Catching the Wave

Alas, it is not a precursor to a tachyon detection grid. But NASA and the European Space Agency have cooked up an idea that is reminiscent of such imagined technology. The Laser Interferometer Space Antenna (LISA) is being developed in the hopes of detecting gravitational waves. Gravitational waves are a phenomena that was predicted by Albert Einstein's general theory of relativity, but so far have never been directly detected. The LISA program aims to do just that, however:

LISA consists of three identical spacecraft flying in a triangular constellation, with equal arms of 5 million kilometers each. As gravitational waves from distant sources reach LISA, they warp space-time, stretching and compressing the triangle. Thus, by precisely monitoring the separation between the spacecraft, we can measure the waves; and by studying the shape and timing of the waves we can learn about the nature and evolution of the systems that emitted them.

These "arms" referred to in the preceding paragraph are actually lasers:

LISA's implementation of interferometric measurements resembles the technique known as spacecraft Doppler tracking, but it is realized with infrared laser light instead of radio waves. The laser light going out from one spacecraft to the other corners is not reflected back directly, because diffraction losses over such long distances would be too great. Instead, the phase of the incoming laser is measured, and used to set the phase of the outgoing laser, which is transmitted back at full intensity: this process is known as transponding. When the transponded laser light arrives back at the original spacecraft, it is superposed with a portion of the original laser beam, and their phases compared.

The physics behind this is quite beyond me, not to mention the challenge of aiming two separate lasers per craft at targets 5 million kilometers away. According to the NASA site, a technology demonstration is scheduled for 2012, so there is still a long way to go before we'll see the fruit of this effort. Nevertheless, if nearly 100 years after Einstein postulated his theory, evidence of gravitation wave energy can be measured, it will say something astounding about the brilliance of a man who did more to shape our modern understanding of physics than anyone else. Dude!

(h/t: Gizmodo)