In more news to terrify you, the US Army has released photographs depicting their new laser-guided lightning gun blowing up a car. They’re calling it the Laser-Induced Plasma Channel (LIPC) because it’s important to make the ability to call down lightning with a laser pointer sound safe.

The science, as described in the press release, is actually sort of neat:

Light travels more slowly in gases and solids than it does in a vacuum… We typically think of the speed of light in each material as constant. There is, however, a very small additional intensity-dependent factor to its speed. In air, this factor is positive, so light slows down by a tiny fraction when the light is more intense.

If a laser puts out a pulse with modest energy, but the time is incredibly tiny, the power can be huge. During the duration of the laser pulse, it can be putting out more power than a large city needs, but the pulse only lasts for two-trillionths of a second…

For very powerful and high intensity laser pulses, the air can act like a lens, keeping the light in a small-diameter filament. We use an ultra-short-pulse laser of modest energy to make a laser beam so intense that it focuses on itself in air and stays focused in a filament.

If a laser beam is intense enough, its electro-magnetic field is strong enough to rip electrons off of air molecules, creating plasma. This plasma is located along the path of the laser beam, so we can direct it wherever we want by moving a mirror. Air is composed of neutral molecules and is an insulator… [But] the plasma channel conducts electricity way better than un-ionized air, so if we set up the laser so that the filament comes near a high voltage source, the electrical energy will travel down the filament.

But at the same time it’s, you know, a laser-guided lightning gun, which is at least moderately horrifying. Have a great weekend.

[Source: U.S. Army]