The experimental atomic clock of the National Institute for Standards and Technology (NIST) has reached three new records. These clocks are not only important to improve timing and navigation, but also apply to detailed gravitational field measurements, gravity wave detection and Dark Matter experiments.
The clock consists of thousands of yterbium atoms trapped in optical grids made of laser beams. Atoms vibrate, switch between two power levels. Such hours are extremely accurate, with 1 second being more than 300 million years old. Most improvements in the last iteration are due to the new heat shield developed by Andrew Ludlow a few years ago. It protects the yterbium atoms from the effects of heat and electric fields that can disrupt their natural oscillations.
With this oscillation frequency yterbium clocks can recognize shifts in the gravitational field of our planet with unprecedented accuracy. Three new records relate to the degree of statistical errors, measurement stability and repeatability. The first record relates to how accurately the clock is accompanied by spontaneous atomic vibrations. NIST researchers say their hours will make 1.4 out of 10 mistakes18 a trillion.
The second record concerns measurement stability, that is to say how "tapping" of clocks change over time. Atomic NIST clocks have shown exceptional stability. The third record concerned the repeatability of the measurement, that is, how the two hours are kept at the same rhythm. According to scientists, the ticking frequency of both hours varied in 10 measurements with less than one billionth.
According to Einstein's general theory of relativity, the movement of time varies depending on whether you are in the gravitational field. The clock at the top of a very high hill, far from the middle of the earth, goes a little faster than at the foot of the same hill. It is not a mechanical error, time flows really faster on the top of the mountain.
However, most hours are not accurate enough to record this extremely soft difference. With a height difference of 1000 meters, it is 31 millionths of a second in 10 years. The new clock, however, can reveal the changes in 1 centimeter of cant, Ludlow said. So he uses these oversensitive clocks even in attempts to find dark matter, a mysterious material that is supposed to be in the universe five times the normal mass.
Scientists are also experimenting with the use of clocks to look for the same types of gravitational waves that were first observed in the LIGO Observatory, confirming an important aspect of Einstein's theory. Despite the incredible accuracy of the new hours, it has not yet reached the limits of its potential and has several ideas that can lead to a significant improvement.
source: nist.gov, Techxplore.com.