As seen in the previous examples, common knowledge can only be attained if the knowledge updates in the relevant agents occur
simultaneously. There exists a strong relation between common knowledge and simultaneity. Above all that, this relation seems
to be a more fundamental one. The Byzantine Generals example showed us, that when actions are performed simultaneously by all
parties, common knowledge is attained the moment the actions are performed. But in the example, common knowledge is needed
to perform the actions. This is a paradox that has been described by Halpern and Moses [4].
Common knowledge can only be attained when there is perfect coordination. In practice, this is impossible to perform. Messages
always take time to send, and agents do not update their knowledge at precicely the same time. This is why in practical situations
a so-called fixed-point-operator is used, which restricts the number of E-operators to attain common knowledge.
The visualization below shows the concept of perfect coordination. All persons know at the same time P, because Ann shouted it very
loud so that everyone has heard it. It is a simultaneous update of the knowledge in all persons (agents).