why does a planet's orbital radius represents that planet's average distance from the sun and not its exact distance?
the orbit is not a circle, but an ellipse. The planet is not always exactly the same distance from the sun.
Read up on Kepler's laws of planetary motion.
A planet's orbital radius represents its average distance from the sun rather than its exact distance due to the nature of its orbit. Planets follow elliptical orbits around the sun, which means their distance from the sun is constantly changing throughout their journey. The average distance, represented by the orbital radius, is calculated by taking the planet's maximum and minimum distances from the sun and finding the average.
This average distance is a useful measure because it provides a representative value of the planet's position relative to the sun. It allows scientists to compare the distances of different planets and understand their relative positions within the solar system. Additionally, using the average distance helps to eliminate the complexities associated with the constantly changing distances caused by elliptical orbits.
A planet's orbital radius represents its average distance from the sun rather than its exact distance because planets have elliptical orbits. An elliptical orbit is not a perfect circle but rather an elongated shape called an ellipse, with the sun at one of its foci.
As a result, a planet's distance from the sun varies throughout its orbit. At certain points, the planet is closer to the sun (perihelion), and at other points, it is farther away (aphelion). This variation occurs due to the gravitational interactions between the planet and the sun.
To calculate the average distance of a planet from the sun, scientists measure the semi-major axis of the elliptical orbit. The semi-major axis is the length of the longest radius of the ellipse, which extends from the center to one of the points where the ellipse intersects the major axis.
By considering the semi-major axis, scientists can determine the average distance between a planet and the sun over the course of one complete orbit. This average distance is the orbital radius. While it's not the exact distance at any given moment, it provides a useful value for describing a planet's distance from the sun on average.