
How Would You Teach Left from Right to an Alien Civilization? - ColinWright
http://blogs.scientificamerican.com/degrees-of-freedom/2011/08/28/handedness-galactic-challenge/
======
Triumvark
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.

~~~
Jach
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."

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nopassrecover
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).

~~~
crististm
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".

~~~
jessriedel
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.

------
ryandvm
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...

~~~
Symmetry
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>

~~~
jerf
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.

------
giberson
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.

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ohyes
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.

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

~~~
ohyes
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.

~~~
exit
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?

------
vacri
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?

~~~
jerf
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.)

~~~
vacri
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.

~~~
jerf
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.

~~~
vacri
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.

------
blauwbilgorgel
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.

------
r0sebush
You don't. They will already know left from right. Right from wrong.

