[solarist]

Like, realy realy realy fast, one billionth of one billionth of a second.

[wiz21c]

what is it useful for ? (honnest question)

[dagw]

You know how strobe light photography lets you 'freeze' very fast moving things so you can study what they look like mid motion. This is used for basically that, except for much much smaller things moving much much faster.

[dotnet00]

Another benefit of pulsing light really fast is that you can more easily perform studies of really delicate things (eg proteins) because you effectively have higher control over the amount of energy you're pouring into the sample. That isn't directly what they were working on here, but a similar extremely high frequency pulsing is one of the things that makes free-electron lasers 'next generation' compared to synchrotrons.

[solarist]

It's like using flash when photographing, with these ultra short pulses one could see how electrons move inside atoms and molecules.