The concept of predictive power, the power of a
scientific theory
A scientific theory is an explanation of an aspect of the universe, natural world that can be or that has been reproducibility, repeatedly tested and has corroborating evidence in accordance with the scientific method, using accepted protocol (s ...
to generate
testable
Testability is a primary aspect of science and the scientific method. There are two components to testability:
#Falsifiability or defeasibility, which means that counterexamples to the hypothesis are logically possible.
#The practical feasibilit ...
predictions, differs from ''
explanatory power
Explanatory power is the ability of a hypothesis or theory to explain the subject matter effectively to which it pertains. Its opposite is ''explanatory impotence''.
In the past, various criteria or measures for explanatory power have been prop ...
'' and ''descriptive power'' (where phenomena that are already known are retrospectively explained or described by a given theory) in that it allows a prospective test of theoretical understanding.
Examples
A classic example of the predictive power of a theory is the
discovery of Neptune
The planet Neptune was mathematically predicted before it was directly observed. With a prediction by Urbain Le Verrier, telescopic observations confirming the existence of a major planet were made on the night of September 23–24, Autumnal Equ ...
as a result of predictions made by mathematicians
John Couch Adams
John Couch Adams ( ; 5 June 1819 – 21 January 1892) was a British mathematician and astronomer. He was born in Laneast, near Launceston, Cornwall, and died in Cambridge.
His most famous achievement was predicting the existence and position o ...
and
Urbain Le Verrier
Urbain Jean Joseph Le Verrier (; 11 March 1811 – 23 September 1877) was a French astronomer and mathematician who specialized in celestial mechanics and is best known for predicting the existence and position of Neptune using only mathematics. ...
, based on
Newton's theory of gravity.
Another example of the predictive power of theories or models is
Dmitri Mendeleev
Dmitri Ivanovich Mendeleev ( ; ) was a Russian chemist known for formulating the periodic law and creating a version of the periodic table of elements. He used the periodic law not only to correct the then-accepted properties of some known ele ...
's use of his
periodic table
The periodic table, also known as the periodic table of the elements, is an ordered arrangement of the chemical elements into rows (" periods") and columns (" groups"). It is an icon of chemistry and is widely used in physics and other s ...
to predict previously undiscovered
chemical element
A chemical element is a chemical substance whose atoms all have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its ...
s and their properties. Though largely correct, he misjudged the relative atomic masses of
tellurium
Tellurium is a chemical element; it has symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally fou ...
and
iodine
Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...
.
Moreover,
Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English Natural history#Before 1900, naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all speci ...
used his knowledge of
evolution
Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...
by
natural selection
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the Heredity, heritable traits characteristic of a population over generation ...
to predict that since a plant (''
Angraecum sesquipedale'') with a long spur in its flowers exists, a complementary animal with a 30 cm
proboscis
A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular arthropod mouthparts, mouthparts used for feeding and sucking. In vertebrates, a pr ...
must also exist to feed on and
pollinate it. Twenty years after his death, a form of
hawk moth (''
Xanthopan morganii'') that did just that was found.
Another example of predictive power is the prediction of
Einstein
Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence f ...
's theory of
general relativity
General relativity, also known as the general theory of relativity, and as Einstein's theory of gravity, is the differential geometry, geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of grav ...
that the path of light would bend in the presence of a strong gravitational field. This was
experimentally verified by an expedition to
Sobral in
Brazil
Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
and the
Atlantic
The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...
island of
Príncipe
Príncipe (; ) is the smaller, northern major island of the country of São Tomé and Príncipe lying off the west coast of Africa in the Gulf of Guinea. It has an area of (including offshore islets) and a population of 7,324 at the 2012 Cens ...
to measure star positions during the solar eclipse of May 29, 1919, when observations made by the astrophysicist
Arthur Eddington
Sir Arthur Stanley Eddington, (28 December 1882 – 22 November 1944) was an English astronomer, physicist, and mathematician. He was also a philosopher of science and a populariser of science. The Eddington limit, the natural limit to the lu ...
seemed to confirm Einstein's predictions. Although the measurements have been criticized by some as utilizing flawed methodology, modern reanalysis of the data suggests that Eddington's analysis of the data was accurate. Later, more precise measurements taken by
radio
Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connec ...
interferometry
Interferometry is a technique which uses the ''interference (wave propagation), interference'' of Superposition principle, superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important inves ...
confirmed the predictions to a high degree of accuracy.
Applications
The predictive power of a theory is closely related to applications.
General relativity not only predicts the bending of light but also predicts several other phenomena. Recently, the calculation of
proper time
In relativity, proper time (from Latin, meaning ''own time'') along a timelike world line is defined as the time as measured by a clock following that line. The proper time interval between two events on a world line is the change in proper time ...
of
satellites
A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scientif ...
has been a successfully-measured prediction that is now incorporated into the method used to calculate positions via
GPS.
If a theory has no predictive power, it cannot be used for applications.
See also
*
Accuracy paradox
*
Forecast verification
*
*
*
Probability of success The probability of success (POS) is a statistics concept commonly used in the pharmaceutical industry including by health authorities to support decision making.
The probability of success is a concept closely related to conditional power and pr ...
*
Problem of induction
The problem of induction is a philosophical problem that questions the rationality of predictions about unobserved things based on previous observations. These inferences from the observed to the unobserved are known as "inductive inferences" ...
*
*
Statistical model validation
References
{{reflist
Philosophy of science
Epistemology