Though we generally call them hourglasses, because an hour was their standard setting, they could be made to measure almost any period of time, by changing the amount of sand or the size of the hole. Hourglasses measured time quite accurately. When we flip the glass, the sand falls though its narrow central hole, in a fixed period of time. Fancy sand glasses like this one were used to mark the passage of minutes and hours. Time can also be measured accurately by letting sand trickle through the narrow opening of a sand or hourglass. We can still buy sundials that will tell the right time, to the minute if we position them correctly - on a flat surface, aligned with the axis of the Earth. It only works in sunlight, as the shadow of the sun moves around a circular surface, marked off in equal intervals. The sundial was one of the earliest devices for measuring the time of day. A month is one-twelfth the time it takes the Earth to complete an orbit about the sun. A year is the time it takes the Earth to travel around the sun. Longer intervals are measured on a calendar. ĭays, Hours, Minutes and Seconds are the time intervals we measure on a clock. Ī day is the time it takes the Earth to rotate once on its axis. The basic units of time measurement are necessarily determined by natural events. Later, once we transfered the approach to the 12 hour clock, and we needed intervals smaller than an hour which was 30 degrees, it was divided into 60 minutes each of which was divided into 60 seconds.

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Each degree was then divided into 60 minutes. Our first chronometers ( instruments to measure time) were designed to measure the apparent movement of the Sun, Moon, Planets and Stars in the sky.Īll this began when the Ancient Babylonians noticed the circular path of the sun in the day sky and divided it into 360 degrees. We needed to know when it would be day or night, winter or summer, when to plant, when to harvest, when to stock up on food to eat during the cold season - and like all our early measuring systems, we used natural objects and events to measure time. Ever since time began, humans have measured it.

Convert clock time to bell system