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Galactic Challenge, Part II: The Richard Feynman Files

The views expressed are those of the author and are not necessarily those of Scientific American.

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Richard Feynman

In a recent post, I proposed a riddle on handedness and how one could communicate one’s notions of left and right to faraway aliens. It should perhaps surprise no one that the way I formulated the riddle was just a more cumbersome and less elegant version of one that Richard Feynman presented to Cornell students in 1964, as I found out thanks to our Blog Network Czar, Bora Zivcovic.

“Suppose that we were in a telephone conversation with a Martian, or an Arcturian or something,” Feynman said in his lecture. “We don’t know where he is and we would like to describe things to him.” One way to establish a communication, Feynman points out, is to start from the basics, and there’s nothng more basic than integer numbers (the same idea that Carl Sagan later exploited in Contact).

At some point, though, we presumably have learned how to communicate, and the Martian is curious to learn about us. “Suppose that he says, ‘You fellas’–after we get familiar with him–’You’re very nice; now I’d like to know what you look like.’”

Describing features such as body size would be easy, Feynman points out, because we could appeal to facts about the world that are the same everywhere–for example the size of a hydrogen atom.

But the Martian wants to know more. “And he says, ‘That’s very interesting; what do you look on the inside?’ So we describe the heart and so on, and we say, ‘Now, put the heart on the left side.’ Now the question is, how can we tell him which side is the left side?”

One point of reference we might be tempted to use is that of biochemistry. “‘Aw, you take beet sugar, see, and you put it in water, and it turns.’ Only trouble is, he has no beets up there.” Here, Feynman was referring to the fact that when polarized light goes through a solution of water and sucrose its polarization twists.

That effect is due to the fact that sucrose comes in two varieties whose molecular structures are mirror images of each other, and which have opposite effects on the polarization of light. (An even mix of the two has no effect on light.) All sucrose of biological origin is of the same variety, called right-handed, but we have no way of knowing if the aliens’ sugars–assuming they have any–have the same handedness as ours do.

The same is true of proteins and DNA. “We have no way of knowing … whether the accidents of evolution would have started with maybe the wrong-headed threads: there’s no way to tell.” (Incidentally, that is one reason why it would be a bad idea to eat alien pizza before doing some chemical analysis.)

Feynman’s lecture, entitled “Symmetry in Physical Law,” was part of a cycle of lectures he gave at Cornell in 1964 called “The Character of Physical Law,” which can be watched in full on a Microsoft educational web site. You can jump to section 11 of the lecture to see the part about handedness. But I recommend watching the whole thing. The presence and wits and charisma of the man were just extraordinary.

Spoiler alert: after talking about sugar Feynman proceeds to give away the solution to the riddle, which was based on physics that at the time was very new, having been discovered in 1957. (More details on that in a follow-up post.) Had he given the same lecture ten years before, one can only wondered what he would have said–perhaps, simply that there was yet no known way of telling left from right using the laws of physics.

To be continued!


This post is part of a series on handedness. Here are the all the posts in the series:

A Galactic Challenge: How Would You Teach Left from Right to an Alien Civilization?

Galactic Challenge, Part II: The Richard Feynman Files

Galactic Challenge Part III: The “Easy” Solutions

Why There’s No Such Thing as North and South

Suggested reading:
The New Ambidextrous Universe: Symmetry and Asymmetry from Mirror Reflections to Superstrings: Third Revised Edition. By Martin Gardner​. 2005.
The Handedness of the Universe. Roger A. Hegstrom and Dilip K. Kondepudi in Scientific American, Vol. 262, pages 108-115; January 1990.
Alien Pizza, Anyone? Davide Castelvecchi in Science News, Vol. 172, No. 7, pages 107-; August 18, 2007

About the Author: Davide Castelvecchi is a freelance science writer based in Rome and a contributing editor for Scientific American magazine. Follow on Twitter @dcastelvecchi.

The views expressed are those of the author and are not necessarily those of Scientific American.

Comments 14 Comments

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  1. 1. infomebaby 2:15 pm 09/4/2011

    so you guys (math astro techies) haven’t figured out the equation for gravity, which would be needed to use as a reference point for explaining left and right, even though we understand the principles associated with it…

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  2. 2. jtdwyer 6:33 pm 09/4/2011

    infomebaby – So you’re far too clever to explain how up & down can be used to define left & right? You just leave us spinning in place! Why don’t you just look into a mirror and explain it to yourself…

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  3. 3. infomebaby 8:29 pm 09/4/2011

    @jtdwyer : nice one…however that comment came from actually watching the video posted, by Microsoft from the Richard Feynman video from the law of gravitation article posted…not my words. I’m actually here to try and learn. My apologies…if you want to laugh at my gamma ray happy face diagram posted in the previous part go ahead but no need to post abusive comments calling me narcissistic…I’ll take that as a compliment from your highly evolved argument.

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  4. 4. jtdwyer 9:00 pm 09/4/2011

    infomebaby – No, it’s for me to apologize again, although your reference was thinly veiled for us uninitiated. Apparently it was Feynman’s clever attitude I was snippily reacting to, not yours – sorry!

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  5. 5. infomebaby 9:48 pm 09/4/2011

    Yes, sorry if I seemed smart there for a second. I thought you guys would know I was talking about someone else…regarding that mix up:

    Quantum theory is not quite right yet (Einstein had to modify it) for gravity. In part II of Richard Feynman’s video series, “Law of Gravitation – An Example of Physical Law”, he talked about how relating planets to each other and the fact all the planets go around in ellipses, equal areas, etc. and taking into account the time it takes light to get to us and the description of the planets around the sun and how symmetry repeats the same patterns throughout the universe. So if we use a main celestial body which has the other planets in a solar system orbiting around it) like the sun, as a reference point, with the earth (planets) going around it, if I heard right and taking inertia into account and constant speeds and keeping in mind “inertia has no known origin but the source of the force is towards the sun […] so all changes are directed towards the sun” but take the “pull on objects as a phenomenon of gravitation” so you could figure out ‘downward’ is the direction of the “pull of gravity” and ‘upward’ would be against the direction of gravity. You would need to have the theory and the formula of gravity right to reference something like ‘Counter-Clockwise’ (the direction the planets spin) and then try figuring left and right…well if it was that easy they would have figured it out by now and not need this article feedback.

    For myself, as a dyslexic human I managed still get enrolled into math expansion classes and all my AP courses and I graduated at 16, but that was ages ago…I can’t figure left to right direction IN earth much less explain it…I have to use visible cues so this article is quite interesting. But you’re right, I’m narcissistic and should be out partying and showing myself off instead of spending my birthday trying to figure out with you, a very helpful, much more fun and sarcastic than my usual peeps, rather than attempt to understand basic concepts of the universe so we can entertain the thought of communicating it with others.

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  6. 6. Dr. Strangelove 11:26 pm 09/4/2011

    Dr. Castelvecchi,

    It’s really very simple. Tell the aliens to observe the beta decay of cobalt-60 and designate the direction where there is more electrons as either left or right.

    Both aliens and earthlings will agree on what is left and right because beta decay of cobalt-60 violates the conservation of parity.

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  7. 7. @dcastelvecchi 5:08 am 09/5/2011

    Dr. Strangelove: Yes, beta decay is the experiment Feynman was talking about. I will talk about that in a follow-up post. I am not sure that the particulars of the experiment are quite as simple as you’re describing. What we are looking for here is not just left and right but an orientation of 3D space.

    infomebaby: Yes, you can use a large body as a point of reference to define up and down. But it would be more helpful to have a way to divide space into two halves, and have one labeled as “up” and the other labeled as “down”. In any case, you can’t really convey your concept of left-handed and right-handed that way to aliens who can’t observe the same objects you are observing. See the discussion on the North Star in Part I of this series:

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  8. 8. infomebaby 11:26 am 09/5/2011

    Okay, so scrap the cobalt 60, not interested in that energy. You did state “In geometry there is no a priori notion of left and right the way that there is an a priori notion of positive and negative numbers.” And the original challenge was to explain the concept of left and right to alien civilization. Your north star Polaris is in the same timeline – 100,000,000,000 AD – when The Virgo Supercluster is converging into a single galaxy. So you’re saying to us everything ‘up’ from the north star would serve as an equator, where ‘downward’ or ‘south’ would be anything under it. In the Richard Feynman video series he had talked about how to know whether the slides had been inverted and noticing the sequence of the rotation and taking symmetry into account he knew if the other slide was flipped from the counterclockwise movement around the planet. Wouldn’t all you really need to know is north, south and counterclockwise? And are we trying to get the aliens here or us out there to ‘save the race’? Would we need to explain to them left and right, or we would just need to know if we’re looking at their map right? You must be laughing but getting no real inspiration, just throw us clue if we’re near the right track…

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  9. 9. @dcastelvecchi 2:33 pm 09/5/2011

    infomebaby: yes, an up and a down plus a notion of clockwise is all you need.

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  10. 10. Dr. Strangelove 9:22 pm 09/5/2011


    Since the aliens were smart enough to build a wormhole traveling machine, I thought they would figure out the 3D orientation with my cryptic message. Here is a more detailed instruction.

    Since we are communicating via radio signals, these electromagnetic waves travel at the speed of light with a fixed direction. Velocity is a vector with both magnitude (speed) and direction (orientation in 3 dimensional space). The aliens can detect the direction of our radio signals.

    The path of the radio waves is a geodesic between two points: earth and their planet. Designate that direction as the y-axis. Designate the direction of the earth in the y-axis as “up” and the opposite direction as “down.”

    Perform the cobalt-60 experiment aligning the direction with excess electrons perpendicular to the y-axis. Designate the direction with excess electrons as “left” and the opposite direction as “right.” The electron’s velocity is also a vector with a direction. Designate that direction as x-axis, which is perpendicular to the y-axis. Designate a z-axis that is perpendicular to both x and y axes.

    Now you have a 3D coordinates. Now you can define a corkscrew motion as a rotation along the z-axis in the “left” direction. Of course if you want a different set of coordinates, you can transform this 3D coordinates to your desired set.

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  11. 11. infomebaby 11:29 am 09/6/2011

    That kinda sorta makes sense Dr. Strangelove, so if we used the VLA (in New Mexico) as the “Y” axis and the VLBA station (on Mauna Kea, Hawaii) is the “X” axis and the North Star as the “Z” reference point should you or “we” or whoever, with your excess electrons would be able to figure out which way was the right and left and counterclockwise?

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  12. 12. Dr. Strangelove 10:28 pm 09/6/2011

    infobaby, yes, “left” and “right” are merely human conventions. They do not have universal meaning. The violation of parity conservation is a universal principle that can be used to designate a “universal” left and right. You only need 3 points in space to designate a 3D coordinates.

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  13. 13. @dcastelvecchi 8:56 am 09/11/2011

    Actually, make that four non-coplanar points plus a fixed ordering of them. An ordered set of 3 points only defines a plane and an orientation of that plane. Orienting a plane is not sufficient to orient 3-D space.

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  14. 14. Dr. Strangelove 12:02 am 09/12/2011

    I beg disagree. If you can define the orientation of a plane, you can also define the orientation of another plane that is perpendicular to it. Just rotate the original plane along its axis until it hits a 90 degree angle. You get two perpendicular planes. That’s a 3-D cartesian plane. You can define the 3-D coordinates of any point in space with respect to these two perpendicular planes.

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