A few atomic hours set "unprecedented" performance records for stability and accuracy, new research said.
Scientists say record-breaking results could help improve timing and navigation.
Physicists from the National Institute of Standardization and Technology (NIST) in the US have said that these two hours will also help in exploring gravity, early universe, and even dark matter.
Experimental devices each capture thousands of atoms of the ytterbium chemical element in laser beam grids.
Inside these optical grilles, atoms are said to "tick" with vibrations between two levels of energy.
In a research that was published in Nature, NIST physicists compared two independent hours and achieved record-breaking performance in areas of systemic uncertainty, stability and reproducibility.
System uncertainty measures how well the clock represents natural vibrations or frequency of atoms.
Scientists have found that each time corresponds to a natural frequency within the error rate of just one billionth billion.
Hourly stability, which varied over the course of one day, was also recorded at a slight level.
The reproducibility of the results, proportional to the same frequency with two hours, again showed a difference of less than one billionth of a billion.
"System uncertainty, stability and reproducibility can be considered a" royal flash "of performance for these hours," said project manager Andrew Ludlow.
"The agreement of these two hours at this unprecedented level, which we call reproducibility, is probably one of the most important results, because it basically requires and justifies two more results."
Mr. Ludlow stated that the overall error of the clock had fallen below the ability of scientists to estimate the influence of gravity on time.
"We assume that hours similar to those used throughout the world or in the world, their relative performance will be limited for the first time by the gravitational effects of the Earth," he said.
According to Albert Einstein's theory of theory of relativity theory, time flows more slowly in places with greater gravity.
The NIST degradation timer is therefore able to help accurate mapping of space-time gravity distortion, researchers say.
They also say it will help with the detection of early space signals, such as the mysterious dark matter.
Ytterbium clocks could also improve the ability to measure Earth's shape based on sea-level surveys.
Devices located on different continents could solve the geodesic measurement for one centimeter.
Atom ytterbium is among the potential candidates for the future redefinition of the second, international time unit in terms of optical frequencies.
New NIST clocks show a 100-fold improvement in accuracy over hours based on the current standard – the cesium atom that vibrates at lower microwave frequencies.
Scientists are now building a portable ytterbium grid clock that could be transported to other laboratories around the world to compare hours.