Students are personally familiar with and can easily visualize:

Time periods in seconds, minutes, hours, days, and years (decades to centuries)

Horizontal distances ranging from a few fractions of an inch to feet, yards, and a few miles.

Vertical distances ranging from inches to a few tens of feet.

Volumes ranging from a few cups to quarts and gallons.

Rates from a few miles per hour up to about 70 miles per hour.

Discharges ranging from a few cups per second to a few gallons per minute (pumping gas, filling a glass or tub).

Densities ranging from less than one to about 2.7 g/cm^{3} (less than water to average rocks).

Students have difficulty visualizing (but commonly encounter in geoscience courses):

Time periods that are very short (fractions of a second) or very long (millions to billions of years).

Horizontal distances that are very small (fractions of a millimeter or smaller) or longer than a few 10s of kms (up to light years); and this is apart from the English-metric conversion issue!!

Vertical distances that are more than a few tens of feet (hundreds of meters to tens or hundreds of kilometers)

Volumes that are either very small (atomic) or larger than a bathtub (km^{3})

Rates that are very slow (e.g., 10^{-14}/sec or 50 km/million years) or very fast (e.g., 7 km/sec)

Discharges that are large (e.g., 45,000 m^{3}/sec)

Densities that are large (e.g., 5 g/cm^{3}; 19 gm/cm^{3})