An Introduction to Astronomy
Part I: The Nature of Science
Lambert E. Murray, Ph.D.
Professor of Physics
Harding University
Astronomy: The Oldest Science
Our ancestors were far more aware of the night
sky than we are today.
 They recognized prominent “groupings” of stars.
 These groupings of stars (or individual stars, like
Polaris) were used as direction indicators, and
where also associated with the seasons.
 They were aware of the intricate motions of the
Sun, the Moon, and the “wandering stars.”
 As time progressed, different “models” of how the
Sun, Moon, and stars “worked” were developed,
and the “science” of astronomy was born.

What is Science?
 A simple
collection of facts regarding the
natural world?
 The ability to predict the outcome of certain
events (e.g., the weather)?
 The ability to change the physical world in
which we live (e.g., the production of
vaccines, genetic alteration of crops)?
A Definition of Science
the Latin word scio for “to know”.
 A method or process whereby one attempts
to understand the rules which govern the
natural world.
 An Example: Determine the rules of chess
simply by watching two people play.
 Knowing the rules may imply the ability to
predict the outcome, or to alter the outcome
of some phenomenon. Does knowing the
rules of Chess enable you to predict or alter
the outcome?
 From
The Fundamental Presupposition of
Science
 There
are basic rules which govern the
natural universe and these rules do not
change. [Uniformitarianism]
– Implicit in this assumption is that the universe
is “real” and has objective existence apart from
the observer.
 This
basic presupposition seems to be
consistent with the Judeo-Christian religion.
Genesis and The Presuppositions of
Science
Part I
The universe is real, and follows a single
set of rules:
“In the beginning God created the heavens and the
earth.” (Gen. 1:1)
 “And God saw that it was good.”(Gen. 1:4)
 “By the seventh day God had finished the work he
had been doing . . .” (Gen. 2:2)

Genesis and The Presuppositions of
Science
Part II
Man has the ability to understand and to alter
nature:
“So God created man is his own image . . . and let
them rule over . . . all the earth, and over all the
creatures . . .” (Gen. 1:26)
 “. . . what is man that thou art mindful of him,. . .
yet thou hast made him a little less than the angels.
(Ps. 8:4-5)
 “It is the Glory of God to conceal a matter; to search
out a matter is the glory of kings.” (Prov. 25: 2)

Genesis and The Presuppositions of
Science
Part III
But man must use experimentation, not
logic, to discern the mysteries of God:

“For my thoughts are not your thoughts, neither
are your ways my ways” (Is. 55:8)
The Scientific Method
 Level
One: Collecting Data
 Level Two: Organization of Data
– Looking for Patterns and Trends
 Level
Three: Model Building
– Developing a hypothetical model
– Testing the model
– Refining the model
Level One: Collecting Data
Good data collection requires critical observations
of the physical universe using all possible means
(this begins with the five senses).
 Good data collection often requires the use of
instruments to
– amplify the senses (e.g., telescopes)
– quantify the senses (e.g., meter sticks,
spectrometers)
 Careful, quantitative observations, faithfully
recorded, produce what we call facts.
 A collection of all the known facts (about a
phenomenon) make up the data.

Making Critical Observations: 1
 Which
central circle appears larger?
Making Critical Observations: 1
 Which
central circle appears larger?
Making Critical Observations: 2
 Which
lines are parallel?
Move the pattern!
Making Critical Observations: 2
 Which
lines are parallel?
Move the pattern!
Level Two: Organization and
Interpretation
 Look
for patterns and trends in the data
Pressure
– Use graphs to plot one quantity against another
(e.g., PVT graphs)
T3
T2
T1
Volume
Observed Patterns or “Laws” are
often expressed Mathematically
 Observed
patterns with widespread
application are often called laws. The
graphic relationship shown on the last page
is the ideal gas law.
 These observed relationships can often be
expressed mathematically. For example, the
ideal gas law can be expressed using the
equation:
PV = nRT
Level Three: Model Building
 Model
building is the most creative activity
of the scientist
 A model is a hypothetical picture used to
explain a phenomenon in terms of
previously known, and familiar concepts (or
in terms of relevant preconceptions).
 These models may be:
– Concrete (e.g., a globe), or
– Abstract (e.g., photon -photon interactions)
An Abstract Model:
The photon-photon interaction
When two “particles” throw a “photon” back and forth, the
particles separate!
Developing Models
One forms a mental picture of a system (which
may or may not really exist) in an attempt to
explain the observed facts [i.e., one uses inductive
reasoning to form an hypothesis].
 If the model successfully predicts the observed
phenomena, and perhaps even predicts previously
unnoticed effects which are later verified [by the
process of deductive reasoning], the model is said
to be a good model, but it is still just a model. If
this model proves useful over an extended period
of time, it becomes accepted and is called a theory.

Scientist begin with simple models.

Nature is typically very complex
– Consider a football thrown through the air which
wobbles and spins and is slowed by friction.

The scientist first forms a simple model to
describe only certain simple aspects of reality
– Treat the football as a simple point with a specific mass,
neglecting its odd shape, the fact that it spins or
wobbles, and neglecting air resistance.

If this simple model seems to work, additional
complexity is then added, and the model is further
modified.
– Add in the spin of the ball, the interaction of the ball
with air (friction), etc.
Side Notes
The scientific process generally progresses on all
levels simultaneously rather than in a predictable
three-step formula.
 One rarely proves that a model is completely
valid.

– Two different models may predict the same observed
phenomena.
– The simpler model is usually the best model (Occam’s
razor)
– A model which cannot be tested may be elegant and
clever, but is not scientifically useful.
Side Notes
(continued)

The process of building models to explain the
world is usually a process of building upon older,
accepted models which were developed by others.
One can become scientifically literate only by
becoming familiar with the currently accepted
models.

One should read all scientific literature with the
understanding that what is being presented is the
currently accepted model, based upon our present
knowledge and certain assumptions. In most
cases, fact and inference are woven together into
the fabric of scientific knowledge.