Good question as always. There are a couple of comments above that I like although I don't think that we need to go to the trouble of utilising neutrinos!

The parity breaking that is touched on above suggests that there is something fundamental about 'left' and 'right', although of course not in the conventional sense. I would hazard that as humans we intrinsically separate space into left and right due to our bilateral symmetry, and would guess that any sufficiently evolved bilaterally symmetric organism would do the same. Naturally, that doesn't help us if our alien friend is something descended from a creature such as a sea star or anenome, or evolved in zero gravity.

So what is almost certainly necessary is for you to be able to define a reference frame for the alien. They have a physics lab so it is probably fair to assume that they have already discovered spherical coordinates (especially the zero gravity alien!). And presumably, as we understand the left and right nature of the levers, we have access to some kind of camera? (If we don't have access to this, we will have difficulty aligning frames of reference if we do not know which way the cockpit is facting).

Anyway, as discussed above, we first need to identify a universal vector system, for example, pointing towards the Earth (as suggested by @Hikmet) and perpendicular to the plane of orbit. Now to define a local frame, we need to define left or right, one experiment that could be performed would be a Hall experiment in a material of known conductivity (sign of dominant charge carrier). Then the deflection of the current with respect to the magnetic field and the two-dimensional conductor could be used to define 'left' and 'right'. For example, using an n-type semiconductor (and here we would have to specify exactly the composition of the semiconductor, but I think that the concepts of n-type and p-type could be easily explained from other physical principles), you could define the current to be in the direction of the Earth, the magnetic field aligned perpendicular to the to the orbit of the Earth, and also perpendicular to the two-dimensional electron gas. Then the deflection can be used to calibrate left and right.

Note that there are several features here, and I suppose that these will be generic to any such solution, namely:

Agreement on some reference frame

Setting up some experiment based on both known elementary particles and that shared reference frame

Results that show a clear chirality.

Of course, another solution (as mentioned above) is communication, although it doesn't have to be as obvious as that of @Murod, which might not actually work in the case that we don't know which way the cabin is pointing! But one way to do it would be to follow the kinds of protocols for aligning frames of reference that have been developed in quantum information processing. Once frames are aligned, then one could send a whole set of photons or orbital angular momentum states to define chirality, and from there, define left and right with respect to the phase of the chiral signal, as implied by @Murod. If would also be possible to use an EPR type experiment and then inform as to which are the appropriate photons to define left/right and up/down, although that seems like overkill to me! And anyway still accords with the above three principles.

More interesting to me is whether it is possible to invoke symmetry breaking to reduce the set of required features I have listed above, and presumably the place to look for such an effect is in parity breaking. But it is not so obvious to me at the moment how to easily do this with either the 60Co or Kaon type approaches - perhaps we need a particle physicist!

The parity is violated by neutrino that has left helicity. This solves your problem.

@Murrod: Thanks You´ve been faster than I was.

Good answer!

Can you show the steps of how to go from this experiment to then telling the alien which button to press? Your answer has to somehow be robust to the alien's orientation to the neutrino experiment. In other words, the set of instructions about the neutrino experiment cannot contain "left" or "right" itself, or that would be cheating.

@Hanno: thanks! but the good question is: Why parity is violated?

Your question is not actually well defined. When you call buttons "left" and "right", what exactly do you mean by that? Left and Right can ONLY be identified w.r.t. Up and Down. That means that at least you shoud agree with the allien what are up and down. Once you have done it, you can explain the allien that Left can be obtained from Up by rotating it counter-clockwise by 90 degrees. And you can use neutrino to demonstrate what is "counter-clockwise", which is the direction of it's angular momentum w.r.t. it's direction of motion.

Dear Derek Abbtt what I understand is that you are asking for some universally "acceptable" Principle/Standard for indication of directions. Is it right? If so then its needed to communicate in language of Nature as you are saying for performing experiments. It’s a good question which also arises the need to present the meanings/thoughts with help of symbols & if symbols are based on everyday facts then it’s easier to convey the correct messages at suitable time. Can you kindly tell something more about the Level of “Understanding” of that only alien left? because all dont depend on our understanding.

And the best answer is: send a laser beam that will point on the right button :)

Good question as always. There are a couple of comments above that I like although I don't think that we need to go to the trouble of utilising neutrinos!

The parity breaking that is touched on above suggests that there is something fundamental about 'left' and 'right', although of course not in the conventional sense. I would hazard that as humans we intrinsically separate space into left and right due to our bilateral symmetry, and would guess that any sufficiently evolved bilaterally symmetric organism would do the same. Naturally, that doesn't help us if our alien friend is something descended from a creature such as a sea star or anenome, or evolved in zero gravity.

So what is almost certainly necessary is for you to be able to define a reference frame for the alien. They have a physics lab so it is probably fair to assume that they have already discovered spherical coordinates (especially the zero gravity alien!). And presumably, as we understand the left and right nature of the levers, we have access to some kind of camera? (If we don't have access to this, we will have difficulty aligning frames of reference if we do not know which way the cockpit is facting).

Anyway, as discussed above, we first need to identify a universal vector system, for example, pointing towards the Earth (as suggested by @Hikmet) and perpendicular to the plane of orbit. Now to define a local frame, we need to define left or right, one experiment that could be performed would be a Hall experiment in a material of known conductivity (sign of dominant charge carrier). Then the deflection of the current with respect to the magnetic field and the two-dimensional conductor could be used to define 'left' and 'right'. For example, using an n-type semiconductor (and here we would have to specify exactly the composition of the semiconductor, but I think that the concepts of n-type and p-type could be easily explained from other physical principles), you could define the current to be in the direction of the Earth, the magnetic field aligned perpendicular to the to the orbit of the Earth, and also perpendicular to the two-dimensional electron gas. Then the deflection can be used to calibrate left and right.

Note that there are several features here, and I suppose that these will be generic to any such solution, namely:

Agreement on some reference frame

Setting up some experiment based on both known elementary particles and that shared reference frame

Results that show a clear chirality.

Of course, another solution (as mentioned above) is communication, although it doesn't have to be as obvious as that of @Murod, which might not actually work in the case that we don't know which way the cabin is pointing! But one way to do it would be to follow the kinds of protocols for aligning frames of reference that have been developed in quantum information processing. Once frames are aligned, then one could send a whole set of photons or orbital angular momentum states to define chirality, and from there, define left and right with respect to the phase of the chiral signal, as implied by @Murod. If would also be possible to use an EPR type experiment and then inform as to which are the appropriate photons to define left/right and up/down, although that seems like overkill to me! And anyway still accords with the above three principles.

More interesting to me is whether it is possible to invoke symmetry breaking to reduce the set of required features I have listed above, and presumably the place to look for such an effect is in parity breaking. But it is not so obvious to me at the moment how to easily do this with either the 60Co or Kaon type approaches - perhaps we need a particle physicist!

Alternatively, left and right can be explained using current positions of moon, sun and earth

This is an interesting question and I’ve enjoyed reading the contributions everyone has made. I’d like to offer a few additional thoughts. It seems that there are several different issues here that need to be separated.

1. “Up” and “down”

As several of us have said, defining right and left depends on being able to distinguish between up and down. For the sake of our discussion, I’ll assume that up and down can be distinguished, for example by detecting the direction of the Earth’s gravity if the alien is close enough to Earth. Or perhaps the spacecraft’s room with the buttons has a clearly accepted floor and ceiling.

2. Direct communication

This is my favorite method for saving Earth! :)

I’d suggest that instead of telling the alien to do an experiment to distinguish right and left, the best procedure is to tell the alien to build an apparatus to attach to the wall that can (1) receive our messages and (2) push either the right or left button at our command when it receives our message. Since we’re assuming we know the difference between “up” and “down,” we can instruct the alien to attach the apparatus to the wall in the correct orientation with the “bottom” of the apparatus facing “down.” Then we send a signal from Earth to the apparatus to push the correct button. This way we never have to teach the alien the difference between right and left. If we want to push the correct button, there’s nothing like doing it ourselves! :)

3. Cross product.

If we still wish to teach the alien to learn to distinguish “right” from “left,” it seems that the best way is through the cross product of two vectors with physical directions. One of the simplest is to use the Coriolis effect, maybe by having the alien set up a rotating table and moving a mass radially in and out. Using the Coriolis force, we can define the direction of the axis of rotation of the rotating table and teach the “right hand rule” (or, if we prefer, the “left hand rule”). Alternately, we might use the cross product in the Lorentz force with a beam of electrons from a hot cathode and a magnetic field to teach the “right hand rule” convention. Or perhaps use the Hall effect as Andrew suggested

4. Cultural conventions

However, even if we do manage to teach the alien the difference between “right” and “left,” what we are transmitting is our cultural convention. Being able to communicate our cultural convention between “right” and “left” might be nice. And it might save Earth.  However, our cultural convention has ultimately little to do with whether left or right handedness is a fundamental property of nature, which is the idea that underlies Derek’s question.

5. Fundamental property of nature?

If we separate out the issue transmitting cultural convention from the question, then the question is about parity and the question of whether a right handed or left handed coordinate system makes a fundamental difference in nature. If we reframe the question in this way, we have quite a bit of information about the question of parity. Parity matters in the realm of weak interactions. (We should also make the qualification that the jury is still out about dark matter and dark energy and parity.) For the other interactions that govern much of the macroscopic world we live in, the right or left handedness of the coordinate system doesn’t matter. This fact again underscores that we are teaching a cultural convention and not a law of nature when we use the cross product as an example to teach the right or left hand rules.

Quick summary:

If we want to save Earth, probably the most foolproof way is to have the alien construct an apparatus so that we and not the alien can push the correct button. 

If we do manage to teach “right” and “left” to the alien, we are teaching cultural convention and not a fundamental property of nature.

On the basic question of whether right or left handedness is a fundamental property of nature: It does make a difference at the level of weak interactions with particles where parity makes a difference, but not for the rest of our “everyday” world where parity is conserved.

Anyway for what it’s worth, these are just some thoughts on an interesting topic.

An excellent answer posted by @Jack_Semura reminded me an essay entitled "Angels on a Pin" by Alexander Calandra published in 1959 in the journal Pride of the American College Public Relations Association.

« Some time ago I received a call from a colleague who asked if I would be the referee on the grading of an examination question. He was about to give a student a zero for his answer to a physics question, while the student claimed he should receive a perfect score and would if the system were not set up against the student: The instructor and the student agreed to submit this to an impartial arbiter, and I was selected.

I went to my colleague's office and read the examination question: "Show how it is possible to determine the height of a tall building with the aid of a barometer."

The student had answered: "Take a barometer to the top of the building, attach a long rope to it, lower the barometer to the street and then bring it up, measuring the length of the rope. The length of the rope is the height of the building."

I pointed out that the student really had a strong case for full credit since he had answered the question completely and correctly. On the other hand, if full credit was given, it could well contribute to a high grade for the student in his physics course. A high grade is supposed to certify competence in physics, but the answer did not confirm this. I suggested that the student have another try at answering the question. I was not surprised that my colleague agreed, but I was surprised that the student did.

I gave the student six minutes to answer the question with the warning that the answer should show some knowledge of physics. At the end of five minutes, he had not written anything. I asked if he wished to give up, but he said no. He had many answers to this problem; he was just thinking of the best one. I excused myself for interrupting him and asked him to please go on. In the next minute he dashed off his answer which read:

"Take the barometer to the top of the building and lean over the edge of the roof. Drop that barometer, timing its fall with a stopwatch. Then using the (well known) formula calculate the height of the building.

At this point I asked my colleague if he would give up. He conceded, and I gave the student almost full credit.

In leaving my colleague's office, I recalled that the student had said he had many other answers to the problem, so I asked him what they were. "Oh yes," said the student. "There are a great many ways of getting the height of a tall building with a barometer. For example, you could take the barometer out on a sunny day and measure the height of the barometer and the length of its shadow, and the length of the shadow of the building and by the use of a simple proportion, determine the height of the building."

"Fine," I asked. "And the others?"

"Yes," said the student. "There is a very basic measurement method that you will like. In this method you take the barometer and begin to walk up the stairs. As you climb the stairs, you mark off the length of the barometer along the wall. You then count the number of marks, and this will give you the height of the building in barometer units. A very direct method."

"Of course, if you want a more sophisticated method, you can tie the barometer to the end of a string, swing it as a pendulum, and determine the value of 'g' at the street level and at the top of the building. From the difference of the two values of 'g' the height of the building can be calculated."

Finally, he concluded, there are many other ways of solving the problem. "Probably the best," he said, "is to take the barometer to the basement and knock on the superintendent's door. When the superintendent answers, you speak to him as follows: "Mr. Superintendent, here I have a fine barometer. If you tell me the height of this building, I will give you this barometer."

At this point I asked the student if he really did know the conventional answer to this question. He admitted that he did, said that he was fed up with high school and college instructors trying to teach him how to think, using the "scientific method," and to explore the deep inner logic of the subject in a pedantic way, as is often done in the new mathematics, rather than teaching him the structure of the subject. With this in mind, he decided to revive scholasticism as an academic lark to challenge the Sputnik-panicked classrooms of America. »

The Hall effect is not the correct idea, since the alien may be taught about magnetic field as a vector opposite to ours. The same goes to the sign of charge carriers.

I would rather think about observing molecules making living organisms on Earth. They are all right-handed, I'm told.

Dear Marek,

I had thought about your objection, and thought I had written it in my solution above - unfortunately my answers tend to get too rambling anyway, but in fact, one can solve the problem rigorously.

Firstly, you do not define the semiconductor in terms such as n-type or p-type, as you are certainly correct that these terms are arbitrary conventions. Instead you specify a type of semiconductor including its composition (whilst taking care to ensure that it is the type of doping, but not the exact doping that is required). You then specify the orientation of the magnetic field with respect to the Zeeman energy associated with the spin of an elementary particle, for example an electron. In this way you can specify aligned parallel or anti-parallel. This gives you the direction of the field that you can specify for the Hall effect.

You will note, of course, that this dovetails with @Jack's solution, and is really getting to the point of specifying up and down. Of course the language is going to get cumbersome, but we have a good universal translator!

Whilst the chirality of molecules is an interesting idea, I'm concerned that this won't work. Firstly, there is no guarantee that similar preference for right or left handed molecules exist in the evolutionary history of the alien, but more importantly, as I understand, whilst most biological molecules that can exist as two enantiomers are typically found in only one of the states (due to enzymatic chemical production), the labels themselves are not so meaningful and uniquely specifying 'left' or 'right' with respect to a given molecule would still require frame alignment.

Nevertheless, you could certainly use a chemical approach to specify the test, and probably the easiest based on the spirit of what you have proposed based on polarisation rotation type experiments.

I'll add another comment below to avoid it turning into another long rant ;).

So I've been thinking further about this problem, and whilst this is a slight digression I hope that it is an interesting one.

Derek originally posed this as if the universal translator (UT) just failed in the specification of left and right. I suppose I was thinking of it in my initial post, but @Jack is clearly articulating the concept that the reason why these terms are not in the UT is because the alien has absolutely no concept of left and right.

As I specified, this is not at all unlikely, IMO, given different assumptions about the evolution and biology of the organism. However, certain concepts must be universal, based on the fact that these space-faring aliens have full physics labs. Physical processes that show helical evolution, for example circularly polarised light or orbital angular momentum states (I suppose that's another way, you could send the plans for a hologram and a diagram for the deflection), mind you, having done that the actual performing of any experiment is unnecessary, the specification of the problem would allow any sufficiently intelligent alien to determine the outcome of the experiment, and hence to divine our intention.

So I think that the more fundamental question here is not whether it is possible to generate a solution: I think it is relatively easy although I'd still like to know if there's a simpler way than the three criteria I specified. What's more to the point is whether it is likely that a non-bilaterally symmetric creature would inherently or 'naturally' know the difference between right and left, or whether such symmetries would be something that they could mathematically calculate, but not naturally look for. My guess to the answer is that non-bilateral creatures would not usually think in such terms, and would look more readily for other symmetries that were important to them. Unfortunately, it might be a while before we can test the idea, and I'm not sure how we could, especially as the non-bilateral creatures on the Earth are probably not up to solving maze type puzzles.

Any thoughts?

Murod,

Thank you for your comments and for the highly amusing story!

"Handedness" is seen in weak intereactions at a fundamental

level involving "elementary particles" causing beta decay.

I am referring to Madam Wu's experiment,

http://en.wikipedia.org/wiki/Wu_experiment

In this experiment it was shown that the theory formed by

Eugine Wigner in 1927, that parity is conserved at a fundamental

level is not entirely true. Though strong interactions

in nuclear domain, as well as electromagnetic interactions

conserve parity, Weak interactions violate them.

But how would you use it to instruct the alien?

Not sure if anybody has mentioned Chen and Yang but they won the Nobel Prize in physics in 1957 for their work on parity violation. Some arrogant physicists said that the experiments showed that nature "misbehaved" - what experiments showed was that nature did not do what physicists predicted. As a side note, Richard Feynman lost a bet worth about $450 in today's currency.