You are getting sleeeeeeepy ...

You are getting sleeeeeeepy ...
blogs.discovermagazine.com

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.

I always assumed this was because people can hear each other and subliminally fall in to syc, whether this is the same or not, Im already internally debating!!!

The construction lights were light sensors. The reason they got into synchronization is because they were triggered to break down at a specific time by the flashes of light from the other lamps.

In a system like this, the voltage on all the lamps is increasing because a charging current is applied to a capacitor that'a connected across the lamp. But the specific time of breakdown, the exact voltage at which the lamp breaks down, depends on the ambient light level. And a nearby flash of light is sufficient to trigger the lamp to break down in sync.

This effect washes out in daylight, or in a place with normal background light. Or if a light source interferes with the delicate balancing act responsible for the synchronization -- like the headlights on a passing car.