Metaphor, Spatial and Map

Metaphors Create Structure

Metaphor is the fundamental mechanism with which humans understand and learn something new, particularly something abstract. A prominent example in science is Rutherford's analogy between the solar system (with planets orbiting the sun) and an atom (with electrons orbiting the nucleus). It exhibits the basic structure of analogies and metaphors (with analogies considered as metaphors made explicit):

• 1.
  A source domain (the solar system) that is assumed to be familiar to the audience at least at the required level of understanding
• 2.
  A target domain (the atom) that is new or unfamiliar or abstract or cannot be observed easily
• 3.
  A partial mapping that carries some properties from the source to the target (the orbiting of several smaller entities around a bigger one)

The power of metaphors results from the logic of the source domain being mapped to the target and allowing for reasoning about the target in terms of the source. The Greek roots of the word metaphor contain this idea of “carrying over.” Thus, Rutherford's analogy carries some properties of the solar system over to atoms and allows us to understand and reason about the behavior of atomic particles in terms of bodies in the solar system. Clearly, this results in only a limited understanding, because the mapping is partial; that is, it maps only some structure from the source to some parts of the target. Every user of a metaphor needs to be aware of this limitation, to exploit the reasoning power without unduly simplifying or distorting the target domain. Yet this structuring power of metaphorical mappings is fundamental to many cognitive tasks. Darwin's conceptualization of evolution as forming a “tree” of living forms, replacing the previous idea of a linear “ladder,” is another example of this foundational power of metaphor.

The Rutherford and Darwin examples are spatial metaphors, in the sense that their source domains are spatial. Rutherford's analogy also has a spatial target, though the spatial source would be enough to make the metaphor spatial. When the two domains are spatial, the set of possible mappings between them is smaller. In the Rutherford case, the mapping is one across scales and goes from a very large (planetary) to a very small (atomic) scale. Another space-to-space mapping across scales, but in the other direction, characterizes the metaphor “Flat elevated landscapes are tables,” which underlies geographical names like “la mesa” or “table mountain” (the one in South Africa even having a typical cloud formation called “tablecloth,” showing that metaphors often occur in “families” of related mappings).

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