Scientists Propose Collider That Could Turn Light Into Matter 223
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.'"
What am I missing here? (Score:5, Informative)
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"?
This was already done back in 2001 (Score:2, Informative)
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]
Re:What am I missing here? (Score:5, Informative)
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.
Re:how soon before (Score:5, Informative)
I believe the summary is confusing concepts. A 'proposal' for how to do something, but not actually having implemented the proposal to see if it actually works IS NOT the same as 'discovering how to do something'.
There is a huge, fundamental gap between
I suggest we try doing X to accomplish Y
and
I did X and accomplished Y
Re:What am I missing here? (Score:4, Informative)
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?
Re:What am I missing here? (Score:4, Informative)
Comment removed (Score:5, Informative)
Re:Discover is the wrong word (Score:2, Informative)
Re:This was already done back in 2001 (Score:5, Informative)
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.
Re:Do it, then report it. (Score:5, Informative)
Saying that they're publishing in an attempt to secure funding is the least insightful comment you could possibly make, because that’s precisely how expensive “serious science” gets done: you put your theory up for peer review in a publication like Nature Photonics, and if it’s sound then you go into the contest for funding an experiment. Using your logic we should’ve built the Large Hadron Collider before the theoretical merit in building it was confirmed; if you can’t see why that's a phenomenally stupid way to allocate finite resources then sorry, but I have to doubt you're clever enough to prove a conjecture theoretically, let alone practically.
Re:Discover is the wrong word (Score:5, Informative)
This was also done back in 1997. (Score:5, Informative)
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.
Re:Energy-matter synthesis (Score:5, Informative)
Total energy output of the sun per second: 3.8×10^26 J (source: wikipedia)
This amounts to 4.22×10^9 grams per second,
or about 18 million cups of tea per second.
Re:how soon before (Score:5, Informative)
Not at all. In science, there is just as much validity to "we did X but didn't get Y" as there is to "when we did X, Y was accomplished." In fact, Michelson and Morley are a prime example of "we did X but didn't get Y" in 1887, and they won the Nobel prize for it in 1907.
Re:how soon before (Score:0, Informative)
That is how it is supposed to work. That was also more than a century ago.
Science these days is not free from politics.
Re:Energy-matter synthesis (Score:4, Informative)
And it's cool to think that, maybe, when you have a warp core that powers a space ship going FTL with many millions of petawatts of energy, some star trek technology like replicators might come true :)
True, but somehow I doubt that anyone will ever be glib while wielding the power of the entire generating output of the Sun, for example (call that 100 billion petawatts). The power at that scale could destroy entire solar systems if a mishap or violent use were to occur.
If you weren't aware of the Kardishev scale [wikipedia.org], you might find it intriguing to consider the implications of a Type II civilization wielding the power of the entire Sun or to think about what a Type III civilization could accomplish.
Re:how soon before (Score:5, Informative)
Not entirely devoid, no, but in my experience (as a former researcher; still have the CERN employee ID card) there is still some that is free of politics. The fact that results need to be reproducible to be accepted helps. The main concern is funding. As long as you can confidently tell your backers that there is money to be made either way, or find different backers with vested interests in different results, there is no pressure to fudge results. In fact, the project I worked on (ATLAS) had no outside input asking for bias in results that I could see in any way, shape or form. Of course, if that was the case universally nobody would question vaccines, but it still happens often, especially in fields like particle physics (which this article is talking about) in which application is so far down the road that most financial backers really are looking for the spinoff technology it takes to produce the result moreso than the result itself.