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. The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

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 t

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