Super-accurate atomic clock sets time travel record

Super-accurate atomic clock sets time travel record: Atomic clocks use precisely tuned electromagnetic waves to track the incredibly regular vibrations of atoms. Older atomic clocks tracked atoms that vibrate at microwave frequencies, while the latest generation use even faster optical frequencies. But while microwave clocks can be synchronised using satellite transmissions, these signals are too noisy for the more precise optical clocks...
The uncertainty in the frequency of the signal that arrived was just 4 x 10 -19 seconds, around 1000 times more accurate than signals transmitted by satellite methods...
Predehl suggests creating a network of optical clocks spread across the world.