A study published in the journal Science explains what researchers believe is now the world’s most precise clock. While we may not need it for punctuality, this new atomic clock will benefit scientific exploration and technological advancements—oh, and put Einstein’s Theory of Relativity to the test.

“The ytterbium optical lattice clock has demonstrated a groundbreaking, new level of clock stability,” said study co-author Andrew Ludlow, researcher at the National Institute of Standards and Technology in Boulder, Colo. “One could say that this is like measuring time over a hundred years to a precision of several nanoseconds.”

Clocks all have a mechanism called an oscillator that changes at a constant rate, which determines a second. An atomic clock emits light at an exact frequency to excite an atom’s electrons. In the clock, the excitation and de-excitation of an electron acts like a pendulum swinging in a grandfather clock. While the pendulum denotes a second with each swing, the light “tick” in an atomic clock designates an extremely small fraction of a second.

Scientists had been using the cesium atomic clock, which excites cesium atoms with a microwave light and defines a unit of a second at 9.19 billion oscillations. The new atomic clock instead uses ytterbium and yellow light—from a laser with a wavelength of 578 nanometers—to excite the atom’s electrons. Those resulting oscillations near one quadrillion per second, according to Ludlow.

This clock serves as a ruler of time, measuring into the equivalent of micrometers while the cesium clock can only measure to millimeters. “You divide time into finer and finer intervals,” Ludlow said.

Scientists hope to use the ytterbium clock to test other theories that seek to explain the relationship between gravity and time. “Today many scientists believe that the theory of relativity is incompatible with other physical theories,” Ludlow says.

Researchers also plan to use the clock to measure more precisely how time varies depending on the surrounding gravity. Einstein had predicted that clocks in varying gravitational fields would “tick” at different speeds. For example, global positioning systems (GPS), being far from Earth, experience less pull than we do and so their measurement of time differs from our perception of it. The team believes a more precise clock such as the ytterbium clock could better handle corrections in this difference.