The science writer Robert P. Crease suggests that there are three crucial properties that units of measurement must possess: accessibility, proportionality, and consistency.35 Accessibility is needed because you can’t measure something if you can’t find your measuring standard. Proportionality is necessary because no one wants to measure mountains with matchsticks. And consistency is perhaps the most important attribute, as a unit of measurement that varies unexpectedly simply can’t do its job (though one that flexes with intention can be useful).
