Scientific Methods in Earth Science

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.”

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.

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.

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.