In many physical situations, the consequences of collisions, bending, twisting and changes of velocity are readily observed and experienced directly, so that the concept of a generalized 'cause' of such changes... called 'force'... is an almost inevitable consequence of observation. When a wheelbarrow is 'lifted' and 'pushed' in order to 'move' its load thru the garden mud, the handles of the wheelbarrow are bent and the arms of the lifter are elongated. When the screw on a G-clamp is 'turned' against the friction of the threads, the disc is squashed and the arms of the clamp are distorted and 'stressed'. We understand 'forces' because we can feel them and use them.

The mathematical modelling of force, as an 'agency' that causes mechanical stress and accelerations... by treating it as a vector quantity that is measured in magnitude and direction... has been a remarkably successful engineering and scientific innovation. It can often be conveniently used in the mathematical analysis of energy redistributions. The energy of the universe appears to manifests itself in numerous forms which have been modelled variously as 'nuclear', 'gravitational', 'chemical', 'electromagnetic', 'capacitive', and so on. Ignoring the influence of life upon its microcosm, those regions in the physical universe that are identified as 'high energy' are associated with such factors as large velocities and sources of radiation. As a generalised simplification therefore, the universe of non-living entities is subject to a continuous and unrelenting redistribution of energy from regions of 'high energy' to those of 'low'energy'. In the process of this redistribution, if the region of 'low energy' has a structure that can arrest the intrusion, it will be distorted and store the energy input in its structure. In this type of situation, it turns out that the energy being redistributed is equal to the product of what we call 'force' and the distance moved by that force... a large force moving a small distance can require a similar amount of energy as a small force moving a large distance. On the other hand, if the region cannot stop the input, then the objects involved will be accelerated. In these situations, the input is converted into energy of motion, where the 'force' involved could be modelled by kinetic energy formula and distances or newtonian ideas of mass, distance and time. Load a beam up with mass to increase the gravitational energy trying to relocate downwards, and the beam will distort and sag and store some energy input in its atomic bonding structure. Overload the beam and it will fracture and the load mass is accelerated downwards and attains kinetic energy. Combine combustible materials in a closed container and the liberated chemical bond energy will stretch the container until its material is ruptured, and thereafter the energy transforms into heat and kinetic forms.

Some energy redistribution scenarios however are best modelled from different perspectives. The flows of volcanic magma, ocean currents, solar wind, and so on, involve such large distributed patterns of energy change, that considerations of 'force' may proved subservient to the more broad-brush analyses of thermodynamics and turbulent flow hydrodynamics. Minute, finite cell analysis may be compelled to have recourse to the fundamentals of 'force', 'energy', 'distance', 'time', and the like, but only the possession of significant computing power, makes such an approach realistic.

For most electro-mechanical engineering situations, any modelling using 'forces' inevitably has to recognize that they need to be considered in pairs. When a wheelbarrow is lifted, the upward force that raises the handles is countered by a downward force that stretches the arms, compresses the spine and legs, and pushes bootmarks into the garden. The downward force of the butterfly's wings against the air is balanced by an upward force of the air upon the wings. Whilst this is admittedly an unsophisticated simplification, it is never-the-less the case, that whenever 'forces' are used as modelling concepts, it is almost unavoidable that eventually they have to be considered in equal and opposite pairs.

When an object is dragged by a chain, the force doing the pulling would have to be modelled by a series of paired forces that are located at each of the link contact points. There is thus a sense in which it might appear that infinite chains of forces are initiated each time there is an energy redistribution. This is to ignore or deny the existence of the chaotic reality substrate. The solitary flapping of an insect wing is only one input into the turbulence of the atmosphere... amongst uncountable and unidentifiable others... and only contributes to the chaotic turbulent disorder at that scale. The unique event of the local flapping of an insect wing, can never have a traceable output in the form of a distant cyclone, because the energy and forces involved will be absorbed anonymously into the disordered background.