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Human scale

Human scale means "of a scale comparable to a human being".

A number of characteristic physical quantities can be associated with the human body, the human mind, and the preservation of human life.

Height: one to two metres
Number: about seven (plus or minus two) seems to be the limit of simultaneous human grasp of number (see George A. Miller[?]'s paper)
Attention span: seconds to hours
Lifespan: approximately seventy years
Force: weight of a bag: 10-200 newtons
Pressure: one standard atmosphere
Temperature: around 300K

Science vs. human scale

Many of the objects of scientific interest in the universe are much larger than human scale (stars, galaxies) or much smaller than human scale (molecules, atoms, subatomic particles).

Similarly, many time periods studied in science involve time scales much greater than human timescales (geological and cosmological time scales) or much shorter than human timescales (atomic and subatomic events).

Mathematicians and scientists use very large and small numbers to describe physical quantities, and have created even larger and smaller numbers for theoretical purposes.

Common sense and human scale

"Common sense" ideas tend to relate to events within human experience, and thus commenurate with these scales. There is thus no commonsense intuition of, for example, interstellar distances or speeds approaching the speed of light.

Weights and measures tend to reflect human scale, and many older systems of measurement featured units based directly on the dimensions of the body. The metric system, which is based on other more reproducible physical quantities, still attempts to keep its base units within the range of human experience. Other systems, such as Planck units are useful for theoretical purposes, but are not useful for everyday purposes.

References:

George A. Miller: The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information

Quotes:

"Man is the measure of all things, of things that are, that they are; and of things that are not, that they are not". -- Protagoras