Q1.
How was time measured when there were no clocks and watches?
Answer
By watching things that repeat themselves after definite intervals of time. People noticed the rising and setting of the Sun, the phases of the Moon and the changing seasons, and used these cycles for timekeeping. First they made calendars, in which a day was defined by one cycle of sunrise and sunset. Then they built devices to measure the smaller intervals within a day.
| Device | What repeats or flows in it | How time was read |
|---|---|---|
| Sundial (Fig. 8.1) | The Sun's daily journey across the sky | From the changing position of the shadow of an object cast by sunlight |
| Water clock, out-flow type (Fig. 8.2a) | Water flowing out of a marked vessel | From the falling water level against the markings for time |
| Water clock, floating-bowl type (Fig. 8.2b) | Water entering a bowl through a fine hole at its bottom | The bowl filled up in a fixed time and sank; it was lifted and floated again |
| Hourglass (Fig. 8.3) | Sand flowing from one bulb to another | From how much sand had run down |
| Candle clock (Fig. 8.4) | A candle burning down steadily | From the markings on the candle that the flame had reached |
Why it happens: every one of these devices — and every clock made since — needs one thing: a process that repeats itself, or goes on at a steady rate. Once you have that, you can cut time into equal pieces and count them.
Did you know? In ancient India the sinking-bowl water clock was called the Ghatika-yantra. Its hole was made so that the bowl took exactly 24 minutes to fill and sink. Since 24 h = 1440 min and 1440 ÷ 24 = 60, the day was divided into 60 equal ghatis. Each time the bowl sank, drums, conch shells or a gong announced it.