Book 4, Question 141
Why Do Some Trees Creak at Night?
Wood is not a silent statue. Wind, cooling air, and branches rubbing together can all make a tree groan. A creak can sound like footsteps, but it is usually just the tree working.
From the book
Page from A Million Whys Book 4
More fun facts
- Trees have their own day-and-night rhythm.
- Scientists using lasers found that birch tree branches sagged by as much as four inches at night.
- Back in 1880, Charles Darwin noticed that some plants change position at night. He called it sleep.
- Trees make sounds that people usually cannot hear.
- When a tree is thirsty during a drought, tiny air bubbles form inside its trunk and make ultrasonic sounds, too high for people to hear.
- Scientists hope that listening to trees can tell them which ones need water most.
Sources: Scientific American, Smithsonian Magazine, National Geographic
Questions kids ask
Do trees really sleep?
Not like people do, but trees have a day-and-night rhythm. Some birch branches droop by up to four inches at night.