How do gravitational forces maintain planetary orbits?

Gravitational forces maintain planetary orbits by pulling planets towards the sun, counteracting their tendency to move in a straight line.

In more detail, every object in the universe, including planets, exerts a gravitational force on every other object. This force is directly proportional to the mass of the objects and inversely proportional to the square of the distance between them. This is known as Newton's Law of Universal Gravitation. The sun, being the most massive object in our solar system, exerts a strong gravitational pull on all the planets, including Earth.

Planets are also in motion. They have a tendency to move in a straight line due to their inertia. This is a property of matter that resists changes in motion. If the sun's gravity were not acting on the planets, they would simply fly off into space in a straight line. However, the sun's gravity pulls them towards it, creating a centripetal force. This force is always directed towards the centre of the orbit.

The balance between the planet's inertia, wanting to move in a straight line, and the gravitational pull of the sun, pulling it inwards, results in an elliptical orbit. This is why planets don't fall into the sun or fly off into space, but instead keep following a stable orbit. The speed of the planet and its distance from the sun determine the shape and size of this orbit.

In summary, the gravitational forces between the sun and the planets are responsible for the planets' orbits. These forces pull the planets towards the sun, counteracting their inertia and causing them to move in elliptical paths rather than straight lines. This delicate balance between gravitational pull and inertia results in the stable orbits we observe.