Scientists Invent Lightsaber, Claim Dubious Blog Headlines
(Image: Lucasfilm)
Physicists Mikhail Lukin (Harvard) and Vladan Vuletic (MIT) claim to have invented a new form of matter: photons that act as though they have mass. I have no idea if it's true. But I am certain that Prof. Lukin knows exactly how to get media attention:
"Photonic molecules," however, behave less like traditional lasers and more like something you might find in science fiction – the light saber.
"Most of the properties of light we know about originate from the fact that photons are massless, and that they do not interact with each other," Lukin said. "What we have done is create a special type of medium in which photons interact with each other so strongly that they begin to act as though they have mass, and they bind together to form molecules. This type of photonic bound state has been discussed theoretically for quite a while, but until now it hadn't been observed.
"It's not an in-apt analogy to compare this to light sabers," Lukin added. "When these photons interact with each other, they're pushing against and deflect each other. The physics of what's happening in these molecules is similar to what we see in the movies."
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The actual research is about the propagation of photons through an ultracold gas of Rubidium atoms, about 35 millionths of a kelvin above absolute zero. Because of the nature of such a cloud, photons traveling through the cloud will change the cloud around them, which then changes how a second photon would travel through it. So the photon-photon interaction is mediated by the cloud they are traveling through. This isn't anywhere close to making photons attract each other in the open, and requires this really cold material under a vacuum in a special containment device. Hitting someone with that, would amount to hitting them with a steel pipe.
There is other work that is similar and a lot more like a light saber to some degree. A strong enough laser focused down in air will cause the air to breakdown into a plasma from the strong electric fields (similar to using a high voltage to turn on a neon light), and heat up the air. Hot air, and especially plasma, will have a different index of refraction and light moving through changing index of refraction will bend, e.g. a lens or a mirage. If you use the right profile, it will actually make the laser beam self-focusing, that the heated air acts like a focusing lens, which keeps the laser focused enough to heat the air in front of that, and the beam will travel without diverging as long as it has enough power to keep heating up the air. This doesn't really stop like a light saber though, and only works in air or a specific material, and where the plasma part stops a rather high power laser beam is still coming out the end.
As a general rule, when I see a news story claiming that a disease has been cured or a widely-accepted principle of modern science has been proven wrong, I assume that the story is wrong.