While lightsabers do seem feasible from a physics point of view, the power requirements for such a device would be immense, especially given that it needs to be contained within the small lightsaber hilt. Huge advances in technology would be required to make lightsabers a reality. But there’s an even bigger problem which would come about if you were to ever have a lightsaber duel like in the movies.
Magnetic reconnection is a fundamental plasma physics process which can occur when plasmas with different magnetic fields collide. As the magnetic fields of each plasma get close to each other, the entire pattern of magnetic field lines changes and everything realigns into a new magnetic configuration – releasing huge amounts of energy.
This is what essentially fuels the aurora or northern lights – energy from the solar wind is released when these particles collide with plasma inside Earth’s magnetic field under a specific set of conditions.
It’s from our studies of the conditions under which reconnection can occur in space that I was able to realise the problem with lightsaber battles. When two plasma blades clash it is almost impossible to avoid magnetic reconnection, with the results being an explosive release of the plasma contained in both sabers. This would mean that, if you were in a lightsaber duel, both you and your opponent would have body parts vaporised in a single clash!