ABSTRACT
The terminology or jargon of an area of science reflects its models in a shorthand form, and we cannot get any real understanding of a model without acquiring familiarity with its language. Although at first it might appear awkward and unnecessary, the jargon is an integral part of any model and we cannot avoid it completely: ‘to name is to know’. From a human perspective there are tremendous ranges in the sizes of quantities to comprehend. Time is an important dimension in materials and processes. Significant times in the study of matter range from thousands of millions of years down to less than a millionth of a nanosecond. The overall properties of gases (unlike those of condensed matter, solids and liquids) are largely independent of the natures of the constituent molecules or atoms and determined by the mean free path. The value of such a ‘typical’ quantity is therefore very important in our understanding of matter and its interactions.
