A new record has been broken, a very short one, the shortest of all in fact. A group of researchers has managed to measure the shortest unit of time ever recorded: 247 zeptoseconds. How much is this? Only 0.000,000,000,000,000,247 seconds.

The record has managed to beat the previous one which was registered at 850 zeptoseconds. This record was registered in 2016 and since then researchers have been working on improving measurement instruments to achieve greater accuracy. In other words, the measurement instruments are now about three times more accurate.
The time it takes a photon to cross the hydrogen molecule

Such exaggeratedly small measurements are not used in real life, but are useful in the field of chemistry and physics for example. Here in fact what is most used to measure the time it takes for molecules to form and break down is the femtosecond, which is two units above zeptoseconds. But if we want to measure how long it takes light to travel through a molecule, we have to go to the smallest unit that we can register at the moment: the zeptosecond.

Zeptosecond measurement
Schematic representation of zeptosecond measurement. The photon (yellow, coming from the left) produces electron waves out of the electron cloud (grey) of the hydrogen molecule (red: nucleus), which interfere with each other (interference pattern: violet-white). The interference pattern is slightly skewed to the right, allowing the calculation of how long the photon required to get from one atom to the next. Photo: Sven Grundmann, Goethe University Frankfurt

In a particle accelerator in Hamburg a group of researchers has managed to measure this extremely short period of time. For this purpose, researchers from Goethe University irradiated a hydrogen molecule (H2) with X-rays. The idea was to shoot a photon onto the molecule to expel its two atoms and measure the reaction. It worked.

When the photon reached the first atom, it generated a wave and later the same thing happened with the second atom. The researchers were able to measure when the two waves collided to cancel each other out. With this and knowing the spatial position that the molecule had in relation to the light, they could determine the time that took the photon to cross the molecule: 247 zeptoseconds. Approximately, because it always depends on how separated are the two atoms in the molecule and the perspective of the light when it arrives (the photon).

Simplifying it a lot, the researchers were able to calculate how long it takes light to cross a hydrogen molecule. Being one of the simplest molecules, it is also one of the smallest, thus one of the shortest distances with a beginning and an end that light can travel. Light is the fastest thing in the Universe and we know the result is the shortest time record we have been able to measure to date.

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