Planets orbit the sun in stretched-out circles

Johannes Kepler's 17th-century laws revealed that planets don't orbit the Sun in perfect circles, but in ellipses, or stretched-out circles. His first law states the Sun sits at one focus of this ellipse. The second law explains that planets speed up when closer to the Sun and slow down when farther away, sweeping equal areas in equal times. His third law mathematically links a planet's orbital period to its distance from the Sun. These insights, based on Tycho Brahe's precise observations, revolutionized astronomy, paving the way for Newton's gravity and guiding modern space missions.