The average distance from Earth to the Sun is about 149.6 million kilometers (or approximately 93 million miles). This distance is often referred to as an astronomical unit (AU), which is a standard unit of measurement used in astronomy to describe distances within our solar system. An astronomical unit is defined as the average distance between the Earth and the Sun.
It's important to note that the Earth's orbit around the Sun is not a perfect circle but rather an ellipse, so the distance between Earth and the Sun varies slightly throughout the year. The value given here represents the average distance. The closest point in Earth's orbit to the Sun is called perihelion, while the farthest point is called aphelion. Perihelion occurs around early January, and aphelion occurs around early July. At perihelion, Earth is approximately 147.1 million kilometers (about 91.4 million miles) from the Sun, while at aphelion, it is about 152.1 million kilometers (around 94.5 million miles) away.
Earth's polar radius, often denoted as "r," is the distance from the center of the Earth to a point on the Earth's surface near either the North Pole or the South Pole. It represents the Earth's radius when measured from its center to a point along its polar axis. The polar radius is shorter than the equatorial 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 polar radius is about 6,357 kilometers (or approximately 3,949 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 polar radius, Earth's equatorial radius (measured from the center to a point on the equator) is slightly longer, approximately 6,378.1 kilometers (3,963.2 miles).