Newton - The First Philosopher Of Falsifiability
We argue that Newton had to introduce the first two Principles of Dynamics from obvious conditions of falsifiability. Take, for instance, the First Principle of Dynamics: in absence of any forces the trajectory of a motion has to be a straight line. If this principle would not be admitted by Newton we wouldn’t have today the concept of gravitation. Indeed, anyone can rightfully reason that we are not entitled to think of the force of gravitation acting on a planet, as long as we don’t know if the absence of this force would change the things as they are observed. As a matter of fact we will never know if the things will be changed indeed, because we just live with the planets apparently rotating around the Sun, so we have to postulate it. Here the experiment with the rotating stone and severed rope helps, in that it shows that the things will be changed: the trajectory will be different after the rope is cut.
The fact that this trajectory is specified as a straight line is immaterial for the concept. The essential point in falsifiability here is that it is different. The specification of trajectory is a particularity of the theory, in this case of Classical Mechanics. Outside Classical Mechanics this proposition is false.
The very same way the Second Principle is falsifiable: the connection between force and acceleration is nowhere to be found but only in Classical Mechanics. Outside its area this correlation is simply false. In the 19th century Helmholtz discovered general conditions to be satisfied by forces, accelerations, velocities and coordinates of a system of material points, in order that its motion may be characterized in a certain way. Therefore the whole system of Classical Mechanics is naturally falsifiable both by particular specification of the trajectory and by denying the premises of the Second Principle. The history of Science plainly proves this assertion: on the first account we have, for instance, the General Relativity, which specifies the trajectory geometrically, as a property of space as an attribute of space-time, while on the second account we can cite the host of mechanical models of point particle motion inspired mostly by the development of Electrodynamics in the second part of 19th century.
Therefore the first two Laws of Motion of the Classical Dynamics are indeed falsifiable, and they were expressly formulated that way by Newton. The Third Law, however, has a quite different status. First formulated with the same care for falsifiability, it stays firmly in place as unbreakable. Indeed, there is no possibility of finding situations where it is false. On one hand, as long as we limit its dominion only to matter, as actually Newton did, it is true. On the other hand, this impossibility of falsifying it has been reinforced, so to speak, mathematically, mostly in the 19th century, by extending the principle to the action and reaction in general, even to non-material structures.
It is obviously the vector model of force that allowed this extension. With the vector model of forces we can imagine equilibrium in a space point in general, even without considering it a material point: a vector is a mathematical figment defined everywhere. There is really no way of finding situations where the Third Principle is false, if we extend the concept of force to include the action at distance.
A situation proper indeed to falsification in the sense of Popper is the action of two forces in two different points of space with no matter joining them. This is the essential attribute of the action at a distance, and here the principle might fail. However, this possibility of failure is actually eliminated on a purely axiomatic basis.
Let’s analyze closely, in the way Newton did, the planetary motion. It reveals that the essential moment in the quantitative definition of the gravitational force is, on one hand, the moment when we assume the existence of the centrifugal force; such a force must indeed act upon planet according to our daily experience. On the other hand, according to the same daily experience, the centrifugal force has to have a counterforce acting upon the very same planet along the direction Sun-planet. It is indeed the static equilibrium of forces in the planet that matters in defining the gravitation as action at a distance; the rest is only imagination!
The simple truth should then be that the Third Principle acts ad litteram only in case where there is a material agent joining the two points of application of the force and its counterforce, as our experience indeed shows. Nothing more! There is no sufficient reason for extending the principle in order to accept that the action of the Sun on Earth, for instance, is manifested by a force on Earth that equals the force on Sun resulting from the action of the Earth upon Sun. In other words, the Third Principle of Dynamics is applicable indeed, but only in the way it was revealed for the first time to our experience and, as such, it is indeed a scientific proposition because it is falsifiable. The classical extension of the concept of force to include the action at a distance precludes its falsifiability and, therefore, cannot be scientifically accepted.
Nicolae Mazilu, PhD Physics and Engineering, occasionally (very often lately!) writer regarding unsettled problems. Usually perceiving these in places where everything seems to be settled: Classical Mechanics, Cosmology, Thermodynamics, Heat Transfer, Continuum Mechanics, Astrology, Relativity.
Tags: Classical Mechanics, Falsifiability, General Relativity, Gravitation, Laws of Motion, Newton, Popper
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