# What's up with "optical tractor beams?" **URL:** \ **Category:** Factual Questions\ **Created:** [January 27, 2013, 5:06pm UTC](https://boards.straightdope.com/t/whats-up-with-optical-tractor-beams/648537 "2013-01-27T17:06:54Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [January 27, 2013, 5:06pm UTC](https://boards.straightdope.com/t/whats-up-with-optical-tractor-beams/648537/1 "2013-01-27T17:06:54Z")
Just read: [Star Trek style ‘tractor beam’ created by scientists](http://m.bbc.co.uk/news/uk-scotland-tayside-central-21187598) Cites article in _Nature Photonics._ In a supreme example of standard journalist practice, BBC News does not have a whit of description, even moronic description, of the technology. ---
**Author:** ![drewtwo99](https://avatars.discourse-cdn.com/v4/letter/d/d07c76/32.png) [@drewtwo99](https://boards.straightdope.com/u/drewtwo99)\ **Post date:** [January 27, 2013, 5:19pm UTC](https://boards.straightdope.com/t/whats-up-with-optical-tractor-beams/648537/2 "2013-01-27T17:19:55Z")
IF I’m understanding the article correctly, these sorts of inventions aren’t even all that new. Seems it is just a form of laser trapping or optical tweezers. Read more about them [on wikipedia](http://en.wikipedia.org/wiki/Optical_tweezers) if you are curious 🙂 ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [January 28, 2013, 3:00pm UTC](https://boards.straightdope.com/t/whats-up-with-optical-tractor-beams/648537/3 "2013-01-28T15:00:51Z")
No, this is something very different from "optical tweezrers, in which something is typically trapped at an interference node between beams, and generally requires a mirror placed beyond the object. this sort of optical trapping has been done since the early 1970s, and is unlikely to “wow” fans of Star Trek, Star Wars, or any other space opera-esque fiction. If you can get a mirror behind the thing you’re trapping, you could just as easily loop a lanyard over it. I had written an article about Tractor Beams a few years ago, giving a Pop Culture history of the concept, and observing that the Tractor Beam as envisioned didn’t actually exist, but it was used by people trying to write popular articles about Optical Tweezers because this non-existent technology got the point across. Besides, i explained, one problem with a tractor beam is that to _pull_ something towards you, you have to produce a change in momentum _toward_ the light source – and photons carry momentum _away_ from the source. You can rig things to give items a “sideways” shove, but a shove towards the light source seemed impossible. My article was cited for the history of the topic in one of the first papers to prove I was wrong. _Sic Transit Gloria Mundi_. What I hadn’t considered was a coherent superposition of two beams of not quite identical wavelength, co-propagating along the same direction.\* What happens in that case is that you get interference nodes along the longth of the beam, but they’re in slight motion. You can make them proceed backwards along the beam and convey a light item back towards the source iof the beam. It isn’t very fast, and you’re not going to use it on spaceship-sized objects, but it will work, and there have been numerous papers on the topic over the past two years. See _On the Topic of “Tractor Beams”_ by S. Sukhov and A. Dogariu _Optics Letters_ **35** (22) 3847- 9 Nov. 15 2010 [http://www.researchgate.net/publication/47809504\_On\_the\_concept\_of\_tractor\_beams/file/79e414fc4cc0ff23a0.pdf](http://www.researchgate.net/publication/47809504_On_the_concept_of_tractor_beams/file/79e414fc4cc0ff23a0.pdf) \*You _can_ interfere two beams that aren’t precisely the same wavelength, but are close. It’s done in four-wave mixing all the time. ---
**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\ **Post date:** [January 29, 2013, 2:07pm UTC](https://boards.straightdope.com/t/whats-up-with-optical-tractor-beams/648537/4 "2013-01-29T14:07:19Z")
Holy cow. Tractor beams! With the NASA news about the Alcubierre warp drive, and evolving 3-D printing technology (a necessary precursor to “replicator” tech), we’re approaching the _Star Trek_ universe much sooner than the 23rd century!