The excellent Proceedings of the Athanasius Kircher Society
has a fascinating article on the phenomenon of odd sympathy.
The term “odd sympathy” was coined by the 17th-century Dutch mathematician and physicist Christiaan Huygens to describe the strange phenonmenon he observed while laying sick in bed and looking up at two of his newly invented pendulum clocks hanging on the wall above him. Inexplicably, the two pendulums always swung in opposite directions. Even when he would release them in different positions, they eventually fell back in synch (or antisynch, to be precise). Huygens had discovered the principle of coupled oscillation, but it took a recent study by physicists at Georgia Tech (image above) to prove that it was the miniscule force of the pendulums operating on a beam in the wall that caused them to link up.
I like about this is that Huygens didn't look for some supernatural or otherworldly explanation for this, but made observations and analyses that were later proved by scientists with better tools. There are some other great example of odd sympathy here to including being able to tell the time form the synchronised chirp of snow crickets!
Its science and I love it, read more!