We think of our bodies as having a curved geometry. Most human-body sculptures reflect this view. Yet it is the right angle that distinguishes the man-made environment from the natural: buildings, streets, furniture—all testify to this.

Physical geometry: Our body and its movements describe straight lines and complex curves in space, like the conical motion of this discus thrower.

Those who live with curved walls often see the practical value of the straight wall and right-angled corner more clearly. Tables, beds and cupboards, for example, are easier to fit into an orthogonal (right-angled) geometry than into a curved one. But the “rightness" of the right angle may be more about the body than about furniture.

Linear thinking

The straight line is integral to the right angle. Two straight lines meeting at 90 degrees form, almost literally, the cornerstone of our “built" environment. And for all the curved and angular modelling of the human body, it is very clearly organized around the right angle.

Chinese-American geographer Yi-Fu Tuan, retired professor-emeritus at the University of Wisconsin, Madison, US, suggests in his classic book Space and Place: The Perspective of Experience that man has for long been considered to be “at the center of a world defined by the cardinal directions". We carry the X, Y and Z axis of Euclidean geometry in our own bodies. The axis “forward-back" is at a right angle to “left-right", and both to “up-down". These axes orient us physically in the world, starting with our bodies. They align also with cardinal directions and the movement of the sun, which partly accounts for the fact that sacred buildings in many cultures are orthogonal and aligned to the cardinal directions.

Functional for the body

Orthogonal furniture design too makes sense, given our body’s geometry. The edge of a table is parallel to the plane of our body. The mattress and bed align with our height, which becomes a “length" when we lie down. Cupboards and shelves stretch parallel to our bodies so that our eyes can see right in.

The geometry of movement is also important. Our body is designed to move most efficiently in a nearly straight line. Thus passages in buildings and streets in cities are basically straight. Also, because we find our way in terms of right or left turns (relative to our body), we find it easier to navigate paths that branch off or intersect at 90 degrees.

Limits to rightness

Taken too far, of course, the right angle starts becoming the wrong angle. We tend to think of endlessly repeated gridiron patterns of American cities as basically orderly. However, many find Chandigarh’s similarly strict grid of streets inhuman.

One reason is our need for variety in what we see (log on to www.livemint.com/seeingbody.htm). However, it might also be that we need some deviation from a perfect 90-degree angle. It is simply not natural for us to move in a perfectly straight line (even when sober), or along any perfectly regular geometry. Which is perhaps why we are attracted to dance, and why it is considered so difficult. Dancers show off the impossible by tracing perfect geometries on the floor (and in empty space) through movement.

Curving in a straight line

Perhaps our discomfort with a single pure geometry emerges from the complex geometry of the body and its movement. Sure, much of our body is organized invisibly around the right angle. But our movements are, in effect, curved, and that too in three dimensions. The design of our joints often allows us to move our limbs in a conical space. Just picture the discus thrower in action.

Our pleasure in walking the old streets of Rajasthan or Italy might well spring from the way the right angle of forward-back and right-left interacts with the rotational movements of our joints. As we walk those streets, we look around, crane our necks, peer ahead, unconsciously tracing all kinds of complex curves in space. Since our bodies “enjoy" being put to work, the joy of these old streets is felt not just by our eyes, but by every muscle and joint that must work to walk the curve in many little straight lines.

Surely, aesthetics does not get any closer to physiology.

Himanshu Burte is a Goa-based architect and writer.

Write to Himanshu at bodylines@livemint.com