Lasers Used to Guide Lightning Strikes to a Safe Target
upstart writes:
Lightning strikes flow along laser's path for tens of meters:
Lightning rods protect buildings by providing a low-resistance path for charges to flow between the clouds and the ground. But they only work if lightning finds that path first. The actual strike is chaotic, and there's never a guarantee that the processes that initiate it will happen close enough to the lightning rod to ensure that things will work as intended.
A team of European researchers decided they didn't like that randomness and managed to direct a few lightning strikes safely into a telecom tower located on top of a Swiss mountain. Their secret? Lasers, which were used to create a path of charged ions to smooth the path to the lightning rod.
The basic challenge with directing lightning bolts is that the atmospheric events that create charged particles occur at significant altitudes relative to lightning rods. This allows lightning to find paths to the ground that don't involve the lightning rod. People have successfully created a connection between the two by using small rockets to shoot conductive cables to the heights where the charges were. But using this regularly would eventually require a lot of rockets and leave the surroundings draped in cables.
The idea of using lasers to guide lightning is an old one, with the suggestion first appearing in the scientific literature back in the 1970s. A sufficiently high-intensity laser beam has a complicated relationship with the air it travels through. The changes it makes to the air help focus the laser, while the electrons it knocks loose tend to disperse it. Meanwhile, the molecules in the atmosphere that absorb the light heat up and shoot out of its path, creating a low-pressure path in the laser's wake. Critically, many of the particles left behind in these low-pressure filaments are charged, providing a potential path for lightning.
It's also possible to shape laser pulses so that you control where the generation of these filaments start-up to a kilometer away from the laser source.
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