This Is Why You See Those Colored Balls Hanging on Power Lines
They're strung across electric wires all over the country. But just what are the balls on power lines for? We solved the mystery.
There’s something about driving that sets the mind wandering: considering your dinner plans, counting down the days to your next vacation or contemplating some interesting facts. For example, why do you see metal wrapped around trees? What’s the story behind colored circles on food packages? Why are there colored squares on toothpaste? And what are the balls on power lines?
You might drive past the same electrical lines daily without knowing the purpose of those colorful spheres. Are they bizarre pieces of public artwork or a scale model of the solar system? Perhaps they’re there to weigh down the power lines, which might otherwise blow in the wind?
We learned more about these colorful markers and why they’re strung on power lines across the country. And it turns out, there’s a pretty simple explanation.
What are the balls on power lines?
Known as marker balls, these brightly colored visibility balls indicate where power lines are so that low-flying aircraft can avoid them. Also called aerial marker balls or visibility markers, they serve a very important purpose, which is why you tend to see them on cables that cross major highways or run through deep gorges or valleys. The Federal Aviation Administration (FAA) mandates that the balls on power lines should appear on wires that cross canyons, lakes and rivers, as well as those that surround airports. How’s that for airplane trivia?
But why are they different colors? The most common colors are aviation orange, white and yellow, because the FAA found they have the best visibility. However, the colors are selected to be as conspicuous as possible against the background landscape, which means you might see other colors, depending on where you live. So the next time your passenger asks, “Hey, what are the balls on power lines for?” you can answer that they’re saving lives.
What are the balls on power lines made of?
For maximum durability and to reduce color fade, the balls on power lines are made of plastic. Plastic is also a good electrical insulator, meaning it conducts neither heat nor electricity.
And while the balls may look small hanging all the way up there, you might be surprised by their size. Much like a traffic light, these colorful markers are unexpectedly large—between 20 and 36 inches (that’s about the circumference of a basketball). But you wouldn’t bounce anything this heavy. These marker balls weigh between 11 and 17 pounds each!
How long have those colorful balls been hung on power lines?
For nearly 50 years, people have been wondering, What are the balls on power lines? In the early 1970s, Winthrop Rockefeller, the late former governor of Arkansas, was on an airplane with the head of the Arkansas Department of Aeronautics, Edward Holland. As the plane was landing, Rockefeller noticed electrical wires close to the aircraft. He immediately ordered Holland to develop a way to make electrical wires more visible to pilots.
Holland enlisted an engineer named Jack Rutledge to create brightly colored balls that could be placed on electrical and telephone lines without slipping in the wind. By the 1980s, Rutledge’s company had become one of the world’s leading suppliers of visibility markers. The invention has saved countless human lives in the decades since, but that’s not all: Canadian geese have also benefited. Before the markers were used, geese would often hit power lines as they tried to land in bad weather, so conservationists and government agencies began marking the lines to help their feathered friends land safely.
If you’ve previously been baffled about the purpose of the colorful balls on power lines, you now have your answer. Looking for more weird facts? Check out the explanation behind those strange purple-painted fences.
- BBC Science Focus: “What are the coloured balls that are attached to power lines for?”
- Federal Aviation Administration: “Obstruction Marking and Lighting”
- Airport Windsock Corporation: “20” Airport Power Line Markers”
- United Press International Archives: “Marker balls for overhead lines”