Remember the time when all

CASE STUDY The Scientific Method Ain’t What It Used to Be By Clyde Freeman Herreid R emember the time when all you had to do was memorize these fiv...
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CASE STUDY

The Scientific Method Ain’t What It Used to Be By Clyde Freeman Herreid

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emember the time when all you had to do was memorize these five steps: ask a question, formulate a hypothesis, perform experiment, collect data, draw conclusions? And you received full credit for defining THE SCIENTIFIC METHOD. Well, those days are gone. Or they should be. Because the folks at University at California, Berkeley (Roy Caldwell, David Lindberg, and Judy Scotchmoor, Anna Thanukos, and team) have put together an outstanding website devoted to Understanding Science: The Way Science Really Works (http://undsci.berkeley.edu). Here are some of their key themes: science in a nutshell, what is science, how science works, scientific evidence, science as a human endeavor, science and society, why science matters, and your science toolkit. This is a treasure trove of information for K–16 teachers, especially for those of us who are interested in using case studies in the classroom. The reason? The use of cases puts science in context. And the context is the real world, and we care how science really works in that world. Among the many gems of the site is a scientific checklist that helps us evaluate fields of study. Science does the following: • Aims to explain the natural world • Uses testable ideas • Relies on evidence 68

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• Involves the scientific community • Leads to ongoing research • Leads to benefits for society The site goes on to compare case studies of Rutherford’s claims about the nature of the atom to claims of astrology and intelligent design (ID). It quickly becomes apparent how astrology and ID fail to live up to the scientific ideals: For example, although ID does focus on the natural world and does aim to explain it, its ideas are generally untestable; it does not specify who or what the Designer is or how it operates. When ID proponents do come up with testable claims, such as the doctrine of irreducible complexity, the evidence refutes the predications. Moreover, the ID advocates resist modifying their ideas in response to the scrutiny of the scientific community. In short, it is clear that we are not dealing with science. Another section of the Berkeley site deals with science’s limitations— a good thing to keep in mind when dealing with the interminable wars between science and religion (a favorite topic of evolutionist Richard Dawkins) or controversial topics of any stripe, including stem cells, cloning, genetically engineered foods, or global warming. Here is their list of limitations to keep in mind: • Science doesn’t make moral judgments.

• Science doesn’t make aesthetic judgments. • Science doesn’t tell you how to use scientific knowledge. • Science doesn’t draw conclusions about supernatural explanations. The Berkeley site also deals with how the average citizen should approach science stories when they don’t know what to believe. The site doesn’t give the reader a blueprint for evaluating sensational claims, but it raises fundamental questions that everyone should ask themselves when they hear a statement about the latest diet fad, cancer cure, or global warming. What is the evidence? Who says so? What does the scientific community at large say? Not surprisingly, there is a fine description of peer review: what it is, how it works, and why it is essential. I have always felt that the essence of peer review is captured in the Russian proverb that Ronald Regan used to quote during the cold war: “Trust, but verify.” This is especially true if the claims are sensational, such as the assertion that an asteroid wiped out the dinosaurs. As Marcello Truzzi, cofounder of the Society for the Scientific Investigation of Claims of the Paranormal, has put it: “Extraordinary claims require extraordinary proof.”

How Science Works

The highlight of the Berkeley website is their model showing that science is

not a linear process. The hypotheticodeductive method of question— hypothesis, experiment, data collection, and conclusion—is just too simplistic. It is not that these elements don’t play a role (they surely are stock and trade of the working scientist) but leaving the process at this point leads to these serious misconceptions enumerated by the Berkeley folks: • Science is a collection of facts. • Science is complete. • There is a single Scientific Method that all scientists follow. • The process of science is purely analytic and does not involve creativity. • When scientists analyze a problem, they must use either inductive or deductive reasoning. • Experiments are a necessary part of the scientific process. Without an experiment, a study is not rigorous or scientific. • “Hard” sciences are more rigorous and scientific than “soft” sciences. • Scientific ideas are absolute and unchanging. • Because scientific ideas are tentative and subject to change, they can’t be trusted. • Scientists’ observations directly tell them how things work (i.e., knowledge is “read off” nature, not built). • Science proves ideas. • Science can only disprove ideas. • If evidence supports a hypothesis, it is upgraded to a theory. If the theory then garners even more support, it may be upgraded to a law. • Scientific ideas are judged democratically based on popularity. • The job of a scientist is to find support for his or her hypotheses. • Scientists are judged on the basis of how many correct hypotheses they propose (i.e., good scientists are the ones who are “right” most often). • Investigations that don’t reach a

FIGURE 1

• • • • • • •

firm conclusion are useless and unpublishable. Scientists are completely objective in their evaluation of scientific ideas and evidence. Science is pure. Scientists work without considering the applications of their ideas. Science contradicts the existence of God. Science and technology can solve all our problems. Science is a solitary pursuit. Science is done by “old, white men.” Scientists are atheists.

The Berkeley Model

Take a look at the diagram in Figure 1 and you will see a cluster of four interlocking spheres: Exploration and Discovery, Testing Ideas, Community Analysis and Feedback, and Benefits and Outcomes. The traditional steps of the “Scientific Method” fall neatly into the two spheres labeled “Exploration and Discovery” and “Testing Ideas.” But there is more to the scientific process. There are all sorts of inputs and outputs from these domains represented by arrows going and coming. Noticeably absent in the traditional model is the influence of July/August 2010

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the scientific community and society at large—represented by the two other spheres. Let me quote a case study from the Berkeley website and see how their model plays out.

Asteroids and dinosaurs: Unexpected twists and an unfinished story

Walter Alvarez, an American geologist, was working with other scientists to look for certain rock patterns that would help to explain part of Earth’s history. He examined rocks from the mountains in Italy. As he explored, he kept finding an unusual layer of clay that marked the 65million-year-old boundary between the Cretaceous and Tertiary periods (referred to as the KT boundary). He noticed that there were many different sorts of marine fossils below the layer of clay, but few above. He questioned: Why the reduction in marine fossils? What had caused this apparent extinction of many types of marine life that seemed to happen so suddenly? And, could it be related to the extinction of dinosaurs that occurred at the same time on land? Alvarez wanted to know how long it took for the mysterious clay layer to be deposited because then he would know how quickly the marine life disappeared. He discussed the question with his father, the physicist Luis Alvarez, who suggested using a chemical element called beryllium-10. Like some other substances, beryllium-10 can act as a timer because it is laid down in rocks at a constant rate. The more beryllium in the clay layer, the longer it must have taken for the layer to be deposited. Unfortunately, this investigation was a dead end. Luis suggested trying another element that acts as a timer: iridium. Iridium is often found in meteorites, and me 70

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teorite dust “rains down” on Earth’s surface at a slow but constant rate. The father-son team recruited scientists Helen Michel and Frank Asaro to help them look for iridium in the clay layer. Their results were a complete surprise! The team found more than 30 times the amount of iridium than regular meteorite dust might have caused. What could have caused this spike in iridium? Did the iridium spike occur in rock layers around the world? Now Alvarez and his team had even more questions. Alvarez began digging through published studies to find the location of other KT boundary rock layers that might have the iridium spike. He eventually found one in Denmark and asked a colleague to check. The results were positive—the big spike in iridium was there too. So, whatever happened at the end of the Cretaceous must have been widespread. Now, another new question: What could have happened to cause these skyhigh iridium levels? It turned out that almost 10 years earlier, two other scientists had proposed the idea that a supernova (an exploding star) at the end of the Cretaceous had caused the extinction of dinosaurs. Because supernovas throw off heavy elements like iridium, the Alvarez discovery seemed to support this hypothesis. To further test the supernova hypothesis, the team needed other lines of evidence. Alvarez realized that if a supernova had occurred, they should find other heavy elements, like plutonium-244, at the KT boundary. At first, the team thought they had found the plutonium! It looked like a supernova had occurred, but after double-checking their results, they found that the sample they used had been contaminated. There was no plutonium in the sample after all—and no evidence for a supernova.

So what could explain these different observations (plenty of iridium, but no plutonium) and tie them together so that they made sense? The team came up with the idea of an asteroid impact. That would explain the iridium because asteroids contain a lot of iridium but no plutonium-244. The hypothesis made sense, but also led to a new question: How could an asteroid impact have caused the dinosaur extinction? After talking with colleagues, Luis Alvarez suggested that a really large asteroid striking Earth would have blown millions of tons of dust into the atmosphere. According to his calculations, this amount of dust would have blotted out the sun around the world, stopping photosynthesis and plant growth. This would have caused a worldwide collapse of food webs, and therefore many animals would go extinct. In 1980, Alvarez’s team published their hypothesis linking the iridium spike and the dinosaur extinction for other scientists to consider. This caused a huge debate and more exploration. Over the next 10 years, more than 2,000 scientific papers were published on the topic. Scientists in the fields of paleontology, geology, chemistry, astronomy, and physics joined the argument, bringing new evidence and new ideas to the table. Alvarez’s team was trying to learn about an event that happened 65 million years ago—when no one was around to see what happened. Many different scientists studied many lines of evidence to help test hypotheses about this ancient event. They studied the following: • Extinctions: If an asteroid impact had actually caused a worldwide environmental disaster, many groups of plants and animals











would not have survived. Therefore, if the asteroid hypothesis were correct, we would expect to find a large increase in the number of extinctions at the KT boundary. We do. The impact: If a huge asteroid had struck Earth at the end of the Cretaceous, it would have flung off particles from the site where it hit. So, if the asteroid hypothesis were correct, we should find these particles at the impact site in the KT boundary layer. We do. Glass: If a huge asteroid had struck Earth at the end of the Cretaceous, it would have caused a lot of heat, melting rock into glass and flinging glass particles away from the impact site. So, if the asteroid hypothesis were correct, we would expect to find glass at the KT boundary. We do. Shockwaves: If a huge asteroid had struck Earth at the end of the Cretaceous, it would have caused powerful shockwaves. So, if the asteroid hypothesis is correct, we would expect to find evidence of these shockwaves (like deformed quartz). We do. Tsunamis: If a huge asteroid had struck one of Earth’s oceans at the end of the Cretaceous, it would have caused tsunamis, which would have moved ocean sediments around and deposited them somewhere else. So, if the asteroid hypothesis were correct, we would expect to see signs of these deposits at the KT boundary. We do. The crater: If a huge asteroid had struck Earth at the end of the Cretaceous, it would have left behind a huge crater. So, if the asteroid hypothesis were correct, we would expect to find a gigantic crater somewhere on Earth dating to the end of the Cretaceous. We

FIGURE 2

do—the Chicxulub crater on the Yucatan peninsula. Scientists agreed that the evidence was strong—dinosaurs had gone extinct and there was a widespread iridium spike at the KT boundary. However, scientists did not all agree that the evidence supported a connection between the two. Scientific ideas are always open to question and to new lines of evi-

dence, so although many observations support the asteroid hypothesis, the investigation continues. The end of the Cretaceous seems to have been a chaotic time on Earth. We have found evidence of massive volcanic eruptions that covered about 200,000 square miles of India with lava. We have found evidence of changes in climate: a general cooling trend and at least one intense period of global warming. We have also found eviJuly/August 2010

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dence that sea levels were changing and continents were moving around. With all this change going on, ecosystems were surely disrupted. These factors could certainly have played a role in triggering the mass extinction—but did they? Scientists are still studying these, and many more, questions.

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Even a cursory look at the Walter Alverez case reveals how this was not a one-man operation. Sure, we can identify the basic elements of the hypothetico-deductive method. There are questions, hypotheses, experiments, data, and conclusions, but these seem intertwined

higgly piggly in the story and keep changing as evidence accumulates and ideas are modified. Most important, the role of the entire scientific community is revealed. Without the help of thousands of other people, the Alvarez ideas would never have been any more than a pipe dream. To follow the unpredictable timeline of the process and see the elements of the model, the authors of the website suggest that students put numbers on each statement in the text where they can spot the key elements in the model. Then they should put the numbers in the correct sphere. Finally, they should connect the numbers in

numerical order to see the flow of the journey of Walter Alverez. Take a look at the flow diagram in Figure 2 and see if you don’t think this a better way to show students how science really works. n Clyde Freeman Herreid (h[email protected] buffalo.edu) is the academic director of the University Honors College and a Distinguished Teaching professor in the Department of Biological Sciences at the State University of New York at Buffalo. He is also the director of the national Center for Case Study Teaching in Science (http://ublib.buffalo.edu/libraries/ projects/cases/case.html).

Save the Date

Celebrate Science Education through Summer PD Institutes in New Orleans Urban Science Education Leaders Institute August 2–5, 2010 - Featured Speakers: Dr. Bernard A. Harris, Jr., and Dr. Adriane Dorrington.

Elementary Education Institute August 5–7, 2010 - Featured Speakers: Rodger Bybee, Linda Froschauer, Tim Cooney, Steve Rich, and Christine Royce. For more information on the summer institutes, or to register email Damaries Blondonville at [email protected] or [email protected]

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