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Scientists Propose Collider That Could Turn Light Into Matter 223

Posted by samzenpus
from the give-me-my-holodeck dept.
An anonymous reader writes "Imperial College London physicists have discovered how to create matter from light — a feat thought impossible when the idea was first theorized 80 years ago. From the article: 'A pair of researchers predicted a method for turning light into matter 80 years ago, and now a new team of scientists are proposing a technique that could make that method happen in the purest way yet. The proposed method involves colliding two photons — the massless particles of light — that have extremely high energies to transform them into two particles with mass, and researchers in the past have been able to prove that it works. But in replicating that old method, known as Breit–Wheeler pair production, they had to introduce particles that did have mass into the process. Imperial College London researchers, however, say that it's now possible to create a collider that only includes photons.'"
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Scientists Propose Collider That Could Turn Light Into Matter

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  • by Tablizer (95088) on Monday May 19, 2014 @02:11AM (#47036101) Homepage Journal

    Dudes, you are solving the problem, in reverse: we want instant energy from dirt.

  • Backwards? (Score:5, Funny)

    by meerling (1487879) on Monday May 19, 2014 @02:23AM (#47036137)
    Aren't you supposed to "make light of the matter", and not the other way around?
  • by bscott (460706) on Monday May 19, 2014 @02:31AM (#47036155)

    I preface this with an admission that my serious physics studies were like 25 years ago now, but - photons are bosons, how can they "collide"?

    • by Anonymous Coward on Monday May 19, 2014 @03:01AM (#47036215)

      Being bosons just means you can pack multiple quanta into the same state.

      All particles interact (otherwise, how would we even know they "exist"?), and photons interact electromagnetically. That means that they can induce the vacuum to produce pairs of electrically charged particles: say, an electron and a positron. Usually, those particles are just quantum fluctuations or "virtual particles", living for a tiny fraction of a second due to Heisenberg uncertainty. However, if two photons have enough energy between them (at least equal to the mass-energy of the pair), they can give their energy to the electron and positron and turn them into real particles. That's what they want to do here: get two photons to give their energy to a virtual particle pair, making it real.

      • by bscott (460706) on Monday May 19, 2014 @03:23AM (#47036271)

        Thanks for that, I knew they interact but I didn't think they could "collide" per se, and from your explanation maybe "collide" is just the wrong word to be using?

        • by WhiteZook (3647835) on Monday May 19, 2014 @03:29AM (#47036297)
          Collide is indeed a wrong word. Particle is a wrong word too. The problem is that there's no easy and correct way to explain what really happens.
          • by DrLudicrous (607375) on Monday May 19, 2014 @09:21AM (#47037557) Homepage
            Think of photons as the central point from which oscillating magnetic and electric fields originate. And that this point moves through space at ~3x10^8 m/s. It is kind of like throwing two stones into water and watching the resulting interference patterns, excepts that the centers of those patterns are moving instead of stationary. Hence, collision isn't really an apt description.
        • They are colliding, even photons can have density events like matter.

          It's all about the speed at which the waveforms can react to the difference imposed on them. At lower energies, the photon waveform can react faster than the energy in the interaction (not a collision). But once you go beyond a certain point, the particle's waveform cannot react fast enough to the interaction and they two collide to cause differences in each particle.
        • by AchilleTalon (540925) on Monday May 19, 2014 @11:09AM (#47038357) Homepage
          Collide is the correct word for this. When two pool balls are colliding, what prevent them to penetrate each other is the electromagnetic force which maintain the integrity of each ball and they interact by this mean. A collision is an interaction when two things are close enough from each other.
      • Apologies, I'm not a physicist but ... if you create electron and positron, wouldn't they annihilate each other immediately again? Or do you somehow find a way to separate them?

        • By the conservation of the momentum, the two created particles will separate each other by going away from each other so the total momentum is still zero.
    • by ssam (2723487)

      photons can scatter from each other (its just that the cross sections are low)
      https://en.wikipedia.org/wiki/... [wikipedia.org]

    • Empty space isn't that empty. You can get virtual pairs of electrons and positrons appearing and disappearing. They pop into existence because they can, even in empty space, but the have negative energy and a virtual wavelength, so they are almost bound to re-coalesce, and the energy of their recombination will exactly equal the energy of their creation, so they pay back all the energy they 'borrowed' and disappear without trace. However, if a photon turns up at this critical moment and pumps in the energy

  • by WhiteZook (3647835) on Monday May 19, 2014 @02:31AM (#47036157)
    These scientist haven't discovered how to create matter from light. That's already standard theory. What they have done is devised a clever experiment to test this.
    • I don't know, if they're the first to devise a working setup to achieve that, haven't they discovered how to do it?
      It was already discovered that it should be possible, but they might be the first to actually describe a possible apparatus to do so, so i guess it's fair to say that they discovered how to do it?

      • by Gaygirlie (1657131) <gaygirlie AT hotmail DOT com> on Monday May 19, 2014 @05:00AM (#47036481) Homepage

        I don't know, if they're the first to devise a working setup to achieve that, haven't they discovered how to do it?

        According to http://www.gizmag.com/experime... [gizmag.com] the Breit-Wheeler theory hasn't actually been proven yet and remains a theory. The scientists in question believe they have found a way of proving the theory and doing it in a manner that requires only a fraction of the amount of energy than believed previously. Ie. they've set out to doing two things: proving a theory or disproving it, and trying out a new, more energy-efficient method of creating these Breit-Wheeler particles. I suggest just reading the article on Gizmag, it's short and kept easy-to-read.

        • Re: (Score:2, Informative)

          by Barsteward (969998)
          Not a theory yet, still a hypothesis
          • by WhiteZook (3647835) on Monday May 19, 2014 @06:53AM (#47036897)
            It is part of the theory of quantum electro dynamics, and even if it has been demonstrated in this form, the virtual possibility must already be accounted for in other quantum calculations that have been verified in experiments. Also, the reverse effects have been demonstrated before, and according to theory these effects are fully reversible. It would be a huge shock if a properly conducted experiment would fail to produce the expected results.
            • by shaitand (626655)
              If it is a prediction of quantum electro dynamics and has not yet been tested and that test replicated you are incorrectly labeling quantum electro dynamics as a theory.

              "It would be a huge shock if a properly conducted experiment would fail to produce the expected results."

              Right. Whereas if it were a theory it would be impossible.
              • I don't think you have the same definition of theory. Here's the one I use: http://en.wikipedia.org/wiki/S... [wikipedia.org]
              • by ceoyoyo (59147)

                You're incorrectly defining theory to mean "truth" or some weaselly variation of that.

                A theory is a descriptive framework, today usually mathematical. A hypothesis is a specific prediction based on a theory. The theory of QED describes how photons can create matter particles under certain circumstances. An experiment can be designed using that theory, with the hypothesis that if you shoot high energy photons into a chamber prepared in such and such a way, electrons and positrons will come out.

                • by shaitand (626655)
                  "A theory is a descriptive framework, today usually mathematical. A hypothesis is a specific prediction based on a theory."

                  A hypothesis is an educated guess to explain an observation of reality. A hypothesis is not a prediction of anything. Predictions are made to test a hypothesis. A hypothesis that is thoroughly tested is called a theory, especially one which encapsulates many tested hypothesis (again, with it's own confirmed predictions).

                  You've got your order of operations wrong. The first step in the s
        • by shaitand (626655)
          "theory hasn't actually been proven yet and remains a theory"

          You keep using that word. I don't think it means what you think it means.

          Something that is probably true but remains unproven is a hypothesis. It doesn't become a theory until it is proven.

          The way the public uses the term is not the same as the way science uses it. The public uses theory to refer to speculation. That would be hypothesis at best. All the predictions that can be derived from your "guess" have to be tested, and then those tests succe
          • by ceoyoyo (59147)

            "Something that is probably true but remains unproven is a hypothesis. It doesn't become a theory until it is proven."

            You're using the term incorrectly. The way the "public" uses it is closer to the scientific definition.

          • Something that is probably true but remains unproven is a hypothesis. It doesn't become a theory until it is proven.

            Well, I apologize for misusing the term, then, and will try to remember the distinction in the future.

    • Well, to be honest, they've asked for funding to do the obvious experiment to test it. It's not particularly clever, only expensive. And, as has been pointed out repeatedly above, they haven't "discovered" this, it is part of the standard lexicon of QED and has been for maybe 60-70 years.

      A clever way of testing it would be to use e.g. a free electron laser like the one we already have at Duke and shoot the laser beam into a "wiggler" -- a region of alternating crossed fields -- well downstream of the circ

    • by shaitand (626655)
      Correct me if I'm wrong but isn't it incorrectly called theory if this prediction has not yet been tested? That would be a very old and widely accepted hypothesis.
      • A hypothesis is an explanation for observation that has not been tested thoroughly. This fails the definition on two accounts: there has not been an observation yet (it's just a proposal for an experiment), and the theory behind it (QED) has been tested thoroughly. So, it's a prediction of an already well-tested theory. And because QED involves integrating over all possible events, it's hard to imagine how QED could be shown to confirm so well with experimental results, if it didn't also correctly represent
        • by shaitand (626655)
          A theory is a hypothesis whose predictions have been confirmed. So it certainly can't be a theory without first being a hypothesis.

          This experiment is testing a prediction of a hypothesis. The hypothesis is based on observation, predictions are based on the hypothesis. QED is being tested here. There being a testable and untested prediction that must be true to confirm QED technically makes it a hypothesis. This prediction was previously thought untestable therefore it was called a theory. All the other test
  • Light was already turned into matter back in 2001 by Lene Hau at Harvard.
    When the light pulse disappeared, the mass of the sodium increased.

    http://www.seas.harvard.edu/ha... [harvard.edu]

    • by Splab (574204)

      You know how we know that you didn't even bother to read the excerpt?

    • by Karma Bandit (1305259) on Monday May 19, 2014 @06:01AM (#47036709)

      What? How can you link a paper like that and completely not understand its contents? No, they did not create matter out of light. The important thing from that paper is that the light was frozen in place while it was traveling through the material. It's a nice experiment, but has absolutely nothing whatsoever to do with photon-photon interactions and creating of particle-antiparticle pairs. The word "mass" doesn't even appear in the paper, for example. The photon energies are eV level in that paper, and photon-photon interactions require billions times more. Like, gamma rays, not visible light.

      You might argue, pedantically, that while the light was trapped in the sodium in that paper, the kinetic energy of the sodium atoms increased. And due to relativity, increase the kinetic energy of something also increases its mass. Well, you would be right, and that happens every time the sun shines on something and warms it up. But when you talk about creating matter from photons, they mean making brand new particles-- that is, making even the *rest mass* portion of their energy out of the photons-- not just speeding up existing particles. And that just cannot be done with light near the visible spectrum.

      • Please mod this up and GP down. +5 Ignorant.
      • by drkim (1559875)

        What? How can you link a paper like that and completely not understand its contents?...

        I was in communication wi. Dr. Hau in 2007, and she indicated that the sodium mass had indeed increased when the probe pulse was stopped.

    • Back in 1997 at Stanford green laser light was smashed into gamma rays to produce matter. [bibliotecapleyades.net]

      Scientists Use Light to Create Particles

      Photons of light from the green laser were allowed to collide almost head-on with 47-billion-electronvolt electrons shot from the Stanford particle accelerator. These collisions transferred some of the electrons' energy to the photons they hit, boosting the photons from green visible light to gamma-ray photons, and forcing the freshly spawned gamma photons to recoil into the oncoming laser beam. The violent collisions that ensued between the gamma photons and the green laser photons created an enormous electromagnetic field.

      This field, Melissinos said, "was so high that the vacuum within the experiment spontaneously broke down, creating real particles of matter and antimatter."

      This breakdown of the vacuum by an ultrastrong electromagnetic field was hypothesized in 1950 by Dr. Julian S. Schwinger, who was awarded a Nobel Prize in physics in 1965.

      Emphasis mine.

      Thus, we do know that we can create matter by colliding photons already. The new experiment proposed could be useful because it does not require the electron-photon collision near the detector in order to produce the gamma photons and subsequent light on light reaction. They'll be firing gamma rays through a cylinder full of black body radiation. A gamma-gamma collision would be more interesting, IMO. The new gamma or black-body radiation collision experiment should be of even lower energy than the gamma and green laser collisions which produced matter in 1997.

      Why even go for a lower energy apparatus than what has been demonstrated at all? Simple: To verify the minimal energy level required to make the vacuum puke.

      • Also see
        http://www.slac.stanford.edu/e... [stanford.edu]

        It was actually done much earlier but generating matter by scattering off of virtual photons. The SLAC experiment was actually looking for (and found) nonlinear interactions in photon / photon collisions. (as were predicted by QED).

  • by Z00L00K (682162) on Monday May 19, 2014 @03:42AM (#47036321) Homepage

    How often do this happen in the "real life" universe?

    What is the threshold for creating matter from light? Can there be some factor not yet discovered where some matter is re-created from light in the universe today?

    • The threshold is energy. You need very energetic photons to create something like an electron/positron pair. Using E = mc^2 you can calculate exactly how much. That kind of energy is not very common around here, but in places where such high energy photons are created, matter is also formed.
      • by Z00L00K (682162)

        But how much energy is required - and which particles don't we know about yet that can lead to a transformation and aggregation into new matter?

    • I experience this on a daily basis. I meet people who appear bright, but soon after turn out to be very dense. I can only guess there is a light to matter conversion there.

    • by Dastardly (4204)

      Very large stars create matter from light in their core. Although, in order to conserve momentum, it happens most commonly near a nucleus with a single photon. The photon converts to a positoron and electron and the nucleus recoils a bit conserving momentum. I expect that in the giant randomness of a stellar core gamma rays occasionally collide head on thus allowing momentum to be conserved that way, but I expect it is much rarer than the other mechanism, since at those densities a gamma ray probably enc

  • So what kind of matter would be produced? Some element we are already familiar with, or something entirely new?

  • by Opportunist (166417) on Monday May 19, 2014 @04:38AM (#47036421)

    No matter the result, they'll surely be able to make grant money go poof at the speed of light.

  • by NemoinSpace (1118137) on Monday May 19, 2014 @06:07AM (#47036727) Homepage Journal
    Good to see. The analogy to theoretical physics I use is, it's the difference between Imagining you are getting laid to getting laid.
    I don't really use that analogy, it just occured to me and now i am sad.
  • Sometime in the next few hours, quantum mechanics would predict a particle or two being emitted.

    Oh, you want to measure that against background noise? I guess you'll need a bigger flashlight. Maybe try the big six-cell ones.

    • With typical flashlight wavelengths, there's not enough energy to create particles. Waiting a few hours isn't going to help.

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