Posted by Richard N Williams on June 16th, 2009
From satellite navigation to the NTP time server, atomic clocks are used the world over.
We are all used to our watches and clocks running a minute or two fast or slow. However, the odd minute doesn’t affect our lives too much and we can get by. However, for some technologies and applications a far greater level of accuracy is needed. Atomic clocks are the most precise time keeping devices on earth. They were invented over fifty years ago when it was discovered that the oscillations of certain atoms at particular energy levels never altered and vibrated at such a high frequency (over 9 trillion times each second for caesium).
Modern atomic clocks are so accurate they will not lose as much as a second in 100 million years but who on earth would need such accuracy? Atomic clocks provide the basis for many modern applications and technologies and have also helped in our understanding of the physical universe.
Atomic clocks form the basis of the GPS satellite navigation system that we use in our cars. The signals from the atomic clocks onboard the satellites are what is used to triangulate accurate positioning. It ca only be done because of the highly precise nature of the time signals. A one second inaccuracy of a GPS clock could see positing information out by 100,000 km as light can travel this far in that time.
Atomic clocks have also been used as a method of testing theories by Einstein and others. Using atomic clocks we can accurately measure gravity and the way it affects time. Modern clocks are so accurate that scientists can even measure the difference in gravity (and therefore time) at each subsequent inch above the earth’s surface. They can also be used to measure slow moving processes like continental drift or the slight changes of the earth’s rotation.
Other applications where accuracy is essential also rely on atomic clocks such as air traffic control where the precise nature enables safe monitoring of air traffic. Road traffic systems like traffic lights are increasingly using time servers hooked up to atomic clocks to ensure perfect synchonization. Even internet the internet relies on atomic clocks, particularly when it is used for time sensitive transactions such as banking, trading in stocks and shares and even online seat reservation. Without accuracy in time then applications like this wouldn’t be possible as too errors could occur such as double booked seats, shares sold before they were bought.
Computer networks synchronize to atomic clocks by using network time servers. Often these devices use the protocol NTP and receive the atomic clock time from either the GPS system or a radio transmission. NTP time servers monitor and adjust all clocks on devices on a computer network to match the atomic clock time.