Early Measurements and Units of Measurement, and How we Obtained the Systems we use To-day

Abstract

Physics is a science of observation. A proper appre-ciation of our observations requires the making of measurements; so that physics teaches us not onlv the habit of obserdng, but also of making definite quantitative observations. From the earliest periods of man, the observer, comparisons have been made between natural objects. At first these comparisons were merely qualitative-big people aud little people, animals that you slung over your prehistoric shoulders and scarcely noticed, and animals that were so heavy that you staggered and eventually devised other means of carrying. There were periods of "light-time" and periods of "dark-time." Early units of length measurement, such as we still see amongst uncivilised peoples, included the combined ideas of length and time-for instance, "as far as one could travel whilst it was light," or a "day's journey." We have come back to one such a combined unit for length today - the "light-year'' is a distance, the distance light will travel during the period of one year, and we employ it in astrophysics anrl astronomy.