His problem was the Whispering Walls. For three nights, a low, mournful hum had drifted from the ancient brick wall behind his bedroom. His little sister Maya claimed it was a ghost. His parents shrugged and blamed the furnace.
Case closed.
"Science is not a spectator sport," Ms. Fermat, his science teacher, always said, quoting the Addison-Wesley book’s opening mantra. "It's a process of asking, investigating, and concluding." addison wesley science and technology grade student book
Reluctantly, Leo cracked open the book to Unit D: "Heat in the Environment."
The first section was on thermal energy transfer. Conduction, convection, radiation. A diagram showed how heat moved through solids, liquids, and gases. Leo’s eyes landed on a sidebar: "Mystery Sound? Check for thermal expansion." His problem was the Whispering Walls
His data was clear. The greater the temperature drop, the louder the sound. The bricks were contracting at a slightly different rate than the steel beam hidden inside the wall, rubbing together and vibrating like a giant, slow cello string.
A spark lit up in Leo’s brain. Not a ghost. A temperature change. His parents shrugged and blamed the furnace
Maya looked disappointed. His parents looked impressed.