The Scientific MethodThe Scientific Method

HypothesisHypothesis An informed guess that tries to explain An informed guess that tries to explain

how or why an event occurs.how or why an event occurs.

A good hypothesis explains known facts.A good hypothesis explains known facts.

– What is one hypothesis that explains What is one hypothesis that explains the origins of the galaxies?the origins of the galaxies?

A suggested solution to a problem A suggested solution to a problem based on background knowledge.based on background knowledge.

It must be testable.It must be testable. Written as an “If, then, because” statement.Written as an “If, then, because” statement.

The Big Bang Theory!The Big Bang Theory!

Big Bang HypothesisBig Bang Hypothesis Originally the universe was packed into Originally the universe was packed into

one dense sphere of hydrogen, probably one dense sphere of hydrogen, probably not much larger than our sun.not much larger than our sun.

About 15 billion years ago this mass of About 15 billion years ago this mass of hydrogen exploded, forming a gigantic hydrogen exploded, forming a gigantic expanding cloud.expanding cloud.

Some parts of the cloud moved faster Some parts of the cloud moved faster than others, but all parts moved than others, but all parts moved outwards, away from the center.outwards, away from the center.

Big Bang (cont.)Big Bang (cont.)

As the clouds moved, the particles As the clouds moved, the particles condensed into billions of galaxies.condensed into billions of galaxies.

They all continued to move outward, They all continued to move outward, away from the center and each other.away from the center and each other.

Those moving at the fastest speeds are Those moving at the fastest speeds are now farthest out in space.now farthest out in space.

What force caused the What force caused the particles to condense?particles to condense?

Gravity!Gravity!

GravityGravity The force of gravity is directly related The force of gravity is directly related

to the mass of the objects and how to the mass of the objects and how close they are to each other.close they are to each other.

Mass – the Mass – the amount of matter amount of matter (stuff) in an object (stuff) in an object or substance.or substance.

Weight – the effect of gravity on an Weight – the effect of gravity on an object or substance.object or substance.

Steps in the Scientific MethodSteps in the Scientific Method Identify the Problem/ Ask a questionIdentify the Problem/ Ask a question

Gather InformationGather Information

Form a HypothesisForm a Hypothesis

– Find out what is already known by Find out what is already known by research and observationresearch and observation

– What am I trying to figure out?What am I trying to figure out?

– Propose a solution based on your Propose a solution based on your informationinformation

– An educated guess about the relationship An educated guess about the relationship between the variables you will be testingbetween the variables you will be testing

Make ObservationsMake Observations

ObservationsObservations Observations are factual statements, not opinions.Observations are factual statements, not opinions. Gathered using your five senses.Gathered using your five senses.

InferencesInferences

A possible explanation based on your A possible explanation based on your observations.observations.

Do the Farside activity!!Do the Farside activity!!

Design and Perform a Controlled Experiment or Collect Field Data

Develop a procedure to Develop a procedure to testtest your hypothesis.your hypothesis.

A good or “valid” experiment A good or “valid” experiment will only have will only have ONE variable! –ONE variable! –its called a FAIR TEST FAIR TEST or a CONTROLLED EXPERIMENTCONTROLLED EXPERIMENT

Scientific Experiments Follow Scientific Experiments Follow RulesRules

An experimenter changes one factor and observes or measures what happens.

The experimenter makes a special The experimenter makes a special effort to keep effort to keep other factors other factors constantconstant so that they will not effect so that they will not effect the outcome.the outcome.

Constants – all factors that remain Constants – all factors that remain the same and have a fixed value in the same and have a fixed value in an experiment.an experiment.

ControlsControls Control - a duplicate setup of the

experiment you are performing with everything identical except for the variable that you are testing

• Controls are NOT being tested• Controls are used for COMPARISON

VariablesVariables Variables are Variables are factors that change.

Factor in the experiment that is Factor in the experiment that is being testedbeing tested

Independent Variable – the variable that is purposefully changed by the experimenter

Dependent Variable – the variable that responds to the change (the outcome). It is measured or observed.

Confounding Variable

Confounding variable – variables that the researcher failed to control, or eliminate, damaging the validity of an experiment

Analyze ResultsAnalyze Results The data is the results

of the experiment May be qualitative or

quantitative

DATADATA Must be organized• Can be organized

into charts, tables, or graphs

DATADATA Accuracy – how

close the value is to the true value

Precision – how close the measured values are to each other

ConclusionsConclusions Based on your

data Do your results

support or reject your hypothesis?

RepeatRepeat

RepeatRepeat

RepeatRepeat

Communicate Communicate ResultsResults

Theory – an explanation supported by much evidence

Law – statements that describe how the natural world works. No exceptions have been found

Perform a Controlled Experiment or Collect Field Data

– Data» Information from experiments, measurement, research

and observation

Propose a TheoryPropose a Theory– Accepted hypothesis based on evidenceAccepted hypothesis based on evidence

TestTest– Again and againAgain and again

Form a ConclusionForm a Conclusion– Based on your resultsBased on your results

Publish your ResultsPublish your Results– So that others may verify your resultsSo that others may verify your results