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On the ontology of handedness
This page is a brief introduction to some basic questions on handedness. It was originally written on December 2nd, 2003, and modified on August 12th, 2009.
Handedness and philosophy
Handedness is a philosophical issue. It is a question about the difference between 'left' and 'right'. How to define those two?
It may seem impossible to define 'left' and 'right' without reference to any particular asymmetric object such as one's body or the Earth. Of course, it is possibly just tell the difference by giving particular examples. But that is not a definition.
There are chiral concepts such as 'clockwise' and 'north'. Nevertheless, to grasp them one has to first understand the difference between 'right' and 'left'. Hence they provide no help in our problem of definition.
Kant and Wittgenstein
There are at least two well-known philosophers who have taken part in the debate on handedness: Immanuel Kant and (1724-1804) and Ludwig Wittgenstein (1889-1951).
Kant asked one to take a look at one's hands. When looking one's right hand in a mirror one sees a left hand. And yet even though your hand is identical with its mirror image you cannot replace one with another. You cannot put right hand glove to your left hand (see Kant's Prolegomena §13).
Take a look at the image on the left. It is a two-dimensional illustration of two hands mirrored by a line. Line is one-dimensional object. Analogically, three-dimensional hands can be mirrored by a two-dimensional plane (such as a mirror on the wall).
Now, if you print this page on a paper you are able to cut either one of the hands out and move it on the other one by turning it around in three-dimensional space.
Ludwig Wittgenstein's answer to Kant is exactly that. He wrote: 'A right-hand glove could be put on the left hand, if it could be turned round in four-dimensional space' (Tractatus 6.36111).
What is needed is just an extra dimension. But is that a real solution? Doesn't it seem that Wittgenstein just moves the problem to another dimension? For four-dimensional objects one needs a five-dimensional space, for five-dimensional ones a six-dimensional space, and so on, ad infinitum.
Solution?
Nevertheless, there is a way to define 'right' and 'left' without any reference to other chiral concepts nor to particular asymmetric objects. The method was revealed by physicist Chien-Shiung Wu in 1958. Just follow the following:
- Cool the atoms of cobalt-60 to near absolute zero.
- Line up their nuclear axes with a powerful magnetic field.
- Count the numbers of electrons flung out by the two ends of the axes.
- The end that flings out the most electrons is the end that we call 'south'.
- It is now possible to label the ends of the magnetic axis of the field used for lining up the nuclei.
- This in turn can be used for labeling the ends of a magnetic needle.
- Put such a needle above a wire in which the current moves away from you.
- The north pole of this needle will point in the direction we call 'left'.
What Wu did was that she demonstrated asymmetry in a physical phenomenon. Prior the her experiments, Wolfgang Pauli, a famous physicist, was sure that she would fail. He said: 'I do not believe that the Lord is a weak left-hander, and I am ready to bet a very high sum that the experiments will give symmetric results.'
I don't know how much Pauli lost. However, if we believe him, even God is a left-hander!
However, is sounds so right-handed to think that left-handedness somehow is more asymmetrical than its right-sided counterpart.
Or maybe not...
Physicists may now have peace in their mind: they succeeded in explaining handedness. Still it is probably better to teach the difference between left and right to a child, for instance, by telling which hand is which one (although kids might find cooling of cobalt-60 atoms thrilling, too).
Nevertheless, in our everyday world handedness has little to do with electrons flinging out of magnetic axes.
On the left, there are two photos of Hernesaarenkatu street in Helsinki, Finland (my home street). One is correct while the other is a mirrored. Can you tell which one is which?
Actually, it is not difficult. Although the image is too small to read the licence plate you might know that driving in Finland is on the right. As most cars consequently use right side of the street for parking one can safely assume that the image on the right is the correct one.
However, if it was a forest photograph, for instance, it would have been much more difficult – or even impossible – to conclude which one is correct. Cultural elements of the world that make us to recognize the difference of right and left. Hence, whatever physicists might say, question of 'left' and 'right' remains a cultural and not a natural phenomenon to us.
References
Gardner, Martin (1991). The Ozma problem and the fall of parity. In James Van Cleve & Robert E. Frederick (eds). The philosophy of right and left. Incongruent counterparts and the nature of space, pp. 75-95. Kluwer, Dordrecht.
Kant, Immanuel. Prolegomena : eli, Johdatus mihin tahansa metafysiikkaan, joka vastaisuudessa voi käydä tieteestä. 254 p. Gaudeamus, Helsinki.
Van Cleve, James (1991). Introduction to the arguments of 1770 and 1783. In James Van Cleve & Robert E. Frederick (eds). The philosophy of right and left. Incongruent counterparts and the nature of space, ss. 15-26. Kluwer, Dordrecht.
Wittgenstein, Ludwig (1933/1996). Tractatus logico-philosophicus. 88 p. WSOY, Juva.
Apart from the books listed above there was a university course that greatly influenced the writing of this article:
Himanka, Juha (1999). Johdatus fenomenologiaan (Introduction to phenomenology). Lecture course, University of Helsinki, Department of Philosophy.
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