Can you imagine that in the future, instead of stepping on the scale, you might look at your watch when you want to weigh yourself? As strange as it may seem, this is theoretically predicted by the laws of quantum mechanics. A team of physicists has thought of exploiting this in practice to create a new type of atomic clock.
The new watch measures time based on a person's mass, and its creators claim that, although it is not currently the most accurate available, it is certainly the most "fundamental" while having an additional virtue - it can help redefine the kilogram.
New type of periodicity
For millennia, humanity has measured time based on some regular periodic movement – such as that of the sun or the pendulum. Atomic clocks, the most accurate timekeepers we have, are based on the transitions of electrons in a cesium atom from one energy level to another: one second of “atomic” time as we know it today is equivalent to about 9,000 such transitions.
Physicists at the University of California, Berkeley, thought of using a different periodicity of the atom as a basis, the so-called Compton frequency. Quantum mechanics predicts that every particle is simultaneously a wave and, as such, has a frequency. This frequency is called the Compton frequency and is completely dependent on its mass.
The main problem in moving from theory to practice is that the Compton frequency of an atom is incomprehensible to human data, being 100 billion times faster than the frequency of visible light. “It is so high that it is far beyond any way of measuring it,” explained Holger Müller, the team leader, speaking to New Scientist.
The twin paradox
To overcome this obstacle, scientists thought of using one of the most popular paradoxes arising from Einstein, the so-called twin paradox. According to it, if one of two twin brothers gets into a spaceship and flies for a while at high speed into space, when he returns to Earth he will have aged less than his brother who remained on the planet.
Mr. Muller and his team took this paradox to the atomic level using a cesium atom and an atomic interferometer. As they describe in their study, published in the journal Science, they split the atomic wave in two, briefly held one of the resulting “twins” stationary while the other continued to move, and then rejoined them into a single wave. In this way, they calculated the Compton frequency indirectly, by measuring the difference in frequencies (about 100,000 Hertz).
The new atomic clock is the most "fundamental" yet built because it uses the behavior of a single particle as a basis for measuring time. However, it is not the most accurate there is. It loses one second every eight years, while the most accurate atomic clock is estimated to lose 4 seconds if it "beats" from the moment of the Big Bang.
However, it has an advantage that none of the atomic clocks known to date possess: because its frequency depends on the mass of an individual, it can be used as a standard for determining the kilogram, solving the problem that metrologists currently face due to the changes that time brings to the gold bar, which currently serves as the "measure" for the global determination of our basic unit of weight.
