A light curve is a graph that shows how the brightness of an object changes over time. It is commonly used in astronomy to study celestial bodies like stars, planets, and supernovae. By observing these changes, scientists can learn about the object's size, distance, and even its composition. Light curves are created by measuring the light intensity from an object at different times. For example, when a planet passes in front of a star, it causes a temporary dip in brightness, which can be recorded as a light curve. This information helps astronomers understand the dynamics of the universe.