What is Science Science scientia knowledge 1 Knowledge

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

Science can only state what is, not what should be. Albert Einstein

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 measurement 2. State an hypothesis 3. Test the hypothesis 4. Publish the results 5. Restate the hypothesis, test again

Observation Ignaz Semmelweis (1856), observed in hospitals in Vienna, that 5 X 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 after cutting his hand with a scalpel during an autopsy. Doctors are often doing autopsies before attending to childbirths.

Observation (inductive reasoning) Hypothesis Semmelweis hypothesized that “cadaveric matter” was transmitted from the autopsy room to the delivery room.

Observation (inductive reasoning) Hypothesis (Deductive Reasoning) Prediction Washing hands would eliminate the cadaveric matter and reduce childbed fever.

Observation (inductive reasoning) Hypothesis (Deductive Reasoning) Prediction Experiment Observation Experimental design • controls • dependent variable (what’s affected) • independent variable (what’s the “cause”) correlation ≠ causation

correlation ≠ causation

Observation (inductive reasoning) Hypothesis (Deductive Reasoning) Prediction [Experiment] Experiment Observation Analysis (Observation = Prediction? ) Childbed fever deaths absent when physicians washed their hands

Childbed fever deaths absent when physicians washed their hands

Semmelweis

Observation (inductive reasoning) Hypothesis (Deductive Reasoning) Prediction [Experiment] Experiment Observation Analysis (Observation = Prediction? ) Conclusion Transmission of cadaveric matter causes childbed fever

Observation (inductive reasoning) Hypothesis (Deductive Reasoning) Prediction [Experiment] Experiment Observation Analysis (Observation = Prediction? ) Conclusion What other hypotheses could be made from the conclusion?

Observation (inductive reasoning) Hypothesis (Deductive Reasoning) Prediction [Experiment] Experiment Observation Analysis (Observation = Prediction? ) Conclusion What would you predict from your hypothesis? How would you test it experimentally?

Observation (inductive reasoning) Hypothesis (Deductive Reasoning) Prediction [Experiment] Experiment Observation Analysis (Observation = Prediction? ) Conclusion Theory Law Fact ion ng) t a z ali asoni r e Gen ive Re uct d e (D

Scientific method Initial Observation reasoning? is a repetitive process that leads Hypothesis to the building of theories New Hypothesis Experiment New Experiment Observation/ Data Analysis New Observation Hypothesis not Supported Interpretation Final Hypothesis Supported Theory

Preconceptions can influence scientific method Identifying Patterns Observations Experimentation Data Preconceptions Hypothesis Prediction “vapors”, spontaneous generation, women as “weak”

accumulated scientific data Theories in science build from the accumulation of multiple investigative efforts formulation of hypothesis observation and experimentation new data conclusions 1 2 3 etc theory 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

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.

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.