4.5 How Small is “Small Enough”?
There is no rule to tell you how small is "small enough" - you must use your
own judgment. Pay attention to units if there is a context. For example, if
“1” represents one light-year but you are measuring the change in a metal
rod’s length as it expands, then what looks like a small number actually
could represent a large length relative to the rod’s expansion.