I’ve heard it was because red light waves don’t travel that far, but I can see the red light on an airplane wing that’s miles away.
In: Technology
It’s primarily to preserve night vision. It takes the eyes a half hour or more to be fully dark adapted. You can easily observe this after you turn out the lights to go to bed. Your bedroom seems completely dark at first. Then you slowly start to see things again. After a long enough time you can once again basically see everything in the room.
Every time you look at a bright light your pupils reduce again and the process starts all over. The optic nerve isn’t as sensitive to red light though, so your pupils remain dilated, preserving your night vision.
I do amateur astronomy. It’s a standard practice in astronomy to use only red light in the field. They are looking at extremely faint objects. Want to make enemies quickly at a star party? Pull up in your car with your headlights on.
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