I have a friend who lives in Orlando, Florida. She and her husband are avid sailors and travelers. They also hunt lighthouses, and have seen over 100 different ones. They're currently on a trip from Florida up the Eastern Seaboard all the way to Nova Scotia.

She's been seeing signs on some beaches in Florida and North Carolina prohibiting the use of artificial lights after 9:00 pm. This includes beach boardwalk lights, headlights, streetlights, and even house lights for people who live on the waterfront. These are mainly in areas where turtles breed.

Why would these rules be in effect?