The atomic clock was developed in the 1950’s and represented a huge step forward in chronology. Before the atomic clock, electronic oscillators, as used in most digital clocks and watches, were providing the best accuracy although these would drift several seconds a month.
The atomic clock used the resonance of the atom caesium -133 which had an exact oscillation of 9,192,631,770 times a second. Because of this exact oscillation atomic clocks soon offered nearnano-second accuracy in that it would take several million years before they would drift by a second.
Atomic clocks were deemed so accurate that the International System of Units (SI) defined the second as this number of oscillations of the caesium atom.
As time-telling became so accurate it was soon discovered that the rotation of the Earth was not as precise as the clocks and that to keep atomic time relevant to Greenwich Meantime (GMT) and to stop night from slowly drifting into day a new timescale was developed calledUTC (Coordinated Universal Time) which accounted for the slowing of the Earth’s spin by adding ‘Leap Seconds’.
UTC is now globally used and allows the entire world to synchronise to the same timescale. This is particularly relevant for computer networks that often have to communicate with other networks across the globe.
UTC can be received by using a time server that can either synchronise to a timing reference across the Internet or for better accuracy an d security a time server can receiveUTC time from the GPS network via a GPS antenna or by receiving national timing broadcasts, transmitted form several countries.
By using a time server that receives UTC time a computer network can be accurate to within a few milliseconds of UTC allowing cross-global communication.