A meter (m) is the base unit of length in the International System of Units (SI), which is the modern metric system used for scientific and everyday measurements in most countries around the world. The meter is defined as the length of the path traveled by light in a vacuum during a time interval of 1/299,792,458 of a second.
In more practical terms, a meter is approximately equal to:
Meters are commonly used for measuring various lengths and distances, including the dimensions of objects, the length of rooms or buildings, and distances between locations on Earth. It is a versatile unit of measurement that is widely used in science, engineering, construction, and everyday life.
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).