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2013/01/25 Roa Zubia, Guillermo - Elhuyar Zientzia Iturria: Elhuyar aldizkaria

• Teknologia
• Fisika

We currently use cesium atoms to define how much a second is. It is a very precise method, but based on a stimulus that affects the atom; in the journal Science, a group of physicists of the University of California has explained that the same can be done by maintaining the atom and measuring its quantum characteristics, but for this it is necessary to use heavy atoms, so the cession is still a good option.

The measurement is not at all simple, since cesium atoms must be dropped between the two lasers emitted in the opposite direction, which are also of different frequency. This combination, which falls the cesium atom and the two lasers, causes a change in space time, as Einstein's theory of relativity explains. The variation is very small, but is measurable in the larger atoms and allows to accurately calculate the frequency of the cesium wave function. Finally, the measure is limited by the mass of the cesium atom, there are no other variables.

Complex, but simpler than it should be measured in the current atomic clocks, where the atoms of cesium are excited with a laser and the atoms of cesium jump from one quantum state to another without stopping, to a certain frequency: Compton frequency. From there, the second is measured by counting a certain number of vibrations between states. And that is the technological difficulty, measuring the number of vibrations. Finally, the new method is a simpler way to measure the second.

In addition, the method has to do with the mass of atoms, so it can allow to define the kilogram. Currently, the kilogram is defined by an object: a platinum and iridium cylinder. In this way, the definition can become something theoretical.