The Scientific Method

The Scientific Method You have spent a lot of time in previous science classes learning about the steps involved in the scientific method. Therefore, the purpose of this discussion is not to revisit the steps involved in the scientific method. Instead, we are going to discuss a brief history of the scientific method, review some vocabulary terms associated with this process, and discuss why the scientific method is, arguable, the most important tool humans have invented. Carl Sagan (Figure 1), was a scientist, professor, and perhaps the most effective science communicator in the 20th century. In 1996, in his last interview he said the following about what science is: “Science is more than a body of knowledge. It is a way of thinking; a way of skeptically interrogating the universe with a fine understanding of human fallibility.” Figure 1. Carl Sagan; astronomer, professor, and science communicator.

The Scientific Method – History More than 2,000 years ago in the midst of the Classical Greek period in which major achievements in art, architecture, literature, philosophy, mathematics, and science were made, was born one of the most famous thinkers; Aristotle (Figure 2). Although the Classical Greek period produced many brilliant thinkers that would change the world forever, Aristotle is the most well known, and deservingly so. He was a student of Plato, who influenced him in many ways. One way that Aristotle was influenced was using logic to uncover truths. However unlike Plato, he emphasized the importance of using observations from the natural world to help shape his logic. His encyclopedic mind allowed him to make lists of everything he could find in nature, and most importantly, he organized these lists and pointed out how things in nature were connected. He took the ideas of those who had come before him, built on those ideas from his own observations, and created a grand theory to explain and classify everything known. Aristotle was human though, which means he was far from perfect. His approach to discovering truths allowed him to make many brilliant assumptions, however many of this ideas were wrong. Because science at the time lacked a very important component, many of this wrong assumptions went unchecked for over a thousand years. So what does modern science do that Aristotle and other brilliant minds before and after him failed to do? Experimentation. Figure 2. Roman copy in marble of a Greek bronze bust of Aristotle.

The Scientific Method – History There is much debate about the origin of experimental science, however it appears to take hold during the Middle Ages. In Europe during this time (the Dark Ages), most of the major achievements made by the Greeks were lost, universities were closed, and free-thought and scientific ideas were thought to be dangerous. However, in Northern Africa, the Middle East, and parts of Spain, the Islamic Golden Age was producing many brilliant minds and ideas. Ibn al-Haytham (Figure 3) was an Arab physicist who combined observations, rational arguments, and experiments to support his theory on optics (how light travels). He also discussed the importance of being a critical thinker, being skeptical, and therefore not believing what other people put forth as truths, but instead to do experiments and see for yourself. If you are looking for the origin of science as we think of it today, this is a pretty good place to start. Near the end of the Middle Ages Roger Bacon (Figure 4), an English philosopher, took hold of this idea and wrote about the importance of making observations, coming of with hypotheses, experimenting, and the need for independent verification of these tests. This “scientific method” or way of thinking took hold in the Renaissance and continues today. Figure 3. Ibn al-Haytham. Figure 4. Roger Bacon.

Importance of the Scientific Method & Good Experimental Design I think it is easier to understand the importance of using the scientific method by providing a simple example. Imagine you are given the following simple problem. Does fertilizer, like Miracle Grow, make tomato plants grow larger? If you take the approach that scientists used during the Classical Greek times, you would think about the problem, use logic, and come up with an answer. That answer may be correct and it may be wrong, but most importantly you would have no evidence to support your claim one way or the other. You could do an experiment in which some tomato plants were given water while others were given Miracle Grow. After a growing season you can look at the results and come up with a conclusion. Although this is an experiment, and your conclusions are supported with evidence it’s not a good experiment and therefore the results and the conclusions are not valid. A good experiment creates an experimental group and a control group. The control group is exactly the same in every way, except for the one thing that is being tested. In this example you would want to make sure that the two groups have the same amount of soil, water, and sunlight. You would also want to make sure the composition of the soil is the same, the type of tomato plants are the same, etc. If all factors between the experimental group and the control group are the same, if there is a difference between the two groups at the end of the experiment the one thing that was changed (in this case the Miracle Grow) must be responsible for that change. If repeated, independent experiments reproduce the same results time after time, the conclusions made from this experiment become a scientific law or scientific theory.

Vocabulary Terms hypothesis – an educated guess observation – recording physical data using your senses inference - a conclusion based on interpretations of data variable – something that is changing independent variable – the variable that is being manipulated by the person running the experiment dependent variable – the variable that is being measured placebo – used as a control in experiments (usually used in pharmaceutical experiments, like a sugar pill) scientific theory – is a well established explanation of the natural world that has been verified with strong evidence, repeated experiments, and can be used to make predictions.