Physical law

A physical law or a law of nature is a scientific generalization based on empirical observations. Laws of nature are conclusions drawn from, or hypotheses confirmed by scientific experiments. The production of a summary description of nature in the form of such laws is the fundamental aim of science. Laws of nature are distinct from legal code and religious Law, and should not be confused with the concept of natural law.

Necessity, origin, and existence

If the universe were purely chaotic, the existence of life as it is known would be impossible, since organized complexity is a defining characteristic of life. The laws of nature create order in the universe, and result in a generally stable environment that, in accordance with the anthropic principle, is permissive of life, including humanity. However, whence the laws of nature originate and exist, and why they are of the particular form that they are, is unknown, and in the purview of metaphysics.

Related Topics:
Chaotic - Life - Anthropic principle - Metaphysics

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Most laws are mathematical consequenses of various symmetries (see Emmy Noether theorem as a proof of this). For example, conservation of energy is a consequence of the symmetry of time (no moment in time is any different than any other), while conservation of momentum is a consequence of the symmetry of space.

Related Topics:
Symmetries - Emmy Noether

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Some laws are not laws at all but simply definitions. For example, F = dp/dt (Newton's second "law" of mechanics) is not a law at all but is a mathemetical definition of force (introduced first by Newton himself). The principle of least action (or principle of stationary action) and few other laws fall into this category.

Related Topics:
Newton - Principle of least action - Principle of stationary action

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It has sometimes been suggested that the laws of nature are not real ? that they are entirely inventions of the human mind, attempting to make sense of the universe. This is very strongly argued against by the spectacular efficacy of science ? its power to solve otherwise intractable problems, and make accurate predictions ? and by the fact that newly-discovered laws have typically suggested the existence of previously unknown or undiscovered phenomena, which have then been confirmed to exist.

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