Physical law

A physical law describes (usually in mathematical form ) states and their changes of a physical system by means of measurable and clearly defined physical quantities (parameters, variables).

Physical laws formulate a rule change in relationships: So you describe how an initial situation is altered by a history feature in a final situation.

A physical law must be compatible with reproducible physical experiments. In common parlance, it is also considered as confirmed.

A physical law is always part of a physical theory, which must be uniform and consistent and needs to be confirmed by the practice. A theory whose predictions have not yet been confirmed, can be more accurate with the term hypothesis characterize (such as string theory ).

A closed theory is the set of laws that describe a whole area completely, as describe all sorts of classical electrodynamics, for example, the Maxwell 's equations. This is true but again only within the defined limits and models ( ideal conductor, ideal vacuum, etc.).

Physical laws are usually written in the language of mathematics, as they have the necessary logical and conceptual clarity. In addition, linguistic descriptions and illustrations of the relationships. Both the individual terms and the scope must be defined here.

The scientifically accepted laws of physics determine the predominant material in the 20th century world view. It is in contrast to a worldview in which nature does not behave strictly according to observable regularities, but also according to other ( unobservable ) principles, such as according to the will of higher beings or the confinement.

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Laws of nature as a mirror of scientific progress

Over time seemingly independent laws have been attributed to a respective underlying connection again. An example of this are the many described in Mechanics forces and the laws of their interaction, which in the end all to electromagnetic interactions and the gravity can be traced between and within the participating bodies.

The transition from classical mechanics to relativity theory shows that as irrefutable recognized believed laws may also prove to be only a model for a special case (in this case: for small velocities and masses).

This consideration leads to the search for the "last" and fundamental laws, a law of the world, with the "everything" can be explained and built, comparable to the mathematical axioms. String Theory, Quantum Gravity and Large unified theory are examples of these efforts.

Each law of nature, which can be attributed to a general law, has only the rank of a model. This is an argument for the conjecture, all known laws of nature are actually only constructs of the human mind.

The term natural " law " suggests the nature behave similarly to persons under the compulsion of law; in fact, the physics but an empirical science, and those presented by their " laws " are just descriptions of the encountered behavior.

Example: formulation of a law

To describe the processes exactly, natural laws are usually formulated mathematically. An example of this is the law of gravity by Isaac Newton. It is: The attractive force F between the two masses and is proportional to the size of the mass, and inversely proportional to the distance squared.

G is a proportionality factor, which sets the masses and the inverse of the square of each distance in the relation. Because of this, known as the gravitational constant factor in all of the physical system has exactly the same value and a fundamental physical interaction ( the attraction of masses below the other) describes, we speak of a fundamental constants.

Examples of laws of nature

• Newton's law of gravitation (see above)
• Light propagates in the vacuum with a universal speed of ( speed of light).
• The laws of thermodynamics
• Thermal equation of state of ideal gases
• Ohm's law

Demarcation

The distinction between natural laws and other confirmed or proven theorems is not always sharp.

Many mathematical theorems have implications and applications that are in the natural sciences or in engineering of central importance. So the sentence is the sum of the angles in a triangle is 180 degrees in the plane itself, correctly; but he is not a natural law, but a mathematical theorem, which is based on certain fundamental axioms of geometry.

In the applied sciences and art, it also uses many formulas which describe certain relationships between physical quantities sufficiently accurately without the underlying relationships are very clear. For all known applications with them is a successful approximation of result values ​​with an accuracy that is sufficient for the intended use, possible ( experience). Such formulas are called empirical formulas or empirical laws. These formulas are no regularities in the physical sense, they lack the theoretical basis. In part, it is but to ideal cases or simplifications of natural laws, whose inaccuracy is kept within a known framework, and is sufficiently accurate for a specific application. On the other hand, have empirical formulas or sets of formulas but not even necessarily refer to the correct units consideration and often use as empirical parameters ( dimensionless values). An extreme case of this form so-called rules of thumb.