Hourglass (timekeeping device)

An hourglass is a simple timekeeping device that measures a fixed interval using two glass chambers connected by a narrow passage. Filled with sand or a similar granular material, the sand flows from the upper chamber to the lower at a steady rate. When all the sand has moved to the bottom, a specific amount of time has elapsed—often used to track periods like cooking or games. Its accuracy depends on consistent sand flow and sealed chambers, making it a reliable, visual way to measure short durations without electricity or complex mechanisms.