Scientific theory

[3] Stephen Jay Gould wrote that "...facts and theories are different things, not rungs in a hierarchy of increasing certainty.

[9] They describe the causes of a particular natural phenomenon and are used to explain and predict aspects of the physical universe or specific areas of inquiry (for example, electricity, chemistry, and astronomy).

The defining characteristic of all scientific knowledge, including theories, is the ability to make falsifiable or testable predictions.

[18]From the American Association for the Advancement of Science: A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment.

But the phenomenon of gravity, like evolution, is an accepted fact.Note that the term theory would not be appropriate for describing untested but intricate hypotheses or even scientific models.

[citation needed] Once all of the criteria have been met, it will be widely accepted by scientists (see scientific consensus) as the best available explanation of at least some phenomena.

The strength of the evidence is evaluated by the scientific community, and the most important experiments will have been replicated by multiple independent groups.

For example, the predictions made by classical mechanics are known to be inaccurate in the relativistic realm, but they are almost exactly correct at the comparatively low velocities of common human experience.

[6] In chemistry, there are many acid-base theories providing highly divergent explanations of the underlying nature of acidic and basic compounds, but they are very useful for predicting their chemical behavior.

[23] Over time, as successive modifications build on top of each other, theories consistently improve and greater predictive accuracy is achieved.

For example, it has been known since 1859 that the observed perihelion precession of Mercury violates Newtonian mechanics,[24] but the theory remained the best explanation available until relativity was supported by sufficient evidence.

Also, while new theories may be proposed by a single person or by many, the cycle of modifications eventually incorporates contributions from many different scientists.

For example, physical theories in the 19th century implied that the Sun could not have been burning long enough to allow certain geological changes as well as the evolution of life.

An elegant theory, special relativity yielded its own consequences,[31] such as the equivalence of mass and energy transforming into one another and the resolution of the paradox that an excitation of the electromagnetic field could be viewed in one reference frame as electricity, but in another as magnetism.

[citation needed] Einstein sought to generalize the invariance principle to all reference frames, whether inertial or accelerating.

Even massless energy exerts gravitational motion on local objects by "curving" the geometrical "surface" of 4D space-time.

Yet unless the energy is vast, its relativistic effects of contracting space and slowing time are negligible when merely predicting motion.

Scientific theories are broader in scope, and give overarching explanations of how nature works and why it exhibits certain characteristics.

In addition to scientific theories, the language also included observation sentences ("the sun rises in the east"), definitions, and mathematical statements.

The phenomena explained by the theories, if they could not be directly observed by the senses (for example, atoms and radio waves), were treated as theoretical concepts.

Software packages for creating the bill of materials for construction allows subcontractors to specialize in assembly processes, which spreads the cost of manufacturing machinery among multiple customers.

The Oxford English Dictionary (OED) and online Wiktionary indicate its Latin source as assumere ("accept, to take to oneself, adopt, usurp"), which is a conjunction of ad- ("to, towards, at") and sumere (to take).

[49] Several philosophers and historians of science have, however, argued that Popper's definition of theory as a set of falsifiable statements is wrong[50] because, as Philip Kitcher has pointed out, if one took a strictly Popperian view of "theory", observations of Uranus when first discovered in 1781 would have "falsified" Newton's celestial mechanics.

He insists we view scientific theories as an "elaborate collection of statements", some of which are not falsifiable, while others—those he calls "auxiliary hypotheses", are.

For example, the logical empiricist Carl Gustav Hempel likened the structure of a scientific theory to a "complex spatial network:" Its terms are represented by the knots, while the threads connecting the latter correspond, in part, to the definitions and, in part, to the fundamental and derivative hypotheses included in the theory.

But even a geographical map fully embodies in itself a set of strict rules for finding one's way through a region of otherwise uncharted experience.

It is written in the language of mathematics, and its characters are triangles, circles, and other geometrical figures, without which it is humanly impossible to understand a single word of it; without these, one is wandering around in a dark labyrinth.

[54]The book metaphor could also be applied in the following passage, by the contemporary philosopher of science Ian Hacking: I myself prefer an Argentine fantasy.

[55]In physics, the term theory is generally used for a mathematical framework—derived from a small set of basic postulates (usually symmetries—like equality of locations in space or in time, or identity of electrons, etc.

Scientific knowledge outside a named theory can still have a high level of certainty, depending on the amount of evidence supporting it.