---
title: "Scientific law"
chunk: 4/6
source: "https://en.wikipedia.org/wiki/Scientific_law"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:45:43.771670+00:00"
instance: "kb-cron"
---

in which the (more famous) mass–energy equivalence E = mc2 is a special case.
General relativity:
General relativity is governed by the Einstein field equations, which describe the curvature of space-time due to mass-energy equivalent to the gravitational field. Solving the equation for the geometry of space warped due to the mass distribution gives the metric tensor. Using the geodesic equation, the motion of masses falling along the geodesics can be calculated.
Gravitoelectromagnetism:
In a relatively flat spacetime due to weak gravitational fields, gravitational analogues of Maxwell's equations can be found; the GEM equations, to describe an analogous gravitomagnetic field. They are well established by the theory, and experimental tests form ongoing research.

==== Classical laws ====

Kepler's laws, though originally discovered from planetary observations (also due to Tycho Brahe), are true for any central forces.

=== Thermodynamics ===

Newton's law of cooling
Fourier's law
Ideal gas law, combines a number of separately developed gas laws;
Boyle's law
Charles's law
Gay-Lussac's law
Avogadro's law, into one
now improved by other equations of state
Dalton's law (of partial pressures)
Boltzmann equation
Carnot's theorem
Kopp's law

=== Electromagnetism ===
Maxwell's equations give the time-evolution of the electric and magnetic fields due to electric charge and current distributions. Given the fields, the Lorentz force law is the equation of motion for charges in the fields.

These equations can be modified to include magnetic monopoles, and are consistent with our observations of monopoles either existing or not existing; if they do not exist, the generalized equations reduce to the ones above, if they do, the equations become fully symmetric in electric and magnetic charges and currents. Indeed, there is a duality transformation where electric and magnetic charges can be "rotated into one another", and still satisfy Maxwell's equations.
Pre-Maxwell laws:
These laws were found before the formulation of Maxwell's equations. They are not fundamental, since they can be derived from Maxwell's equations. Coulomb's law can be found from Gauss's law (electrostatic form) and the Biot–Savart law can be deduced from Ampere's law (magnetostatic form). Lenz's law and Faraday's law can be incorporated into the Maxwell–Faraday equation. Nonetheless, they are still very effective for simple calculations.

Lenz's law
Coulomb's law
Biot–Savart law
Other laws:

Ohm's law
Kirchhoff's laws
Joule's law

=== Photonics ===
Classically, optics is based on a variational principle: light travels from one point in space to another in the shortest time.

Fermat's principle
In geometric optics laws are based on approximations in Euclidean geometry (such as the paraxial approximation).

Law of reflection
Law of refraction, Snell's law
In physical optics, laws are based on physical properties of materials.

Brewster's angle
Malus's law
Beer–Lambert law
In actuality, optical properties of matter are significantly more complex and require quantum mechanics.

=== Laws of quantum mechanics ===
Quantum mechanics has its roots in postulates. This leads to results which are not usually called "laws", but hold the same status, in that all of quantum mechanics follows from them. These postulates can be summarized as follows:

The state of a physical system, be it a particle or a system of many particles, is described by a wavefunction.
Every physical quantity is described by an operator acting on the system; the measured quantity has a probabilistic nature.
The wavefunction obeys the Schrödinger equation. Solving this wave equation predicts the time-evolution of the system's behavior, analogous to solving Newton's laws in classical mechanics.
Two identical particles, such as two electrons, cannot be distinguished from one another by any means. Physical systems are classified by their symmetry properties.
These postulates in turn imply many other phenomena, e.g., uncertainty principles and the Pauli exclusion principle.

=== Radiation laws ===
Applying electromagnetism, thermodynamics, and quantum mechanics, to atoms and molecules, some laws of electromagnetic radiation and light are as follows.

Stefan–Boltzmann law
Planck's law of black-body radiation
Wien's displacement law
Radioactive decay law

== Laws of chemistry ==

Chemical laws are those laws of nature relevant to chemistry. Historically, observations led to many empirical laws, though now it is known that chemistry has its foundations in quantum mechanics.
Quantitative analysis:
The most fundamental concept in chemistry is the law of conservation of mass, which states that there is no detectable change in the quantity of matter during an ordinary chemical reaction. Modern physics shows that it is actually energy that is conserved, and that energy and mass are related; a concept which becomes important in nuclear chemistry. Conservation of energy leads to the important concepts of equilibrium, thermodynamics, and kinetics.
Additional laws of chemistry elaborate on the law of conservation of mass. Joseph Proust's law of definite composition says that pure chemicals are composed of elements in a definite formulation; we now know that the structural arrangement of these elements is also important.
Dalton's law of multiple proportions says that these chemicals will present themselves in proportions that are small whole numbers; although in many systems (notably biomacromolecules and minerals) the ratios tend to require large numbers, and are frequently represented as a fraction.
The law of definite composition and the law of multiple proportions are the first two of the three laws of stoichiometry, the proportions by which the chemical elements combine to form chemical compounds. The third law of stoichiometry is the law of reciprocal proportions, which provides the basis for establishing equivalent weights for each chemical element. Elemental equivalent weights can then be used to derive atomic weights for each element.
More modern laws of chemistry define the relationship between energy and its transformations.
Reaction kinetics and equilibria: