History Decoded on Instagram: "Long before digital clocks existed, humans used fire to track time. A candle burns at a nearly constant rate when the wax, wick, and airflow remain stable. As the candle shortens, equal amounts of wax melt over equal intervals of time. By marking the candle or placing objects at specific heights, people could measure the passing of minutes and hours. one of This principle is called a candle clock the earliest timekeeping methods, powered purely by physics, heat tra