The clock is one of the most important devices of all civilization. It is simply a gadget that we use to tell the exact time of day. Its name was borrowed from a Greek term that meant the ringing of a bell. Now since clocks would make some sort of sound after every hour, it was dubbed with this name.
We are living in a civilized time that has put such a heavy importance on time. Everything is dependent on it. That is how important therefore that the clock is. Due to this importance there are clocks all around us. In a developed area you can not walk for five minutes before you see a clock somewhere.
The clocks we have in our society today all have a common ancestor. Their common ancestor is the sun dial. It would cast the sun's shadow around its fixed center to show us the time. The sun dial had a huge disadvantage that today's clocks do not have. It only worked during the day.
The water clock came soon after the sun dial. As a matter of fact it is not known exactly when both these clocks were first invented. Let us just say that it was a long time ago. The sun dial was used to set the water clock which would then tell fairly accurate time. Yes, even through the night.
The pendulum clock brought a fresh sense of accurate timing in the world of clocks. It would rarely lose time like the water clock. It therefore became a huge success. I am sure we have all at one time or the other seen one. Many of us just know it as the grandfather clock.
The next evolution in clocks came with the electrical era. The clocks would have electric motors wound electromagnetically that would run for days. There are many forms of electrical clocks still in use today. One does not have to worry about winding them every six hours.
With the introduction of electricity into the world of clock manufacture, came even further advances. There was the invention of the batteries. The two together led the inventors to digital clocks. These were clocks that did not need mechanically moving components. They are now the most common clocks in the outdoors of most urban places.
The alarm clock is another important development of the simple clock. You set the time that you want to wake up and it will go off at that time. There are very old models that were highly mechanical but today we have even digital ones that will wake you up to your favorite tune.
We may categorize the alarm clock with the auditory clock. A lot of people call the auditory clock the talking clock. You just press a button and it says the time out loud for you. This is very good for example when you are sleep and do not want to get up and switch on the lights.
This last one is not literally a clock. It is symbolically a clock. It is called the doomsday clock. It counts the threats to human existence in the number of minutes before the clock strikes twelve. These threats are for example the nuclear weapons we build. There will be total human annihilation when the doomsday clock strikes midnight.