The "cubit" (Greek: πῆχυς, pēchys) in ancient Greece was a unit of length used in antiquity for measuring various objects, including architectural dimensions. Like many ancient units of measurement, the length of the Greek cubit could vary over time and by region.
The most commonly referenced Greek cubit is the "common" or "short" cubit, which is believed to have been approximately 45 centimeters (about 17.7 inches) in length. However, there were variations in the length of the cubit in different parts of Greece and during different periods in ancient history.
The Greek cubit was used for measuring building dimensions, as well as in various crafts and trades. It was often based on the length of the forearm from the elbow to the tip of the middle finger, much like other cubits used in different ancient cultures.
It's important to note that the length of the Greek cubit is a matter of historical interpretation and may not be precisely defined due to variations in antiquity.
The Planck length, denoted as "ℓ," is a fundamental unit of length in the realm of quantum mechanics and theoretical physics. It is named after the physicist Max Planck, who made significant contributions to the field of quantum theory.
The Planck length is defined as:
ℓ = √(ħG / c³),
where:
When you calculate the Planck length using these constants, you get a value of approximately 1.616255 x 10⁻35 meters. This extremely tiny length scale is believed to be the smallest meaningful length that can exist in the universe, according to current physical theories.
The Planck length plays a crucial role in theories of quantum gravity, including string theory and loop quantum gravity, where it is considered a fundamental limit for the precision of measurements and the size of structures in the fabric of spacetime. At scales smaller than the Planck length, the classical notions of space and time break down, and a more complete theory of quantum gravity is expected to be necessary to describe the physics of such extreme conditions.