Reflections on Special Relativity, with an inter-disciplinary approach.
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# Can Cinderella be violated?

Posted Mar15-12 at 09:36 AM by Saw

Last post ended with a question: when a physicist plays with clocks and rods and kinematic concepts like time, displacement, velocity, acceleration… what is his or her Cinderella, that is to say, the practical purpose that he or she has in mind?

Seeking an illustration for the answer, I reviewed the problems posed in a standard physics book. Unfortunately, the questions stopped at the abstract level. They asked, for example, about the velocity of a projectile after the lapse of a time interval. However, they would have been more amusing (and probably more pedagogical) if they had spoken out any reason why that velocity might matter. For instance: will the projectile fired by the villain arrive “in time” to hit the heroine, before the latter receives a warning message from the hero? We could think of many analogous situations and, in my opinion, in all of them should we find the same leitmotiv: they sound like causality. The shape of the question may be whether an agent causes an effect or whether it avoids it or how many times it does it…; all those are variations over the same theme, which is the old story about causes and effects.

So causality is the Cinderella of motion concepts. This is the essence, the “spirit” of these notions, which –as you can appreciate- is, paradoxically, a pretty material thing: our pious Cinderella is a practical goal, made of tangible matter.

Thus we have identified the end. The means, as commented in the previous post, is the physical instrument with which we measure: in my metaphor, it is Cinderella’s slipper; in the context of kinematics, it is clocks and rods (or, if we take a modern stance, based on Special Relativity, electromagnetic waves with which you measure both space and time). In between those two elements, there lies the third ingredient of concepts: the logical reasoning explaining how, on the basis of what the instruments have measured, you can find the solution to the problem at hand.

Given this, how come that, according to certain interpretations, causality (our lovely Cinderella!) can be violated?

So… you have a challenge, you need to find Cinderella, you get hold of one of her slippers as a clue for unmasking her identity, you start playing with this instrument and… the mother of all wonders! Just because of these manipulations, you suggest that… somewhere else, Cinderella may be suffering some nasty effect… she is negated, she is somehow vexed, she is breached …

Yes, it sounds ridiculous but that is the nature of intellectual process leading to the fantasies that put in question causality. It is a simple epistemological error. You invent a concept for solving a problem and in the end you get so entangled in the intricacies of the idea, you fall so much in love with it, that you become sort of fetishist: you forget your problem and feed upon the instrument.

I will finish with another metaphor borrowed from the philosopher Eckhart Tolle. Concepts are pointers at solutions to practical concerns. For instance, a signboard with an arrow pointing to Rome. However, you do not remain there, gazing at the arrow. That may be entertaining if the arrow is beautifully drawn. But it is not the aim. And for sure you would never pay attention to the bizarre idea that, because of the very existence of the signboard, Rome may be set on fire.
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