Planets take different times to orbit the sun because of Kepler's Third Law of Planetary Motion. This law states that the square of a planet's orbital period (the time it takes to complete one orbit) is proportional to the cube of its average distance from the sun.

Here's a breakdown:

* Distance from the Sun: Planets that are farther away from the sun have a longer path to travel. This means they have to move slower to maintain a stable orbit.

* Orbital Speed: Planets closer to the sun experience a stronger gravitational pull, making them move faster.

* Kepler's Third Law: The mathematical relationship between distance and orbital period ensures that planets further out will take longer to complete a single orbit.

Example:

* Mercury: The closest planet to the sun, orbits in just 88 Earth days.

* Earth: Our planet takes approximately 365 days to complete one orbit.

* Neptune: The farthest planet from the sun, takes over 164 Earth years to orbit once!

Therefore, the time it takes a planet to orbit the sun is directly related to its average distance from the sun.