Neil deGrasse Tyson Discusses Lightsaber Physics

Of course we've all played with fake light saber toys, but could would it be physically possible for actual lightsabers to exist in real life?

In this National Geographic video, StarTalk with Neil deGrasse Tyson, an astrophysicist, Tyson and British physicist Brian Cox debate whether lightsabers could ever exist. For the Star Wars newbies out there, a light saber is a fictional weapon comprised of a metal hilt that projects energy in the shape of a sword. The lightsaber can melt, cut, and burn through objects, wound flesh, and even cause bleeding. Usually, the lightsaber energy can be deflected with a blade or energy shield.

If lightsabers are made of light they could damage by cutting things, but they can't stop one another the same way two swords would, said Tyson. Cox, however, argues that a lightsaber battle would entail photon-photon, or "gamma gamma scattering", in which one photon scatters or deflects from another. At high energy collisions it's probable that the photons would actually bounce off one another rather than pass through each other.

In fact, Cox continued, at high energies the probability increases that the photons would collide with one another. "There's a cut off," he said, "where the cosmic rays can be such high energy that the probability that they'll bounce off photons and cosmic microwave background becomes high."

Cox and Tyson admit how nerdy it is to even speculate the feasibility with which people could use lightsabers in real life. But should the technology ever exist, the light sabers would need to be high energy in order to have a proper lightsaber sword fight.

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