With some exceptions the scientific method involves the following sequence:
1. observations and search for data
2. hypotheses to explain observations
3. experiments to test hypotheses
4. formulation of theory
5. experimental confirmation of theory
6. mathematical or empirical confirmation of theory into scientific law
7. use of scientific law to predict behaviour of nature
The scientific method is a continuous interplay of observation and hypothesis; observations lead to new hypotheses, which guide more experiments, which help to change existing theories.

HYPOTHESIS:
A tentative explanation of observed facts. A hypothesis is assumed to be tenable for the purposes of investigation. Every theory or law in science begins as a hypothesis. A hypothesis can be confirmed by experiments, which are observations under controlled conditions. When observations or experimental data do not support the hypothesis, it must be changed or discarded.

THEORY:
A theory is a hypothesis that has been tested by experiments, and to which exceptions have been found. A theory can be used to predict phenomena.

SCIENTIFIC LAW:
A theory that has been verified mathematically. A law, such as Newton’s law of gravitation, is a concise and general statement about how nature behaves, and brings unity to many observations. All scientific laws are provisional approximations that are valid to a high degree of accuracy and are used until something better is described.
For less general statements the term scientific principle (Archimedes principle) is used.

MODEL:
A mathematical or visual picture of a particular set of phenomena. A model may be mathematical or physical. A mathematical model consists of equations and stepbystep rules that reflect what happens in a real event.
A physical model represents a real object. A model is never perfect and scientists continually update their models on the basis of new observations.

RULE:
A set of directions concerning method or procedure.

POSTULATE or AXIOM:
A generally accepted principle or proposition.

THEOREM:
A statement of a mathematical truth together with any qualifying conditions.

SYSTEM:
A part of the material world that scientists select for study and experimentation. For example, astronomers study stars and the solar system; biologists study living systems and geologists study rocks and minerals.

EQUATION:
An equation shows the relationship between two or more quantities. For example, Einstein’s equation E = mc^{2} shows the relationship between energy (E) and mass (m); the speed of light (c) is a fundamental constant. A fundamental constant relates two or more variables and never changes its value.

(Calculations are only as good as the premises on which they are based)
‘The fascinating impressiveness of rigorous mathematical analyses, with its atmosphere of precision and elegance, should not blind us to the defects of the premises that condition the whole process. There is perhaps no beguilement more insidious and dangerous than an elaborate and elegant mathematical process built upon unfortified premises’
 – Chamberlain 1899
SCIENCE & PSEUDOSCIENCE
Pseudoscience is ideas and beliefs, such as astrology and telepathy, which masquerade as science but have little or no relationship to the scientific method. Theories of real science are continually being added to and updated, but the ideologies of pseudoscience are fixed.
‘As the circle of light increases, so does the circumference of darkness around it’
 – Albert Einstein
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