What is a theory? What makes a good theory? We also look at accuracy and precision, historic examples, Karl Popper's ideas of a theories, Occam's razor, the scientific model etc. for an extensive look into the concept of a theory and its place in any discipline.

1. ON THEORIES
V . H . B E L V A D I @ vhbelvadi v h b e l v a d i . c o m p h y s i c s c a p s u l e . c o m
what are they and how do they work?
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2. Scope
!
You will be able to answer
!
What is a theory?
What are accuracy and precision?
What are the characteristics of a good theory?
What are theories in philosophy and in physics
What is the scientific method?
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3. Contents
1 Definition of a theory
2 Systems and phenomena
3 Levels of theorising
4 Accuracy and precision
5 Good theory as a machine
6 Karl Popper’s characteristics
7 Provable v. unfalsifiable
8 Theories of philosophy v. theories of physics
9 Five more characteristics of a theory
10 Assumptions
11 The scientific method
12 Lex Parsimoniae

4. A man may die,
nations may rise
and fall, but an
idea lives on.
!
JOHN F. KENNEDY
flickr.com/andrewtarvin

5. Theories
are
ideas

6. A supposition or
a system of ideas
intended to explain
something.
Oxford Dictionary

7. &the something
is generally a
phenomenon
the explanation
must be
independent of
the something
Something

8. Let us examine this
1. How does a door rotate?
2. It works like one-quarter of a revolving door.
3. It works based on a hinge.
—————————————————————————
Depends on
another door
1. Why does a coin have two sides?———————————————————
Not a phenomenon

9. What is a phenomenon?
φαίνειν - to manifest (itself)
!
An event that is observable,
occurs over a period of time and
is measurable in some units and may or
may not require the use of instruments.
In physics:
[phai-no-me-non]

10. System or phenomenon?
A system is a portion of the universe chosen for study,
which responds to any number of varying conditions.
An event inside a system is a phenomenon.

11. Example 1 A aquarium is a system.
When an aquarium is kept on fire, its water boils.
When water is drained out, plants and fish die.
When fish swim, their fins move to and fro.
Phenomena
Example 2 A panchayat is a system.
When somebody throws a stone, others react.
If it does not function well, people protest.
If it rains, the panchayat meet is cancelled.
Phenomena
All these are simply parts of a system reacting to
some occurrence inside or from outside that system

12. THEORY
Hypothesis
Law
UNPROVEN SPECULATIVE
PROVEN
RESULTS, NOT
MECHANISMS
PROOFS MECHANISMS
Facts

13. Terms
in brief
Axiom — the starting point of a reasoning, cannot be proven
e.g. a line can be drawn between any two points
Postulate — similar to an axiom, often only slightly more accurate
Theorem — a logical consequence of a set of axioms with proof
Corollary — a trivial theorem with little consequence to the problem
it is often very close in similarity to a previous axiom or theorem
Hypothesis — a statement capable of being proven, not yet proved
Law — a proven statement, often tested over time with certainty

14. Accuracy+precision
or,degreeofbeingunquestionable
Axiom
Postulate
H
ypothesis
Theory
Law
Scientific process of thought

15. What are accuracy and precision?
Accuracy
Precision
= Experimental or
observational result
Expected or known
correct result
Accurate,preciseAccurate,imprecise
Inaccurate,impreciseInaccurate,precise

16. A theory must
be precise
and make
accurate
predictions.

17. So, when people say,!
“I have a theory…”
they actually mean!
they have a hypothesis

18. A theory
is like
a machine
Image: Frédéric Bisson

19. Takes in
known facts
Provides
explanations
Makes
predictions
THEORY

20. The unknown
In other words:
A good theory
The known
Discovery
A useless
theory
Also
useless

21. Karl PopperKarl Popper’s
CHARACTERISTICS OF A
GOOD SCIENTIFIC THEORY

22. 1
Easy
to
verify

23. 2 Make
predictions

24. 3Make
prohibitions

25. 4Must be
testable

26. 5Failed tests
of falsification
are supportive
evidences

27. But let us not forget that
Popper supported
Empirical falsification

28. whereas most science
is still based on
Francis Bacon’s Inductivism

29. Stephen
Hawking
sums it up

30. A theory is a
good theory if
it satisfies two
requirements

31. It must accurately
describe a large class
of observations by
relying on few
arbitrary elements

32. It must make
definite predictions
about the results of
future observations

33. Provable?!
or
Unfalsifiable?

34. Provable
Unfalsifiable

35. Provable
Unfalsifiable
= can be proved

36. Provable
Unfalsifiable
= can be proved
= cannot be disproved

37. Example
What is a flame?

38. Example
What is a flame?
Lighting into a flame can be a phenomenon

39. A flame is a!
body that!
gives out!
light and is!
too hot to!
hold in!
one’s hand
Proposed!
theory

40. Provable?

41. Provable?
Yes.
All flames are hot and glowing.

42. Unfalsifiable?

43. Unfalsifiable?
No.
The cold flame experiment.

44. Find experiment instructions at
j.mp/1tK5L0S

45. A glowing!
body of!
ignited gas!
that is!
generated by!
something!
on fire.
Alternate!
theory

46. Provable?

47. Provable?
Clearly.

48. Unfalsifiable?

49. Unfalsifiable?
Yes.
All known flames are generated by things on fire
and all known flames are composed of gasses.

50. TYPES OF THEORIES
Theories of philosophy
Theories in physics

51. TYPES OF THEORIES
Theories of philosophy
Theories in physics
used in all sciences/social sciences;
stated in english etc.
used in physics, in addition to theories of philosophy;
stated in mathematics

52. Theories in physics
e.g. (James Clerk) Maxwell’s theory of electromagnetism

53. How does it work?
The mathematics
Dx Dy Dz charge
volume
=

54. How does it work?
Electric flux
!
(amount of electric
field vectors
emanating
from a point)
Amount of
Amount of charge
per unit volume
The English

55. }
These equations give
us a physical picture
of
LIGHT
Physical meaning —
Light is a wave
that looks like this:

56. If it is a good theory,
What does it explain?
What does it predict?

57. What does it explain?
What does it predict?

58. What does it explain?
What does it predict?
The use of magnetism to
store computer memory
* Remember!
The theory is from the
1860s, so it was a
prediction then: this form
of computer memory was
used until the 1980s.

59. Some more
characteristics

60. Replication

61. Unity
One technique applicable to
a wide range of problems

62. Fecundity
The ability to give rise to new ideas

63. Independence
of auxiliary hypotheses arising for
or as a result of a given theory

64. Iteration
Improve accuracy to improve/retain validity

65. Iteration
Improve accuracy to improve/retain validity
e.g. The orbit of planet Mercury

66. 7%

67. Assumptions
An assumption can be a theory
only if it is meant to be applied only in
cases when the assumption is true

68. The scientific method
Ask a question
Formulate a hypothesis
Determine the predictions of the hypothesis
Theory,
law etc.if correct
make
corrections
if wrong
Test the hypothesis
Compare results & hypothesis

69. Occam’s razorwhen multiple explanations seem to exist
among competing hypotheses,
the one with the fewest
assumptions should
be selected
William of Ockham
late 1200s - early 1300s
Lex Parsimoniae
‘leks - par - see - ‘moan - e - yea

70. Thank you
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