On Nov 24, 2013, at 10:50 PM, Joe Niederberger <email@example.com> wrote:
>> From a rather naive perspective, it seems that arrows >visually >> differentiate between segments, rays and lines. >> I'm more interested in how one might draw a rational (or >irrational) >> number 'line'. (as distinct from the Real counterparts.) >> >> Gary Tupper >> Terrace BC > > It depends on context. > > Cheers, > Joe N
In general, I think he is asking for a physical model of rational (or irrational) numbers. Specifically, something like a line.
 Physical model - A physical object or drawing whereby there is an explicit mapping between elements of the theory and physical measures of the object or drawing, such as quantity, length, height, etc.
A troublesome (impossible) task given the nature of these sets. At a deeper level, probably similar to the fact that we cannot make certain constructions with compass and straightedge.
It is a very good question though, and an example of how much math exists that we cannot "see".