I think I am losing my mind.
A few years ago, I was reading yet another popular science book—I think it was Brian Greene’s The Elegant Universe—when I came across a reference to one of those barroom brain teasers. It goes like this: if your image in a mirror is reversed with regard to right/left and left/right, why is not also reversed from up/down and down/up?
The answer, while elementary, is surprisingly difficult to articulate. It helps to imagine yourself, not face-to-face with your reflection, but back-to-back, with the plane of the mirror between you and your mirror-doppelgänger. Now stick your arms out and waggle your fingers. For both you and your reflection, up is still up, and down is still down. This side (left to you, right to your doppelgänger) is still this side, and that side (right) is still that side.
The only real difference is that up/down has an objective definition; that is, which direction is the earth and which the sky. But left/right has a purely subjective definition, relative to whose set of eyes one is looking through.
Simple, right?
Any “normal” person reading this answer would have smiled, grunted, and moved on. But for some reason, it led me down an intellectual rabbit hole—rather, through an intellectual looking glass—that I haven’t escaped since. Specifically, it got me thinking about the bizarre, almost metaphysical nature of left and right.
The difference between left and right is one of the first abstract concepts we learn as children. It’s also a concept that cannot be taught with words—only from direct demonstration. Think about it. Unlike up/down, there is no way to explain objectively the difference between left and right. Unlike up/down (which is really determined by our sensation of gravity) or forward/back (which is based on the physiological fact of our bodies, i.e., which direction we walk in), left/right has no tangible, physical referent. Rather, left/right (which I will henceforth refer to as L/R) is purely a matter of demonstration and memorization.
When we’re children, around the age of four or five, our parents teach us that this shoe is the leftie and that shoe is the righty. And, somehow, we remember.
But this ephemeral quality of L/R really got to me when I thought about the Voyager probes sailing out of the Solar System. As every science nerd knows, both the Voyager I and II space probes are fitted with a golden phonograph record containing visual and auditory data that some distant alien race might find interesting should they ever recover it. Most of the information will be easily understandable to the aliens (once they figure out how to play the record), including the crude drawing of a human being on its surface. I don’t know if this record has any references regarding our human definition of L/R, but if it does, it would have to be in this drawing itself (or in one of the images encoded in the on the disk), because L/R cannot be easily explained with math or symbols. L/R, like an old phonograph record, is an analog technology.
But wait! Surely there’s got to be some way of explaining to an alien our definition of left/right without labeling a picture of a human body?
Well, there is. But it would be very difficult. In fact, it would require other kinds of drawings which would be even more complex.
We could, for example, refer our ET friend to some common reference point in the natural world. Chemistry is full of objects that display the same kind of three-dimensional asymmetry that we know from our hands. The technical term for this “handedness” is chirality, which I stumbled upon when researching this topic. The organic compound Carvone, for example, comes in two varieties, left-handed (negative) and right-handed (positive), which the human nose distinguishes as spearmint and carraway, respectively.
So, assuming we have already taught ET our words for “up” and “down” (so he knows which way to hold the Carvone molecular diagrams), we could show him a picture of these two molecules and label them left and right.
Once I realized how hard it is to explain the concept of L/R, my next question was: how the hell do we remember it? That is, how do our brains manage to process the difference, with no physical markers to remind us?
The answer, as it turns out, is: “…with some difficulty.” Identifying left from right is a higher-brained activity that is actually very easy to screw up, especially in moments of high stress that require quick thinking. A certain mechanism in the brain called the angular gyrus is in charge of handling the matter. (The angular gyrus is also concerned with language and mathematically ability.)
Of course, exactly how the angular gyrus keeps L/R straight is an even bigger mystery, getting at matters of consciousness and self-awareness. For me, it seems to reinforce my belief that there is something ineffable about the human experience—something not necessarily limited to the human brain, and not purely explicable with science.
But that’s a subject for another post…
Ash Clifton, Writer 