Classwork Series and Exercises {Physics- SS1}: Concepts of Time

Concepts of Time

Time itself can be defined as that in which developments and happenings can be distinguishably analyzed with reference to before and after.

In the International System of Units (SI), the unit of time is the second (symbol is S). The most natural time unit is the solar day which is manifested by the passing of day and night. It takes the earth one solar day to complete one revolution about it axis. There is also a different time scale known as sidereal used for astronomical purpose, this is the time interval between two successive passages of a star over the meridian. The essential mechanism of the devices used for marking the passage of time are masses so mounted or suspended that when set in motion under the influence of forces they repeat with great regularity fixed cycles of their motion. The pendulum of a clock and the balance wheel of a watch are two of such mechanisms.

The Modern Time

Today we measure and indicate time with clocks. In the laboratory time is measured with a stop-clock or a stop-watch and both can be started and stopped with the use of a knob which can be pressed and pushed, the stop-watch enables us to accurately measure small intervals of time to 0.1 seconds.

For instance 60 seconds = 1 minutes, 60 miniutes = 1 hour,  24 hours = 1 day

The Old Time

Prehistoric man, by simple observation of the stars, changes in the seasons, day and night began to come up with very primitive methods of measuring time. This was necessary for planning nomadic activity, farming, sacred feasts, etc..

The earliest time measurement devices before clocks and watches were the sundial, hourglass and water clock.

The forerunners to the sundial were poles and sticks as well as larger objects such as pyramids and other tall structures. Later the more formal sundial was invented. It is generally a round disk marked with the hours like a clock. It has an upright structure that casts a shadow on the disk – this is how time is measured with the sundial.

The hourglass was also used in ancient times. It was made up of two rounded glass bulbs connected by a narrow neck of glass between them. When the hourglass is turned upside down, a measured amount of sand particles stream through from the top to bottom bulb of glass. Today’s egg timers are modern versions of the hourglass.

Another ancient time measurer was the water clock or clepsydra. It was an evenly marked container with a spout in which water dripped out. As the water dripped out of the container one could note by the water level against the markings what time it was.

One of the earliest clocks was invented by Pope Sylvester II in the 990s. Later on chimes or bells were added as well as dials to the clocks.

Early clocks were powered by falling weights and springs. Later clocks with pendulums came into existence in 1657.

Electric clocks came into being after 1850, but were not popular until the twentieth century. An electric motor with alternating current powers these clocks. Later digital clocks with LCD (liquid crystal displays) rivaled the electric clocks. Quartz clocks use the vibrations of a quartz crystal to power the clock.

Watches are different than clocks in that they are carried about or worn. The first watches appeared by the 1500s and were made by hand. They were very fancy and their faces were covered by fine metal strips to protect the markings. Watches were manufactured by machine in the mid 1800s.

At first watches had knobs on the outside that the wearer wound to keep the mainspring powered inside. Later on, self-winding watches derived power from the movement of the wearer. With the advent of quartz crystal watches with digital displays, the need for motors for watches has decreased.

Today’s clocks and watches are increasingly digital devices, often set via satellite guidance, the reason we now have the Greenwich meridian time (GMT), central european time (CET) etc, such that around the world countries operate on different time zones, e.g. in USA there are different states with time differences of hours, same applies to continent to continent and country to country.

EXERCISES

Lets see how much you’ve learnt, attach the following answers to the comment below

1. An ancient method of measuring time that made use of shadows formed by the sun was a A. water clock B. hourglass C. sundial
2. A device consisting of several glass bulbs connected by a narrow glass neck with grains of sand that flowed from one bulb to the other is a A. water clock B. hourglass C. sundial
3. A container that had liquid pour into it slowly marked at regular intervals that denoted the time was a A. water clock B. hourglass C. sundial
4. The earliest clocks were powered by A. electricity B. quartz crystals C. Falling weights and springs
5. Watches that show numbers with the exact time rather than with hands and numbers are A. digital B. standard C. timex

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