Physical Law - Description

Description

Several general properties of physical laws have been identified (see Davies (1992) and Feynman (1965) as noted, although each of the characterizations are not necessarily original to them). Physical laws are:

• True, at least within their regime of validity. By definition, there have never been repeatable contradicting observations.
• Universal. They appear to apply everywhere in the universe. (Davies, 1992:82)
• Simple. They are typically expressed in terms of a single mathematical equation. (Davies)
• Absolute. Nothing in the universe appears to affect them. (Davies, 1992:82)
• Stable. Unchanged since first discovered (although they may have been shown to be approximations of more accurate laws—see "Laws as approximations" below),
• Omnipotent. Everything in the universe apparently must comply with them (according to observations). (Davies, 1992:83)
• Generally conservative of quantity. (Feynman, 1965:59)
• Often expressions of existing homogeneities (symmetries) of space and time. (Feynman)
• Typically theoretically reversible in time (if non-quantum), although time itself is irreversible. (Feynman)

Physical laws are distinguished from scientific theories by their simplicity. Scientific theories are generally more complex than laws; they have many component parts, and are more likely to be changed as the body of available experimental data and analysis develops. This is because a physical law is a summary observation of strictly empirical matters, whereas a theory is a model that accounts for the observation, explains it, relates it to other observations, and makes testable predictions based upon it. Simply stated, while a law notes that something happens, a theory explains why and how something happens.