Even the most dedicated of timekeepers would struggle to record the event recently measured by researchers from Germany’s Goethe University Frankfurt. That’s putting it mildly. In fact, the event lasted just 247 zeptoseconds, a measure that, chances are, you’ve not encountered before. That’s because it’s so ridiculously rapid that it strains the definition of “event” in its brevity. One zeptosecond is a trillionth of a billionth of a second.

The event in question was the length of time that it takes for a photon to cross a hydrogen molecule. The significance of this is not that it takes so little time (at this unimaginably tiny scale, a single second may as well be a year), but rather that it is possible to record it.

“We used a so-called reaction microscope to determine the three-dimensional momentum of all fragments from the double ionization of the hydrogen molecule: Two protons and two electrons,” Sven Grundmann, one of the researchers on the project, told Digital Trends. “The molecules were prepared in a molecular beam that was crossed with light from the PETRA III synchrotron at DESY, Hamburg. With the momenta of all fragments available, we were able to transform the photoelectron momentum into the molecular frame of reference to unveil the interference pattern. The central interference maximum served the pointer of a clock on which we could measure the delay in electron emission between the two atoms of the hydrogen molecule.”

Grundmann suggested that the previous fastest measured event was the “delay between photoelectron emission from the Neon 2s and 2p shell,” describing two different atomic orbitals, published in 2010. That comparatively languorous duration? A veritable dawdle of 21 attoseconds, approximately 100 times longer than it takes for the passage of light through a hydrogen molecule.

And does he think that this latest record will one day be smashed by a physics event the equivalent of a nanoscale Usain Bolt? “I am sure somebody will think of a clever way to measure something even shorter,” Grundmann said. “[However,] in the area of atomic and molecular physics, we may have reached an end. We have tracked how the fastest object passes the shortest distance. But I guess I will be surprised.”

A paper describing the work, titled “Zeptosecond Birth Time Delay in Molecular Photoionization,” was recently published in the journal Science.