Take a look at any overhead power lines in the US and you’ll perhaps see a number of big yellow, orange, red, or white balls gripping the wires. Some people have speculated that they are weights for the lines, weather sensors, or even surveillance systems. However, none of these guesses are correct.
Along with jazzing up an unattractive sight, the purpose of the colorful balls is to serve as visibility markers for pilots to make sure airplanes don’t crash into the power lines.
As explained by the electric utility company Edison International, the US Federal Aviation Administration (FAA) requires these spherical visibility markers to be placed on power lines in certain places where there’s a higher chance of a plane pilot might not spot the hard-to-see obstacle.
This is predominately in areas near busy airports, but you’re also likely to see them in mountain passes, in canyons, over bodies of water, open fields, and near major freeway crossings
It’s hard to discern their size from the ground, but the diameter of marker balls is typically larger than 91 centimeters (36 inches), around the size of a very large beach ball, according to regulations set out by the FAA. However, smaller 51-cm (20-inch) balls are allowed on power lines lower than 15 meters (50 feet).
The flight authority also suggests that the balls are placed on the highest wire at spaced equally along the wire at approximately 61-meter (200-foot) intervals.
As for the colors, the FAA recommends "aviation orange, white, or yellow" balls be used on power lines, perhaps with an "alternating color scheme. “International orange” is one of the most used, as it’s a color commonly used in the aerospace industry and engineering because it set clearly objects apart from their surroundings.
Despite their best efforts, it’s still not unheard of for planes, helicopters, and drones to collide with power lines. Late last year, four people died after their business jet flew into power lines and crushed into a San Diego suburb.
So there you have it, another great question of the universe answered. In a similar vein, have you ever wondered what that hole in the front of boxer shorts is for? Fortunately, an underwear brand has explained the mystery.