10
the mystery of Time
Why is not the time the same in every country ?
It is so confusable to see that your favorite movie will be shown at 9:00 p.m. GMT, and you start turning on the T.V at 8:55 p.m. and there is no movie. Here you remember that there is time difference between every country; this 9:00 p.m. at Greenwich could be 8:00 p.m. at your country, consequently you start yelling “ Why there is that stupid time difference ?!”
In fact, this time difference is a basic rule in nature that came up due to the earth’s rotation around its axis. When earth in one position, the sun rays reach on half of the earth leaving the other half in darkness. So, it is day at the first half and night at the other one. When earth rotates half a period the roles exchange. It is dark at the first half and day at the second one. The earth’s rotation causes variant sun light distribution in different parts of the earth, and so different times.
Scientists divided the whole earth into 360 imaginary longitudes, starting from line (0) Greenwich. The time between every two longitudes is 4 minutes. If to the right of Greenwich the 4 minutes adds to the Greenwich time, and vice versa.
A second isn't what you think it is. Scientifically, it's not defined as 1/60th of a minute, but as "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom".