“What Time Is It?”
By “Awake!” correspondent in the Federal Republic of Germany
“WHAT time is it?” “Exactly 8:30,” was the reply. “Thank you, I have to catch a train, and my watch stopped.”
Today such precise time consciousness is taken for granted. During much of man’s history, however, concern about seconds, minutes and even hours was unknown. Eventually, though, efforts were made to measure short periods of time.
Doubtless the earliest time measuring device made by man was the sundial. Its basic disadvantage is well expressed in the proverb: “Do like the sundial. Count only the sunny days.” For greater dependability, a timepiece was needed that could function without the benefit of fair weather. The water clock, later called a clepsydra, filled this need. As water flowed from a vessel through a small opening into a cylinder, the gradually rising water level in the cylinder furnished the basis for reading time.
The sand clock or hourglass worked according to the same principle. It is still used occasionally as a timer for boiling eggs. Then, there was the oil clock. The oil served as fuel for a lamp, and time could be measured by how much oil was used up.
Both sand and oil clocks had their limitations. For one thing, they did not function properly when moved about. As time passed, men began to recognize that there was a need for a portable clock that would continue to measure time. This was first possible with the discovery of the wheel clock, the next step in the development of measuring time.
The Wheelwork Clock
Large wheelwork clocks are mentioned in Dante’s Divine Comedy, written in the 13th century. These clocks were used extensively in the 14th century. The first portable clocks can be traced back to the mechanic Peter Henlein of Nuremberg, Germany. Around the year 1500, he developed the first pocket watch. It ran for 40 hours and struck every hour.
Since then many improvements have been made. Dependability and accuracy have been perfected, weight has been lessened and mass production has been introduced. As a result, the clock has come into universal use.
But just how accurate can a wheelwork clock be? Shocks, temperature changes, positional errors and those of isochronism affect the accuracy. What is considered to be a very accurate wheelwork clock is one that varies no more than 0.6 of a second per day with a temperature change of one degree Celsius.
More Precise Timepieces
However, today’s high degree of mechanization, automation and scientific research demand a more precise time measuring device. The first real breakthrough in this field was the development of the quartz-crystal clock. It was introduced to the world in 1934. The quartz-crystal clock surpassed the accuracy of the precision pendulum clock, being about 10 times as accurate.
How does it work? While there are various systems, the basics are always the same. The vibrations of a quartz crystal determine the frequency of an alternating current. This current can be amplified and reduced by a frequency divider and, by means of mechanical gearing, can be applied to a clock dial. Let us say, for example, that a quartz crystal has a vibration frequency of one megahertz (one million cycles per second). This would mean that it vibrates one million times per second. It is possible to make these electrical vibrations of a quartz crystal visible on an oscillograph.
Doubtless you have seen the mechanism of a clock or a watch and may have noted that the rapid movement of the balance wheel is converted to the slower movement of the second hand. This reduction is accomplished mechanically. In a quartz clock, however, it is achieved electrically. The frequency is divided progressively until it can drive a synchronous or step motor that is connected to mechanical gearing and is applied to a clock dial, or until it can show time by means of an electrical digital display. In this way, it would theoretically be possible to keep error down to 0.0001 second per day—an error of only one second every 10 years. However, quartz begins to vibrate more rapidly as it gets older, thus affecting the accuracy of the quartz-crystal clock.
Hence, for certain scientific research, a more precise time measuring device is essential. The atomic clock fills this role. Such a clock measures the frequency of light that is either given off or absorbed by molecules or atoms. There are atomic clocks that are expected to vary only one second in 1,000 years, or even one second in 100,000 years.
But let us pause for a moment. If not working in a laboratory or some scientific institute, would a person be concerned with one millionth of a second? Often when on a vacation or doing enjoyable work, people tend to forget about time. Also, who would want to know what time it is when viewing a spectacular sunset? Hence, depending on circumstances, the question, “What time is it?” may be either appropriate or out of place.