More precise clock

2001/07/13 Roa Zubia, Guillermo - Elhuyar Zientzia

• Fisika

Scott Diddams and his team, physicists at the National Institute of Standards and Technology (NIST), have crafted the most accurate watch ever made. The exact measure of time will allow them to perform very accurate measurements of the constants of the universe.

A clock needs a rhythm generator that gives it cadence. The more uniform this rhythm is, the more accurate the clock will be. For example, at one time that rhythm was achieved through pendulums. XX. In the twentieth century, new rhythmic generators were invented. One of the most prestigious uses the vibrations of a quartz crystal, with which very precise wrist watches are made.

Physicists began to use as a rhythm generator the vibrations of atoms in 1951; any mechanical pendulum based vibrator and any crystal are more accurate. Therefore, the atomic clocks used in recent years have been based on the excitation of cesium atoms by microwave. These watches present an error of approximately a second for 30 million years. Even though these watches are sufficient in the life of anyone, it should be more accurate to measure certain constants of the universe.

For this reason, scientists have developed a new type of atomic clock. The cession has been replaced by mercury atoms and microwave by visible radiation. The oscillation of mercury with visible light is more frequent, so it gives more precision to the computation of time than to the cessions.

The slower the atoms move, the less interferences occur between their movement and their vibration. For this reason, the researchers have managed to cool the mercury atoms and excite a single specimen. The fast signals generated by the activity of the mercury are converted by the laser into a slower microwave signal and, like the cesium clocks, a precise reading is performed to launch the clock. The researchers are satisfied in addition to the stability of this watch.