Scientific Method

Beginnings Aristotle (384 BCE - 322 BCE) ancient Greek philosopher

Aristotle was so famous that his work influenced thinking in the Western world from his time to the present. This was fine when he was right. But he was so influential that his mistakes were never noticed.

Aristotle believed that all problems could be solved by thinking about them. Sometimes this worked, other times it did not. For example, Aristotle thought that heavy objects would fall faster than lighter ones.

Now that does seem reasonable at first Now that does seem reasonable at first. And this is how “science” was done in ancient times. But what did Aristotle NOT DO? He never tested his ideas! The world would have to wait almost 2000 years for that to happen.

Galileo Galilei 1564-1642 AD or CE Lived in what is today Italy Is considered to be the first true scientist. Why???? Because he actually developed an experiment to test the hypothesis

Aristotle said that heavy objects fall faster than lighter ones. So Galileo asked, “How much faster?” He and several students tried it out! They dropped a heavy and a light ball to see what happened. Do you know what happened???

Much to everyone’s surprise both balls hit the ground at about the same time! This shows that it is better to TEST your ideas rather than merely think about them. “One test is worth a thousand expert opinions.” - Bill Nye

Key Idea When conducting an experiment, change one factor and keep everything else exactly the same. The one thing you change is called the variable. All the things you keep the same are called constants.

Galileo’s Experiment What was the variable in Galileo’s experiment? The weight of the balls. What were some constants? Dropped from same height. Dropped at same time. Balls had same shape/size.

The variable that was manipulated or changed is called the INDEPENDENT VARIABLE. The result of the independent variable is called the DEPENDENT VARIABLE. (It depends on the independent variable.)

Scientific Method Steps State the problem. Research the problem. Make a hypothesis. Conduct the experiment. Record/analyze data. Make a conclusion. Report findings to others so they can repeat the experiment.

Hypothesis An educated guess; a prediction Use “If”, “then” format “If” is the manipulated (independent) variable. “Then” is the responding (dependent) variable.

Other experiments to discuss… How would you test whether or not a medication was effective for a disease? If your plant was healthier living in the sunlight or living in darkness? If your goldfish grew bigger eating human food or regular fish food?

What is a control group??? Why is it important to have a control? A control group is for comparing your experimental group. In an experiment where fish are given different foods, the fish getting human food is the experimental group (independent variable – the thing you change) and the regular fish food is the control group (the group you are comparing to).

Qualitative and Quantitative Observations Observations: We use our senses to gather information about the world around us. There are two types of observations: Qualitative and Quantitative

Qualitative Qualitative observation: (quality) A descriptive statement Color, shape, feel, taste, sound. Olivia is wearing a blue sweater. Ms. Monroe’s dog has a long nose.

Quantitative Quantitative observation: (quantity) How many? Will always be a number. Based on exact measurement. The room is 8 meters across. My pet iguana weighs 4 kg. That amazing little slug is 12 cm long.

Inferences Inference: A logical interpretation of an event that is based on observations and prior knowledge. What does this mean?

Making Inferences You are at the counter in the office to check in. You see a student leave the principal’s office crying and upset. We could make an inference as to why the student is upset. Could be in trouble (ISS, OSS, expelled) Family problems at home (sick, accident) Student not feeling well Student has poor grades (failing, retention)

Theory Has a very different meaning in science than in everyday life. “The detective has a theory about who robbed the bank.” This is a guess. When scientists use the word theory it is not used as a guess!

A theory is… An explanation based on many observations during repeated experiments that is consistent with observations, makes predictions that can be tested, and is the simplest explanation. NOT A GUESS!!! A logical, time tested explanation for events that occur in nature.

Some theories: theory of gravity theory of electricity germ theory of disease theory of evolution Theories are are tested, accepted explanations for events that occur in nature. Theories can really never be completely proven, only disproven. When new evidence comes along, we must modify our theory or at times even get rid of it and start over again.

Any Questions???