The tubes of the Internet saw some extra traffic recently when NASA announced funding for a team of researchers to study tractor beams. That’s right, tractor beams, as in Star Trek and Star Wars (and countless other science fiction settings). The goal here isn’t to grab spacecraft (at least, not at first); instead, NASA wants to use the technology to collect particle samples for analysis on rovers and spacecraft.
This may sound like science fiction, but a few days after this announcement, a pair of papers appeared in Physical Review Letters, discussing the theory behind two approaches the NASA team plans to study (the papers' authors appear to be unaffiliated with that team).
In general, shining light on something will cause it to move away from you as the photons are either absorbed or scattered—the conservation of momentum requires that the lost momentum is compensated by the object gaining some momentum in the photon's original direction of movement. This is great if you want to push objects away, but how do you pull them toward you? By manipulating the light beams in different ways, you can force photons to scatter off the object in a way that causes motion in the opposite direction. The two papers present different methods of doing just this.
The first paper, from a team at the University of Central Florida, approaches this problem by using a light beam that consists of multiple plane-wave components with different directions. In practical terms, this means you focus a bunch of laser beams on the objects, ensuring that they hit from angles that differ from the direction you want the object to move. The beams can then be adjusted based on the size and shape of the specific object to optimize the resulting force.
http://arstechnica.com/science/news/2011/11/tractors-on-full-the-first-steps-towards-light-based-tractor-beams.arsIf I had been born 500 years in the future.......
Printer-friendly format
Email this thread to a friend
Bookmark this thread
(1000+ posts)
Send PM |
Profile |
Ignore
