How Would You Teach Left from Right to an Alien Civilization? | Hacker News Reader

How Would You Teach Left from Right to an Alien Civilization?

blogs.scientificamerican.com

34 pointsColinWright25 comments

Feynmann discusses this problem in one of his lectures on symmetry. He seemed to suggest that chirality of any physical system was relative, though you may have to down to the subatomic level to completely reverse everything.

If I recall correctly, this segment ended urging listeners to beware of new friends who, after hearing about all our customs, reach out to shake with the wrong hand.

Yes, one of my favorite Feynman lectures I was going to comment on, it re-appears in written form in the symmetry chapter in "Six Not-So-Easy Pieces". (Originally from his massive Feynman Lectures on Physics.)

He starts from after you've described the basic exterior human anatomy, which is mostly symmetrical, then he starts with the interior and tells the alien to 'put the heart on the left'. But the alien doesn't understand the direction. So Feynman says:

"Listen, build yourself a magnet, and put the coils in, and put the current on, and then take some cobalt and lower the temperature. Arrange the experiment so the electrons go from the foot to the head, then the direction in which the current goes through the coils is the direction that goes in on what we call the right and comes out on the left."

For anyone who doesn't get the wrong hand joke, the physical reason to watch out is: "matter to the right is symmetrical with antimatter to the left."

The article seems to ask how to define a referential term without using reference (i.e. left/right, up/down, clockwise/anti-clockwise, without reference to a static point). Using the example of radio waves, if I wanted to express a basic kind of reference I would start by using pitch (e.g. low pitches to high).

For direction (left vs right), I would broadcast a "beam", increasing in strength on one side, so hopefully an intelligent enough civilization could measure that from "left" to "right" the beam got stronger, perhaps again using pitch to help guide. The problem then would be conveying whether they should follow the broadcast "left to right" or the received "left to right" (i.e. imagine someone holding up their left hand, do they mean your left hand, as in match them, or your right hand, as in mirror them).

Exactly. How do you teach children left from right? "Left" and "right" are arbitrary names for a position relative to where the heart is. You have to point to it.

It's the same as teaching the difference between "tomorrow" and "yesterday".

There's a huge difference between tomorrow and yesterday! We can define yesterday as the stuff we can remember, and tomorrow as the stuff we can't. (Time asymmetry is huge.) But without common observation (or an appeal to parity violation in the weak force) there is no way to similarly define left and right.

I would use the phenomenon of the "right hand rule" from electrical engineering as the frame of reference. This is a universal chirality inherent in the use of electronics. And if we're communicating with them via radio waves, we can safely assume they're comfortable with the domain.

Of course, that is assuming that they don't exist in some sort of weird bubble of the universe that operates with antimatter instead of regular matter (and is therefore using some mysterious positron-based "electricity"). I suppose if that were the case, our rendezvous would be disastrous anyway, so destruction of the gate would probably be the best possible outcome...

Doesn't that require that you agree on what "North" and "South" mean with regards magnetic fields?

But the direction of a magnetic field is an arbitrary convention. If we used the left hand rule consistently we would make all the same predictions for the forces exerted on particles thanks to two reversals cancelling out.

Now, if the aliens were sending us transmissions through circularly polarized waveforms that would be different, that's a matter of observation rather than communication.

Now, there is a phenomenon where if some particles decay in a magnetic field the products tend to have their products go in different directions depending on the magnetic field. This was a bit of a shock since physicists had assumed left-right symmetry until then. http://en.wikipedia.org/wiki/Asymmetry

Circular polarization is the solution I immediately thought of as well, but I'm actually replying to put up this link: http://en.wikipedia.org/wiki/Circular_polarization It has a nice animation of what it is.

Using some form of symmetry breaking works too but is a much worse solution from an engineering perspective since the circular polarization is so much simpler and more direct. But it would work.

Physics grad student here. Commenter Symmetry is right; there is no inherent chirality in electromagnetism. If we're really not allowing anything that could be construed as a common observation, I think the only thing is to exploit parity violation in the weak force.

http://en.wikipedia.org/wiki/Parity_violation#Parity_violati...

Now, the weak force is pretty weak, so you usually have to do sensitive experiments to isolate it. But it's conceivable that there is macroscopic evidence of parity violation sitting around the cosmos which don't require common observation, e.g. maybe black holes have a slight statistical preference for clockwise vs. counter-clockwise jets. (Ultimately, such evidence would have to be traceable back to the weak force.) I'm not sure.

The right hand rule is simplistic (as the direction is arbitrary); however, using physical laws (assumed to be universal) is the way to, I think. Even if the aliens wouldn't understand our concept of left and right, if they are sufficiently advanced, their physical theories should contain the concept of symmetry (the mathematical concept, not the colloquial one), see this PSE questions and answers: http://physics.stackexchange.com/questions/2690/what-is-the-....

Once that commonality is established we can start to explain to them the everyday concept of symmetry and how we give different names to different directions of symmetry.

If you can make the assumption that alien creatures have a concept of three dimensions (and later in his article he flips the question around and asserts they do [since they sent us 3d blueprints]) then it's a relatively simple task.

The author said you can't draw pictures, use gestures or images to show the aliens, but that doesn't mean you can't have the aliens use their own imagery.

So, to explain left handedness:

  Picture a 3D coordinate system. With X, Y, and Z axis.     
  Vector is represented by the notation of (X, Y, Z).
  Draw a vector (0,0,1). This is the "Forward" vector.
  Draw a vector (0,1,0). This is the "Up" vector. 
  Cross vector (0,0,1) with (0,1,0). The resultant vector (-1,0,0) is the "Left" vector.
  For all points Y, and Z of -X (not including 0) lie to the "Left" of the plane ZY.

We don't need to convey a sense of forward and upwards as to how it relates to the alien beings--only how it relates to the coordinate system.

A simple solution might be to devise a test with non-expensive results for failure.

For example, we could teach them to construct and transmit a jpeg using their words for left and right. If the jpeg comes through flipped, we got it wrong, and switch the words. If it comes through correctly, we got it right.

for that to work you would have to have already communicated that the x-axis component in a 2-dimentional image increases rightwards..

Exactly, that we have sent that instructions correctly is what we are testing.

Then they take a picture of something that we both can see (like a star), and if the image is actually 'mirror flipped' of what they would see, we know the instructions were wrong.

You are testing the instructions, not the picture itself.

they would have to send the image back to us also encoded. if they misinterpret the instructions, why would we notice when they use the same encoding scheme to send us back a picture?

I think one of the constraints is that you can't use illustrations.

How do you explain it without any common experience?

Well, that introduces a further problem - if you have no common experience... how do you communicate with them at all?

Agreed. The setup of this question struck me as a bit of an arbitrary "moving goalposts" problem.

We all live in the same universe with the same physics and have a great deal of common experiences and mathematics with which to potentially have this sort of conversation with them. (Yeah, ye olde "they might be totally incomprehensible" is still there, but in this case we're talking about the flip side... it isn't impossible that we could in fact understand them.) Nevertheless, there are some fundamental symmetries that are so symmetric that we could understand vast swathes of their communication and still not know whether perhaps we inverted their entire communication, lock stock and barrel, because the difference between left and right is actually very, very subtle, subtle nearly to the point of nonexistence. (For a long time we thought they were nonexistent, but we've since found some down at the base of physics.)

The "Contact" model of an enormous transmission that can be progressively decoded can not be ruled out, though we have experimental evidence that it's harder than it seems at first blush. (Still, those experiments tend to focus on having our 'top minds' decode pictures that amount to a few hundred bits; arguably it would actually be easier to decode an entire mathematical codex as we would have a lot more to work with, much like cyphertexts actually get somewhat easier to crack as they get larger.)

But if you have to work verbally only, and can never point to something to say "this is -foo-", how do you communicate? It doesn't really matter that we live in the same universe - how the hell do we say "Hey, you know DNA?" when we can't even make an arbitrary point. The article is saying that we can't communicate things about constellations or other simple-yet-arbitrary points, but that we can happily communicate about things we can't even sense ourselves (who knows about the aliens senses?). Sure, we can verbally define what a Volt is, but the words we use to make that definition require common experience at some point to make sense.

Remember that the rosetta stone was so useful because it provided a reference point to help decode a previously incomprehensible language. In order to communicate with someone, you must have a common experience somewhere.

We don't have to work verbally only. As I said, the "Contact" scenario is perfectly plausible and you can send diagrams just fine. Also recall as I said we're not talking worst-case scenarios where the intelligence is utterly incomprehensible, which frankly I'm pretty down on anyhow (I don't think "utterly incomprehensible" and "able to survive in our universe" work together, personally), we're talking about some reasonable alien that we actually can communicate with. And the idea that they might not have a concept of diagrams isn't the point, the point is that they might today.

The whole "But they might be incomprehensible and we might have zero common reference frames" is not really applicable here, just a fashionable knee-jerk reaction to "the alien question". As a possible outcome, sure, as the only outcome, no way.

I'm working from the original article's demands, which deny diagrams or being able to point at something:

And imagine, moreover, that you had to do so in a purely verbal manner, that is, without drawing pictures or pointing at things or otherwise making gestures.

With diagrams or pointing, showing what left and right mean becomes trivial.

On the knee-jerk reaction thing, it's more pointing out that it's a matter of moving the goalposts as mentioned below. It's making an arbitrary line of what can be communicated

I agree with you that the incomprehensible alien form is pointless, but as soon as we have a common frame of reference, we can drill down to defining right and left. All you need is four points: Point A is 'up', Point B is 'down', put your viewing position so that Point C is between you and the line AB. With A being 'up', Point D is on the left side of the line AB. Whether you use stars, a mountainside, a tree, galaxies, or jellyfish, that's all you need - but you still need a common point to refer to.

I think a better way of phrasing the problem would be: You have a communications conduit to a parallel universe and we only have the ability to speak through it. The alien understands us but has no prior concept of right and left. We can't point or refer to bodies in our universe as they can't see them, but apart from that, all physical rules are the same and they have the same level of science knowledge as us. How do we tell them right from left in this instance? We can get the concept across with left- and right-handed molecules (though DNA may be out as they may not have it), but how to indicate which is left and right in verbiage only, I'm not sure.

Phrased this way, you don't have to do silly logical twists to have the alien living in our universe yet still somehow preventing them from seeing the same things we do.

Interesting thought experiment. I see many overlap with existing questions from philosophy (of meaning and language), and I think at its core this question is a philosophical one, not about physics.

  The aliens’ language does include words for "left" and 
  "right" and for "left-handed screw" and "right-handed 
  screw". But in all our communications with them, we were 
  never able to figure out which was which. We need them to 
  explain to us which of their words corresponds to our 
  word "left," and which to our word "right." To do so, 
  they will need to appeal to some common point of 
  reference or phenomenon.

Eerily follows the Twin Earth Thought Experiment and its conclusion:

  Yet, at least according to Putnam, when Oscar says water,
  the term refers to H2O, whereas when Twin Oscar says 
  'water' it refers to XYZ. The result of this is that the 
  contents of a person's brain are not sufficient to 
  determine the reference of terms they use, as one must 
  also examine the causal history that led to this 
  individual acquiring the term. (Oscar, for instance,
  learned the word 'water' in a world filled with H2O, 
  whereas Twin Oscar learned 'water' in a world filled with 
  XYZ.)
  ...
  Meanings' just ain't in the head.

This is at the core of semantic externalism. Relating Putnam's view to the OP question:

What if I don't know the difference between left or right? Maybe a brain lesion caused me to skew the concept so that everything would be "left" to me. When I say "move left to avoid hitting a wall" out of this ignorance, this statement can be true or false. If it is true or false, doesn't depend on my flawed concept of "left" or "right", but on those who hear my statement, and correctly know the difference between "left" and "right" and notice the wall on the left side. The true meaning of "Left" is filled in by the language community.

- This could also mean that our community concept of "Left" is objectively false or obsolete. We deem it to be true and meaningful, the aliens don't.

- Or that "Turn Left" could mean "Turn Right" when some time has passed (a dynamic rigid designator?)

- Or that the researchers that communicate with the aliens have a different concept of "Left" than the language community majority.

- Or that their concept of "Left" is simply incommensurable with our concept of "Left". If here on earth scientists "think differently, speak a different language, live in a different world.", imagine how badly alien thoughts, language and experience would translate, if at all.

- If it is true that the structure of language affects the way speakers conceptualize the world, then that would mean that to learn "Alien Left", one would need to learn (some say experience) the entire alien language.

All these things an alien should take into account when entering our language field.

  So they begin to beam information to us in the form of a 
  3-D technical drawing, encoded as a set of 3-D 
  coordinates in space.

A (probably too) simple solution would be for the aliens to send us a 3-D model along with time data. Observing the resulting simulation already implies a perspective and we could reference the first state of the model.

You don't. They will already know left from right. Right from wrong.

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