Have you ever seen a face in a cloud? Maybe you saw one in a rock or in tree bark.

People see faces in clouds, rocks and tree bark. Our brains are very good at spotting faces.

Seeing faces in things that have no faces has a name. It is called pareidolia.

Shadows can make a face too. In one old photo, a hill on Mars looked like a face because of shadows.

Later, sharper photos came. They showed that it is just a hill. There are dozens of hills like it nearby.

Here is another shadow. On a mountain, your own shadow can fall on fog or cloud below you.

Now think of a house at night. Houses make creaks and pops. Wood floors and pipes make them.

Wood, metal and glass get a tiny bit bigger when they warm up. They get a tiny bit smaller when they cool down.

In winter, wood floors can creak more. Dry air makes the boards shrink and pull apart a little.

Metal air ducts can pop when they warm up. A draft is moving air. It slips in through gaps around windows and doors.

Long ago, a stage had a see-through ghost. People made it with a sheet of glass and a hidden actor in bright light.

So a face in a cloud is a cloud, and a creak is a house. What else will you look at twice?

Words to know

• pareidolia: seeing faces
• shadows: dark shapes
• draft: moving air
• ducts: air tubes