## Students' Frame of Reference

### 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})