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Star-Trek physics getting real - Physicists create "tractor beam"

Christian Klippel

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Christian Klippel
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You probably know the tractor-beam-thingy from Star Trek? Well, a duo of physicists has replicated just that in small-scale:

http://phys.org/news/2012-10-physics-duo-tractor-dual-bessel.html

Abstract
We experimentally demonstrate a class of tractor beams created by coherently superposing coaxial Bessel beams. These optical conveyors have periodic intensity variations along their axes that act as highly effective optical traps for micrometer-scale objects. Trapped objects can be moved selectively upstream or downstream along the conveyor by appropriately changing the Bessel beams' relative phase. The same methods used to project a single optical conveyor can project arrays of independent optical conveyors, allowing bidirectional transport in three dimensions.
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Fascinating! :D

Greetings,

Chris
 
Very cool, unfortunately it'll only ever work on objects tiny enough to be pushed around by photons.
 
Heh -- I just did a report on the commercial potential for tractor beams!
 
I used to understand Bessel stuff once... but I am so out of practice that it would all be close to gibberish to me now.

By the way, I thought Star Trek tractor beams were made of gravitons. And not to get too grouchy, since when did "tractor" become an adjective?
 
Hellbound said:
Size isn't a hard limitation (http://en.wikipedia.org/wiki/Solar_sail).

Of course, putting solar sails on everything we want to tractor could pose some practicality issues...
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You don't even need solar sails. Photons exert force on everything. The reason spacecraft need would need sails is simply that ambient photons in the solar system don't exert very much force, so you want as big a surface area as possible to catch more of them. In theory you could use this method to move anything you liked, no matter how big. It's just that you'd need a really big laser to do so. And there would probably be more use of the word "vaporised" than "moved".
 
Cuddles said:
You don't even need solar sails. Photons exert force on everything. The reason spacecraft need would need sails is simply that ambient photons in the solar system don't exert very much force, so you want as big a surface area as possible to catch more of them. In theory you could use this method to move anything you liked, no matter how big. It's just that you'd need a really big laser to do so. And there would probably be more use of the word "vaporised" than "moved".
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Well, yes. But non-vaporizing, you'd need something to increase the surface area.

Although, vaporization could definitely get it moving.
 
Brown said:
And not to get too grouchy, since when did "tractor" become an adjective?
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Tractor has been used as part of compound nouns at least as early as "tractor trailer" more than 60 years ago.

Generically, a tractor is "something that provides a large pulling or towing force," so the term "tractor beam" fits quite nicely. :)
 
AvalonXQ said:
Generically, a tractor is "something that provides a large pulling or towing force," so the term "tractor beam" fits quite nicely. :)
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Ah, but shouldn't it then be a hyphenated "tractor-beam," as a combination or cooperation of nouns, a single thing that includes the qualities of each of the nouns that make it up? If I can't contribute to the technology, perhaps I can contribute to the grammar.

But don't get me started on "to tractor," which uses the word as a VERB! Someone ought to wheelbarrow that one right out to the grammatical dump!
 
Cuddles said:
You don't even need solar sails. Photons exert force on everything. The reason spacecraft need would need sails is simply that ambient photons in the solar system don't exert very much force, so you want as big a surface area as possible to catch more of them. In theory you could use this method to move anything you liked, no matter how big. It's just that you'd need a really big laser to do so. And there would probably be more use of the word "vaporised" than "moved".
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Yeah but they are calling this a tractor beam because it can pull on things, not just push. To do that, the waves defract around the object and constructively interfere behind it. This is where size becomes the major limiting factor.
 
It's a noun, a tractor beam, as opposed to a My Little Pony beam.
 
Actually I think it's an adjective describing 'beam' in this case. :)
 
Beerina said:
It's a noun, a tractor beam, as opposed to a My Little Pony beam.
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That's what I'm saying, these so-called scientists are improperly using the word "tractor" as an adjective, to specify what kind of beam it is. And what I'm saying is, that until the dictionaries generally recognize the word as a modifier, these guys ought not to get a Nobel Prize or whatever it is. Never mind that this might be the most significant technological breakthrough since fire.
 
Brown said:
Never mind that this might be the most significant technological breakthrough since fire.
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So you figure an impeller beam beats out electricity, radio, internal combustion, powered flight, antibiotics, vaccination, anasthetics, or the transistor? I don't see it.
 
Brown said:
That's what I'm saying, these so-called scientists are improperly using the word "tractor" as an adjective, to specify what kind of beam it is. And what I'm saying is, that until the dictionaries generally recognize the word as a modifier, these guys ought not to get a Nobel Prize or whatever it is. Never mind that this might be the most significant technological breakthrough since fire.
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I'm sure you're just kidding, but the grammar nazi in me feels compelled to point out that a noun can be used as an adjective in the English language without being explicitly defined as one.
 
phunk said:
I'm sure you're just kidding, but the grammar nazi in me feels compelled to point out that a noun can be used as an adjective in the English language without being explicitly defined as one.
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Yeah, I'm just kidding around. Bessel stuff --especially Bessel functions (wait a minute: is "Bessel" an adjective??)--can get quite complicated from a mathematical standpoint. By contrast, complaining about grammar is something anyone can do.

But don't get me started on the good-natured debate I entered into a few years ago, in which the question was whether a "key card" was a kind of a key in the form of a card, or a kind of a card that served the function of being a key.

Enough of this derailing. It's gotten silly. Any comments on tractor beams?
 
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