Commentary
Hermann and most modern mathematicians like to disarmingly say:
"Well now I can throw away the picture and just do this Algebraiclly! I could just define this product or sum algebraically ".
Well of course we could, but what happens then is one psychologically starts to look for "meaning" in all this " algebra". One tries to " interpret" what one is doing!
Algebra in the vernacular Arabic means " mind fluff! ", or less venally "mind contortions!". It has taken me a while to see the joke Al Khwarzimi has played on us, in succeeding generations! The Indian system of numerical notation is based on cycles and Gunas and Ganitas. The modulo or clock arithmetics form the fundamentals of their system position and order carry significance in terms of size, thus the decimal system of the Hindis reduced calculation, aggregation and dis aggregation to a mechanical whirring and rotation and twisting of the clock or dial indicators!
This subtle replacement of one to one counters, beads, pebbles etc by a mechanical clock system where Shunya meaning " full" tipped the mechanism into the next cycle or circuit for accounting, is what we call the decimal placeholder system. In this system Shunya takes on a dual role" full/empty".
Shunya can never mean empty or nothing, it always means full or everything. But in this system, once a pot is full ( Shunya) it is moved into a different cycle and sn empty pot replaces it. The empty pot has no name! Shunya is not its name. That is the name of the completion of the filling process.
Given this mechanization of calculation by the Hindis, Brahmans Harappians and other Dravidian or Indus Valley peoples, the Arabs found this constant cycling very disconcerting. Thus the term Al Jibr was used, which, as I say has a vernacular meaning that is apt!
Thus we deal not with mythical Algrbra but actually with Greek geometrical mosaics. These space filling forms were counted, identified and related meaningfully to space and spatio temporal events.
The greatest mystery was our interaction with space . Psychologically we needed to have things or experiences called seemeioon ( singular) or seemeia( plural). These terms are usually translated as point or points, but they are more related to signal or signals. Thus space attracts our attention or focus in some way that directs us to investigate, to understand, to find meaning. Seemeia are all those signals that define a region of interest.
The Pythagoreans over time aggregated these geometrical regions into standard measuring patterns or mosaics called Arithmoi. It is these Arithmoi that we inhabit and name when we count.
Lest we forget the Indian contribution to this process I coined the term Shunyasutras.. These are the same Arithmoi but without the rectilinear bias one picks up from being taught legendary geometry books 1 to 7.
Of course Euclids Stoikeia is all supposed to be introductory and in that sense elementary, but after book 7 Arithmoi theory predominates, untill the treatment of solids and spheres is introduced. By this time a solid reference frame experience applied flexibly to measurement and proportion should have been ncountered by the student.
If the whole course was taught now as Euclid laid it out, I doubt if it could be done in less than 2 years!
This was and is sn undergraduate course in Pythagorean philosophy! That it has been mistaken for a mathematical text book is due to a misuse of the degree status "Mathmatikos!" Mathematikos is a qualification in Astrology. One would need to study more thn the Stoikeia to obtain it.
Both Plato and Aristotle were studying for this qualification. I do not know if Plato ever achieved it, but Aristotle certainly never did. In fact he rejected the qualification on several key points to do with Arithmoi!
Dissent was not uncommon, so it was an unfortunate political situation that prevented Arstole from perhaps resolving his difficulties with some Pythagoren concepts through further study in the Academy. Certainly both Eudoxus and Euclid obtained the qualification, and it would seem that both Archimedes and Apollonius obtained it also.
Aristotles Lyceum granted a rival qualification, for a while, until geopolitics again disrupted his school of thought, transferring it into the hands of Islamic scholars, who were much persuaded by it!
At the end of history, the clear, spatial mosaics of the Pythagoreans were obscured by the later interpretations of succeeding generations who did not always get it, and often covered true descriptions by mistaken ones.
Whatever we claim to be doing Algebraically is in fact being done arithmetically, by the methods derived for the Arithmoi. Symbolic arithmetic is a very powerful and cogent interaction ith space.
In this regard all Grassmann did was to not leave out orientation, but further to make it explicit and in combination with the quantity of the magnitude.
We do not use magnitude in its Grrek sense much, nowadays, so the distinction between quantum and magnitude is not clear. A quantum is a heap or a lump of some magnitude. A magnitude is an extensive experience.of something.
Thus the magnitude of space is an experience of its extensivenesses. But a quantum of space is a defined regional and bounded amount of space. These bounds do not necessarily have to be physical, as one can mentally bound or envisage a boundary to a region.
So
When R
n is used to specify a set of ordered real numbers, it's use is I'll defined at the level of "number". Confusingly it is used to specify points in a reference frame And vectors in that reference frame. The reference frame is not defined.
Grassmann's method starts with the primitives that define a reference frame, and these primitives are lines!
Usually hey are termed unit lines, and for that reason the concept of a unit has to be added to the fundamental definition.. Because these primitives are lines we can in fact model the primitive reference frame by the unit sphere in hich any radial represents a primitive line of unit length.
To define a unit length one radial is distinguished as the fundamental Scalar of the whole system or reference frame. Which one it is is a matter of choice, but some conventions exist around the use of this choice.
Thus we can hold a primitive sphere in our minds as modelling not only the primitive reference frame but any reference frame. We can then constrain the elements according to our design purpose.
Once you have a model of a primitive reference frame, one can understnd definitions of points as vertices of parallelapioeds or spherical pyramids with apexes at the centre.
In this regard, the dot product can distinguish angles between radials in the same great circle.
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