In the scientific history of various measurable quantities it has been found fruitful to recast their form from time to time; usually A dropping the natural intuitive concept in favour of one apparently more artificial, but nevertheless much more powerful both for measuring and for framing theories. The time has come to do this for length.
Most of the earlier changes have met some degrees of incredulity and opposition, and this is likely to be so with the present proposition. A brief look at some earlier occasions may therefore be worthwhile.Hotness and Coldness.
The human receptor arrangements can distinguish degrees of warmth, and can set them in sequential order from very cold to very hot. It is not a denial of this direct and practical experience to say that little progress was made in this subject until two new, related variables, Heat and Temperature, were devised to replace the original intuitive single variable.
But each measurable has its own solution, take for example, Fire.Fire.
The early philosophers noted that the world is built of materials, of which they noted four kinds: Earth; Air; Water; Fire. Later workers found it possible to subdivide these into constituent Elements of remarkable repeatability of characteristic, and of remarkable consistency of measurement. One Element was anomalous - phlogiston, and proved particularly recalcitrant. The solution was not to find two related variables as above, but to describe the material as a process; combustion. The necessary act is to look behind the intuitive observation; and although to contemporaries this may appear to be denying an obvious observed fact, for after all, fire exists and is concrete, and combustion is an abstraction; the denial is in the mind of the objector rather than in the subject matter, as is now easily accepted.Weight.
The ponderousness of material objects is directly experienced as weight. In a terrestrial environment it is nearly always weights that are compared in experiments involving measurements. The Newtonian laws of dynamics draw attention to a less obvious characteristic - Mass. Both are measurable, weight very readily and in line with the intuitive idea associated with the word Heavy. In spite of the practical advantages of Weight and its naturalness as a unit, there is no doubt that Mass is the unit on which to base theory. The particular merit of Mass is that it stays invariant - or is conserved - over a wide range of circumstances.
This third example differs from both the earlier two in that there is here a choice between two units which are related by an almost constant ratio for all practical terrestrial measurements. Nevertheless the less natural unit is the one to adopt.Extension.
Man's personal experience, in addition to the above, includes evidence of extension outside himself. Current usage is to have two units of extension, length and time. Length has the familiar advantages of being intuitive, and of being readily measured in terrestrial circumstances where change is minimal. Time is elusive conceptually, and until recently not measurable in small quantities; but as a fundamental unit it has the advantage. It is the unit of change, it is the unit of communication and information; and it is centrally derived and based - corresponding to man's central situation. Length calls for at least two ends, and probably needs points in between to be fully defined; and although the two ends can be separately experienced or deduced, this needs time and cannot be speeded up indefinitely. Time becomes the arbiter of the validity of a length measurement.
It may be taken that there is an underlying unit of extension common to all pattern groups, however separated, and that time is the unit involved. The original instrumental difficulties have not disappeared and numbers can not only be allocated from a common clock source, they can more ain more be measured against a clock.
If all non-present structures could be allocated fixed numbers there would be no experience, but since there is a continuing flow of information and experience, and a conviction of lapse of time, some patterns must be allocated decreasing numbers, and some allocated increasing numbers.
Present usage allocates parallel decreasing numbers, which reach zero at the same time and otherwise keep in step, to two startlingly different verbal explanations. A future event is allocated a decreasing number, and an approaching photon is allocated a decreasing number. The numbers, apart from a constant ratio, keep faithfully in step. It is only habit, and a failure to recognise that length is a secondary property subject to severe restrictions, that keeps the two separately defined.
There are thus two descriptions for a common phenomenon - lapse of time, and velocity of light, and the one to be dropped is without question the latter.
It cuts across fatuous statements such as "For all we know, that star we are looking at now may have ceased to exist for millions of years". Such a statement assumes a universal NOW which extends infinitely. No one would expect HERE to extend infinitely, but if Here-and-now is taken in a common unit, and refers to accessibility in the same unit, it begins to be possible to put numbers and a possible distribution to NOW, to HERE, or to Here-and-now. Perhaps it is a Gaussian curve; possibly an Amoeba-like multi-dimensional solid, but its mean extension is almost certainly not in excess of small fractions of seconds.Acceptability.
The great hurdle to acceptance is the apparent contradiction that light has no velocity. * This is correct, but should not be taken as a denial of the observed fact conventionally known as the velocity of light; this is not challenged. It is merely that velocity is of terrestrial-scale validity, a first order valid approximation in certain circumstances, and must not be exceeded. For conventional velocity there must be an object which moves. This must all be deduced from information reaching an observer, and he infers an object, when the information settles down to repeating itself in a pattern, the form of the pattern defining the object. If there and now a small perturbation, and if this perturbation can be largely offset by a continuing correction, the whole can be re-defined as a moving object.
If the perturbation becomes significantly large or incoherent, the recognition of the object becomes uncertain. There must always be a large amount of recognisable invariability, and a small component of variability. Variability must certainly never approach 10% or the whole concept is untenable. It is quite unacceptable and absurd to take a particular method of treating incoming information, and use it to describe the flow of information itself. At the most it can be accepted in a highly metaphoric sense.
Free electro magnetic energy, remote from us but approaching, is as .inaccessible and uninfluenceable as a date in the future. Some choice exists as to what will be accepted and what diverted, but this affects the content of that future NOW when it occurs. It does not affect the rate at which it approaches — one second per second. This tick of time is the universal constant.
* The Sun has no velocity either, but we all have seen it "rise", move across the sky and "set". By common sense it has velocity, certainly movement; by saying it has no velocity we do not deny the observation but re-describe it from a different vantage point.