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The Death Star's planet-destroying weapon is said in the Star Wars Encyclopedia to be a super-laser. While a laser is basically just light, it is light that can be focused onto a precise spot and can have high, extremely concentrated power. Lasers can produce a steady beam for long periods, or they can produce a very intense beam in short pulses, occurring thousands or millions of times per second. The amplified light of lasers can also be very powerful. A series of pulses can drill through hard materials like titanium or diamond.
A megawatt laser can burn a hole through a jet up to six miles away—though it needs to maintain contact with the aircraft for one to two seconds. In a 1998 test, MlRACL, a 2.2-megawatt laser, was able to hit a satellite in Earth orbit. MlRACL purposely did not destroy the satellite, since the test was designed merely to show that the laser could target and hit the satellite. But researchers say the laser could just as easily have melted it.
Thus it seems the lasers we have today would be capable of doing many of the things we see in Star Wars. We could injure or kill people; we could burn structures or melt holes in walls; we could destroy targeted areas of spaceships, assuming we could keep a beam on them for long enough. The main difference between Star Wars lasers and ours is the size. While we can create lasers that emit extremely powerful energies, we need to pump great energies into them to make them work. That energy source takes space, which the Death Star, at least, provides.
To vaporize a planet, we'd need a laser with a billion trillion times the energy of MIRACL. But perhaps we don't need to vaporize it. Dr. Stuart Penn, senior research fellow at South Bank University in London, suggests another way a laser might destroy a planet: "The laser could vaporize a narrow tunnel to the core of the planet. Then heat the core so it expands and melts. I'm not sure the planet would actually explode, but the laser would probably rearrange it."
The biggest difficulty in generating a beam powerful enough for either of these options would be in finding a stable lasing material—the material whose electrons are amplifying light inside it. Lasing materials can be gases, crystals, or even semiconductors. But in very powerful lasers, these materials are subjected to extreme heat.
Yet Dr. Michio Kaku, Henry Semat Professor of Theoretical Physics at the City University of New York and author of Hyperspace and Visions,believes that if the Empire could overcome this limitation, they could build the Death Star's weapon. Dr. Kaku even seems to admire the Death Star a bit. "The Death Star is very practical," he says. "We could even build it ourselves, if we had enough gross national product. We have nuclear weapons that could crack the Earth. ... They could build a laser powered by a hydrogen bomb, an X-ray laser. I've got no problems with the Death Star."
I have one, actually. When the Death Star fires, six laser beams are generated around the circumference of a circular depression on the exterior of the space station. The six beams meet at the center of the circle and head down toward the planet as a single, huge beam. What would actually happen, I'm afraid, is the six beams would pass through each other and head off in six different directions, probably all of them missing the planet. If we're lucky, maybe they'd run into some star destroyers.