Scientists have measured the shortest unit of time ever measured

Scientists have measured the shortest unit of time ever: the time it takes a light particle to cross a Hydrogen molecule. 

That time, for the record, is 247 Zeptoseconds.

A Zeptosecond is a trillionth of a billionth of a second, or (a decimal point followed by 20 zeroes and a 1).

Previously, researchers had dipped into the realm of Zeptoseconds; in 2016, researchers reporting used lasers to measure time in increments down to 850 Zeptoseconds. This accuracy is a huge leap from the 1999 Nobel Prize-winning work that first measured time in Femtoseconds, which are millionths of a billionths of seconds. 

It takes Femtoseconds for chemical bonds to break and form, but it takes Zeptoseconds for light to travel across a single Hydrogen molecule (H₂). To measure this very short trip, physicist shot X-rays from a particle accelerator. 

The researchers set the energy of the X-rays so that a single photon, or particle of light, knocked the two electrons out of the Hydrogen molecule. The photon bounced one electron out of the molecule, and then the other, a bit like a pebble skipping over the top of a pond. These interactions created a wave pattern called an interference pattern, which scientists could measure with a tool called a Cold Target Recoil Ion Momentum Spectroscopy reaction microscope. This tool is essentially a very sensitive particle detector that can record extremely fast atomic and molecular reactions. The microscope recorded both the interference pattern and the position of the Hydrogen molecule throughout the interaction.

Since we knew the spatial orientation of the Hydrogen molecule, we used the interference of the two electron waves to precisely calculate when the photon reached the first and when it reached the second Hydrogen atom.

That time? Tow 247 Zeptoseconds, with some wiggle room depending on the distance between the Hydrogen atoms within the molecule at the precise moment the photon winged by. The measurement is essentially capturing the speed of light within the atom.