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Scientists discover how to turn light into matter after 80-year quest
- Noxchi 12y agoSo it's turning light into electrons? Isn't that already done with solar panels?
- pjc50 12y agoNo, solar panels turn light into the change of energy state of an existing electron. This is why they operate at the characteristic band gap voltage of the semiconductor from which they are made. This experiment is about creating an entirely new electron/positron pair.
- tannerc 12y agoSolar panels wouldn't be the ideal use of this ability if it were made real, would they? I haven't looked through the full article yet, but would this new approach help overcome the problem of Carnot's theorem in any way?
- pjc50 12y agoCarnot's theorem is irrelevant to solar cells, as they aren't expanding-fluid-driven heat engines. Multijunction cells are the way to go for increased W/m^2, but are very bad W/$ at the moment.
- chris_va 12y agoSolar panels add momentum to existing electrons. This is actually quite exciting.
- Toenex 12y agoI see what you did there.
- frozenport 12y agoI'll count my chickens when they hatch, lets wait until they do it.
- JacobAldridge 12y agoTo be clearer, Theoretical Physicists have a theory about an experiment that would allow Experimental Physicists to prove a theory made by earlier Theoretical Physicists. They haven't actually conducted the Experiment. "In Theory, there is no difference between Theory and Reality. But in Reality there is."
- scott_s 12y agoI prefer the phrasing, The only difference between theory and practice is that in theory, there is no difference between theory and practice.
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- cLeEOGPw 12y agoImperial mages learn conjuration.
- gregorkas 12y ago1. grab a flashlight 2. make your friend grab a flash light 3. turn them on and point them at each other 4. make it rain
- tlholaday 12y agoMy friend is so obstinate I cannot complete step 2, and now there is severe drought.
- nkozyra 12y agoBy no means is this my forte, but would this violate the conservation of mass?
- cboursnell 12y agoNope. As energy equals mass times the speed of light squared you're just converting energy into matter. It's just the opposite of what the atomic bomb does.
- asolove 12y agoConservation of mass is not applicable in the conditions under discussion, see Wikipedia's fun list of exceptions to conservation of mass: http://en.wikipedia.org/wiki/Conservation_of_mass#Exceptions_or_caveats_to_mass.2Fmatter_conservation http://en.wikipedia.org/wiki/Conservation_of_mass#Exceptions...
- leephillips 12y agoMass by itself is only conserved in nonrelativistic classical physics. When you are in a relativistic regime the conserved quantity is a combination of momentum and energy. (You've probably seen E = mc^2, which shows that mass and energy can be transformed into each other.)
- ktran03 12y agoWiki: The law of conservation of mass, or principle of mass conservation, states that for any system closed to all transfers of matter and energy (both of which have mass), the mass of the system must remain constant over time, as system mass cannot change quantity if it is not added or removed.
- th0ma5 12y agoBlack holes probably do this?
- ToastyMallows 12y agoHow much energy is this photon/photon collier going to take? If a future experiment works, could we use this created matter to turn around and use it as energy? Or would that not be possible (i.e. - The energy used is far greater than the energy gained)
- timnic 12y agoNo, the energy gained will be equal or (most likely) less than the energy used. This is because we have conservation of energy, so a process like energy (the original photons) -> matter (electron/positron) -> energy can not produce more energy than was put in.
- Retric 12y agoIn cases like this energy is not really what you want to talk about as that's always constant it's USEFUL ENERGY which is interesting.
- ximeng 12y agoCan anyone explain the vertical lines in the space time diagrams? Presumably not infinite velocity?
- yk 12y agoThey are not space time diagrams, they are Feynman graphs. Technically they are a clever way to write down the terms of a series expansion. In the convention used, on the left hand side are the incoming particles and the outgoing particles are on the right. The internal lines and vertices are just representations of formulas, and the important thing is only the topology of the graph. However one of the really great things of Feynman graphs is, that they admit a easy interpretation about what is happening. Then the interior lines are interpreted as virtual particles that are created during the reaction, but since they are virtual they do not really have a defined speed, so the lines are just drawn like that.
- jessriedel 12y agoIn fact, Feynman diagrams are spacetime diagrams. (They are commonly computed in momentum space, i.e. Fourier space, but you can also do them in normal position space.) When you draw a Feynman diagram, the vertices correspond to actual points in spacetime, which are then integrated over a la the path integral.
- jessriedel 12y agoYes, it's infinite velocity. When you compute an amplitude from a Feynman diagram, you sum (integrate) over intermediate particle paths that are superluminal. The math is structured in a way that these contributions cannot actually be used to send signals, but the contributions are crucial and cannot be discarded. Essentially, they represent the relativistic generalization of the effect where one particle in a Bell pair "influences" another over a spacelike separation, but in a subtle and spooky way that cannot produce superluminal signaling.
- dmead 12y agothere is no way this is not sensationalized.
- NickM 12y agoProbably a long way off, but I can't help but imagine the kind of amazing applications something like this might have. If we could reliably capture and store the resulting positrons, then recombine them with electrons later to release the energy and harness it somehow, I'd imagine this could make for an energy storage system with some really interesting properties.
- fixedd 12y agoLike the fact that light doesn't take up any space, so you could theoretically store an infinite amount of energy?
- troymc 12y agoThe idea is to store the positrons, and positrons aren't light.
- gliese1337 12y agoSorry, doesn't work. Light still exerts pressure, so even if you could losslessly trap light in a storage container indefinitely, the container would explode long before the energy density became 'infinite'. Furthermore, the energy and momentum in light contributes to the gravitational field, so even if you could make an infinitely strong mirror-box, pumping too much energy into it would eventually result in collapsing into a black hole.
- troymc 12y agoIt is an interesting idea, but there are other ways, probably easier, to get the positrons. For example, some radioisotopes emit positrons as part of their natural radioactive decay process. See: http://arstechnica.com/science/2011/02/positrons-at-center-of-recent-anti-progress-in-matter-research/ http://arstechnica.com/science/2011/02/positrons-at-center-o...
- dang 12y agoA dupe of https://news.ycombinator.com/item?id=7763711 https://news.ycombinator.com/item?id=7763711.
- menubar 12y agoSounds like this theory could lead to creating one heck of a weapon, Dr. Venture.