"Boring" cesium atomic clocks can do 50 ps per day with the best cutting edge optical clocks coming in at ~739 fs per day. Optical clocks would only need to res

"Boring" cesium atomic clocks can do 50 ps per day with the best cutting edge optical clocks coming in at ~739 fs per day. Optical clocks would only need to resynchronize once every ~ 135 days while cesium clocks would need to do it every 2 days to get 0.1ns of accuracy. I think the bigger challenge may be how you would transport the clocks after synchronization to maintain it across astronomical distances since they're very sensitive to any kind of acceleration. Since you have to regularly re-synchronize them in space anyway, that feels like the engineering problem you'd have to solve - how do you synchronize two atomic; the current record is synchronizing to within 0.32fs at a distance of 300km [1]. [1] https://spectrum.ieee.org/atomic-clock-femtosecond-accuracy https://spectrum.ieee.org/atomic-clock-femtosecond-accuracy