Natural units
Introduction
Natural units are a system of units of measurement where some fundamental physical constants are set to unity. This system simplifies certain physical laws and is widely used in quantum mechanics, general relativity, and many other areas of physics.
Definition
In natural units, certain fundamental constants such as the speed of light (c), Planck's constant (h) and the gravitational constant (G) are normalized to 1. The choice of which constants to normalize is not unique, and often depends on the field of physics or the specific problem being considered.
History
The concept of natural units was introduced in the early 20th century, as physicists began to explore the fundamental nature of the universe. The idea was to create a system of units that was more closely aligned with the underlying physics, rather than arbitrary human constructs.
Types of Natural Units
There are several different types of natural units, each of which normalizes a different set of fundamental constants. The most common types are:
Planck Units
Planck units are a system of natural units that normalize the speed of light, Planck's constant, the gravitational constant, the Coulomb constant, and Boltzmann's constant. They are named after the physicist Max Planck, who first proposed them.
Atomic Units
Atomic units are a system of natural units that are particularly useful in atomic physics and quantum chemistry. They normalize the electron mass, elementary charge, reduced Planck's constant, and the Coulomb constant.
Geometric Units
Geometric units are a system of natural units that are particularly useful in general relativity. They normalize the speed of light and the gravitational constant.
Advantages and Disadvantages
Natural units have several advantages over other systems of units. They simplify many equations in physics, and they provide a way of comparing quantities that would otherwise be difficult to compare. However, they also have some disadvantages. They are not as intuitive as other systems of units, and they can make it difficult to compare results from different fields of physics.