July 8, Introduction to Scientific Thought Observations, Hypotheses, and Theories

July 8, Where Do We Start? What do you think of when you hear the word “observation”? …when you hear the word “hypothesis”? …when you hear the word “law”? …when you hear the word “theory”?

July 8, Observations – just the facts. Observations are statements of FACT They are non-judgmental They offer no conclusions about the cause or effect of the fact For example – the average temperature of the Arctic Ocean has been increasing since 1980.

July 8, Observations – just the facts, ma’am Good Observations are… Accurate Detailed As brief as possible! For example – “When the chemicals mixed, the solution turned blue and a sour odor was detected.”

July 8, Inferences – the next step… For example – “When the two chemicals mixed, a reaction occurred and a gas was given off.”

July 8, Hypotheses – the questioning begins A hypothesis is an educated guess based on observations. It is specific to one situation It has knowledge behind it and testing ahead of it.

July 8, Hypotheses – the questioning begins It clearly states a problem and the believed answer to that problem. For example – “If hydrochloric acid mixes with sodium, hydrogen gas will be given off.” A hypothesis often sounds like a statement of fact, but it has yet to be tested.

July 8, Hypotheses – the questioning begins Once a scientist makes a hypothesis, it is tested via an experiment. The experiment will either nullify (prove wrong) or verify the hypothesis. A nullified hypothesis is rejected; it can be revised for additional testing or forgotten. A verified hypothesis is tested over again and is subject to scientific scrutiny before it is accepted.

July 8, Hypotheses – the questioning begins All verified hypotheses are subject to intense review by other scientists. Once a hypothesis passes this rigorous review period, it can be added to the scientific knowledge base as a “law” or principle. Scientific “laws” refer to specific ideas that have not been contradicted by testing.

July 8, Experimentation “Classic” experiments have a control and an experiment group The control is used as a comparison – it is baseline conditions – nothing altered The experiment group has one (and only one) altered variable – this allows you to determine exactly what happened Other experiments can be surveys, “what if’s”, and logical reasoning

July 8, Experimentation In any test there is a dependent variable and an independent variable The dependent variable changes due to changes in the independent variable For example, as temperature decreases, trees leaves begin to change color The drop in temperature (independent) causes the color change (dependent)

July 8, Theories – more than “just a guess” Theories are the backbone of scientific thought. They are NOT guesses!! Theories link accepted principles together.

July 8, Theories – more than “just a guess” They explain a wide variety of phenomena observed in the natural world. For example – plate tectonics explains why fossils of the same species are found on opposite sides of the ocean AND why earthquakes occur in certain zones.

July 8, In Conclusion… Observations are facts without judgments. Hypotheses are educated guesses based on inferences. Experiments test hypotheses. Principles (“laws”) are based on accepted hypotheses. Theories are the synthesis of well-tested hypotheses and principles that explain many aspects of the natural world.