihilations that would be occurring all around us after the positrons had been created. Would you get the same result by pointing laser beams at each other?

      Again, not unless the total energy of the colliding photons was very, very high.

    • In reply to #21 by A.Porto:

      Important in the first 100 seconds of the universe? Who saw, or marked time?

      I don’t care how religiously deluded someone is; why does anyone think “Were you there?” is a good argument? Don’t they know evidence can prove things without being an eyewitness account? Haven’t they heard of forensics? There are a lot of police/detective shows!

      Maybe your question was rhetorical; maybe it was honest. If it was honest, go read cosmology. We base our account of the early history of the universe on a lot of science. I gather The First Three Minutes gives a good explanation of this.

    • In reply to #21 by A.Porto:

      Important in the first 100 seconds of the universe?
      Who saw, or marked time?

      Hello,

      Einstien’s Field Equations (EFE) “mark the time” as they give the description of space and time. It is an observational fact that earlier times in our universe were denser and hotter. We can use EFE plus some thermodynamics to determine at what times the temperature was high enough to produce electron / positron pairs for example (~ 1 second). Reaction rates were orders of magnitude larger than the expansion rate means these particles were in equilibrium: a gas of approximately equal numbers of photons, electrons and positrons.

      As has been said particle accelerators have verified these reactions in one direction but not the other. Maybe one could say herding photons is like organizing atheists.

      Edit: If you meant this question as a general logical challenge then see #23 by Jos Gibbons.

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