Scientific Thinking
Early Thinking on the Natural World
± Learn by seeing it for oneself
± Learn by hearing about it from a trusted source
± Accept without questioning
± Seek understanding only when food or safety is at risk
Mid-1600s: A New Way of Thinking
± Logic and Reason Are Used to Study The Natural World
±  Observation
±  Questioning
±  Experimentation
±  Discussion
1
Early Ideas On Animal Life
(Biblical Times to 1600s)
± "Simple" animals arise from "non-life." Fleas come
from soiled clothing, mice from dirty hay, flies from
rotting meat, alligators from fallen tree trunks "
± If eggs were invisible to the naked eye, or birth wasnʼt
witnessed, spontaneous generation was assumed "
Early Ideas On Animal Life
(Biblical Times to 1600s)
± The sequence of copulation,
pregnancy and birth was
accepted for "complex" animals "
The details of how it occurred
were a complete mystery !
2
± Observation…
± Discussion…..
± Observation….
± Discussion….
The First Experiment
LIFE from NON-LIFE
solving the puzzle of
Spontaneous Generation
Meat and Maggots
± Most said maggots grew from rotting
flesh – spontaneous generation
± Others thought that they were related to
flies landing on the meat
3
Italian Physician Francesco Redi (1668)
±  Challenged the commonly held assumption that
maggots sprang from rotting flesh
±  He asserted that the appearance of maggots was
related to allowing flies to land on the meat
±  Redi designed an experiment to test his belief
How are observations turned
into proof?
4
Observation: an idea originating from an appreciation
of patterns and inconsistencies
Meat wrapped in cheesecloth lasts longer
Food kept in jars, doesn’t spoil as easily
The more flies, the more spoilage
OBSERVATION: When food is stored so that flies
can’t touch it, maggots don’t grow on it.
Proposed Explanation =
Hypothesis: an educated prediction of a
natural occurrence
For maggots to grow on food, flies have to
land on it
± Observation
± Discussion
± More Observation
± Proposed Explanation
± Test that demonstrates validity of
explanation
5
The Experiment:
Looking for Greater
Understanding: !
Developing an Hypothesis (a justified prediction) !
An hypothesis is a statement, not a question. "
It must be a testable prediction of some element of the natural world.
"
±  Maggots hatch from eggs that are laid by adult flies"
±  Tobacco smoke exposure worsens asthma episodes"
±  Cattle treated with antibiotics grow faster than those untreated "
±  Men gossip more than women"
±  Chickens lay more eggs when provided with natural light"
±  Captive elephants have a shorter lifespan than wild elephants "
"
!
!
Controls
±  Experimental results cannot be trusted if outside
influences are not eliminated or at least factored into
the interpretation
6
Determining the type and
amount of data needed for
valid results:!
"
Results/Data
REQUIREMENTS!
±  What measurements will be taken?!
"Tests? Physical data? Census? "
±  How will measurements be taken?!
!Who will measure? When? Where? "
±  Error / accuracy – difficulty with measurements or
data collection!
!What are the challenges? How can they be
overcome? Trial Run? "
±  Unexpected influences!
Discussion of results !
±  Identify general trends "
±  Interpret significance of results"
±  Compare to hypothesis"
±  Compare with literature "
±  Identify sources of error - method,
manipulation, analysis"
±  Improvements for next study"
±  Who paid for the science? "
7
Science doesn’t always test a
hypothesis
±  Describe
±  Document
±  Explore
Science asks about the natural world in an
effort to understand its workings
Scientific inquiry doesn’t require a defined purpose or goal.
More Understanding = Best
Science makes tentative
conclusions
Science never stops asking questions.
Tinkering and improving is part of the process.
Science challenges its own thinking and
modifies concepts as data demands
Science seeks out and respects
unexpected results
8
Science makes
tentative
conclusions
Science doesn’t make value
judgments: best looking, best
tasting, most lovable
Science asks questions with
provable answers
Science proposes mechanisms that
predict the behavior of the
observable world.
Science is falsifiable
Science is never based on faith
Science doesn’t say, "We don’t
care what the facts show…..
……We still believe…"
If it can’t be proved wrong, it isn’t science!
9
Science is testable
Science is testable
ifi
c
Observe Hypothesize
Construct a Controlled Situation or Test
Collect Data
Analyze and Conclude Present to Peers
Debate
Re-Hypothesize Sc
ie
nt
§ 
§ 
§ 
§ 
§ 
§ 
§ 
§ 
M
et
ho
d
How does science seek to
understand?
10
Theory: a well-substantiated
explanation of some aspect of the
natural world
When scientists talk about the theory of
evolution--or the atomic theory or the theory
of relativity, they are not expressing
reservations about its truth.
11