Tractor Beams Are Getting Closer (Sort of)

xt writes "A recently submitted paper in arXiv claims that by using Bessel beams it is theoretically possible to pull particles towards the light source, opening up new avenues for optical micromanipulation (the direction of the force is size dependent, so it could be used for particle sorting). There is also a simpler article translated in English (original article in Greek)."

Comments

Frist

[defnoz]

There's something strangely attractive about this idea...

Re:What's next?

[Yvan256]

Well, we already have Quantum drives, how hard can it be to warp them?

Re:It's theoretically possible this'll never happe

[SuricouRaven]

Science fiction technologies can be divided into two classes. Those which are merely incredibly difficult, and those to which the laws of physics have raised a comic middle finger to our dreams.

The former include interstellar travel, nano-assemblers, immortality and brain uploading. The latter perpetual motion, time travel, antigravity and anything faster than light. Anything in the first category you can hope will, one day, be achiveable... even though it may take centuries of advancement.

I'm not sure where tractor beams fall.

Particle sorting...Isotopes, perhaps?

[dfetter]

Actually, this could be pretty significant if it takes some clever machine rather than a host of gigantic centrifuges to do the job.

Re:Particle sorting...Isotopes, perhaps?

[Anonymous Coward]

The wavelengths at which different isotopes absorb light are slightly different (Hyperfine structure), so if you tune the wavelength of your laser just right, you can use radiation pressure rather than the (typically weaker) optical gradient force to at least identify different isotopes. (I work in cold atom physics and was just doing this in the lab with Rubidium 85 and 87).

However, the radiation pressure on an atom is limited by the atom, whereas the optical gradient force is limited by the power of your laser. At room temperature, you can't use radiation pressure to separate Rb 85 and 87. There is considerably more freedom to engineer the forces experienced by the particle if you use the optical gradient forces and tricks, like Bessel beams, or more generally SLMs, which are essentially computer-programmable holograms. See, for example, the excellent experimental work of the Dholakia and Padgett groups.

Who wants a tractor beam?

[valinor89]

I want a repulsor beam. Fuck antigravity I only want to repel the ground.

Re:Who wants a tractor beam?

[countertrolling]

I want a repulsor beam.

That would be a mirror. Don't look into it :-)

Re:Who wants a tractor beam?

[Anonymous Coward]

You expend all that time and energy to push the opposition into a decaying orbit (which, due to simple Newtonian physics, also costs you momentum in the opposing direction and requires that you make adjustments yourself). Meanwhile, the enemy have engines and can easily compensate for your push/pull, and take a few seconds out of their not-terribly-busy schedule compensating for your attempts to throw them off, and blow your ass out of the sky. With real weapons that actually do immediate damage.

This is kind of the same argument as "why shoot the gunfighter? Why not just walk up to him and push him to the ground?" Because, assuming you make it all the way to where he is and succeed in having him fall, he'll simply stand back up, dust himself off, give you a short nonplussed look, and increase your daily intake of lead by a few ounces of lethal speed-of-sound injection.

I did always wonder why "we're stranded!" stories never involved taking an object of significant mass nearby and using it as a target practice for a tractor or repulsor beam, though. Grab on to a moon, use it to push/pull yourself around until you can develop enough speed to establish a decent gravity slingshot, and off you go.

Guess it's not sexy enough in special effects.

Star Trek in our time...

[turthalion]

All we need to do is add atomic power, and bingo, nuclear bessels!

Re:What's next?

[Ced_Ex]

Toss them into the microwave, they warp just fine.