Wednesday, September 16, 2009
We all think we know what time is because we refer to it on a daily basis. Without a clock we could not synchronize our comings and goings. For sure, we use watches or clocks to help us start work on time, or we use them for prearranged meetings, and without synchronized timepieces we could not be certain of success. I’m a frequent clock-watcher, forever looking at my wristwatch. I never like to be late for an appointment, and I even regulate the time when get out of bed and when I return by checking my watch. Without a means of accurately knowing local time I would have to refer to ‘nature’s clock’, i.e., the sun, and as the sun rises and sets at different times throughout the year, I could not accurately rely upon it.
In antiquity sundials* were used to tell the time. Even as far back as 5,100 years ago astronomers may have constructed Stonehenge as a precise timepiece recording the time of sunrise on the morning of the summer solstice. The regular periodic motion of the earth and moon in relation to the sun and other planets give a sense of time in terms of seasons, movements of the tides etc. A complete circuit of the sun by the earth takes on average just over 365 days, while each day consists of 24 hours. The number of days the earth takes to revolve around the sun is determined by the laws of the Universe, whereas the unit of time known as an hour is an abstract division of a period of time devised by man; so is the division of the hour into 60 minutes and minutes into 60 seconds. Without the invention of a mechanical timepiece there would be no accurate way of recording periods of time; hence the invention of the hourglass.
The very first mechanical clock was devised by Taqi al-Din at the Istanbul observatory of al-Dan in about 1580 and it was capable of measuring intervals of hours, minutes and seconds, but it wasn’t until the 17th century in Europe that a clock capable of recording intervals of seconds was built in Switzerland. The use of pendulums was the breakthrough needed for accurately measuring seconds. In more recent times the invention of very accurate atomic clocks has facilitated the establishment of an internationally agreed time. The atomic clock can maintain a continuous stable time scale, known as International Atomic Time (TAI), but for civil use, Coordinated Universal Time (UTC) is the preferred system which incorporates ‘leap seconds’ based on actual rotations of the earth in relation to the ‘mean sun’.
Despite knowing how to record intervals of time, we cannot agree how to define time, because much depends on our understanding of it from our viewpoint. Do we interpret time mathematically, philosophically, in terms of astronomical age of the stars and planets or light years etc.? Is time continuous without end, embracing the past, present and future? Do we visualize it as string-like in nature, separate or joined units, spiral or wavelike? Do we comprehend it as a dimension or a spatial volume or a mass? Do we believe it’s a warped variable incapable of being measured?
Well, my internal time clock tells me it’s time to go to bed; my eyelids are drooping and I’m falling asleep. Goodnight!
*2 Kings 20:11 (The sundial of Ahaz, about 680 BC)