APAKAH ILMU PENGETAHUAN?(What is Science?)

Science: [scientia, knowledge]

1. Knowledge gained through experience…2. Accumulated and accepted knowledge that has

been systematized and formulated with reference to the discovery of general truths or the operation of general laws

3. Branch of study that is concerned with observation and classification of facts concerned with the physical world and its phenomena

In order to do science we have to make the following assumptions:

• There is order to the universe (even if it is chaotic order)

• The human mind is capable of comprehending this order

• If conditions are the same, the results of any study will be the same

Which of the following statements can be tested scientifically?

• Most of the energy coming from the sun is in the form of visible light.

• Unicorns exist.• Shelley wrote beautiful poetry.• The Earth was created over four billion years

ago.• Diamond is harder than steel.• Diamonds are more beautiful than rubies.

• The claim is sometimes made that the scientific method produces closer and closer approximations to "reality."

• Is this a scientific statement? Why or why not?

The Scientific Method

Scientists develop their knowledge by observation and experimentation

Observation is used in two ways:1. Inductive reasoning - discovering general principles

by the careful examination of specific cases. Here the scientist organizes data (facts) into categories and asks what they have in common

2. Deductive reasoning starts with general cases and proceeds to specific cases - it makes relationships clearer and allows predictions to be made

Scientific knowledge advances by a method known as "strong inference"

Strong inference works as follows:1. Make an observation or measurement2. State an hypothesis 3. Test the hypothesis 4. Publish the results5. Restate the hypothesis, test again

Observation

Semmelweis (1856), observed in hospitals inVienna, that 5X the number of women died during childbirth if they were attended by a physician as compared to being attended by a nurse(“childbed fever”).

One of his colleagues died of childbed fever aftercutting his hand with a scalpel during anautopsy.

Doctors are often doing autopsies beforeattending to childbirths.

Observation

Hypothesis(inductive reasoning)

Semmelweis hypothesized that “cadaveric matter” was transmitted from the autopsy room to the delivery room.

Observation

Hypothesis

Prediction

(DeductiveReasoning)

(inductive reasoning)

null hypothesis vs.alternative hypothesis

Washing hands would eliminate thecadaveric matter and reduce childbedfever.

Observation

Hypothesis

Prediction

Experiment

Observation

(DeductiveReasoning)

(inductive reasoning)

Experimental design•controls•dependent variable (what’s affected)•independent variable (what’s the “cause”)•predicted data (must be able to differentiate between null and alternative hypotheses)

correlation ≠ causation

correlation ≠ causation

Observation

Hypothesis

Prediction

Experiment

Observation

Analysis(Observation = Prediction?)

(DeductiveReasoning)

[Experiment]

(inductive reasoning)

Childbed fever deaths absentwhen physicians washedtheir hands

Observation

Hypothesis

Prediction

Experiment

Observation

Analysis(Observation = Prediction?)

Conclusion

(DeductiveReasoning)

[Experiment]

(inductive reasoning)

Transmission ofcadaveric matter causeschildbed fever

Observation

Hypothesis

Prediction

Experiment

Observation

Analysis(Observation = Prediction?)

Conclusion

(DeductiveReasoning)

[Experiment]

(inductive reasoning)

What other hypothesescould be made from theconclusion?

Observation

Hypothesis

Prediction

Experiment

Observation

Analysis(Observation = Prediction?)

Conclusion

(DeductiveReasoning)

[Experiment]

(inductive reasoning)

What would youpredict from yourhypothesis?

How would youtest it experimentally?

Observation

Hypothesis

Prediction

Experiment

Observation

Analysis(Observation = Prediction?)

Conclusion

(DeductiveReasoning)

TheoryLawFact

Generalization

(Deductive Reasoning)

[Experiment]

(inductive reasoning)

Initial Observation

Hypothesis

reasoning?

Experiment

Observation/Data Analysis

Interpretation

Hypothesis not Supported

NewHypothesis

NewExperiment

NewObservation

Final Hypothesis Supported

Theory

Scientific methodis a repetitiveprocess that leadsto the buildingof theories

Identifying Patterns

Hypothesis

Prediction

Preconceptions ObservationsExperimentation Data

Preconceptions can influence scientific method

“vapors”, spontaneous generation, women as “weak”

accumulatedscientific data

formulation of hypothesis

observation andexperimentation

new data conclusions

1 2 3 etc

theory

Theories in sciencebuild from theaccumulation of multipleinvestigative efforts

communicable disease

Summary

• The scientific method is in essence a process of observing natural phenomena which leads to the asking of questions about those phenomena which leads to the offering of explanations that can subsequently be tested

Mystery Box

• Hand out mystery boxes• Do hypothesis testing exercise

Types of hypotheses:• Conjectural hypotheses: something that is surmised

based on reasonable evidence, but that offers nothing testable. "I believe that there is intelligent life somewhere in the universe other than earth."

• Explanatory hypotheses: a proposed explanation that needs to be tested. "Salmon swim up streams to breed so that predation on their young is reduced."

Explanations can be of three different types of claims:

1. Causal mechanisms – cause: men who take a single buffered aspirin each day have a 50% lower chance of heart attack than men who do not take aspirin.

2. Laws – When heat is applied to a container of gas, the pressure increases. Why? Guy-Lussac’s Law – If volume is held constant, the pressure exerted by a gas will vary directly with the temperature.

3. Underlying processes - A tungsten bulb is only 10% efficient, but a fluorescent bulb is 90% efficient.Tungsten filament is heated until it glows – 90% of the energy is lost as heat.Mercury vapor in an enclosed tube is energized by electrons, causing it to be absorbed by a phosphorescent coating, causing the coating to fluoresce – only 10% of the energy lost as heat.

Before beginning to test an explanation....

1. Is there an accurate description of the phenomenon to be explained?

2. Are more plausible rival explanations available?

Occam’s Razor

Given competing explanations – any of which would, if true, explain a given puzzle – we should initially opt for the explanation that itself contains the least number of puzzling notions.

Types of hypotheses:

• Conjectural hypotheses: something that is surmised based on reasonable evidence, but that offers nothing testable.

• Explanatory hypotheses: a proposed explanation that needs to be tested.

How to test an explanatory hypothesis

• We must devise a set of experimental conditions under which something specific will occur if the hypothesis is correct but will not occur if the hypothesis is incorrect.

• Therefore our test must meet two exacting criteria:– 1. It must predict what will happen if the

explanation is correct– 2. It must predict what will not happen if the

explanation is wrong.

Francesco Redi

He who experiments increases knowledge. He who speculates piles error upon error. – Arabic epigraph quoted by Redi

Spontaneous generation of vermin?

Done in 1668

Redi’s experiment only used open and sealed jars.The jar with a screen was from a repeat of his work.