💡 How do streetlights know it's bedtime?

Look out the window at the street lights by the houses and shops. A street light is a tall pole with a lamp on top. It helps us see at night. But how does it know when it's getting dark?

Many street lights have a tiny light helper on top, like a little eye. It watches the sky all day long. When the sun goes down, the sky gets dim. The little eye feels less light, so it tells the lamp to turn on!

In the morning, sunlight comes back, and it tells the lamp to turn off. So street lights sleep all day, just like an owl! Other street lights use a special clock that knows when dark is coming. Can you count the street lights you see?

On this town street, tall poles stand along the road with lamps on top. Those are streetlights. But here's a puzzle: how do they know when it's bedtime? Let's follow one streetlight through its day. All morning it stands very still, lamp off, like a tall sleepy giraffe. And it never gets to sit down, not even once!

Long ago, before there were cars, a person walked down the street every evening with a long pole and lit each lamp, one by one. Today, many streetlights do it all by themselves. On top, our streetlight has a tiny eye that feels light. In the daytime, sunshine pours into that little eye, so the lamp stays off. As the sun goes down, less and less light gets in. When it's dim enough, the eye tells the lamp it's time to wake up, and on it comes!

Sometimes a giant dark storm cloud tricks it, and the lamp turns on in the afternoon. Other streetlights use a special clock instead, one that knows when the dark is coming each day. Count how many streetlights you can spot as we drive. Every night, they wake up just as we get sleepy. And all night long, they keep the street bright so everyone gets home safe.