Earth Science and the Scientific Method

Earth Science

Earth science is the study of Earth and its processes. Earth scientists also study Earth relative to other objects in the solar system. The four main branches of Earth science are geology, oceanography, meteorology, and astronomy.

Geology

Geology means “study of the earth.” Geologists study the materials that make up the earth, such as rocks and minerals. They study the interior and exterior structures of Earth and its processes, such as the rock cycle. Many geologists learn about Earth’s history by studying evidence recorded in rocks, such as fossils.

Oceanography

Oceanography is the study of Earth’s oceans and the organisms that live in them. Oceanographers analyze the composition and movement of ocean waters and study how ocean waters affect weather and climate. They research ways to protect and preserve Earth’s oceans and marine life.

Meteorology

Meteorology is the study of Earth’s atmosphere or the mass of air that surrounds Earth. Processes in Earth’s atmosphere are responsible for the weather and climate that occur on Earth’s surface. Meteorologists measure data such as air temperature, wind speed or direction, and humidity. By studying the data, meteorologists attempt to predict the weather. In addition, meteorologists study the history of climate, which helps them learn more about the earth’s current climate and how it is changing.

Astronomy

Astronomy is the study of celestial objects beyond Earth’s atmosphere. The reason these astronomical objects are important to earth science is that they affect systems and processes on Earth. For example, the gravitational pull of Earth’s moon affects ocean tides. Energy from the sun contributes to many Earth processes, such as evaporation and precipitation. Objects such as meteors and asteroids may enter Earth’s atmosphere and strike Earth’s surface. These objects can cause significant changes on Earth.

Why Studying Earth Science is Important

¹ Earth science is important because:

• Earth provides valuable resources such as soil, water, metals, industrial minerals, and energy. People need to know how to find these resources and use them sustainably.
• The study of rocks and the fossils they contain is important to understand the evolution of the environment and the life within it.
• You can learn to minimize risks from earthquakes, volcanoes, damaging storms, and other natural disasters.
• You can learn how and why Earth’s climate has changed in the past, and use that knowledge to understand both natural and human-caused climate change.
• You can recognize how human activities have altered the environment and the climate in increasingly serious ways. Society can learn how to avoid more severe changes in the future.
• You can use knowledge of Earth to understand other planets in the solar system and other galaxies.

How Scientists Study Earth

Like scientists in other fields, Earth scientists make observations, ask questions, make predictions, and conduct experiments. They draw conclusions and report their findings.

The scientific method is a systematic method of research that includes specific steps to test a hypothesis. The scientific method involves carefully going through these steps to find an answer to a problem. The scientific method was first documented by England’s Sir Francis Bacon (1561–1626). The scientific method is an organized process by which anyone can solve a problem. The method includes seven steps:

1. Make observations
2. State the problem
3. Identify variables
4. Create a hypothesis
5. Design an experiment
6. Collect data
7. Draw a conclusion

This process can be repeated, even within the same experiment, depending on the results of the experiment.

Each step of the scientific method has a purpose, so it’s important to include each step. Below, details are given about each step in the scientific method. After reading through the steps, you’ll practice with the key terms.

Make Observations

All research starts with an observation about something that’s occurring naturally. You make observations every day. Being curious about the world you see and thinking about why something is happening is the first step in the scientific process. If you want to learn more about the topic, then the next step is to conduct research. You would look up information at a library or on the internet to see what other people have already studied on this topic. This background research helps you make an informed decision about the next step in the scientific method.

State the Problem

After making observations and conducting research, the next step in the scientific method is to state the problem. The researcher takes the observation and turns it into a question. Examples of scientific problems are: Why are the glaciers disappearing? How does climate change affect reptiles?

Identify Variables

Controlled experiments have a control group and an experimental group. The control group is a group that continues under normal conditions. The experimental group is exposed to something that’s being tested in the experiment. A variable is a factor, condition, or relationship that can be changed in an experiment.

• The factors or conditions in the experiment that don’t change are called controlled variables. Don’t confuse a controlled variable with the control group.
• A variable that you purposely change between the control group and the experimental group is called the manipulated or independent variable. It’s important during an experiment to test only one independent variable at a time.
• The result of the change in the experimental group as a result of the manipulated variable is called the responding or dependent variable.

These terms can be confusing when you first learn about them. You’ll see several examples of these variables in a practice experiment that you’ll complete later in this lesson.

Formulate a Hypothesis

A hypothesis is a possible explanation for the problem being studied. It’s often written as an if/then statement. The hypothesis combines information about the variables to be used in an experiment. It identifies the independent variable and a possible outcome—the dependent variable. When the experiment is complete, the researcher will decide whether the research supported the hypothesis or not.

Design an Experiment

After identifying the problem and writing a hypothesis, the researcher next designs the experiment. This means determining what materials will be used in the experiment and writing a procedure, the step-by-step directions for the experiment. The researcher pays careful attention to the variables so that only the independent variable is different between the control group and the experimental group.

Collect Data

The researcher is now ready to carry out the experiment. During the experiment, observations are made. These observations, called data, are written down. Data can be quantitative or qualitative.

• Observations that are made or measured using numbers are called quantitative data. An example of quantitative data includes an object’s measured mass or temperature.
• Data that describes observations is called qualitative data. Qualitative data would involve using the five senses to make observations—describing what you see, hear, taste, feel, and smell.

If you were to describe the color of soil, you would be recording qualitative data. However, you could also use a tool called a spectrophotometer to record the wavelengths of light that the soil absorbs to collect quantitative data. To remember the difference between these types of data, look at the root words: “qualitative” refers to quality, and “quantitative” refers to quantity.

Draw a Conclusion

After conducting an experiment and recording data, the results need to be analyzed. After analyzing the data, the researcher decides if the data supports the hypothesis. If the data matches the researcher’s prediction of what would happen, then the hypothesis is supported. If the data doesn’t match what the researcher thought would happen, then the hypothesis isn’t supported. If the hypothesis isn’t supported, the researcher goes back to the third step: He or she considers this new data and writes a new hypothesis, then designs and carries out a new experiment to test that prediction.

To draw a conclusion about the experiment, the researcher must make inferences. An inference is a logical explanation based on an observation. For example, you might observe that the grass grows after it rains. And, you might observe that the grass dies when it doesn’t rain. You might make a logical conclusion, or inference, that the amount of rain impacts how much the grass grows.

Watch this video to learn more about the differences between inferences and observations.

Application of the Scientific Method

The scientific method was developed to organize natural human thinking. Consider the following example about a farmer and one of his crops. Read through the experiment. Then, you’ll have a chance to identify aspects of the scientific method in another experiment.

1. Make an observation—If a farmer observed a decline of his tomato crops in the last harvest season, he naturally would want to understand why. During this step, the farmer thinks about what might be causing the problem. The farmer would begin asking questions about what led to the crop decline. To answer the questions, the farmer might study the quality of the soil, research any pests or bugs that might eat or destroy the plants, or consider other environmental factors such as pollution. This might be done by talking with other farmers, or it might involve research to determine acceptable levels of soil pH in the area. This background research will inform the future hypothesis.
2. State the problem—Recall that the problem is written as a question. Some examples of a problem in this example would be: What’s causing the tomato plants to decrease in productivity? Does the pH of the soil affect plant growth and reproduction?
3. Identify variables—In this case, the variable the farmer wants to investigate, or the independent variable, is the quality of the soil, specifically the pH of the soil. The farmer wants to improve the number of tomatoes produced by the plants, so the number of tomatoes produced is the dependent variable, or the responding variable. Remember that to test the independent variable, all of the other variables should be the same: the amount of water, amount of sunlight, type of container, length of time to grow the plants, and so on.
4. Formulate a hypothesis—Remember that a hypothesis is written as an if/then statement. “If the soil is too acidic or too basic, then crop performance will be adversely affected.” Or, written another way: “Will pH affect tomato plant production?” In other words, if the soil has the wrong pH, then the tomato plants will produce fewer tomatoes. In this example, the farmer would think about the most likely reasons why the plants are producing less fruit. To test the hypothesis, the farmer would test the acidity of the soil with a pH test, since the nutrients valuable to plants—nitrogen, phosphorus, and potassium—are most easily absorbed in an environment that isn’t too acidic.
5. Design the experiment—An experiment is used to test the hypothesis and collect data. Conducting experiments is a central part of science. In this example, the farmer would conduct an experiment to test for the effect of pH on tomato production. The farmer would set up two groups of plants, a control group that’s exposed to soil similar to his soil, and an experimental group grown in soil with a different pH than the control group. All other variables should be kept constant, such as water, light, type of plant, and length of growing time.
6. Collect data—The farmer would need both quantitative and qualitative data. Quantitative observations might include measuring the pH of the soil and the height of the plants each week, counting the number of fruits on each plant, or measuring the average size of the fruit. Qualitative data might be observing the color of the leaves, looking for any brown spots on the leaves, or observing the color of the fruit as it develops.
7. Draw conclusions—After collecting the data each week, the farmer would compare the data from the control group and the experimental group. Inferences or logical conclusions will be made about the data. If the tomatoes grow better and produce more fruit with a different pH level, then the hypothesis is supported. The farmer decides to change his fertilizer to one with a higher pH. A few months after changing the fertilizer, the farmer sees an improvement in the tomato crops and performs the soil test again, noting that the acidity of the soil is within an acceptable range. This testing would prompt the conclusion that the hypothesis was correct, confirming a relationship between soil pH and the number of tomatoes grown.

In this example, the farmer may discuss what was learned with other farmers growing tomatoes in the local area. In the scientific community, results obtained from scientific research are often shared via presentations, journals, and other publications.

How Scientists Communicate

An important aspect of a scientist’s work is presenting results and communicating with peers. Scientists may present results at scientific meetings or conferences. This approach reaches only those present at the conference.

Most scientists present their results in peer-reviewed articles published in scientific journals. Peer-reviewed articles are scientific papers that are reviewed by fellow scientists who have agreed to read and comment on the paper. These peers are assigned by the journal’s editorial board, and assumed to be unbiased professionals. Their names are often withheld from the author. The reviewers, experts in a particular research area, judge whether the scientist’s work is suitable for publication according to rigorous standards. The process of peer review helps ensure that the research described in a scientific paper is original, significant, logical, ethical, and thorough.

Scientists publish their work so other scientists can share their results and reproduce their experiments under different conditions to expand on the findings. The original experimental results must be consistent with the findings of other scientists to be considered accurate. Most scientific papers follow a similar format and include these sections:

• Abstract: A brief (usually 100–200 words) summary of the entire paper
• Introduction: Identifies the problem or question scientists intended to solve or answer through their research, describes background information on similar studies, and states the hypothesis
• Materials and Methods: Describes the materials used and explains the steps scientists followed to perform the experiment or study
• Results: Presents the data scientists collected without any interpretation of that information; typically includes graphs, charts, and/or tables of data
• Discussion/Conclusions: Includes the scientist’s interpretation of the data; explains how the data relate to the problem, question, or hypothesis; and offers the scientist’s final thoughts as to why the results may have occurred

Qualitative and Quantitative Data

The two main types of data that scientists share are qualitative and quantitative. Qualitative data include descriptions, observations, and explanations. Quantitative data is information that can be verified, measured, or calculated, such as numbers, values, and percentages. Qualitative data considers the quality of something, which is not measured numerically, but by traits or categories. Examples of qualitative data are interviews, case studies, and written documents.

Scientists often organize quantitative data visually using graphics, such as charts, graphs, or tables. The following are some common graphics scientists use to present data.

Bar Graph

A bar graph has horizontal or vertical bars. Each bar represents a numerical value—the higher the value, the higher or longer the bar. Bar graphs are very helpful for comparing categories of information. Information is charted along a horizontal x-axis and a vertical y-axis.

Pie Chart

A pie chart is a circular chart divided into slices, each representing a proportion of the whole, or a percentage. Pie charts are helpful in presenting statistical data.

Line Graph

A line graph features a series of points connected by lines. Some line graphs have a single line. Others feature multiple lines that can be compared. Line graphs are especially helpful in showing changes over time.

Scatterplot

On a scatterplot, each piece of data is represented by a dot. Scatterplots are used to find the relationship between two or more variables. Scatterplots make it easy to identify outliers in data. Outliers are values that are very different from the rest of the data.

Timeline

A timeline lists events in the order in which they occurred. Scientists often use timelines to identify significant moments in Earth’s history, such as the first appearance of plant life or the disappearance of dinosaurs.

Table

A table arranges data into vertical columns and horizontal rows. The point at which a row and a column intersect is known as a cell. Scientists may include text and/or numerical data in tables.

High Temperatures (°F) in Three Eastern Cities (January 2019)

	Boston, MA	Philadelphia, PA	Miami, FL
Monday, 1/7	32	37	77
Tuesday, 1/8	45	54	80
Wednesday, 1/9	43	44	78
Thursday, 1/10	34	38	74
Friday, 1/11	33	42	74
Saturday, 1/12	40	44	77
Sunday, 1/13	41	44	75

Sharing Data and Results

When other scientists are able to replicate the results of an experiment, support for the hypothesis grows. Over time, a well-tested hypothesis may lead to the development of a scientific theory. A scientific theory is a thoroughly tested and confirmed explanation for a set of observations or phenomena. Scientific theory is the foundation of scientific knowledge. With time, as a theory gathers consensus, it becomes widely accepted as it replaces other theories. For example, the theory of plate tectonics suggests that Earth’s surface is composed of several large, moving parts, called plates. As these plates move, they may pull apart, crash into, or slide past one another. Rift valleys, mountains, and earthquakes may result from these movements. The theory of plate tectonics explains why scientists find mountains in certain locations, why animals have similarities across continents, and a host of other observations.

A popular misconception is that theories are like guesses and that with time, “true” theories mature into “facts.” This is absolutely false—theories never become facts in a scientific sense. A theory is an explanation supported by evidence that hasn’t been falsified. Once proposed, a theory is subject to challenges by other scientists, who try to falsify or disprove it. Once falsified, a theory ceases to be a theory. The longer a theory withstands these challenges, the stronger it becomes.

A scientific theory shouldn’t be confused with a scientific law. Scientific laws are often expressed as mathematical formulas. They describe how elements of nature behave under certain conditions, but they don’t explain why they occur. An example of a scientific law is Newton’s Universal Law of Gravitation, expressed as the formula F_g = G(m₁m₂/r²). According to this law, any object in the universe attracts any other with a force (F_g) that’s directly proportional to the product of their masses (m₁m₂) and inversely proportional to the square of the distance between them (r²). The letter G in the formula represents the universal gravitational constant.

To summarize, scientists use the scientific method to develop hypotheses, theories, and laws. Hypotheses offer possible explanations. Scientific theories offer thoroughly tested and widely accepted explanations. Scientific laws offer observations without explanation.1. 1.2 The Process of Science by Matthew R. Fisher, Editor is licensed under a Creative Commons Attribution 4.0 International License.