Human scale is the set of physical qualities, and quantities of information, characterizing the human body, its motor, sensory, or mental capabilities, and human social institutions.
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.
Human scale measurements, however, are more in the order of:
Humans interact with their environments based on their physical dimensions, capabilities and limits. The field of anthropometrics (human measurement) has unanswered questions, but it's still true that human physical characteristics are fairly predictable and objectively measurable. Buildings scaled to human physical capabilities have steps, doorways, railings, work surfaces, seating, shelves, fixtures, walking distances, and other features that fit well to the average person.
Humans also interact with their environments based on their sensory capabilities. The fields of human perception systems, like perceptual psychology and cognitive psychology, are not exact sciences, because human information processing is not a purely physical act, and because perception is affected by cultural factors, personal preferences, experiences, and expectations. So human scale in architecture can also describe buildings with sightlines, acoustic properties, task lighting, ambient lighting, and spatial grammar that fit well with human senses. However, one important caveat is that human perceptions are always going to be less predictable and less measurable than physical dimensions.
Human scale in architecture is deliberately violated:
"Common sense" ideas tend to relate to events within human experience, and thus commensurate 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, such as the foot and the cubit. The metric system, which is based on precisely reproducible and measurable physical quantities such as the speed of light, still attempts to keep its base units within the range of human experience. Systems of natural units (such as Planck units) are useful in theoretical physics, but are not suitable for everyday purposes; because the SI units are defined in terms of constants of nature they can be thought of as natural units rescaled to human proportions.