What is the Accurate TimeWhat's the exact time?
This new watch is a variation of the nuclear watches that were published in the fifties. As a rule, the atomic clocks function by determining the frequencies with which atom resonate. Thus, for example, the external electron of a caesium-133 is oscillating between two energetic states exactly 9,192,631,770 x per second and emits a microwave with exactly this number.
Since 1967 this feature has been used to determine what we mean by 1 second - it is formally the time it would take a ceasium cell to vibrate 9,192,631,770 time. This could be attributed to an exactness of 1 part in 1010 by the first nuclear watches. Today's cesium watches can accurately clock the time with an precision of 1 in 1015 or 1 second in about 30 million years.
So, what ticking quicker than a case of cesium? Among the studied metals are jtterbium, quicksilver and strontium, which resonate 429,228,004,229,952 x per second. However, so far it has been virtually unthinkable to develop a useful nuclear Strontium watch. Basically, there are two possibilities to make a chronometer: to use the vibrations of a singular nucleus or to do the same with many nucleus simultaneously.
One of the advantages of using a singular nucleus is that it is relatively simple to screen it from outside electro-magnetic waves that disturb its vibrational wave. However, the drawback is that it is incredibly hard to precisely detect a singular nucleus that vibrates at such a high rate. Polyatomic clocks produce a much brighter sound, but are less accurate because the electro-magnetic field of the nuclei interferes with each other.
As a result, a range of sources of energy is created, each of which carries a strontium nucleus, much like any well in an eggs container contains an egg (see diagram). In this way, the electro-magnetic field of single atomic particles is prevented from disturbing their neighbors, and the vibration signal of many atomic particles can be detected at once.
Experiments so far to produce watches in this way have been unsuccessful because the laser traps themselves interfere with the vibrational frequence of the atom. Katori's group has bypassed this by adjusting the laser intensities so that they change the higher and lower transitional energies of the strontium by exactly the same amount so that the vibrational frequencies remain unchanged.
The Katori claim that this "optical grating clock" will keep time with an exactness of 1 part in 1018.