Models of conduction

Science, by definition, is about knowing.  But often it tries to know things which cannot be thought - like the counter-intuitive ideas of quantum mechanics - or at least cannot normally be grasped - the microscopic or galactic.  To get round this fundamental problem, science resorts to models.  For example, if something has a wave-like nature, it can be thought of as ripples on a pond; the model may be loose, but at least it is concrete.  It can be thought, and through those thoughts we can begin to understand, and then to learn.

One of the classic cases of such modelling occurs with electricity.  How can we conceive of something so powerful, so apparently protean, which conveniently comes out of holes in the wall, and yet which is not visible in itself, but only through its effects?  One of the commonest models for the electric current is the flow of water in tubes: the bigger the flow, the greater the current, the greater the pressure behind the flow, the higher the equivalent voltage.  Wiring in a house becomes like plumbing.  

The nice thing about models is that they can be mapped on to other fields.  For example, the electricity/water one is about flow in wires/tubes.  It has much in common with the flow of traffic along roads.  There is even the same concept of current - the rate of flow of traffic.

Finding a traffic voltage is more interesting.  Electrical voltage and fluid pressure are about potential to do work; so it is tempting to equate traffic's equivalent with the pent-up pressure within a driver - his or her desire to get moving, to do something rather than just slowly pootle along.  There is a capacity in this pressure, a potential, but unlike that of water or electricity, this potential has a more complex nature.

Voltage can be good or bad.  It is bad when somebody carves us up on the road, and we spend the next minutes trying to take our vengeance.  Along the way we will probably drive recklessly - and carve up others, who will then spread the bad voltage further.  Surprisingly, perhaps, good voltage seems to work in a similar way.  If somebody lets us out, or waves us across a road, we feel disposed to do the same to others, who then tend to spread this good electricity a little further. 

Bad traffic voltage may seem to speed the traffic flow locally, but ultimately it causes bad, inefficient use of road space and may even bring flow to a halt when a crash occurs.  The corollary is that good traffic voltage does speed traffic flow, even though locally it seems to slow you down.  Road space is used more efficiently, and the crazy, infuriating junction gridlocks - where everyone piles in rather than allowing others to move and so clear the way - are absent, greatly increasing flow rates. 

Just as the ideas of electricity/water can be extended to that of the streets, so the above model of traffic electricity can be applied to other areas.  For example, the concepts of good and bad voltage are nothing but simplified versions of good and bad conduct in daily life.  The nicer we are to people, the nicer the world gets, and vice versa.  Perhaps we could learn a thing or two, even from this trivial model of traffic conduction. 

(21.3.92)

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