Scientific theory

A scientific theory is an explanation of an aspect of the <a href="/facts/Universe/XbfpnDmM">natural world</a> that can be or that has been <a href="/facts/Reproducibility/yh5pawMj">repeatedly tested</a> and has <a href="/facts/Corroborating_evidence/RHDsPxLv">corroborating evidence</a> in accordance with the <a href="/facts/Scientific_method/182j8RWE">scientific method</a>, using accepted <a href="/facts/Protocol_(science)/CgKlqHj2">protocols</a> of <a href="/facts/Observation/NTodmzCo">observation</a>, measurement, and evaluation of results. Where possible, theories are tested under controlled conditions in an <a href="/facts/Experiment/esltM54f">experiment</a>. In circumstances not amenable to experimental testing, theories are evaluated through principles of <a href="/facts/Abductive_reasoning/QoHNqvKT">abductive reasoning</a>. Established scientific theories have withstood rigorous scrutiny and embody scientific <a href="/facts/Knowledge/joozoaup">knowledge</a>.
A scientific theory differs from a <a href="/facts/Scientific_fact/vNPzHxtf">scientific fact</a>: a fact is an observation and a theory organizes and explains multiple observations. Furthermore, a theory is expected to make predictions which could be confirmed or refuted with addition observations. <a href="/facts/Stephen_Jay_Gould/FtAcabjg">Stephen Jay Gould</a> wrote that "...facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world's data. Theories are structures of ideas that explain and interpret facts."
A theory differs from a <a href="/facts/Scientific_law/aVtc4wpk">scientific law</a> in that a law is an empirical description of a relationship between facts and/or other laws. For example, <a href="/facts/Newton%2527s_law_of_universal_gravitation/F6qH2XC3">Newton's Law of Gravity</a> is a mathematical equation that can be used to predict the attraction between bodies, but it is not a theory to explain how <a href="/facts/Gravity/bqAN7DdQ">gravity</a> works.
The meaning of the term scientific theory (often contracted to theory for brevity) as used in the <a href="/facts/Branches_of_science/tKykGyUj">disciplines of science</a> is significantly different from the common <a href="/facts/Vernacular/DEmxDgM3">vernacular</a> usage of theory. In everyday speech, theory can imply an explanation that represents an unsubstantiated and speculative <a href="/facts/Conjecture/oPWUb7SF">guess</a>, whereas in a scientific context it most often refers to an explanation that has already been tested and is widely accepted as valid.
The strength of a scientific theory is related to the diversity of phenomena it can explain and its simplicity. As additional <a href="/facts/Scientific_evidence/ChQVqPcP">scientific evidence</a> is gathered, a scientific theory may be modified and ultimately rejected if it cannot be made to fit the new findings; in such circumstances, a more accurate theory is then required. Some theories are so well-established that they are unlikely ever to be fundamentally changed (for example, scientific theories such as <a href="/facts/Evolution/Hj0qAaBk">evolution</a>, <a href="/facts/Heliocentrism/4hoCMs7P">heliocentric theory</a>, <a href="/facts/Cell_theory/71xtwL7f">cell theory</a>, <a href="/facts/Plate_tectonics/RtRG5lY4">theory of plate tectonics</a>, <a href="/facts/Germ_theory_of_disease/VReJjyw7">germ theory of disease</a>, etc.). In certain cases, a scientific theory or scientific law that fails to fit all data can still be useful (due to its simplicity) as an approximation under specific conditions. An example is <a href="/facts/Newton%2527s_laws_of_motion/XKzGTXK1">Newton's laws of motion</a>, which are a highly accurate approximation to <a href="/facts/Special_relativity/vsFFc63E">special relativity</a> at velocities that are small relative to the <a href="/facts/Speed_of_light/sKSQwdNx">speed of light</a>.
Scientific theories are <a href="/facts/Testability/6soVx1nE">testable</a> and make verifiable <a href="/facts/Prediction_in_science/0w4XXB33">predictions</a>. They describe the causes of a particular natural phenomenon and are used to explain and predict aspects of the physical <a href="/facts/Universe/XbfpnDmM">universe</a> or specific areas of inquiry (for example, electricity, chemistry, and astronomy). As with other forms of scientific knowledge, scientific theories are both <a href="/facts/Deductive_reasoning/HadA1zWS">deductive</a> and <a href="/facts/Inductive_reasoning/EJ992JJ9">inductive</a>, aiming for <a href="/facts/Predictive_power/SBBA4w4s">predictive</a> and <a href="/facts/Explanatory_power/fV2TfhPo">explanatory power</a>. Scientists use theories to further scientific knowledge, as well as to facilitate advances in <a href="/facts/Technology/9Uav5WVR">technology</a> or <a href="/facts/Medicine/2fnp90Je">medicine</a>. Scientific hypotheses can never be "proven" because scientists are not able to fully confirm that their hypothesis is true. Instead, scientists say that the study "supports" or is consistent with their hypothesis.

Scientific theory open-in-new

Scientific theory