The previous example illustrates the utility of the Google calculator in unit checking, a task that otherwise is only adequately described by the word tedium. Although SI units have solid footing as a scientific standard, it is sometimes useful to employ others, or variants of SI units. This is not only because many classic texts and some individual fields in physics employ units other than SI, but mainly because these are not necessarily the units in which we understand the world. In the United States, a comfortable room is one that is cooled to around 70°F, not 21.1°C or 294.3 K.