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).
The "long cubit" is a historical unit of length used in various ancient cultures, including ancient Egypt and Mesopotamia. It was a longer version of the standard cubit, which was used for measuring length in these civilizations.
The exact length of the long cubit could vary depending on the region and time period, but it was typically longer than the standard cubit. In ancient Egypt, for example, the long cubit was approximately 52.3 centimeters (about 20.6 inches), while the standard cubit was around 45 centimeters (about 17.7 inches).
These cubits were often used in construction, architecture, and other applications where length measurements were needed. The long cubit was particularly useful for larger and more precise construction projects.
It's important to note that the long cubit is a historical unit of measurement and is not part of modern measurement systems like the metric system or the imperial system.