The rotation of the Earth on its axis causes the alternation of day and night. The Earth also revolves around the sun. As a result of both these movements, the Earth does not get continuous light from the sun. This means when countries such as India faces the sun and has a bright day, the areas on the other side of the globe, such as the united States, are immersed in complete darkness. Sunshine duration per day depends on the season, i.e.. the distance between the Earth and the sun



HOW FAST DOES THE EARTH ROTATE ? 

one rotation of the Earth takes one day. If at 12 noon the sun is at the highest point in the sky, then after 24 hours it will come back again to the same position. It was the Babylonians who first divided the day into 24. hours. They could have counted the hours from 1 to 10. then to 20, and so on, but instead they calculated from 1 to 60, then to 120, and so on. For this reason. time is divided into parts of 60 (1 hour has 60 minutes, 1 minute has 60 seconds) or in parts of 6 (one day has 24 hours. i.e.. 4 X 6 hours).




WHAT IS THE TIME IN JAPAN, WHEN IT IS 12 NOON IN INDIA ?


when it is 12 noon in India. it is 3:30 pm in Japan. since the Earth rotates on its axis once every 24 hours during which time all parts of the Earth face the sun one by one; i.e.. the time is 12 noon at all places turn by turn. Such a ‘time shift takes place between many countries. Between India and Japan it is 3 hours and 30 minutes. between India and Malaysia 2 hours and 30 minutes. with the help of 'time-zone maps we can find out the time in other countries. From these maps, we can read the time between places far apart. This is a good help, for instance, if you want to say happy birthday to your friend staying in San Francisco, but do not want to disturb him in his sleep because there it is eleven o'clock in the night. although it is 11:30 am where you reside.


WHY ARE DAYS LONGER IN SUMMER THAN IN WINTER ?


The axis of rotation of the Earth is titled and this can be seen clearly in a globe. Around June 21, the axis points clearly towards the sun . As a result,  a large part of  northern hemisphere is illuminated by a strong sun and daytime remains long till the rotation of the Earth causes this area to move away from the direct glare of sunlight. The place, thus, has long hours of sunlight and the days are long. In fact, the sun shines over the north pole continuously for several weeks without setting even once. This period is known as the ‘polar day’. During Christmas, the axis of the Earth points away from the sun. During these days, the northern hemisphere remains dark for a longer period of time and a 'polar night' sets in at the north pole. on the other hand. the southern hemisphere enjoys long hours of sun.