Maths begins with 1, 2, 3, and so forth; and a natural next step is to include fractions, and at some point we include 0 and negative numbers. In my last post I wondered if the adjunction of negative numbers should be construed as the introduction of directions. If so then when we include negative numbers we should also be exchanging our original unsigned numbers for explicitly positive numbers (the unsigned amount in the positive direction), but the question then arises of what we should do with 0. There is no numerical difference between negative zero and positive zero, both are just zero, and so we might leave 0 unsigned; but in my 2005 paper I presumed (on page 99) that 0 could be assigned both directions (and that in the case of complex numbers, 0 could have all the infinitely many directions of the complex plane). Intuitions for both views come from the use of 0 to label the origin of geometrical coordinates: To get to 0 from 0 we don't actually go in any direction; but then, to get to 0 from 0 we could travel no distance in any direction. So I'm wondering if there are any good reasons to favour one view over the other (aside from my 2005, which is a reason to favour the latter).
(PS: This post is linked to in the Carnival of Mathematics 63:)
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