What is a Law in Science? Definition of Scientific Law

While scientific theories and laws are both based on hypotheses, a scientific theory is an explanation of the observed phenomenon, while a scientific law is a description of an observed phenomenon.

Kepler's Laws of Planetary Motion, for example, describe the motions of planets but do not provide an explanation for their movements.

Both scientific laws and theories are supported by a large body of empirical data; both help unify a particular field of scientific study; and both are widely accepted by the vast majority of scientists within a discipline.

While a scientific theory can become a scientific law, it does not happen often and each process has a revered and separate purpose as part of the scientific method. A common misconception is that a theory becomes a law after a certain amount of data has accumulated. That is not the case.

Scientific laws are typically applied to a specific discipline such as biology, physics or chemistry. Since it requires years and even decades of accumulating knowledge, few scientific laws transcend more than one field of science.

While scientific law is generally associated with the natural sciences, there are some scientific laws that apply to the social sciences such as archeology, economics and linguistics.

Many scientific laws can be boiled down to a mathematical equation. For example, Newton's Law of Universal Gravitation states: F=Gm1m2/d2, where F is the force of gravity, G is a constant (the Gravitational Constant) that can be measured, m1 and m2 are the masses of the two objects, and d is the distance between them.

Some disciplines, such as physics and chemistry, have many laws because a large number of the principles behind these sciences can be related as mathematical equations. Comparatively, biology has fewer laws and more theories because there are many aspects of this field of science that cannot be broken down in mathematical terms.

While scientific laws are universally accepted by scientists in a particular field, they are meant to be questioned and challenged. Some of the best science has come from questioning accepted knowledge. Einstein, for example, showed that the Newtonian "Laws" of mechanics did not explain everything.

That said, scientific laws are rarely refuted.


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Kim Ann Zimmermann

Kim Ann Zimmermann is a contributor to Live Science. She holds a bachelor’s degree in communications from Glassboro State College.
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