Inability to determine one's true body position, motion, and altitude (or, in water, depth) relative to the Earth or one's surroundings. It may result from a brain or nerve disorder or from limitations in the normal sensory apparatus. Most clues to orientation are relayed from the eyes, ears, muscles, and skin. The senses may not perceive gradual changes in motion and may overestimate the degree of abrupt changes and overcompensate when motion stops. Airplane pilots and divers also contend with apparent changes in gravitational pull, which can lead to dangerous situations and must be overcome by training. Seealso inner ear; proprioception.

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Spatial scale provides a "shorthand" form for discussing relative lengths, areas, distances and sizes. A microclimate, for instance, is one which might occur in a mountain valley or near a lakeshore, whereas a megatrend is one which involves the whole planet.

It is important to realize that these divisions are more or less arbitrary, and where, on this table, mega- is assigned global scope, it may only apply continentally or even regionally in other contexts. The interpretations of meso- and macro- must then be adjusted accordingly.

See also

• astronomical units of length
• cosmic distance ladder
• orders of magnitude (length)

External links

• A sense of scale by Paul Falstad — visual depictions of the relative scale of various distances, ranging from the Planck length to the furthest known object in the Universe.