1. Scientific Methods in Earth Science

2. What You Will Learn  Explain how scientists begin to learn about the natural world.  Explain what scientific methods are and how scientists use them.  Identify the importance of communicating the results of a scientific investigation.  Describe how scientific investigations often lead to new investigations.

4. Learning About the Natural World  The description of the Seismosaurus hallorum is not based on imagination alone. Scientists have been studying dinosaurs since the 1800s.  Scientists gather bits and pieces of information about dinosaurs and their environment.  Then, they recreate what dinosaurs might have been like 150 million years ago.  But how do scientists put it all together? How do they know if they have discovered a new species?  Asking questions like these is the beginning of a process scientists use to learn more about the natural world.

5. What Are Scientific Methods?  When scientists observe the natural world, they often think of a question or problem.  Scientists don’t just guess answers. Instead, they follow a series of steps called scientific methods.  Scientific methods are a series of steps that scientists use to answer questions and solve problems.

7. Ask a Question  Asking a question helps focus the purpose of an investigation.  For example, David D. Gillette, a scientist who studies fossils, examined some bones found by hikers in New Mexico in 1979.  He could tell they were bones of a dinosaur. But he didn’t know what kind of dinosaur.  Gillette may have asked, “What kind of dinosaur did these bones come from?”  Gillette knew that in order to answer this question, he would have to use scientific methods.

8. Form a Hypothesis  When scientists want to investigate a question, they form a hypothesis (hie PAHTH uh sis).  A hypothesis is a possible explanation or answer to a question that can be tested.  Based on his observations and on what he already knew, Gillette said that the bones, shown in Figure 3, came from a kind of dinosaur not yet known to scientists.  This hypothesis was Gillette’s best testable explanation for what kind of dinosaur the bones came from.

10. Test the Hypothesis  Once a hypothesis is formed, it must be tested.  Scientists test hypotheses by gathering data.  The data can help scientists tell if the hypotheses are valid or not.  To test his hypothesis, Gillette studied the dinosaur bones.

11. Controlled Experiments  A controlled experiment is an experiment that tests only one factor, or variable, at a time.  All other variables remain constant.  By changing only one variable, scientists can see the results of just that one change.  If more than one variable is changed, scientists cannot easily determine which variable caused the outcome.

12. Example - Controlled Experiments  For example, let’s say you tried to make a gelatin fruit mold, but the gelatin would not harden.  The next time you made the gelatin fruit mold, you take out the oranges and pineapples.  The gelatin might harden this time, but you won’t know whether the pineapples or the oranges caused the gelatin not to harden the first time.

13. Making Observations  Controlled experiments are important for testing hypotheses.  Some scientists, however, often depend more on observations than experiments to test their hypotheses.  Because scientists cannot always control all variables, some scientists often observe nature and collect large amounts of data.  Gillette took hundreds of measurements of the dinosaur bones  He compared his measurements with those of bones from known dinosaurs. He also visited museums and talked with other scientists.

15. Keeping Accurate Records  When testing a hypothesis, a scientist’s expectations can affect what he or she actually observes.  For this reason, it is important for scientists to keep clear, honest, and accurate records of their experiments and observations.  Scientists should present findings supported by scientific data, not by opinions.  Just one example is never enough to prove something true. However, one example could prove that something is not true.

16. Analyze the Results  Once scientists finish their tests, they must analyze the results.  Scientists often make tables and graphs to organize and summarize their data.  When Gillette analyzed his results, he found that the bones of the mystery dinosaur did not match the bones of any known dinosaur.  The bones were either too large or too different in shape.

17. Draw Conclusions  After carefully analyzing the results of their tests, scientists must conclude whether the results supported the hypothesis.  Hypotheses are valuable even if they turn out not to be true.  If a hypothesis is not supported by the tests, scientists may repeat the investigation to check for errors.  Or they may ask new questions and form new hypotheses.

18. Gillette’s Findings  Based on all his studies, Gillette concluded that the bones found in New Mexico were indeed from an unknown dinosaur.  This dinosaur, shown in Figure 5, was probably 33 m long and weighed between 13 and 20 tons.  The creature certainly fit the name Gillette gave it—Seismosaurus hallorum, the “earth shaker.”

20. Communicate Results  After finishing an investigation, scientists communicate their results.  In this way, scientists share with others what they have learned.  Science depends on the sharing of information.  Scientists share information by writing reports for scientific journals and giving lectures on their results.

21. Gillette’s Communicates to his Peers  Gillette shared his discovery of Seismosaurus at a press conference at the New Mexico Museum of Natural History and Science.  He later sent a report that described his investigation to the Journal of Vertebrate Paleontology.

22. Section Summary  Scientists begin to learn about the natural world by asking questions.  The steps of scientific methods are to ask a question, form a hypothesis, test the hypothesis, analyze the results, draw conclusions, and communicate results.  Communicating results allows the evidence to be reviewed for accuracy by other scientists.  Scientific investigations often lead people to ask new questions about the topic.