# Conveying left/right to alien by description **URL:** \ **Category:** Factual Questions\ **Created:** [February 14, 2016, 3:17pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120 "2016-02-14T15:17:34Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [February 14, 2016, 9:03pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/21 "2016-02-14T21:03:22Z")
A similar conundrum occurred in my own life. I was about 7, and my father yelled at me to turn off the backyard faucet. I didn’t know which way to turn it, so he yelled to turn it “to the right.” I knew left from right, but it was clear that whichever way I turned the round faucet handle, the top and bottom would be moving in opposite directions. Since I couldn’t decide, my father came and shoved me out of the way, cursing “I’ve gotta do every goddamn thing around here myself!” ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [February 14, 2016, 10:18pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/22 "2016-02-14T22:18:57Z")
> [@panache45](#): > > I didn’t know which way to turn it, so he yelled to turn it “to the right.” Tip: Turn it either direction - if it stops, that was “right”; if not, that was “left”. ---
**Author:** ![Nefario](https://avatars.discourse-cdn.com/v4/letter/n/59ef9b/32.png) [@Nefario](https://boards.straightdope.com/u/Nefario)\ **Post date:** [February 14, 2016, 10:26pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/23 "2016-02-14T22:26:48Z")
> [@Vetinari42](#): > > Now, it was stated that this is impossible, but I think I’ve missed something as it seems a fairly simple thing to do. > > Does anyone know the full rules to the problem that make it impossible? There MUST be a rule that we share a spoken or written language. Otherwise how does one convert between our air-powered grunts and their vibratory ultrasonic beeps. 😕 Or their chameleon color flashes? ---
**Author:** ![Mnemnosyne](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mnemnosyne/32/3347_2.png) [@Mnemnosyne](https://boards.straightdope.com/u/Mnemnosyne)\ **Post date:** [February 15, 2016, 1:13am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/24 "2016-02-15T01:13:57Z")
Yeah, indeed, if they can read our language, it’s eminently simple to explain in the sense that you can just say ‘you are reading this message left-to-right.’ And if they can’t read our language, how are we even communicating? ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [February 15, 2016, 2:00am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/25 "2016-02-15T02:00:46Z")
> [@Mnemnosyne](#): > > Yeah, indeed, if they can read our language, it’s eminently simple to explain in the sense that you can just say ‘you are reading this message left-to-right.’ And if they can’t read our language, how are we even communicating? Morse code. No “lefts and rights” in sequence communication. ---
**Author:** ![TimeWinder](https://avatars.discourse-cdn.com/v4/letter/t/bcef8e/32.png) [@TimeWinder](https://boards.straightdope.com/u/TimeWinder)\ **Post date:** [February 15, 2016, 2:29am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/26 "2016-02-15T02:29:09Z")
> [@usedtobe](#): > > (if anyone actually does NOT see the problem: "Describe the shape of the letter “L”.) But that’s a different problem. If your answer to every given response is “OK, then define those terms, too,” sure, you can make _any_ problem unsolvable, but that’s a bit of a ridiculous position to take. ---
**Author:** ![robert\_columbia](https://avatars.discourse-cdn.com/v4/letter/r/e79b87/32.png) [@robert\_columbia](https://boards.straightdope.com/u/robert_columbia)\ **Post date:** [February 15, 2016, 2:39am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/27 "2016-02-15T02:39:34Z")
> [@TimeWinder](#): > > This is going to come down to what you consider a “scientific attribute.” > > If that phrase covers all of observation and physics, it’s impossible because you can no longer use any words that are in any way related to the topic you’re talking about. Heck, “left” and “right” are explanatory descriptions of the world, which makes the very words themselves “scientific attributes” and hence verboten. > > It’s like trying to describe the number “2” without being allowed to directly or indirectly reference counting of anything, numbers, mathematics, etc. Yes, I think the OP is getting very close to a “move the goalposts” question. “Describe A without using B or C.” “Well, you could use X and Y.” “Well, what if you couldn’t use X or Y either? How would you describe A?” “Well, you could try Z.” “You can’t use that either. How would you describe A without B, C, X, Y, or Z?” > [@usedtobe](#): > > This is a classic. > … > (if anyone actually does NOT see the problem: "Describe the shape of the letter “L”.) Wait, is this the Star Trek universe? If so, then we know that nearly every civilization out there speaks English. Problem solved. Oh, wait, did you mean to say that you are communicating with an _illiterate_ alien? ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [February 15, 2016, 2:49am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/28 "2016-02-15T02:49:55Z")
Martin Gardner was fond of talking/writing about this problem. In fact, he wrote a whole book about it: [The Ambidextrous Universe](https://en.wikipedia.org/wiki/The_Ambidextrous_Universe) which has gone through several editions, including at least one edition after Gardner died. > [@](#): > > The 18th chapter, “The Ozma Problem”, poses a problem that Gardner claims would arise if Earth should ever enter into communication with life on another planet through [Project Ozma](https://en.wikipedia.org/wiki/Project_Ozma). This is the problem of how to communicate the meaning of left and right, where the two communicants are conditionally not allowed to view any one object in common. The problem was first implied in Immanuel Kant’s discussion of left and right, and William James mentioned it in his chapter on “The Perception of Space” in The Principles of Psychology (1890). It is also mentioned by Charles Howard Hinton. Gardner follows the thread of several false leads on the road to the solution of the Ozma Problem, in each case presenting an apparent solution which, on closer examination, turns out to be a false one. > > The solution to the Ozma Problem was finally embodied in the famous “Wu experiment” — which was conducted in 1956 by Chinese-American physicist Chien-Shiung Wu (1912-1997) — involving the beta decay of cobalt-60. This experiment was the first to disprove the conservation of parity. At long last, according to Gardner, it is believed that one could carefully describe the Wu experiment to a distant extraterrestrial intelligence and thereby convey the exact meaning of left/right. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [February 15, 2016, 3:33am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/29 "2016-02-15T03:33:34Z")
IANA expert on this problem. Plus, I didn’t read the Sci-Am article from post #4. Explaining that we’re trying to label in 3-space the two opposite directions that are not up nor down & also are not towards nor away is trivial, given some common language and a communications mechanism. And thereby we reduce the problem to simply which of the remaining two orthogonal directions is left & which is right. What they are, how they relate to up, down, towards, and away, and which two they are would not by doubted by our aliens. The sole remaining non-trivial issue is which of the two is which? ISTR there are lots of chiral molecules that only fold or coil or … one way. There might even be some macroscopic crystals that exhibit that behavior. So grab one of those molecules. Made up example: hold it so the Nitrogen is up, the carbon is away, and look at the oxygen; it’ll be on the right every time. ISTR there are also chemicals that do come in stereo pairs. But one pair is significantly more likely than the other. So grab a sample and look at a bunch of molecules. Made up example: hold each so the Nitrogen is up, the carbon is away, and look at the oxygen; The direction the oxygen points in 75% of the samples is right. What am I missing or screwing up here? ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [February 15, 2016, 3:45am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/30 "2016-02-15T03:45:07Z")
> [@LSLGuy](#): > > . . . ISTR there are lots of chiral molecules that only fold or coil or … one way. There might even be some macroscopic crystals that exhibit that behavior. So grab one of those molecules. Made up example: hold it so the Nitrogen is up, the carbon is away, and look at the oxygen; it’ll be on the right every time. . . . But doesn’t that depend on which way up the guy is holding it? I remember Martin Gardner’s article, and I believe Isaac Asimov dealt with it too. They both said that, before the asymmetry of certain Weak Force interactions, there was no possible answer. But nowadays, we know that (as Scotty said in an old Star Trek novel) the universe has a left-hand twist. ---
**Author:** ![usedtobe](https://avatars.discourse-cdn.com/v4/letter/u/ec9cab/32.png) [@usedtobe](https://boards.straightdope.com/u/usedtobe)\ **Post date:** [February 15, 2016, 4:32am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/31 "2016-02-15T04:32:06Z")
Describe the location of the numbers on a clock face. Describe the location of "N’, ‘S’, ‘E’ and ‘W’ on the compass. And: just to preclude: describe the direction of the hands on a clock. ‘N’ is at the ‘top’ (which is legit), 'S; is at the bottom (ditto); ‘E’ is at/ to the \_\_\_\_\_\_\_. It gets back to ‘right’ is ‘right’ and ‘left’ is ‘left’. Now you know why it takes children so long to get it right. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [February 15, 2016, 5:07am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/32 "2016-02-15T05:07:57Z")
> [@robert\_columbia](#): > > Yes, I think the OP is getting very close to a “move the goalposts” question. Not really, it’s a pretty well known and well established thought experiment: based only on exchanging a series of messages with an alien civilization (i.e. you can’t send a polarized beam, you can’t point to some astronomical object you can both see, etc), can you communicate to the alien which of its hands is the “right” hand? It’s just an illustration of how symmetric our universe is, and how all the laws of nature work equally well when the orientation is reversed. As already mentioned, the answer is, the only way to communicate right/left is to refer to the [violation of symmetry in weak interactions](https://en.wikipedia.org/wiki/Weak_interaction#Violation_of_symmetry). But if I remember correctly, even this is not 100% unambiguous - it only works if you’re sure that your aliens are not made of antimatter. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [February 15, 2016, 5:17am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/33 "2016-02-15T05:17:45Z")
> [@LSLGuy](#): > > ISTR there are lots of chiral molecules that only fold or coil or … one way. There might even be some macroscopic crystals that exhibit that behavior. No, if a molecule is stable, its mirror image is equally stable. They may behave differently in chemical reactions, but only if the other molecules involved are asymmetric. They will behave exactly the same way _if_ you replace all the other molecules involved in the reaction with their mirror images. (I think Asimov had a short story about a man who was thrown up into a higher dimension and came back reversed; he almost died of malnutrition until they figured out how to synthesize mirror images of certain nutrients.) > [@](#): > > ISTR there are also chemicals that do come in stereo pairs. But one pair is significantly more likely than the other. I think this is only true for certain organic molecules. And the only reason one orientation is more likely is because they are synthesized by organisms or molecules that are themselves all one of 2 possible orientations. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [February 15, 2016, 8:28am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/34 "2016-02-15T08:28:50Z")
> [@jtur88](#): > > If the planet has a magnetic field, it can be defined. Really, and how are you going to convey the definition of magnetic north and south? ---
**Author:** ![Nancarrow](https://avatars.discourse-cdn.com/v4/letter/n/c37758/32.png) [@Nancarrow](https://boards.straightdope.com/u/Nancarrow)\ **Post date:** [February 15, 2016, 11:16am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/35 "2016-02-15T11:16:18Z")
I see people have already mentioned the whole breaking-conservation-of-parity thing, but here’s another reference for that, the first place I heard of it: [http://www.feynmanlectures.caltech.edu/I\_52.html](http://www.feynmanlectures.caltech.edu/I_52.html) Sections 52.6 to 52.8, though 52.4-5 are also useful for background. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [February 15, 2016, 11:36am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/36 "2016-02-15T11:36:20Z")
> [@naita](#): > > Really, and how are you going to convey the definition of magnetic north and south? You don’t have to - you do it in terms of direction of electron flow in a wire. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [February 15, 2016, 11:50am UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/37 "2016-02-15T11:50:02Z")
> [@MrDibble](#): > > You don’t have to - you do it in terms of direction of electron flow in a wire. Give it a go. But remember, left and right are currently not defined. As to using this to define north and south poles, you might ask if the technique will even work consistently here on Earth. 800,000 years ago you would have got the opposite answer. ---
**Author:** ![Don\_t\_Panic](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/don_t_panic/32/398_2.png) [@Don\_t\_Panic](https://boards.straightdope.com/u/Don_t_Panic)\ **Post date:** [February 15, 2016, 12:03pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/38 "2016-02-15T12:03:02Z")
> [@scr4](#): > > But if I remember correctly, even this is not 100% unambiguous - it only works if you’re sure that your aliens are not made of antimatter. I probably don’t understand this correctly at all, but for it not to work, I think the aliens would also have to be moving backwards in time. Which seems unlikely to be an issue. [CPT symmetry.](https://en.wikipedia.org/wiki/CPT_symmetry) > [@](#): > > The implication of CPT symmetry is that a “mirror-image” of our universe — with all objects having their positions reflected by an arbitrary plane (corresponding to a parity inversion), all momenta reversed (corresponding to a time inversion) and with all matter replaced by antimatter (corresponding to a charge inversion)— would evolve under exactly our physical laws. The CPT transformation turns our universe into its “mirror image” and vice versa. Flip left and right, replace matter with antimatter, and flip time to the other direction, and you have a universe that looks identical to ours. Do only one or two of those, and you can tell the difference. Again, if I understand this correctly at all. This stuff is mostly way, way over my head. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [February 15, 2016, 12:37pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/39 "2016-02-15T12:37:13Z")
> [@MrDibble](#): > > You don’t have to - you do it in terms of direction of electron flow in a wire. Interesting. This seems achievable. We can define an anode and a cathode easily enough. That means we can construct a circuit wire with a known anode and cathode. We can also therefore build a magnet with a known north and south pole, and from that define a north and south pole of the planet. We can then align a compass along a circuit wire with a known orientation. Then we just repeat the Orsted experiment. [If the north pole of your compass is facing the cathode, then it will deflect to the right. If it’s facing the anode, it will deflect to the left.](http://www.ekshiksha.org.in/image_magnetic_effect_of_electric_10/Figure_5.JPG) Thus left is the direction that the north pole of a north-facing a compass needle will deflect when current is run under it from a cathode in the south. Can anyone see why this wouldn’t work? ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [February 15, 2016, 12:50pm UTC](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120/40 "2016-02-15T12:50:35Z")
> [@Blake](#): > > Thus left is the direction that the north pole of a north-facing a compass needle will deflect when current is run under it from a cathode in the south. > > Can anyone see why this wouldn’t work? You are just transferring the problem to north and south… what does north mean ? [Previous page](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120.md?page=1) [Next page](https://boards.straightdope.com/t/conveying-left-right-to-alien-by-description/746120.md?page=3)