to figure out the cause of the problem. You do this by speculating what may be wrong with the car, and then you experiment by testing each of your

Transcription

1 Scientific Method Paleobiology, the study of the biological information preserved in fossils, which includes the study of dinosaurs, is a science, and as such, uses scientific procedures to further our understanding of life. Although we tend to think of science as a specific field of study or body of knowledge, it is, in fact, a much broader phenomenon. Science is the process that allows us to better understand our world. Science is actually a method that has resulted in the various fields of study and the accumulated knowledge with which we associate the term science. But science is not simply what is known through human inquiry, rather it is the search itself. Each of us was born a scientist. Initially, we used our eyes, ears, and hands to gather data, studying shape, movement, sound, and texture. We stored the information gained by our brains and used it to evaluate other experiences in such a way that some things became better understood or more familiar. When we first started to toddle about, we were setting out to gather information that would help us understand our surroundings. When we tasted certain foods, we quickly learned which ones tasted better to us, and unconsciously started to prefer foods that looked similar to those our studies had proven palatable. We did these things naturally as we explored our world; no one had to teach us how to do science. We were born with curiosity and a desire to investigate the world beyond ourselves. This characteristic of learning through experimentation continues well into our adult lives. When you first drive to a new job or class, you determine a specific route to take. If it takes longer than you expected, you may change the route to improve your drive time. Your commute to work or class then becomes an experiment. Your hypothesis is that taking the new route should result in arrival by a certain time. If your drive takes a longer time than the original route, you reject your hypothesis and conduct another experiment, this time choosing yet another route. Eventually, your experiments will enable you to find the shortest route. Another example of how you use the scientific method in your daily life is when cooking. You may observe that a new dish is too salty for your liking, so the next time you cook it, you experiment with the amount of salt until you get it right. You are also thinking scientifically when your car won t start and you use a step-wise process of trying

2 to figure out the cause of the problem. You do this by speculating what may be wrong with the car, and then you experiment by testing each of your ideas until you identify the malfunction. That process of experimenting is what makes science different from other ways of knowing. To conduct science, you must use the scientific method, which in its simplest form consists of observation, hypothesis, experiment, and theory. Like all methods of study, the scientific method is limited. For example, it can tell you how Da Vinci painted the Mona Lisa, but it cannot tell you if the Mona Lisa is a good painting. The scientific method cannot be used to test opinions or other subjective matters, nor can it be used to test things that individuals may choose to accept on faith. Those types of ideas cannot properly be examined by the scientific method, and as such, they do not belong to the realm of science. In short, ideas that are not testable cannot and do not belong to science. The scientific method is the cornerstone of all science, and everything proposed to be science must pass its tests. Let s look at the scientific method, first in terms of its basic steps and how scientists use it to understand the world, and then by illustrating it with some examples. The first step in the scientific method is making an observation about something in the natural world. Having a critical eye and a questioning mind is crucial to being a scientist. Once a scientist has made an observation, she or he develops a possible explanation, called a hypothesis, about the observation. A hypothesis has no value in science, other than as a starting point for an investigation. It is essentially a guess as to what has resulted in the observation. It is the experiment that follows that determines if the hypothesis has any explanatory value, and is therefore a worthy hypothesis, or whether the hypothesis is incorrect and should be discarded as an explanation for the observation. Experiments must be carefully designed in order to be a valid test of a hypothesis. First, they must have controls, meaning that the procedures involved must keep all the experimental conditions constant except for the one variable being tested. That is the only way to hold other things still and look at a single element of the problem at a time. Second, an experiment must be repeatable, such that the same experiment should always

3 produce the same results, whether conducted by the original scientist or by other scientists. Finally, the most valuable experiment should actually set out to disprove the hypothesis, rather than to prove it. This is because it is never possible to prove a hypothesis true with a single experiment; however, it is possible to disprove a hypothesis with a simple, well-designed experiment. Keep in mind that it is not essential that the experiment set out to disprove the hypothesis, and in fact, an experiment can just as easily be designed to attempt to support a hypothesis, but if so, repeated experimentation is needed to substantiate validity. As an example, consider the observations of the sun at the horizon that made early explorers believe that the horizon was the end of the earth. A willingness to undertake travel beyond the horizon would be a simple (but undoubtedly harrowing) experiment that would disprove the original hypothesis. In this example, moving beyond a landmark originally seen on the horizon would easily disprove the end of the earth hypothesis. When that particular hypothesis is voided, however, the observation remains, and so other explanations can then be developed for the phenomenon of a horizon that appears to drop off, and further experiments can be devised. Consider the case where experimentation supports a hypothesis, rather than disproves it. Now the hypothesis may take on a different role. If it is a valid explanation for observations, it should stand the tests of time and lead to predictions about future and related observations. A single experiment cannot prove a hypothesis; the hypothesis must be made reliable through further experimentation that is repeatable and from which scientists obtain consistent results. The hypothesis must be predictive, and those predictions can also be tested through experimentation. If the predictions are verified, time and time again, then the hypothesis becomes more robust in its explanatory power, what science terms a theory. People who object to the theory of evolution often say it is just a theory. In science, however, a theory is not a hunch ; a theory is as close to a fact as science can get. The equation one plus one equals two is explained by the number theory developed in the field of mathematics. All life on earth shares common ancestry, as explained by evolutionary theory developed in science. To a scientist, a theory is extremely robust in its explanatory power, and it furthers our understanding by leading to

4 predictions that may result in future knowledge. Therefore, to use the term theory within science means that there is powerful and compelling evidence for the idea as fact. Using the scientific method The scientific method is the foundation to how science works. In its simplest form it consists of four basic points: Observation Hypothesis Experiment Theory Doing science is a creative process. It involves observing some phenomenon and coming up with explanations about the observations. Those explanations are hypotheses. But hypotheses have no real value other than guesses. In doing science, you must test the hypothesis with an experiment. Each sentence below describes a step of the scientific method. Match each sentence with a step of the scientific method listed below. A. Recognize a problem or make an observation B. Form a hypothesis C. Test the hypothesis with an experiment D. Draw conclusions 1. John predicted that insects would grow faster if they were placed in a warm incubator. 2. Jane said, If I place plants in sunlight they will grow taller. 3. John s data showed that cockroaches are repelled by baking soda. 4. Jane obtained bacteria from various surfaces and exposed them to various cleaners. 5. John rolled a dice one hundred times to determine the frequencies of the numbers that occurred. 6. Jane noticed woodpeckers pecking on trees and thought, I think they are searching for insects below the bark 7. Leonardo wondered if he dropped a heavy ball and a feather from a tower that the

5 heavy ball would hit the ground before the feather. 8. Jane grew apple seeds in different kinds of soil to determine if they would all germinate at the same rate. 9. Charles Darwin noticed that some plants were missing on islands. 10. Darwin wondered how long seeds would survive in salt water. 11. Darwin placed seeds in a barrel of sea water, and removed one each day and planted it to see if it would germinate. He did this for three months. 12. A paleobiologist examining thin sections of tyrannosaur bone found structures that looked like blood cells. 13. The above paleobiologist analyzed the blood cells for the presence of iron. 14. The paleobiologist found that antibiodies made from the dinos blood reacted with bird antigens. She felt this showed a close relationship between dinosaurs and birds. Designing an experiment Experimental design is a detailed process. The best experiments should be those that would disprove the hypothesis. That means that the hypothesis must be capable of being disproved. If it is not, then it is beyond the scientific method and is of little explanatory value. Moreover, valid experiments meet several requirements. They must include a Dependent variable what is measured during the experiment or what is affected by the experiment Independent variable what is varied during the experiment. It is also under the control of the experimenter. Controlled variables all the other variables other than the independent variable, must be the same in all trials or kept constant. There can be only one independent variable in an experiment, thus all other factors that might affect the experiment must remain constant. There must also be a control that essentially keeps the independent variables constant or eliminates them. Experiments must also be repeatable. Identify the dependent and independent variables in the following examples. Example: The number of mosquito larvae that are produced over a two-week period.

6 In this case the number of mosquitoes is the dependent variable, and time is the independent variable. Identify the dependent and independent variables in the following experiments by marking the correct response on the scantron sheet. 15. The germination rate of seeds after soaking in salt water of different concentrations The different concentrations of salt water are variables. A. Dependent B. Independent 16. The germination rate is the variable. A. Dependent B. Independent The weight of mice grown at different temperatures 17. The weight of the mice is the variable. A. Dependent B. Independent 18. The different temperatures are variables. A. Dependent B. Independent When doing any experiment, you should have an idea of what results to expect if the hypothesis is valid, and what results to expect if the experiment disproves the hypothesis. If the experiment disproves the hypothesis, it might lead to a refinement of the hypothesis, which can then be retested. After a hypothesis has survived testing, it can lead to predictions of other phenomenon that would result if the hypothesis is valid. If these predictions are verified with further testing, then the hypothesis attains the robust status of a theory. Which of the following hypotheses are capable of being falsified? 19. The more water is added to a plant, the faster it grows. A. This can be falsified B. This cannot be falsified. 20. Cats are happy when they are scratched A. This can be falsified B. This cannot be falsified. 21. Smoking causes lung cancer A. This can be falsified B. This cannot be falsified. Scientific inquiry is based on observations. A hypothesis can be put forth as a way of explaining the phenomenon observed. A hypothesis is tested through experimentation, and further observations may result in refinement and revision of the original hypothesis (in other words, science doesn t advance unless we question it!). If a hypothesis stands up to repeated testing (using controls and variables), it may become a theory. Remember that in science a theory is held at a higher level than a hypothesis,

7 and represents knowledge of which we are very sure. (While, often, in laymen s terms, a theory is likened to a guess or a hunch.) 22. The first step in the scientific method is a. experiment b. observation c. controls d. developing a hypothesis 23. Which has a greater value as a scientific explanation? a. theory c. fact b. hypothesis d. observation 24. A well designed experiment should have all of the following except a. controls c. independent variables b. two variables d. be repeatable 25. The various space probes we have sent to Mercury, the Moon, Mars, the moons of Jupiter and Saturn have revealed that the most common geological feature was impact craters. Moreover, there is ample evidence of impact craters on the Earth. This led to a hypothesis that the dinosaurs became extinct after the impact of a meteorite on the earth at the end of the Cretaceous. This was tested by examining the rocks at the Cretaceous Paleogene boundary to determine if elements form meteorites could be found. What was the observation that led to the hypothesis? A. The examination of rocks at the end of the Cretaceous. B. The examination of photographs of extra terrestrial bodies. C. The examination of the fossil plants of the Cretaceous. D. The analysis of meteorites 26. They hypothesis was tested by A. looking at fossils of dinosaurs B. examining fossils from throughout the time dinosaurs lived. C. looking for minerals common to meteorites in rocks contemporary with the dinosaur extinction D. looking a fossil mammals. Pseudoscience The scientific method is ideal at debunking pseudoscience. Pseudoscience is a belief that does not have experimental evidence to support the claims of the belief. We recently had nearly 100 students examined a list of personality characteristics. They were asked to select the characteristics that they felt best described them. They also reported their birthday as part of the experiment. They did not know that the characteristics were used to describe the characteristics of people born under different astrological signs. The collected data was used to determine the correlation of someone s astrological sign and their likes and dislikes. If astrology is a valid science we would predict a high

8 correlation. If there is not relationship, then any correlation would simple chance, which would be one in twelve should be correlated. If there is a correlation, we would expect a much higher correlation. In science, we would like the correlation to be 9 of 10. The results of the test showed that of the 92 students who participated that personality trait, 12 (13%) student s personality matched their astrological sign. 27. In our experiment, was dependent on birthdate, and as such was the dependent variable. A. gender C. personality traits B. hair color D. right or left handedness 28. Did results of the experiment support or reject our hypothesis that the pseudoscience was valid? A. Support B. Reject 29. Can you use the scientific method to test a pseudoscience? A. Yes B. No 30. Other examples of pseudosciences include A. Foot reflexology B. Special Creation C. the flat earth hypothesis D. geocentric solar system E. All of the above are pseudosciences