The Scientific Method

Hypothesis An informed guess that tries to explain how or why an event occurs. A suggested solution to a problem based on background knowledge. A good hypothesis explains known facts. It must be testable. Written as an “If, then, because” statement. What is one hypothesis that explains the origins of the galaxies?

The Big Bang Theory!

Big Bang Hypothesis Originally the universe was packed into one dense sphere of hydrogen, probably not much larger than our sun. About 15 billion years ago this mass of hydrogen exploded, forming a gigantic expanding cloud. Some parts of the cloud moved faster than others, but all parts moved outwards, away from the center.

Big Bang (cont.) As the clouds moved, the particles condensed into billions of galaxies. They all continued to move outward, away from the center and each other. Those moving at the fastest speeds are now farthest out in space.

What force caused the particles to condense? Gravity!

Gravity The force of gravity is directly related to the mass of the objects and how close they are to each other. Mass – the amount of matter (stuff) in an object or substance. Weight – the effect of gravity on an object or substance.

Steps in the Scientific Method Identify the Problem/ Ask a question What am I trying to figure out? Make Observations Gather Information Find out what is already known by research and observation Form a Hypothesis Propose a solution based on your information An educated guess about the relationship between the variables you will be testing

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

Inferences Do the Farside activity!! A possible explanation based on your observations. Do the Farside activity!!

Design and Perform a Controlled Experiment or Collect Field Data Develop a procedure to test your hypothesis. A good or “valid” experiment will only have ONE variable! –its called a FAIR TEST or a CONTROLLED EXPERIMENT

Scientific Experiments Follow Rules An experimenter changes one factor and observes or measures what happens. The experimenter makes a special effort to keep other factors constant so that they will not effect the outcome. Constants – all factors that remain the same and have a fixed value in an experiment.

Controls Controls are NOT being tested 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

Variables Variables are factors that change. Factor in the experiment that is being 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 Results The data is the results of the experiment May be qualitative or quantitative

DATA Must be organized Can be organized into charts, tables, or graphs

DATA Precision – how close the measured values are to each other Accuracy – how close the value is to the true value Precision – how close the measured values are to each other

Conclusions Based on your data Do your results support or reject your hypothesis?

Repeat Repeat Repeat

Communicate Results 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 Information from experiments, measurement, research and observation

Form a Conclusion Propose a Theory Test Publish your Results Based on your results Propose a Theory Accepted hypothesis based on evidence Test Again and again Publish your Results So that others may verify your results