# Laws of science

The

**laws of science**are various establishedscientific law s, orphysical law s as they are sometimes called, that are considered universal and invariable facts of the physical world. Laws of science may, however, be disproved if new facts or evidence contradicts them. A "law" differs fromhypotheses ,theories ,postulates ,principle s, etc., in that a law is an analytic statement, usually with an empirically determined constant. A theory may contain a set of laws, or a theory may be implied from an empirically determined law.**Overview**Conservative estimates indicate that there are 18 basic physical laws in the universe: [

*cite book | last = Powell | first = Michael | title = Stuff You Should Have Learned at School | publisher = Barnes & Noble Books | year = 2004 | id = ISBN 0-7607-6279-1*]**Fluid mechanics**

*Archimedes’ principle **Force, mass, and inertia**

*Kepler’s three laws of planetary motion

*Newton’s three laws of motion

*Newton’slaw of universal gravitation **Heat, energy, and temperature**

*Newton’s law of cooling

*Boyle’s law

*Law ofconservation of energy

*Joule’s first and second law

*The fourlaws of thermodynamics **Quantum mechanics**

*Heisenberg’suncertainty principle Others, such asRoger Penrose with his 2004 bookThe Road to Reality – a complete guide to the laws of the universe, argues that there are a large number of established laws of science. Some laws, such asDescartes ’ "first law of nature", have become obsolete. A rough outline of the basic laws in science is as follows:**Conservation laws**Most significant laws in science are

conservation laws :*

Conservation of mass law

*Conservation of energy law

* Conservation of momentum law

* Conservation of angular momentum law

*Charge conservation lawThese fundamental laws follow from homogeneity of

space ,time and phase (seeEmmy Noether theorem ).**Gas laws**Other less significant (non fundamental) laws are the mathematical consequences of the above conservation laws for derivative physical quantities (mathematically defined as

force ,pressure ,temperature ,density , force fields, etc):*

Boyle's Law (pressure andvolume ofideal gas )

* Charles & Gay-Lussac (gases expand equally with the same change oftemperature )

*Ideal Gas Law "$PV\; =\; nRT$"**Einstein's laws****Einstein**:*Energy ofphoton s - Energy equalsPlanck's constant multiplied by thefrequency of thelight . :*: $E\; =\; hf$:::* Constancy of theSpecial Relativity speed of light ::*Lorentz transformations - Transformations of Cartesian coordinates between relatively movingreference frame s.::*: $x\text{'}\; =\; (x\; -\; vt)\; /\; sqrt\{1\; -\; v^2/c^2\}$::*: $y\text{'}\; =\; y$::*: $z\text{'}\; =\; z$::*: $t\text{'}\; =\; (t\; -\; vx/c^2)\; /\; sqrt\{1\; -\; v^2/c^2\}$::*Mass-energy equivalence::*:$E\; =\; mc^2$ (Energy =mass ×speed of light ^{2}):::* Energy-momentum (including mass via "E=mc"General Relativity ^{2}) curves spacetime.::*: This is described by theEinstein field equations :::*: $R\_\{ab\}\; -\; \{1\; over\; 2\}R,g\_\{ab\}\; =\; \{8\; pi\; G\; over\; c^4\}\; T\_\{ab\}.$::*: $R\_\{ab\}$ is theRicci tensor , $R$ is theRicci scalar , $g\_\{ab\}$ is the metric tensor, $T\_\{ab\}$ is thestress-energy tensor , and the constant is given in terms of $pi$ (pi ), $c$ (thespeed of light ) and $G$ (thegravitational constant ).::*: E=mc^{2}where m=m_{0}/sqrt(1-(v^{2}/c^{2})**Newton's laws****Newton**:*Newton's laws of motion - Replaced with relativity:*: *1. Law of Inertia:*: *2. $F\; =\; d(vec\; p)/dt$ Although it implies $F\; =\; ma$, that is not necessarily true.:*: *3. $F\_\{ab\}=-F\_\{ba\}$ Force of a on b equals the negative force of b on a, or for every action there is an equal and oppositereaction .:*Law of heat conduction :* General law of gravitation -Gravitational force between two objects equals thegravitational constant times the product of the masses divided by thedistance between them squared.:*:$F\_g\; =\; G\; frac\{m\_1m\_2\}\; \{r^2\}$:*:This law is really just the low limit solution ofEinstein's field equations and is not accurate with modern high precision gravitational measurements.**Chemical laws****Chemical laws**are thoselaws of nature relevant tochemistry . The most fundamental concept in chemistry is thelaw of conservation of mass , which states that there is no detectable change in the quantity of matter during an ordinarychemical reaction . Modern physics shows that it is actuallyenergy that is conserved, and that energy and mass are related; a concept which becomes important innuclear 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 'slaw 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 (i.e. 1:2 O:H in water); although in many systems (notably biomacromolecules and minerals) the ratios tend to require large numbers, and are frequently represented as a fraction. Such compounds are known as non-stoichiometric compoundsMore modern laws of chemistry define the relationship between energy and transformations.

* In equilibrium, molecules exist in mixture defined by the transformations possible on the timescale of the equilibrium, and are in a ratio defined by the intrinsic energy of the molecules—the lower the intrinsic energy, the more abundant the molecule.

* Transforming one structure to another requires the input of energy to cross an energy barrier; this can come from the intrinsic energy of the molecules themselves, or from an external source which will generally accelerate transformations. The higher the energy barrier, the slower the transformation occurs.

* There is a hypothetical intermediate, or "transition structure", that corresponds to the structure at the top of the energy barrier. TheHammond-Leffler Postulate states that this structure looks most similar to the product or starting material which has intrinsic energy closest to that of the energy barrier. Stabilizing this hypothetical intermediate through chemical interaction is one way to achievecatalysis .

* All chemical processes are reversible (law ofmicroscopic reversibility ) although some processes have such an energy bias, they are essentially irreversible.**Electromagnetic laws***

Coulomb's law -Force between any two charges is equal to theabsolute value of the multiple of the charges divided by 4pi times the vacuum permittivity times thedistance squared between the two charges.:$F\; =\; frac\{left|q\_1\; q\_2\; ight\{4\; pi\; epsilon\_0\; r^2\}$

*Ohm's Law :$V\; =\; I\; cdot\; R$

*Kirchhoff's circuit laws (current andvoltage laws)

*Kirchhoff's law of thermal radiation

*Maxwell's equations (electric andmagnetic field s):**Thermodynamic laws**:*Thermodynamics Zeroth law of thermodynamics :*:$A\; sim\; B\; wedge\; B\; sim\; C\; Rightarrow\; A\; sim\; C$:*First law of thermodynamics :*:$mathrm\{d\}U=delta\; Q-delta\; W,$:*Second law of thermodynamics :*:$int\; frac\{delta\; Q\}\{T\}\; ge\; 0$:*Third law of thermodynamics :*: $T\; Rightarrow\; 0,\; S\; Rightarrow\; C$:*Onsager reciprocal relations - sometimes called the "Fourth Law of Thermodynamics":*: $mathbf\{J\}\_\{u\}\; =\; L\_\{uu\},\; abla(1/T)\; -\; L\_\{ur\},\; abla(m/T)\; !$;:*: $mathbf\{J\}\_\{r\}\; =\; L\_\{ru\},\; abla(1/T)\; -\; L\_\{rr\},\; abla(m/T)\; !$.**Quantum laws**:*Quantum Mechanics Heisenberg Uncertainty Principle -Uncertainty inposition multiplied by uncertainty inmomentum is equal to or greater thanDirac's constant divided by 2.:*: $Delta\; x\; Delta\; p\; ge\; frac\{hbar\}\{2\}$:*De Broglie hypothesis - Laid the foundations ofparticle-wave duality and was the key idea in the Schrödinger equation.:*:$lambda\; =\; frac\; \{hc\}\{mc^2\}\; =\; frac\; \{h\}\{mc\}\; =\; frac\; \{h\}\{p\}$:*Schrödinger equation - Describes the time dependence of a quantum mechanical system.:*: $H(t)\; left|\; psi\; (t)\; ight\; angle\; =\; i\; hbar\; \{partialoverpartial\; t\}\; left|\; psi\; (t)\; ight\; angle$:*: The Hamiltonian "H"("t") is aself-adjoint operator acting on the state space, $psi\; (t)$ is the instantaneousstate vector at time "t", "i" is the unit imaginary number, $hbar$ isPlanck's constant divided by 2πIt is thought that the successful integration of

Einstein's field equations with theuncertainty principle andSchrödinger equation , something no one has achieved so far with a testabletheory , will lead to a theory ofquantum gravity , the most basic physical law sought after today.**Other laws***

Navier-Stokes equations offluid dynamics : $-\; abla\; p\; +mu\; left(\; abla^2\; mathbf\{u\}\; +\; \{1\; over\; 3\}\; abla\; (\; abla\; cdot\; mathbf\{u\}\; )\; ight)\; +\; ho\; mathbf\{u\}=\; ho\; left(\; \{\; partialmathbf\{u\}\; over\; partial\; t\}\; +mathbf\{u\}\; cdot\; abla\; mathbf\{u\}\; ight)$

*Poiseuille's law (voluminallaminar stationary flow of incompressible uniform viscous liquid through a cylindrical tube with the constant circular cross-section):$Phi\_\{V\}\; =\; \{pi\; r^\{4\}over\; 8\; eta\}\; \{\; riangle\; p^\{star\}\; over\; l\}$**Radiation laws**:*Planck's law of black body radiation (spectral density in aradiation of ablack-body ):*Wien's law (wavelength of the peak of the emission of a black body) :"λ_{0}T" = "k_{w}":*Stefan-Boltzmann law (total radiation from a black body):*: $j^\{star\}\; =\; sigma\; T^4$

*Laws of Kepler (planetary motion )

*Beer-Lambert (light absorption )

*Dulong-Petit law (specific heat capacity at constant volume)

*:$c\_V\; =\; frac\{3R\}\; \{M\}$

*Buys-Ballot's law (wind travels counterclockwise aroundlow pressure system s in theNorthern Hemisphere )**References****ee also***

Physical law - includes discussion of what constitutes a law

*Scientific laws named after people

*Wikimedia Foundation.
2010.*

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