Nature of Science&

Scientific Investigations

The Scientific Method

• “The Scientific Method”– FORGET IT!!!

• There isn’t ONE right way to do science!– The Scientific Method– Scientific Methods

• Not all scientific knowledge comes from “experiments”.

Systematic Observation

• “What happens when…?”– Examples:

• Is cooking oil more dense than water?– What happens when I pour water over cooking oil?

• What are the migratory habits of geese?– What happens when geese migrate?

Scientific Experiment• “How does x affect y?”• Clearly defined independent (test)

variable, dependent (outcome) variable, and controlled variables.– Examples:

• Do dark colored cars get hotter than light colored cars in the sunlight?

– How does the color of a car affect the temperature inside the car?

• Which brand of paper towel absorbs the most water?

– How does the brand of paper towel affect how much water is absorbed?

Independent vs. Dependent• Independent (Test) Variable

– Variable that is changed on purpose– Variable being tested

• Dependent (Outcome) Variable– Variable that may or may not be affected by

changing the independent variable (it DEPENDS on the IV)

– Usually measured or observed

• Controlled Variables (constants)– Variables that are kept constant (the same)

• Control– Sample treated like others except without the IV.

How does the type of water affect plant growth?

1. What is the independent variable?2. What is the dependent variable?3. What variables need to be controlled (or kept the same)?

How does the brand of battery affect how long the battery lasts?

1. What is the independent variable?2. What is the dependent variable?3. What variables need to be controlled (or kept the same)?

Graphing Your Results• Title – should explain what information can

be gained from the graph• Grid – x and y axis should be appropriately

scaled to fit the whole paper and labeled with appropriate units

• Independent Variable – should be labeled on the x axis

• Dependent Variable – should be labeled on the y axis

• Data – should be carefully plotted

Confirmation

• Search for consistent and predictable results– Does NOT mean we “confirm” that we got the

right answer!• Repetition & Replication

Repetition• When a scientist performs multiple trials of

an experiment to make sure he/she is getting consistent and predictable results.

• Ex: Which type of soil do worms like best?– What does it mean if…

• they like soil A the first time, soil A the second time, and soil A the third time?

• they like soil A the first time, soil B the second time, and soil C the third time?

Replication• When other scientists try to replicate an

experiment done by a colleague to see if they get consistent and predictable results.

• What does it mean if…– they follow your procedures and reach the

same conclusion as you?– they follow your procedures and reach a

different conclusion than you?

Theory vs. Law

• Many people have the misconception that a theory is a law that hasn’t been proven yet…

• This is INCORRECT!!!• Scientific theories DO NOT become

scientific laws!– theories and laws are two different things!

Scientific Law• A statement about WHAT HAPPENS in

nature that seems to be true all the time.• A law will tell you…

– WHAT is expected to happen every time under certain conditions.

• A law will NOT tell you…– WHY it happens.

• Ex: The Law of Gravity– On Earth, in the absence of other forces, objects

will fall toward the center of the Earth.

Scientific Theory• An EXPLANATION of things or events based

on knowledge gained through many observations and investigations.

• A theory will tell you…– WHY something happens (at least why we

THINK something happens)• Theories can be used to explain laws.• Ex: The Theory of Gravity

– There is a force in nature called the gravitational force that causes an attraction between any two objects with mass.

Theory vs. Law• So…

– Laws describe WHAT happens– Theories explain WHY it happens

• Sometimes, competing theories offer different explanations for the same law.– What happens then?

• Scientists test the theories to gather evidence that may support or dispute them

• If disputing evidence is found, a theory can either be changed or discarded

Scientific Knowledge

• Science is not a list of facts and information to be memorized!– Scientific knowledge changes as new

understanding evolves• Scientific explanations are based on

empirical evidence.– Cumulative body of observations of a natural

phenomenon

• Scientific Knowledge is the result of a great deal of:– Testing and/or Observation– Debate (argumentation)– Confirmation (repetition and replication)

Scientific Knowledge

What is the Purpose of Science?

• Science is about questioning.– Asking questions– Searching for answers– Discovering new questions

• Science is ONE of many ways of understanding the world we live in.– But it is limited in what it can help us

understand.

What are the Limits of Science?

• Science Cannot:– Answer questions about the supernatural

world.– Understand matters of faith, artisitc

expression, feeling.• Science Can:

– Ask/Answer questions about the NATURAL world.

– Only understand observable/testable topics.

What are the Limits of Science?

• Science Cannot:– “Prove” an idea.– Offer a concrete, 100%, no-doubt-about-it

answer.• Science Can:

– Provide evidence that supports an idea.– Provide evidence that disputes an idea.– Offer answers under specific criteria/limitations.

What are the Limits of Science?

• Science Cannot:– Assume outcomes without testing.– Disregard evidence that does not support a claim.

• Science Can:– Predict likely outcomes.– Offer explanations to make sense of empirical

evidence.

So…What IS Science?• Science is a limited discipline that studies

only naturally occurring events, while offering natural explanations for the phenomenon under study.

• The characteristics of science:

- Consistent - Predictable

- Observable - Testable

- Natural - Tentative