I believe that we are in agreement that the Euclidian model for space as I have been talking about can be defined as having three (type a) dimensions of length which are mutually perpendicular to each other. We can express this space using vectors and when we do, the vector space is orthogonal.
Here, I think you are trying to say,
|1 0 0| |
i|
|0 1 0| |
j|
|0 0 1| |
k|
is the only basis for R
3. This is incorrect. It is a basis, and as I've presented it, is an orthonormal basis (and
i, j, k are typically used in engineering), but it is not the
only basis of R
3, in general. Moreover, it is not even the only basis for the subset of R
3 that we call the space we live in and experience, since both have the same algebraic properties (the one is generalized from the other, after all).
Fredrik has explained this.
Fredrik is saying this is false.
If I understand what is going on, Fredrik is correct.
If you restrict "dimensions (type a)" to length, then they must be mutually perpendicular.
But you don't need to have three lengths to define a space. You just need three "independent axes". "Independent axes" are spatial axes such that a change in the measure along one axis causes no change in any of the remaining axes.
Perpendicular linear axes are independent, but not all independent axes are perpendicular, nor are all axes linear.
Here, I think Godmark is largely correct, and largely in line with what everyone else is saying. I'm not quite sure about the phrase, "length, then they must be mutually perpendicular." however. GM, maybe you could clear this up? Are you simply saying that 'length' is just a word that we've associated with
i, j and
k? The rest makes sense.
Jimbo07,
By narrowing things down hopefully we can limit the subject to one thing we disagree on at a time and work that out. Id does seem hard to narrow things down to a single thing, but I think we have such a single thing now.
Give we are talking about the real physical space we exist in and are using the most common model for this space which is a flat uniform Euclidean space with 3 (type a) dimensions of length.
So... just to be quite sure I understand: "type a" is the algebraic definition?
I think we can all agree on what space we are talking about and that this space can be defined as having 3 (type a) dimensions of length.
Do you agree with this?
I think so...
I state the 3 (type a) dimensions of length must be mutually perpendicular for this space.
Waaaah!

Now I don't know how 'length' is being used. Are we simply stating that the word 'length' is mapped to
i j k?
Fredrik states these 3 (type a) dimensions of length do not have to be mutually perpendicular to each other.
They would only have to... by convention, not by the algebra.
GodMark2 states 3 (type a) dimensions of length must be mutually perpendicular for this space, but GodMark2 does not seem to be arguing this with Fredrik.
boohoohoohoo... I'm so confused, now...
What do you think, do these (type a) dimensions of length need to be mutually perpendicular for this space or not?
If there's any hope in heck of me understanding what we're takling about...
I don't think Fredrik, Godmark, danielk, etc. are talking at cross-purposes (except for that one part of GM's post I found confusing).
Any 3-dimensional space (be it conceptual, or the space of our experience) has three basis vectors, regardless of the notation you choose. Basis vectors must be linearly independent. Understanding it for the space of our experience should help lead to the generalized case (because that's what's happened algebraically).