Greatest precision to record a physical event

The physical event recorded with the highest precision is the photoionisation of a helium atom; it was recorded with a precision of 850 zeptoseconds by researchers from LMU Munich, led by Martin Schultze, and from the Max Planck Institute of Quantum Optics (Germany), in November 2016. The photoionisation is the physical process in which an electron is removed from an atom after irradiation with an appropriate light source; the process is very, very fast, as the interval between the light hitting the atom and the electron being removed is much shorter than a second.

A zeptosecond is a trillionth of billionth of a second, 10 to the power of 21, or 0.000000000000000000001 seconds. It was the first time a physical event was measured with zeptosecond precision.