What Is Scientific Hypothesis And Scientific Theory? Hypothesis and Theory in Science

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Hypothesis and Theory in Science

The confusion over the use of the terms hypothesis and theory can be difficult to sort out.

 

Popularly, hypothesis and theory are used almost interchangeable to refer to some idea which is vague or fuzzy and which seems to have a low probability of being true

 

Thus, an idea is just a "hypothesis" when it is new and relatively untested or it is being actively tested and investigated. In other words, whenther probability of error and correction is still relatively high. However, one it has successfully survived repeated testing, has become more complex, is found to explain a great deal, and has made many interesting predictions, it achieves the status of "theory."

Source http://atheism.about.com/index.htm

 

In reality, however, such differentiation is notoriously difficult to make. Exactly how much testing is really required to move from hypothesis to theory? How much complexity is needed to stop being a hypothesis and start being a theory?

 

If you try to use hypothesis to refer to more tentative ideas and theory to refer to more established ideas, you aren't doing anything wrong - especially if you make that clear at the beginning. But don't insist that others do so as well.

Scientific Theories

 

Theories are what allow scientists to organize and understand earlier observations, then predict and create future observations.

 

The word theory is misunderstood particularly often by puplic. The common usage of the word "theory" refers to ideas that is just a vague and fuzzy and have no firm proof or support. In science "theory" is a conceptual structure which is used to explain existing facts and predict new ones. To say "the apple fell" is to state a fact, whereas Newton's theory of universal gravitation is a body of ideas that explain why the apple fell. Thus a multitude of falling objects are reduced to a few concepts or abstractions interacting according to a small set of laws, allowing a scientist to make predictions about the behaviour of falling objects in general.

[from http://atheism.about.com/index.htm ]

 

Some universally accepted models such as atomic theory are so well-established that it is nearly impossible to imagine them ever being falsified. Others, such as relativity and electromagnetism have survived rigorous empirical testing without being contradicted, but it is nevertheless conceivable that they will some day be supplanted. Younger theories such as string theory may provide promising ideas, but have yet to receive the same level of scrutiny.

 

Scientific theories can be described by characteristics which they share in common and which differentiate them from unscientific theories.

 

A scientific theory must be:

1. a simple unifying idea that postulates nothing unnecessary

 

2. logically consistent (internally and externally)

 

3. Useful (describes and explains observed phenomena)

 

4. logically "OR" Empirically tested and based upon Controlled, Repeated Experiments . A theory which cannot be tested empirically is useless for researchers.

 

5. lead to predictions or retrodictions that are testable. A theory which has not made any actually verified predictions might prove useful in the future when its predictions are verified, but not currently. A theory which cannot provide retrodictions (to utilize present information or ideas to infer or explain a past event or state of affairs) may also be useful in the future, but not currently. If a theory's results cannot be reproduced, it is impossible to determine if those results were ever actually valid (rather than the result of error or fraud).

 

6. falsifiable (i.e., cases must exist in which the theory can be imagined to be invalid). For example saying "Things fall down" will be invalid if we find an object fall up. When a theory is not falsifiable, it is impossible to tell if it is true or not, and thus it won't be possible to correct it via experimentation. & Falsifiable

 

7. Clearly limited by explicit boundary conditions so that it is clear whether or not particular data are or are not relevant to verification or falsification. Newton's laws of motion is not valid to very big speed. It is a famous example of a law which was found not to hold in experiments involving motion at speeds close to the speed of light or in close proximity to strong gravitational fields. Outside those conditions, Newton's Laws remain an excellent model of motion and gravity. Einstien Mechanic is for cases with high speed.Because general relativity accounts for all of the phenomena that Newton's Laws do and more, general relativity is now regarded as a better theory.Quantum mechanics examines phenomena that seem to defy our most basic postulates about causality and fundamental understanding of the world around us.. Euclidian Geometry valid in small distance where assumed the area is flat. Otherwisw we need spherical geometry. When there aren't any clear boundaries, we'll never know if particular observations count for or against it.

 

8. Correctable & Dynamic (changes are made as new data is discovered)

 

9. Progressive i.e. it must be superior to theories which people have offered in the past i.e:

i). meet or surpass all of the criteria set by its predecessors or demonstrate that any abandoned criteria are artifactual

ii) be able to explain all of the data gathered under previous relevant theories in terms either of fact or artifact (no anomalies allowed)

iii) be consistent with all preexisting ancillary theories that already have established scientific validity

For example: Eistein Mechanics is the Newton mechanics when spead is low.

 

10. Tentative (admits that it might not be correct rather than asserting certainty) .

 

Notice that:

i) Lacking one or two might not mean that a theory isn't scientific, but only if there are very, very good reasons; lacking most or all, however, will certainly disqualify an idea from being genuinely scientific.

 

ii) The fact that a theory passed an empirical test does not prove the theory, however. The greater the number of severe tests a theory has passed, the greater its degree of confirmation and the more reasonable it is to accept it. However, to confirm is not the same as to prove logically or mathematically. No scientific theory can be proved with absolute certainty.

 

iii) True Scientists never claim absolute knowledge. Unlike a mathematical proof, a "proven" scientific theory is always open to falsification if new evidence is presented. Even the most basic and fundamental theories may turn out to be imperfect if new observations are inconsistent with them.

Newton's scientific theory of universal gravitation predicts that the force between two masses should be inversely proportional to the square of the distance between them (otherwise known as the "inverse square law"). In principle, we could take measurements which indicated that the force is actually inversely proportional to the cube of the distance. Such an observation would be inconsistent with the predictions of Newton's universal theory of gravitation, and thus this theory is falsifiable.

 

iv) The validity of a hypothesis does not stand or fall based on just a few confirmations or contradictions, but on the totality of the evidence. Often, data that initially may seem to be inconsistent with a theory will in fact lead to new important predictions. The history of Newtonian physics gives a clear example. The abnormal movement of Uranus was initially considered a potential falsification of Newton's new theory. However, by claiming the existence of an unseen planet, the anomaly was explained within Newton's paradigm. In general, an explanation for anomalous behavior should be considered ad hoc unless it is independently verifiable. Sugesting a new, unseen planet might be considered hedging if there were no independent way to detect if a new planet actually existed. Nevertheless, when technology had advanced enough to reliably test the new prediction, the unseen planet was found to be Neptune. So alternate explanations for inconsistancy should be treated like any other hypotheses i.e. they should be weighed, tested, and either ruled out or confirmed. But a hypothesis should not be considered falsified until thorough testing has produced multiple lines of positive evidence indicating that the hypothesis is truly inconsistent with the empirical data.

 

v) However, even if a theory is very rich and even if it passes many severe tests, it is always possible that it will fail the next test or some other theory will be proposed that explains things even better. Logically speaking, a currently accepted scientific theory could even fail the same tests it has passed many times in the past.

Edited March 6, 2006 by kasm (see edit history)