Earth's equatorial radius, often denoted as "R," is the distance from the center of the Earth to the point on the Earth's surface that lies along the equator. It represents the Earth's average radius when measured from its center to its equatorial surface. The equatorial radius is greater than the polar radius because the Earth is slightly flattened at the poles and bulges at the equator due to its rotation.
The approximate value for Earth's equatorial radius is about 6,378.1 kilometers (or approximately 3,963.2 miles). This value may vary slightly depending on the reference ellipsoid used for modeling the Earth's shape, but the given value is a commonly used and accurate approximation for most purposes.
In contrast to the equatorial radius, Earth's polar radius (measured from the center to a point on the Earth's surface at the North or South Pole) is slightly shorter, approximately 6,357 kilometers (3,949 miles).
The Sun's radius, often denoted as "R☉," is the distance from the center of the Sun to its outer edge or surface. The Sun is not a solid object but a massive, hot, and highly compressed ball of gas, primarily hydrogen and helium.
The average or mean radius of the Sun is approximately 696,340 kilometers (about 432,685 miles). Keep in mind that the Sun's outer boundary is not sharply defined, and its structure consists of different layers, including the core, radiative zone, convective zone, and the visible surface known as the photosphere.
The Sun's radius is a fundamental parameter in astronomy and solar physics and is used as a reference point for measuring distances within the solar system and studying the properties and behavior of the Sun.