When asked to name, without reflection, the greatest scientific work that has ever been done, people who are themselves scientists will usually say “Newton’s Laws of Motion” or “Einstein’s Theory of Relativity.” Such answers are revealing of the image of ideal science with which we have been brought up, an image that has been of immense importance in the intellectual formation of working scientists. What we might call the “Newtonian Ideal” in science is the formulation of some principle of great generality, if not universality, a law or small set of laws that applies at all times and in all places.
This emphasis on the Newtonian Ideal differentiates the awarding of prestige within the community of scientists from the awarding of prizes and of popular recognition which, quite properly, often give considerable weight to the impact of science on the human condition. One can get a Nobel Prize for inventing a very useful gadget like the transistor1 or for finding a treatment for prostate cancer,2 and we are reminded daily at breakfast that Louis Pasteur invented a way to keep milk from growing bacteria before we can pour it on our cereal. Scientists, however, value most those assertions about nature that apply to the broadest possible domain of the material world, giving short notice, if any, to revelations about nature that apply only to a particular chemical or physical or biological object. There is a new crop of Nobel laureates every year, but there was only one Isaac Newton.
One consequence of the value placed on great generality is that there is necessarily a tenuous connection between what has actually been observed in the world of physical phenomena and the theoretical claim. Between the idea and the reality falls the shadow of abstraction. Newton’s First Law, that bodies at rest tend to stay at rest and bodies in motion tend to stay in motion in a straight line unless perturbed by an external force, could not possibly have been a generalization of the motions actually observed by him. Neither he nor any other seventeenth-century observer ever watched a body move in a perfect vacuum with no external forces operating on it.
The secret is in the word “tend.” Tendencies are not observable. They are an abstraction around which the observations of the actual movement of bodies in different circumstances can be organized, in an attempt to understand the “perturbing” forces. In a world in which real material objects have a diversity of sizes and composition and are being acted upon by a variety of forces, Newton’s First Law does not describe the motion of any particular object. The law that for every action there is an equal and opposite reaction may tell us what happens in the collision between two perfectly elastic bodies, but it is a poor prescription for winning at billiards.
The problem of the relation between…
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