This is really the key point, and the main thing that many people overlook. The purpose of TrueTime in Spanner is not gained by absolute accuracy. It's gained b

This is really the key point, and the main thing that many people overlook. The purpose of TrueTime in Spanner is not gained by absolute accuracy. It's gained by knowing the clock uncertainty across all participants and affirmatively ejecting any participant with excessive uncertainty. The atomic clocks are totally besides the point.