Years ago, at highway construction sites, sawhorses would be erected that were equipped with flashing lights for safety after dark. In those days the flashing lights were gas-discharge lamps connected to a simple charging circuit consisting of a capacitor connected across the lamp and charged by way of a resistor -- a very simple arrangement, but one that would reliably flash the light all night long.
It turns out that the specific moment the lamp broke down and flashed could be affected by nearby lights of the same kind. As a result, if a large number of sawhorses were erected in a dark location, eventually all the lights would get into synchronization. I can remember on a number of occasions on long trips through dark countrysides, cresting a hill and seeing a construction site in the distance, with all the lights flashing as one.
As I would approach closer, as my headlights shone more brightly on the construction lights, they would go out of sync.
This is a purely historical note, because modern construction sawhorses use LEDs instead of high-voltage gas-discharge lamps -- cheaper and more reliable. The LED's never become synchronized, of course.