One reason science is difficult to define is that not all science works in the same way. Let’s start by exploring the approach you may have used if you’ve ever done a science fair project, and then we’ll look more generally at how we can distinguish science from other ways of seeking knowledge.
The “Scientific Method”
If you’ve done science fair projects, you were probably expected to follow something that is usually called the “scientific method,” as illustrated in Figure 3.15.
As a simple example of this method in action, imagine that you have a battery-powered flashlight that has suddenly stopped working. Following the method of Figure 3.15, try to answer each question below for this example, discussing with classmates if you wish. Then click to check your answers.
- What is the observation you have made and the question you are asking?
You’ve observed that the flashlight has stopped working, so you are essentially asking: Why has the flashlight stopped working and how can I fix it?
- A hypothesis , sometimes called an educated guess, is a tentative explanation that you can test. What is a reasonable hypothesis in this case, and what is “educated” about your guess?
A reasonable hypothesis is that the batteries have died, and this guess is “educated” because you already know that the flashlight needs batteries to work.
- What simple prediction can you make based on your hypothesis?
You predict that once you replace the batteries with new ones, the flashlight should work.
- Suppose you replace the batteries and the flashlight still doesn’t work. Where are you in the flow chart of Figure 3.15? What hypothesis might you suggest next?
You are on the left branch labeled “Test does not support hypothesis.” Your next hypothesis might be, for example, that it is the bulb that no longer works.
Group Discussion
The Scientific Method in Everyday Life
Work in small groups to do the following.
- Each member of the group should try to come up with at least one example from your own life in which you either did or could have applied the scientific method to help solve a problem. Describe the case to the rest of your group. (If you’ve done science fairs in the past, you can use your projects as examples.)
- As a group, briefly discuss each person’s example, and discuss whether the approach worked or if it might have been improved upon.
- Briefly identify a few examples of everyday problems that you could not solve by the scientific method, and then try to generalize to discuss how you can distinguish between problems for which the scientific method is useful and those for which it is not.
This will likely work best with relatively small groups of 3 to 4 students.
(1) Students should look for simple examples, like the flashlight example above.
(2) Here, we hope that students will see how the scientific method was valuable, or could have been of more value if applied more carefully.
(3) Discussion on this question should be interesting. We hope that students will recognize that the scientific method applies to well-defined problems with well-defined solutions, but does not apply well to more open-ended problems, such as personal problems or to learning new skills. In setting the stage for the next subsection, it is also useful if students think about problems that just involve curiosity and exploration that are scientific but not necessarily amenable to the “scientific method” as described in Figure 3.15.
Hallmarks of Science
The scientific method can be very useful when you have a well-defined problem in search of a well-defined solution, such as figuring out what is wrong with a flashlight or finding out whether a new cancer treatment works. However, science as a whole rarely progresses in such an orderly way.
- Would you say that Galileo was following the “scientific method” of Figure 3.15 when he made his important telescopic discoveries? Why or why not?
Galileo wasn’t following the standard “scientific method,” because he didn’t start with any particular question in mind. Rather, he was simply curious about what he might see when he built his telescope and pointed it up at the sky.
As the case of Galileo illustrates, scientific progress often begins with curiosity rather than a well-defined question or problem. Moreover, scientists are human beings, which means that their work is often influenced by their personal beliefs and intuition. Sometimes this can prove beneficial. For example, Copernicus chose to work on a Sun-centered system at a time before clear evidence in its favor existed, so it must have been his personal intuition that led him in the correct direction. Of course, relying on personal beliefs and intuition can also sometimes lead us astray.
- Give at least two examples in which personal belief or intuition helped keep the incorrect Earth-centered system in favor until the time of Kepler and Galileo.
There are numerous possible examples you could cite, but two that were particularly important in keeping the incorrect model in favor were: (1) The “lack of imagination” that made most people unable to believe in the possibility that the absence of detectable stellar parallax could simply mean the stars were too far away for us to notice it. (2) The idea that all heavenly motion must be in perfect circles.
Given that science does not always follow the “scientific method,” how can we tell what is science and what is not? Many people have come up with many different answers to this question, but for our purposes, we will focus on three key “hallmarks” that are shared by essentially all real scientific work (Figure 3.16):
- Modern science seeks explanations for observed phenomena that rely solely on natural causes.
- Science progresses through the creation and testing of models of nature that explain the observations as simply as possible.
- A scientific model must make testable predictions about natural phenomena that would force us to revise or abandon the model if the predictions did not agree with observations.
Key Concepts: Distinguishing Science from Nonscience
It is not always easy to decide what counts as “science” rather than as something else, such as personal belief. However, you can generally decide by checking whether the topic under study meets the three “hallmarks of science” shown in Figure 3.16. If it meets all three, then it probably counts as science; if it is missing one or more of the three, then it does not.
Group Discussion
Hallmarks of Science in the Copernican Revolution
Your teacher will write the three hallmarks of science on a board. For each one, discuss and list ways in which the hallmark is evident in the Copernican revolution’s overturning of the ancient Earth-centered belief.
This discussion is best done as a full class, with you leading it. You should prepare in advance by writing the three hallmarks on a board; best to write them each at the top of a blank column, so you can add notes below each one based on the class discussion. A few notes on key ideas that students will hopefully recognize with regard to each of the three hallmarks above.
- (hallmark 1)
- Both ancient and Copernican-era scientists were seeking to explain observations of planetary positions.
- Recognizing the importance of observations, Tycho improved significantly on prior measurements of planetary positions.
- Earlier mythology had “explained” planetary motion by suggesting, e.g., that planets were gods (hence the reason that the planets carry the names of mythological gods). In contrast, the scientific explanations assumed that there was some natural reason behind the observed motions.
- (hallmark 2)
- We see the use of models at every stage in the process, including Ptolemy’s Earth-centered model, Copernicus’s model, and Kepler’s model.
- The importance of explaining “as simply as possible” is evident in the way that Aristarchus in ancient times and Copernicus later adopted a Sun-centered model at least in part because it offered a much simpler explanation for apparent retrograde motion.
- (hallmark 3)
- All of the models made predictions about where planets should appear in the sky. This allowed for the accuracy of each model to be tested against how well their predictions matched real observations of where the planets appeared.
- Kepler’s model gained acceptance because it worked, while the other models gave inaccurate predictions.
- The Sun-centered model also made numerous other predictions that were borne out, including the phases of Venus and, later, the discovery of stellar parallax.
Teacher Notes: The following two boxes are optional, but they cover ideas that are implicit to the hallmarks that many students might be wondering about. If you have the time, it is worth discussing them briefly.
Testability
The third hallmark is often the most important in distinguishing science from nonscience, because it requires that a model make predictions that can be tested and verified. One way to decide whether a statement or model is testable is to determine whether it is falsifiable , meaning that we could in principle make future discoveries that would cause us to reconsider whether the statement or model is correct.
Note that a statement can be falsifiable regardless of whether it is true or false. Being falsifiable only means that we can imagine observations that would disprove it, even if those observations are only hypothetical (that is, fictional observations that might never actually occur). In other words, a falsifiable statement is one that we can put to the test, and we may consider it to be true if it passes all tests. As a simple example, consider the statement “All people need food to survive.” This statement is clearly true, but it is still falsifiable because it would be disproven if we were ever to observe a person who could survive without food.
Activity
Falsifiable Statements in Everyday Life
Work in small groups to consider the following claims. For each claim, decide whether it is falsifiable, and explain why.
- John F. Kennedy was the 35th president of the United States.
- If he had not been assassinated, Kennedy would have ended the Vietnam War.
- I believe that Shakespeare was the greatest writer in history.
- Shakespeare wrote the play Romeo and Juliet.
- LeBron James is the greatest basketball player in history.
- China has a larger land area than India.
- I believe that God is present in all aspects of our lives.
This activity should help your students understand the concept of falsifiability in a social studies realm before we move to the scientific realm below. Key points for each:
- “John F. Kennedy was the 35th president of the United States.” This statement is falsifiable because you could use historical records (observations) to check whether or not it is true.
- “If he had not been assassinated, Kennedy would have ended the Vietnam War.” This statement is not falsifiable, because there is no way to observe what might have happened if he had not been assassinated.
- “I believe that Shakespeare was the greatest writer in history.” This statement is not falsifiable, because it is a personal belief.
- “Shakespeare wrote the play Romeo and Juliet.” This statement is falsifiable, because he either did or did not write the play, and historical evidence can in principle establish which is correct (and the evidence indicates he did).
- “LeBron James is the greatest basketball player in history.” This statement is not falsifiable, because it is a matter of personal opinion and there is no consistent measure of skills to establish one player as statistically better than the other.
- “China has a larger land area than India.” This statement is falsifiable because measurements and records can be consulted to verify the relative sizes of India and China.
- “I believe that God is present in all aspects of our lives.” This statement is not falsifiable, because it is stated as a personal belief.
Let’s move now to a more scientific example. Consider the fact that the Sun, Moon, planets, and stars all rise in the east and set in the west each day. In the ancient Earth-centered model, people assumed this happened because those objects actually circled around Earth each day. In contrast, our modern model of the universe explains those motions as consequences of us living on an Earth that rotates from west to east each day.
- Can you think of a way in which the rotating Earth model is falsifiable? That is, could you imagine some hypothetical observation that would cause us to think the model is wrong? Think about this question, then check your answer.
A Hypothetical Observation That Would Disprove the Rotating Earth: In the model of a rotating Earth, the daily motion through our sky of distant celestial objects occurs because Earth is moving, not because those objects are moving. In other words, this model predicts that we would have to see the same daily pattern of motion for all celestial objects that we ever discover. Therefore, if we were to discover some distant planet that rises in the west and sets in the east, we would not be able to explain it with the rotating Earth model. (Note that this does not apply to artificial satellites that are orbiting Earth, for reasons discussed in the “I was Wondering” box that follows.)
Figure 2.9b (repeat) – Earth’s west to east is the cause of the apparent east to west motion of celestial objects. Therefore, all celestial objects must appear to move in the same direction, since Earth’s rotation direction is always the same. (This does not apply to artificial satellites orbiting Earth.)
Turning this idea around, you’ll realize a remarkable fact: Every time astronomers observe a new planet or star or galaxy (something that, with modern telescopes, happens many times each day), they are in essence testing and verifying the rotating model. This “perfect track record” for the rotating model explains why we now consider the idea of a rotating Earth to be much more than just a model, and instead to be an established fact.
Key Concepts: Models and Facts
A model can come be considered an established “fact” if it has been so well-tested and verified that there is no longer any reason to doubt that it reflects reality. That is why, for example, we no longer distinguish between a Sun-centered “model” of the solar system and simply stating that it is a fact that Earth and other planets orbit the Sun.
Activity
Falsifiable Statements in Science
Work in small groups to consider the following statements. For each statement, decide whether it is falsifiable, and explain why or why not. If it is falsifiable, also decide whether it is true, false, or whether its truth or falsehood is still unknown.
- Earth orbits the Sun.
- Earth is flat.
- Trees are built of cells that contain DNA.
- There are hidden forces that control our individual destinies.
- We are all play things in a computer program created by advanced aliens.
- There is life on Mars.
- Your astrological sign determines your personality.
- The universe as a whole is kind and benevolent.
This continues the prior activity, but with more scientific sounding statements. Key points for each:
- “Earth orbits the Sun.” This statement is falsifiable because we can make observations that test whether it is true, and countless tests have established that it is true.
- “Earth is flat.” This statement is both falsifiable and false because, as you have discussed earlier in this chapter, there are many observations we can make that test whether Earth is flat or round, and all of these observations indicate that Earth is round.
- “Trees are built of cells that contain DNA.” This statement is falsifiable because we can observe the biological structure of trees and examine their cells under a microscope. These observations indicate that the statement is true.
- “There are hidden forces that control our individual destinies.” This statement is not falsifiable because it is using the term “hidden forces” in a way that indicates that we cannot observe them.
- “We are all play things in a computer program created by advanced aliens.” This statement is not falsifiable because it implies we are part of something that we cannot observe, because its nature is being deliberately hidden from us.
- “There is life on Mars.” This statement is falsifiable because we can in principle search for life on Mars (and would then either find it or not find it). However, we do not yet know whether it is true or false, because we do not yet have the capability of conducting a complete search for life on Mars.
- “Your astrological sign determines your personality.” This statement is both falsifiable and false, because we can create experiments to see how personality traits are linked to astrological sign, and many such experiments have found no linkage.
- “The universe as a whole is kind and benevolent.” This statement is not falsifiable because there is no objective method for measuring attributes such as “kindness” or “benevolence” for physical objects like stars and galaxies; this statement therefore represents a matter of opinion or belief.