33. The inertia of biologists

Although science now has clear definitions for mass, inertia, momentum, and kinetic energy, there have been many changes in both concepts and meanings over scientific–historical time. Unfortunately, far too many biologists and ecologists have failed to note them. For this reason, the biological understanding of mass is still stuck in scientific ancient history and differs sharply from that used throughout the rest of science. Biologists still mistake mass, and still do not apply it correctly to biological entities. If they did, there would be no confusions and the subject would have far greater logic and order. That confusions and a lack of rigour still exist on these topics is made evident by contemplating our line segment or tunnel of molecules.

As we have already noted, Aristotle’s biology was little different from his physics, which did no real harm to his biology. Since his physics preached that everything sought for its ‘natural place’, he never needed to distinguish between weight and what was called quantitas materiae or the ‘quantity of matter’. Velocity was always in his view directly proportional to weight.

Our line segment or tunnel of molecules is a vector. By Law 1, Proviso 2, which is the law of existence, δW = (δQ - dU) > 0. Work is always done along that line segment. Therefore: a force must constantly arise that is capable of doing that work upon that path … and that force also has a sense. It is being exerted on and by the molecules as biological entities progress along t and move closer to T. It can be integrated and differentiated; and it again has magnitude and all other vector properties such as divergence and curl, and as are applicable to the molecules upon that path or line segment. The question is … is there a difference between ‘biological weight’ or ‘biological inertia’, and biological ‘quantity of matter’? If so, how should the difference be measured, and how is it expressed?

Since mass and inertia are critical to science, then there must be no etymological fallacies. “Inertia” comes from the Latin iners meaning idle, or lazy. Physicists argued long and hard, following Aristotle, about the implications of this concept, and about the differences between weight and quantity of matter. They also argued long and hard about the difference between the p = mv of momentum and the Ek = mv2/2 of kinetic energy.

Although scientific understanding has progressed quite considerably since Newton offered his most important of all definitions, most biologists and ecologists have unfortunately not. In Book I, “Of the Motion of Bodies”, Definition III, in his Principia, Newton gives the classic statement which still defines mass for almost all working biologists and ecologists:

The vis insita, or innate force of matter, is a power of resisting, by which every body, as much as in it lies, endeavours to persevere in its present state, whether it be of rest, or of moving uniformly forward in a right line (Newton, 1686).

The McGraw-Hill Concise Encyclopedia of Science clarifies Newton’s definition by saying that inertia is:

That property of matter which manifests itself as a resistance to any change in the motion of a body. Thus when no external force is acting, a body at rest remains at rest and a body in motion continues moving in a straight line with a uniform speed (Newton’s first law of motion). The mass of a body is a measure of its inertia. [See mass] (Parker, 1998).

Since the definition refers us to “mass”, we consult it and duly find:

The quantitative or numerical measure of a body’s inertia, that is, of its resistance to being accelerated. … All matter possesses two properties, gravitation and inertia. The property of gravitation is that every material body attracts every other material body. The property of inertia is that every material body resists any attempt to change its motion. … Because of its inertia a body cannot be accelerated unless a force is exerted on it. The greater the inertia of a body, the less will be the acceleration produced by a given force (Parker, 1998).

But by Newton’s second law, F = ma, wherever there is force, then there is also mass and inertia. Therefore, some kind of “biological inertia”—an expression of the work and energy—must exist on our line segment. We surely need to find it. Unfortunately—and as we have seen with ‘volume’—due to widespread confusion over concepts, finding biological inertia rarely proves straight forwards.