Physicist Patrick Johnson, an associate teaching professor at Georgetown University and author of The Physics Of Star Wars, suggests two options.

“The first is that it is exactly what it is described as, a sabre made of light, a laser sword,” he says. “The problem with it being a laser, though, is that because photons move at the speed of light, the laser will just keep going until it runs into something. Lasers don’t stay in a self-contained beam.”

The more plausible option, says Johnson, is that lightsabers are made of plasma, the electrically charged gas that makes up lightning and the Sun. Plasma cutting machines are often used in manufacturing to slice through materials such as steel.

“Plasma is hot enough to melt metal, it can change colour depending on the material you’re using and is able to cauterise wounds, just like in the movies,” explains Johnson. “But the problem is that it’s really, really hot. We’re talking about holding something that is the temperature of the Sun in your hand, which is not going to be pleasant for you without special equipment.”