Here's why:
* Gravity: The sun's gravity pulls on the planets, causing them to curve in their path. But a planet's motion also has inertia (the tendency to keep moving in a straight line). The combination of these forces results in an elliptical path.
* Focus Points: An ellipse has two focus points. The sun is located at one of these focus points. This means the planet is sometimes closer to the sun and sometimes farther away.
* Kepler's Laws: Johannes Kepler's laws of planetary motion describe the elliptical orbits of planets. His first law states that planets orbit the sun in elliptical paths with the sun at one focus.
It's important to note: While most planets have orbits that are close to circular, they are still technically ellipses. Some planets, like Mercury, have more pronounced elliptical orbits than others.
