A Classical Perspective
Again, this section is not intended to be a physics tutorial, but rather a review of the classical perspective of physics. While there are aspects of the classical model that are still relevant today, it is possibly true to say that this model is more reflective of scientific thinking prior to the 20th century. At this time, the Church was still a powerful social institution, which undoubtedly influenced many areas of scientific thinking. Even so, by this time, science had essentially embraced what might be called a deterministic philosophy, which is sometimes referred to as the `clockwork universe`. This idea embodied a model of the universe that essentially ran by a process of `cause and effect` as described by Newton’s laws of motion. However, we shall start this discussion with the premise that everything in science, and the rest of the universe, can be described in terms of 4 basic quantities:
In a wider context, we might recognise that our understanding of these quantities reflects our experience of the world, which in-turn reflects the sensory and intellectual evolution of homosapiens, as a species. As such, the initial understanding of the real nature of these quantities is often intuitive, subjective and wrong. Therefore, we will start this aspect of the discussion by introducing these basic quantities in a little more detail, first within the constraint of a classical model, but then followed by latter day notes in italics suggesting a possibly different nature. However, in some respects, many of the arguments in modern science today still relate to the conflicts between our interpretation of the physical and mathematical reality of these quantities:
We normally perceive length as a comparative measure, i.e. x=1 metre. The concept of length is one that natural selection has evolved to help us intuitively understand distance, albeit in the limited scope of length extending in 3 perpendicular directions, i.e. essentially a Cartesian model involving xyz directions. As a consequence, the concept of area, i.e. xy, and volume, i.e. xyz, are also intuitively understood based on the same caveat.
Note: While we might feel that we have a good grasp of these various manifestations of length, science has come to challenge some of these intuitive perceptions when considering the true nature of space between sub-atomic particles or the light-year distances between galaxies. However, for the moment, we shall simply flag this complexity for later discussion - see link in inset right.
The concept of time is possibly less tangible than length, simply because it cannot be sensed directly, although it could be argued that we do have some in-built sense of the passage of time. However, without any concise definition of the mechanism of time, we might simply define time as a fourth dimension through which objects in xyz space can passed from one second to the next.
Note: Again, we might flag that subsequent ideas, such as special relativity, suggest a far more profound relationship between space and time, but again, we are trying not to run too far ahead of the classical model at this point. However, the following discussion related to the idea of time might provide some food for thought for those interested in this aspect.
In evolutionary terms, we probably have had little need for an intuitive understanding of the concept of charge, although we may have observed static charge effects, e.g. lighting storms and static charge on a cat’s fur. However, the notion of charge has come to be described as a fundamental property of some particles, such as protons and electrons, which is expressed in multiple units of the elementary charge [e] on an electron. Electrons are said to have a charge of [e-], while protons have the opposite charge of [e+]. Normally, the charge of a macroscopic object is typically zero, as the number of electrons in every atom is typically equal to the number of the protons, so their charge cancels out.
Note: It is possibly important to make a couple of clarifications so as not to lose sight of the current scientific model. During the 20th century, the particle model divided the structure of a proton into quarks, which were considered to have a fractional charge of −1/3 or +2/3, but which can be combined to form either the positively charged proton, i.e. 2/3+2/3-1/3=+1, or the neutron, i.e. 2/3-1/3-1/3=0. Also, there is a sense that describing a single particle, in isolation, as having a charge may be essentially meaningless, because charge is said to only exist between two charged particles. There is also a fundamental relationship between an accelerating charge and electromagnetic radiation, which is encrypted into Maxwell’s equations. Again, more speculative ideas on the idea of charge will be deferred to subsequent sections.
Our intuitive understanding of mass is normally considered in terms of the weight of an object, which is specific to the force of gravity on the surface of Earth, but mass is not weight. This situation is compounded because the units of mass and weight are both measured in kilograms [kg]. In space, where the effects of gravity are minimal, a mass would have no apparent weight, but still require a force [F=ma] to overcome its inertial mass. This complexity is linked to what really amounts to two different definitions of mass, i.e. gravitational and inertial.
Note: Today, Einstein’s famous equation E=m0c2 suggests the rest mass [m0] is proportional to energy divided by the speed of light squared [c2]. This equation can also be combined with Planck’s equation E=hf to give m0c2=hf, where [h] and [c] are constants. On this basis, it would also appear that mass is a manifestation of energy, which in-turn is related to frequency, but more on this aspect in a later section entitled the idea of energy.
So while these quantities are still considered to be fundamental
units within a basic particle model; the subsequent development of
quantum theory might suggest
that all notions of particles must ultimately disappear into a
probability wave function. In fact, there are number of alternative
theories that suggest that matter is only a manifestation of scale
the fundamental units, as described, are only an emergence property
of the underlying wave structure of matter. However, irrespective of
whether this is the case, or not, developments in science have always
proceeded by making models that allow behavioural predictions to be
made, which have then been subsequently proved to be only an approximation
of reality. In many respects, the classical model has stood the test
of time better than most.