In the vast majority of cases involving sine waves, the correlation between A and B is due to the common cause of time. Space is also a common cause of such correlations.
However, if you imagine a sine wave in time and another sine wave in space, they have no correlation until you impose a correlation between space and time (e.g., by using a mapping from x to t). In that case, Armok's comment about a logical rather than physical cause might apply.
the common cause of time
I don't understand what does that mean. In which sense can time be thought of as a cause?
People want to tell everything instead of telling the best 15 words. They want to learn everything instead of the best 15 words. In this thread, instead post the best 15-words from a book you've read recently (or anything else). It has to stand on its own. It's not a summary, the whole value needs to be contained in those words.
I'll start in the comments below.
(Voted by the Schelling study group as the best exercise of the meeting.)