1. Learning How To Do Science Frontiers in Science Presentation
Fred C. Dyer
Department of Zoology
3/12/2011

2. Doing Science Elements of the scientific method: Observe patterns
2. Ask questions
3. Formulate hypotheses that make specific predictions
Perform experiments or observations to test hypotheses
Analyze Data

3. Starting a scientific inquiry…. Inheritance
Offspring tend to resemble their parents
F Galton (1886): inheritance of height
What do parents and offspring have in common?
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4. Starting Point: OBSERVATIONS
Description of PATTERN and PROCESS
You see a pattern in nature
You also observe other information that may help you understand the processes underlying it
To understand processes, ask focused QUESTIONS

5. Asking Questions
Watch video and write down at least 3 questions about what you see
archer fish

7. Refining questions about pattern
Sometimes it helps first to find out more details about the thing we are trying to understand:
Often this involves asking quantitative questions
Not just whether archer fish eat only insects, but what percentage of their diet of insects
Not just whether archer fish sometimes feed alone, but what is the distribution of group sizes when fish are feeding
Also: What percentage of times do fish jump vs. shoot? What is success rate for jumping vs. shooting? Just how accurate are
It may also be useful to ask qualitative questions
For example: make a detailed list of the prey types that the animal feeds on, or the habitats where it feeds

8. Answering the questions
Formulate hypotheses:
A hypothesis is a plausible guess as to answer
Hypotheses are in the form of statements
Usually it is possible to generate several reasonable hypotheses
Why do archer fish sometimes jump and sometimes shoot? Write down at least three distinct hypotheses that would answer that question

10. Steps so far:
Observations: the patterns/puzzles we see
Questions: what processes may explain these patterns?
Hypotheses: statements of possible answers
Next Step: TESTING hypotheses

11. Testing Hypotheses
A hypothesis is a guess about an explanation for a phenomenon
To “explain” something means you understand the cause
What does it mean to say that A causes B?
It means that B’s occurrence depends upon A occurring
It also means that there is some material connection that mediates the causal relationship between A and B
Testing a hypothesis means gathering evidence to determine whether the hypothesis is correct.

12. Logic of Hypothesis Testing
Here’s the logic:
Formulate hypothesis, e.g. H1: “A causes B”:
Determine the predictions that this hypothesis makes.
For example, if Hypothesis 1 is correct, then
every time A occurs, B should occur, and
B never occurs without A occurring
Perform additional observations to determine whether predictions are upheld.
The observations may be aided by doing experiments that control the variables of interest (though sometimes experiments aren’t possible).

13. Steps so far…. In the following example, write down:
Observations about particular natural patterns
Questions about the causes/explanations for these patterns
Hypotheses about the possible causes of the phenomenon
Predictions that each hypothesis makes if it is true
An additional observation or experiment that you could do that would allow you to test this prediction

14. Why do archer fish sometimes jump and sometimes shoot?
Example:
Why do archer fish sometimes jump and sometimes shoot?
Some hypotheses to consider:
Height of prey
Whether prey is moving
Experience of predator
Whether predator is in a group
Pick ONE of these and propose a test

15. Generalizations About Scientific Hypotheses
A good hypothesis:
Is consistent with other known facts about nature
Can potentially be falsified (proven wrong)
Uncertainty always exists:
You can’t prove a hypothesis right, you can only fail to falsify it: other hypotheses might make same prediction
But you may not be able to falsify it with absolute certainty: failure to see effect predicted by hypothesis may occur because experimental conditions weren’t present
Value of considering multiple hypotheses:
There are often multiple causes for phenomena
Considering multiple causes helps in designing experimental controls

16. An aside…
Hypothesis vs. Theory

17. Much scientific evidence is indirect
Some difficulties that make science hard or confusing
Applying scientific method to the past: what is role of “prediction” and nature of evidence for testing these predictions?
Much scientific evidence is indirect
Patterns of causation: multiple direct or indirect causes may explain phenomena
Some hypotheses are represented as complex computational functions

18. Difficulty 1: Hypotheses about the past
E.g., when did dinosaurs live; why did they go extinct?
Common view of science:
repeatable observations
controlled experiments (perhaps replicated many times)
test hypotheses by making predictions about outcome of experiments
How can one do science when dealing with unique past events?

19. Dealing with unique past events
Suggest some hypotheses, and the predictions of these hypotheses
The pattern (ie. the evidence):
A body with a gunshot wound to the temple
A revolver on the floor near the body
The question: whodunit?

20. Number of families (types) of marine invertebrates
Mass extinctions as a “whodunit”
Why do mass extinctions happen?
Number of families (types) of marine invertebrates
Event that wiped out dinosaurs
Mass extinctions
Total number of families of marine invertebrates over 600 million years
Background extinction rate

21. What killed the dinosaurs?
H1: Climate change caused by terrestrial processes
H2: Extra-terrestrial impact by asteroid
Basis of H2: Iridium in some sediments deposited around the time of extinction)
Other predictions:
Iridium found worldwide
Shocked quartz in same sediments
Impact crater
THESE ARE PREDICTIONS ABOUT FUTURE OBSERVATIONS

22. Difficulty 2: indirect evidence
Some processes happen on a scale that is too small, too fast, too large, or two slow for direct observation, and so observations are mediated by instruments or indirect measures
Also, a LOT of scientific observations are based on testimony of other experts—importance of trust

23. Difficulty 3: Multiple causes
We’re interested in causes, but…..
All we can really see are correlations among events or objects
Multiple causes may explain given correlation
Example: diet and cancer
Observations: Japanese have lower incidence of colon cancer than Americans, and have less (and different) fat in their diets
H1: type and amount of fat in diet is cause of cancer
Correlation between diet and cancer rate doesn’t prove causation
Other hypotheses may explain the same pattern -- SUCH AS?

24. Difficulty 3: Multiple causes (cont’d)
Example: diet and cancer
Proving that a high fat diet increases likelihood of colon cancer doesn’t rule out possibility that other factors also cause colon cancer
Proving that a high fat diet increases the likelihood of colon cancer doesn’t mean that a high fat diet will necessarily lead to colon cancer
In both cases, diet may be only one of several factors leading to cancer (or preventing it)

25. Hypotheses formulated as computational models
Difficulty 4:
Hypotheses formulated as computational models
Patterns: Direct evidence earth is warming…

26. Global Warming: direct and reconstructed
Patterns: …and warming is recent
Earth’s temperature changes inferred from actual measurements or indirect evidence (e.g., air bubbles in ice cores; glacial structure)

27. What causes warming? H1: Natural “drivers” Solar irradiance
Actual
Predicted
H1: Natural “drivers”
Solar irradiance
Volcanic gases
Gases from forest fires
Gases from decomposition
H2: Natural + anthropogenic drivers
Gases from burning of carbon-based fuels
Digestive gases from livestock and humans
Test by building mathematical models that predict temperature given specific inputs