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Laws differ from [[scientific theory|scientific theories]] in that they do not posit a mechanism or explanation of phenomena: they are merely distillations of the results of repeated observation. As such, a law is limited in applicability to circumstances resembling those already observed, and may be found false when extrapolated. [[Ohm's law]] only applies to linear networks, [[Newton's law of universal gravitation]] only applies in weak gravitational fields, the early laws of [[aerodynamics]] such as [[Bernoulli's principle]] do not apply in case of [[compressible flow]] such as occurs in [[transonic]] and [[supersonic]] flight, [[Hooke's law]] only applies to [[strain (physics)|strain]] below the [[elastic limit]], [[Boyle's law]] applies with perfect accuracy only to the ideal gas, etc. These laws remain useful, but only under the conditions where they apply.

Many laws take [[mathematics|mathematical]] forms, and thus can be stated as an ~~equation~~equator; for example, the [[law of conservation of energy]] can be written as <math>\Delta E = 0</math>, where E is the total amount of energy in the universe. Similarly, the [[first law of thermodynamics]] can be written as <math>\mathrm{d}U=\delta Q-\delta W\,</math>, and [[Newton's laws of motion|Newton's Second law]] can be written as ''F'' = {{frac|dp|dt}}. While these scientific laws explain what our senses perceive, they are still empirical, and so are not like mathematical theorems (which can be proved purely by mathematics and not by scientific experiment).

Like theories and hypotheses, laws make predictions (specifically, they predict that new observations will conform to the law), and can be [[Falsifiability|falsified]] if they are found in contradiction with new data.