1. Hypothesis, Laws,
Theories
Thanks to T Landry

2. Hypothesis:
 Thisis an educated guess based upon
observation. It is a rational explanation of a
single event or phenomenon based upon what
is observed, but which has not been proved.
 Mosthypotheses can be supported or refuted
by experimentation or continued observation.

3. Scientific Law
 Thisis a statement of fact meant to describe,
in concise terms, an action or set of actions. It
is generally accepted to be true and universal,
and can sometimes be expressed in terms of a
single mathematical equation.
 Scientific
laws must be simple, true, universal,
and absolute.

4. Scientific Law
A scientific law must always apply under the
same conditions, and implies a causal
relationship between its elements.
 Thelaw must be confirmed and broadly agreed
upon through the process of inductive
reasoning.
 However, factual and well-confirmed
statements like "Mercury is liquid at standard
temperature and pressure" are considered to
be too specific to qualify as scientific laws.

5. Examples of Laws
 Law of gravity
 Newton's laws of motion
 the laws of thermodynamics
 Boyle's law of gases
 the law of conservation of mass
and energy,
 Hook’s law of elasticity.

6. Examples of Laws
 Law of gravity
 Newton's laws of motion
 the laws of thermodynamics
 Boyle's law of gases
 the law of conservation of mass
and energy,
 Hook’s law of elasticity.

7. Examples of Laws
 Law of gravity
 Newton's laws of motion
 the laws of thermodynamics
 Boyle's law of gases
 the law of conservation of mass
and energy,
 Hook’s law of elasticity.

8. Examples of Laws
 Law of gravity
 Newton's laws of motion
 the laws of thermodynamics
 Boyle's law of gases
Hooke's law accurately
 the law of conservation of mass models the physical
and energy, properties of common
mechanical springs for small
 Hook’s law of elasticity. changes in length

9. Laws Come With Specific
Conditions
 Ohm's law only applies to constant currents
 Newton's law of universal gravitation only
applies in weak gravitational fields
 earlylaws of aerodynamics such as Bernoulli's
principle do not apply in case of compressible
flow such as occurs in transonic and
supersonic flight

10. Theories
A theory, in the scientific sense of the word, is
an analytic structure designed to explain a
set of empirical observations. Theories are
constructed to explain, predict, and master
phenomena.
A scientific theory does two things:
 it
identifies this set of distinct observations as
a class of phenomena
 makes assertions about the underlying reality
that brings about or affects this class.

11. Theories in Science –
Logical Criteria
1. a simple unifying idea that postulates nothing
unnecessary ("Occam's Razor")
2. logically consistent
3. logically falsifiable (i.e., cases must exist in which
the theory can be imagined to be invalid)
4. 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

12. Theories in Science –
Empirical Criteria
A scientific theory must:
1. be empirically testable or lead to predictions or
retrodictions that are testable
2. actually make verified predictions and/or
retrodictions
3. involve reproducible results
4. provide criteria for the interpretation of data as
factual, artifactual, anomalous or irrelevant

13. Theories in Science –
Sociological Criteria
A scientific theory must:
1. resolve recognized problems, paradoxes, and/or
anomalies irresolvable on the basis of preexisting
theories
2. pose a new set of scientific problems upon which
scientists may work
3. suggest a "paradigm" or problem solving model to
help resolve these new problems

14. Theories in Science –
Historical Criteria
A scientific theory must:
1. meet or surpass all of the criteria set by its
predecessors or demonstrate that any abandoned
criteria are artifactual
2. be able to explain all of the data gathered under
previous relevant theories in terms either of fact or
artifact (no anomalies allowed)
3. be consistent with all preexisting ancillary theories
that already have established scientific validity

15. Laws vs theories
 Thebiggest difference between a law and a
theory is that a theory is much more complex
and dynamic.
A law describes a single action, whereas a
theory explains an entire group of related
phenomena.
A law differs from a scientific theory in that it
does not posit a mechanism or explanation of
phenomena: it is merely a distillation of the
results of repeated observation.

16. How come this class is
called Theory of
Knowledge? There’s no
theory, is there?

17. Other uses of the word.
 Fieldsof study are sometimes named "theory"
because their basis is some initial set of
assumptions describing the field's approach to
a subject matter:
 Music theory
 Literary theory
 Game theory

18. Theories NOT Theorems
 Theories are distinct from theorems:
 theoremsare derived deductively from axioms
(in mathematics) or theories (in science)
according to a formal system of rules

19. Right or Wrong?
 Theories are abstract and conceptual, and to
this end they are never considered right or
wrong.
 Instead,
they are supported or challenged by
observations in the world.
 They are 'rigorously tentative', meaning that
they are proposed as true but expected to
satisfy careful examination to account for the
possibility of faulty inference or incorrect
observation.

20. Falsified, Revised,
Shelved
 Sometimes theories are falsified, meaning that
an explicit set of observations contradicts
some fundamental assumption of the theory
 More often theories are revised to conform to
new observations, by restricting the class of
phenomena the theory applies to or changing
the assertions made.
 Sometimes a theory is set aside by scholars
because there is no way to examine its
assertions analytically.

21. Examples of Scientific
Theories
Astronomy: Big Bang Theory
Biology: Cell theory — Evolution — Germ theory
Chemistry: Atomic theory — Kinetic theory of gases
Climatology: Theory of Global Climate Change (due to
anthropogenic activity)
Geology: Plate tectonics
Physics: Theory of relativity, Quantum field theory,
Electro-magnetic Theory

22. Obsolete Theories
A superseded, or obsolete,
scientific theory is a scientific
theory that was once commonly
accepted, but that is no longer
considered the most complete
description of reality by a
mainstream scientific
consensus; or a falsifiable
theory which has been shown to
be false.

23. Biology
Miasma theory of disease
 A representation of the cholera
epidemic of the nineteenth
century depicts the spread of
the disease in the form of
poisonous air.

24. Biology
 Theory of the four bodily
humors - discredited by
Rhazes, Avenzoar, Ibn al-Nafis,
Ibn al-Lubudi and William
Harvey
 The four temperaments
(Clockwise from top right;
choleric; melancholic; sanguine;
phlegmatic).

25. Geology
Continental drift was
superseded by plate tectonics
 Plate tectonics, a modern
update of the old ideas of
Wegener about "plowing"
continents, accommodates
continental motion through the
mechanism of seafloor
spreading.

26. Progression of atomic
theory
 Plum pudding model of the atom -
assuming the protons and electrons
were mixed together in a single mass
 Rutherford model of the atom with an
impenetrable nucleus orbited by
electrons.
 Bohr model with quantized orbits
 Electron cloud model following the
invention of Quantum Mechanics in
1925 and the eventual atomic orbital
models derived from the quantum A schematic representation of the
mechanical solution to the hydrogen Plum pudding model of the atom.
atom.

27. Progression of atomic
theory
 Plum pudding model of the atom -
assuming the protons and electrons
were mixed together in a single mass
 Rutherford model of the atom with an
impenetrable nucleus orbited by
electrons.
 Bohr model with quantized orbits
 Electron cloud model following the
invention of Quantum Mechanics in
1925 and the eventual atomic orbital
models derived from the quantum
mechanical solution to the hydrogen Rutherford Model
atom.

28. Progression of atomic
theory
 Plum pudding model of the atom -
assuming the protons and electrons
were mixed together in a single mass
 Rutherford model of the atom with an
impenetrable nucleus orbited by
electrons.
 Bohr model with quantized orbits
 Electron cloud model following the
invention of Quantum Mechanics in
1925 and the eventual atomic orbital
models derived from the quantum
mechanical solution to the hydrogen Rutherford Bohr Model
atom.

29. Progression of atomic
theory
 Plum pudding model of the atom -
assuming the protons and electrons
were mixed together in a single mass
 Rutherford model of the atom with an
impenetrable nucleus orbited by
electrons.
 Bohr model with quantized orbits
 Electron cloud model following the
invention of Quantum Mechanics in
1925 and the eventual atomic orbital
models derived from the quantum
mechanical solution to the hydrogen
atom.

30. Physics
 SteadyState was replaced by an expanding
universe model starting with the Big Bang
 Newtonian mechanics was extended by
Theory of Relativity and quantum mechanics.
It is still the standard tool in engineering and
physics at atomic or larger scales and
velocities not approaching the speed of light.