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What are those orange balls on some power lines? – Maggie, age 8, West Chester, Pennsylvania
Have you ever looked up while driving on a highway and spotted those big orange balls hanging on power lines? They look a bit like giant toy beads strung along the electric wires.
What in the world are those overgrown basketballs doing up there?
I’m a professor who teaches about and researches power systems, the big networks that move electricity from power plants to our homes, schools and businesses.
Those big orange balls don’t help with electricity flow or improve the efficiency of the power lines, but they do have a very important job. Officially called aviation marker balls or spherical markers, they’re there to help pilots see power lines so airplanes and helicopters don’t crash into them. They’re like bright warning signs in the sky, protecting pilots, passengers and people on the ground below.
Sometimes these markers are on wires that are pretty close to the ground.
Zen Rial/Moment via Getty Images
Big round warning signs in the sky
Power lines can be very hard to see from an airplane or helicopter, especially when pilots are flying low. Thin metal wires can visually blend into the background of nature.
The orange balls help the lines stand out. You can think of them as being like reflective tape on a bike – just a little something simple that helps people notice a danger before it’s too late.
Orange isn’t a random choice. This vibrant color is very visible to the human eye and especially stands out against the more muted colors of nature – blue sky, green trees or gray clouds. Sometimes the balls are red or white, or even striped, but orange is the most common because it works well in most lighting conditions.
Aviation safety rules in many countries explain which colors should be used so pilots can quickly recognize hazards. Organizations like the U.S. Federal Aviation Administration publish guidelines you can check out about marking obstacles near flight paths.
People on the ground prepare a ball for installation.
Lisa Meiman/Western Area Power/Flickr, CC BY
These balls may look like slightly oversized ping-pong balls from your perspective on the ground. But most are actually much bigger, about the size of a large beach ball, roughly 2 to 3 feet (0.6 to 1 meter) across. Each one can weigh 10 to 25 pounds (4.5 to 11 kilograms), about as heavy as a large backpack full of books.
They’re usually made from strong plastic or fiberglass, similar to materials used in boats or playground equipment. That way, they can survive years of sun, rain, snow, wind – and even the occasional bird landing on them.
Even though they sit on wires that…
