T HE WORLD ’ S MOST renowned scientists once believed that the Earth was flat, that the sun revolved around the Earth, and that human beings were already fully formed within a woman’s body and sim- ply had to grow to full size in the womb. Science has a rich and often tumultuous history. Driven by curiosity and desire to help humanity, scientists have made great progress in understanding nature. This knowl- edge was, in most cases, accumulated incrementally, with one small discovery leading to another. Theories were developed to unify and explain available facts. Different interpretation of facts by different scientists has lead to controversies in the past. Some major scientific discoveries created dramatic paradigm shifts—revolutions in our understanding of nature.  Science as a Human Endeavor What can possibly get someone to study for years, read science journals, repeat experiments countless times, write applications for funding, and present results? Just like a child reaches for a new object, touches it, looks at it, takes it apart, and tries to make it work again, so the scientist looks at nature and tries to understand it. The curiosity CHAPTER History and Nature of Science IN THIS chapter, you will read about what drives science, the nature of scientific knowledge, and how the body of scientific knowledge grows and changes over time. You will also find a brief description of some foundation-shaking advances in science. 28 257 almost seems to be innate, and the thrill that comes from understanding nature or making a new experiment work is well expressed in the following quote: “I do not think there is any thrill that can go through the human heart like that felt by the inventor as he sees some creation of the brain unfolding to success .Such emotions make a man forget food, sleep, friends, love, everything.” —Nikola Tesla, physicist and inventor Scientists are driven by curiosity and the thrill that comes from understanding or creating something. At the same time, they are motivated by the desire to improve the quality of life—making everyday chores easier, curing diseases, and solving global and environmental prob- lems. Scientists also seek to use, predict, and control nature—to use sunlight and water for electrical power generation, to forecast the weather and earthquakes, to prevent floods, and to prevent infection of crops and cattle. The result is that over the years, our understanding of science has greatly improved. Humanity has gone from attributing disease to supernatural beings to developing vaccines, antibiotics, and gene therapy to prevent and cure disease. Since Thales of Miletus proposed in 625 B . C . that the Earth is a disc that floats on water, humans have discovered the true nature of their planet, have observed other galaxies, and have landed on the moon. The im- mense progress people have made in science is well expressed in this quote: “The simplest schoolboy is now familiar with truths for which Archimedes would have sacrificed his life.” —Ernest Renan, philosopher  The Nature of Scientific Knowledge Scientific knowledge is rooted in factual information that is compiled and interpreted to develop theories. While scientists can’t help believing and hoping—that their experiments or inventions will work; that they will solve a problem; that their theories are correct—experiments are designed to eliminate, as much as possible, the effects of the beliefs and hopes of the scientist performing them. Different scientists often get conflicting data. Even the same scientist’s data is not always consistent. Differences in experimental procedure, which the scientists may or may not be aware of, can all lead different scientists to different conclusions or even the same scientist to dif- ferent conclusions at two different times. Occasionally, this leads to controversy. In the sections below, we will briefly describe the nature of scientific knowledge and how beliefs and controversies play a part. Facts Scientific knowledge is dependent and inseparable from facts. The principles of the scientific method guide sci- entists to observe facts and to propose hypotheses that can be tested by observing other facts. A hypothesis that can’t be verified by collecting scientific facts is not con- sidered part of the domain of science. Theories Just as a collection of bricks does not equal a house, a col- lection of facts does not equal science. Scientific facts, like bricks, need to be sorted and stacked properly. Their relationships to each other matter and need to be estab- lished. Scientists must be able to envision the end result, the way an architect needs to have an idea of what a house should look like. For scientists, the house is the theory—something that unites the facts and makes them meaningful and useful. Theories are formed when a con- nection between facts is first observed. The theories are then developed by looking for more facts that fit into the theory and by modifying the theory to include or explain the facts that do not fit. Beliefs One of the most difficult tasks of a scientist is to remain objective and prevent beliefs from affecting observations. This is not to say that scientists purposely hide facts that don’t support their hypotheses or that are in conflict with their beliefs. Most scientists are well trained to report everything they observe, even if it’s inconsistent with what was previously observed and even if it seems unim- portant. However, it is in human nature to notice and remember the things that we believe in and that we expect. This is a form of intellectual prejudice. If Bob believes that Julie hates him, he will tend to notice only Julie’s negative behavior toward him such as not saying – HISTORY AND NATURE OF SCIENCE – 258 hello and making a joke about him. He will also tend to interpret Julie’s actions in a negative way. For example, if Julie says that she can’t go to the movies, Bob will take that as evidence for his hypothesis that Julie hates him. However, this is not necessarily true—Julie may have too much homework. Bob could also disregard or misinter- pret the nice things that Julie does—it could be a coinci- dence that Julie sat next to him and that she called him (maybe she just needed something). Scientists can’t help but occasionally do the same thing. For example, a sci- entist who smokes may note the great number of people who smoke and don’t get cancer, and attribute the fact that some people who smoke and do get cancer to pol- lution sensitivity or lack of proper nutrition. Marie Curie, a two-time Nobel Prize winner, refused to note overwhelming data that suggested that radium, an element she had discovered, was a health hazard. This inability to see was not caused by lack of training, as Curie was a sufficiently trained scientist whose doctoral thesis was considered the greatest single contribution to science by a doctoral student. The inability to see is caused by a blindfold made of hopes and beliefs that scientists, like all other people, can’t help having once in a while. “Man can’t help hoping even if he’s a scientist. He can only hope more accurately.” —Karl Menninger, psychiatrist Controversies Conflicting data, or facts that seemingly can’t be incor- porated into the same theory, often cause controversies among scientists. The controversies can polarize the sci- entific community, as well as the general population, especially in matters of public or social importance. In the past, controversies also sprang up between scientists and religious establishments. Copernicus shook up the church when he proposed that planets revolved around the sun. Similarly, Darwin caused a lot of controversy when he presented his theory of evolution. There is still some debate on whether evolution theory should be taught in public schools. The nature of light was not very well understood for a long time. There were observations that suggested that light is a stream of particles, as well as that light is a wave. Newton’s belief that light was a series of particles pre- vailed from the 1700s until 1873, when James Clerk Maxwell showed that light is an electromagnetic phenomenon. Although many scientists before Maxwell found evidence for the wave nature of light, Newton’s great reputation and social class allowed his ideas to pre- vail until there was enough evidence to the contrary. Max Planck’s theory about the resolution of controversies is slightly more cynical: “A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new genera- tion grows up that is familiar with it.” —Max Planck, physicist  Historical Perspectives All sciences are rooted in philosophy, which they stemmed from, as knowledge in different sciences accu- mulated and became more specialized. Areas of science today include very specific subjects, such as oceanogra- phy, crystallography, and genetic engineering, as well as interdisciplinary subjects, such as biochemistry and bio- physics. Progress in science usually occurs in small incremen- tal steps. For example, nucleic acids (building blocks of DNA) were discovered in the nuclei of cells in 1869. After that, progress was made. Different scientists made con- tributions to the study of DNA. However, scientists did not solve the structure of DNA until 1953, when Ros- alind Franklin, James Watson, and Francis Crick obtained their results. About twenty years later, the first genome sequencing was presented—for a virus that had a relatively small amount of genetic material. More recently, the Human Genome Project was completed. Hundreds of scientists worked on this largest single fed- erally funded project to date with the goal of identifying all human genes and mapping out the human DNA. Sci- entific advances usually depend on other scientific advances, and progress is usually gradual. Many scien- tists put in a lot of time before a new concept becomes completely understood and before a new area of science develops. Occasionally, however, there are leaps in scientific progress. Such leaps represent major discoveries that – HISTORY AND NATURE OF SCIENCE – 259 shake the foundations of understanding and lead to new modes of thinking. Thomas Kuhn, philosopher of sci- ence, called such discoveries paradigm shifts. Here are some major advances in science. ■ 420 B . C .: Hippocrates begins the scientific study of medicine by maintaining that diseases have common causes. ■ 260 B . C .: Archimedes discovers the principle of buoyancy. ■ 180 A . D .: Galen studies the connection between paralysis and severance of the spinal cord. ■ 1473: Copernicus proposes a heliocentric system. ■ 1581: Galileo finds that objects fall with the same acceleration. ■ 1611: Kepler discovers total internal reflection and thin lens optics. ■ 1620: Francis Bacon discusses the principles of the scientific method. ■ 1687: Newton formulates the laws of gravity. ■ 1789: Lavoisier states the law of conservation of energy. ■ 1837: Darwin uses natural selection to explain evolution. ■ 1864: James Clerk Maxwell shows that light is an electromagnetic phenomenon. – HISTORY AND NATURE OF SCIENCE – 260 N OW THAT YOU have reviewed the information you need to know, it’s time to think about strate- gies you can use at test time. Throughout this chapter, you will review the structure of the science exam and learn specific tips you can use to improve your score on the test. Read this chapter care- fully, and then review your notes from the science section. When you are ready, move on to the practice ques- tions that follow.  Multiple-Choice Questions The good thing about multiple-choice questions is that the answer is right in front of you. All you need to do is find it, or at least eliminate some of the clearly wrong choices. At times, you may not be able to eliminate all four of the incorrect choices. But there is no penalty for guess- ing on the GED. If you can eliminate one of the wrong choices, you will have a 25% chance of guessing correctly, and that is still better than leaving it blank. If you can eliminate three choices, you have a 50% chance of getting the question right. When answering multiple-choice questions, make sure you have read the question carefully. Often, the ques- tion will ask you to chose a statement that is NOT true or find an exception to the rule. CHAPTER Tips and Strategies for the GED Science Exam IN THIS chapter, you will briefly review some tips you can use on the GED Science Exam. Several tips apply to other sections of the GED as well. 29 261 Even when you think you have found the correct choice, quickly glance at the other choices to make sure that no other choice is better or more specific. Also, check whether one of the choices is “All of the above.” You may well have picked out a correct statement, but if the rest of the statements are also correct, the answer needs to be, “All of the above.”  Types of Questions Two types of questions appear on the GED—conceptual understanding and problem solving. Conceptual understanding questions require you to read and understand the information provided or to recall basic knowledge you have acquired through prior schooling or everyday life. Read the question and infor- mation provided along with it carefully. Often, a ques- tion will ask you to restate what was already said or to make a generalization about the facts presented in a pas- sage. By reading carefully and making notes on a piece of scratch paper as you go along, you increase your chances of understanding the provided information correctly. Problem-solving questions require you to apply what you have read or learned. As you are studying for the exam, when presented with a scientific fact, such as “energy can be converted from one form to another,” think about the situations in which that fact is apparent. Think about a car—using the chemical energy in the fuel causes the car to move and the engine to heat. Think about how the fuel level decreases as the car moves. Where is the fuel going? What is happening to the exhaust gases? The principles of science are all around you. By paying attention to them in your everyday life, you will be better prepared to answer problem-solving questions on the GED.  Reading and Understanding Graphics About half of all GED Science questions include graph- ics. By becoming familiar with different types of graph- ics and learning about their essential components, you will be better prepared to answer GED Science questions that contain graphical information. When looking at a chart or a graph, look at the title or caption first. This will give you an overview of what the graphic is showing. Next, look at any legends or axis labels provided. This will give you an idea of what vari- ables are shown. Make a list of the variables. Once you have done that, you can try to interpret the chart or graph by noting any trends you may see. How is one vari- able changing in response to the other? Next, you can read the question and attempt to answer it. Here is more specific information about graphics. Charts All charts are composed of rows (horizontal) and columns (vertical). Entries in a single row of a chart usu- ally have something in common, and so do entries in a single column. Determine what the common elements are when you try to answer the questions on the GED Science Exam. Graphs Three common types of graphs are scatter plots, bar graphs, and pie graphs. This section provides a brief description of each. Whenever a variable depends continuously on another variable, this dependence can be visually repre- sented in a scatter plot. An example includes a change in a property (such as human population) as a function of time. A scatter plot consists of the horizontal (x) axis, the vertical (y) axis, and collected data points for variable y, measured at variable x. The variable points are often connected with a line or a curve. A graph often contains a legend, especially if there is more than one data set or more than one variable. A legend is a key for interpret- ing the graph. Look at the sample graph above. The essential elements of the graph—the x- and y-axes—are labeled. The legend to the right of the graph shows that dots are used to represent the variable points in data set 1, Graph Title 100 120 140 80 60 40 20 0 024 6810 data set 1 data set 2 y-axis x-axis – TIPS AND STRATEGIES FOR THE GED SCIENCE EXAM – 262 while squares are used to represent the variable points in data set 2. If only one data set exists, the use of a legend is not essential. Bar graphs are similar to scatter plots. Both have a variable y plotted against a variable x. However, in bar graphs, data is represented by bars, rather than by points connected with a line. Bar graphs are often used to indi- cate an amount or level, as opposed to a continuous change. Pie graphs are often used to show what percent- age of a total is taken up by different components of that whole. Diagrams Diagrams could be used to show a sequence of events, a chemical or biological process, the setup of a science experiment, a phenomenon, the relationship between different events or beings, and so forth. When you see a diagram, first determine its purpose. What is it trying to illustrate? Then, look at the different labeled parts of the diagram. What is their function? How are they interrelated?  Reading and Understanding Scientific Passages When reading a scientific passage, the most important thing is to focus on the big picture, or on the subject of the passage. In many ways, the reading passages in the science part of the GED are the same as the reading pas- sages in other areas. One important difference is that sci- ence passages may expose you to science jargon, specialized vocabulary you may not be familiar with. Try not to let new words throw you off. You may be able to guess their meaning from the context. Even if you can’t, keep reading. The questions following the passage may not require you to understand that particular word.  Series of Questions Based on a Passage or Graphic On the GED, you will sometimes be asked more than one question based on the same graphic or passage. When this is the case, it is worth your while to invest a little more time to understand the graphic or passage. Even if you are unsure about the first one, try answering the remaining questions—they may be easier for you.  Experiment Skills Experiments should be designed and conducted in accordance with the principles of the scientific method. This means that the goal of the experiment should be carefully formulated and the experiment should be set up to yield factual results. Review the concepts of the sci- entific method in Chapter 22 if the tips included in this section are unfamiliar to you. Setting Up an Experiment Experiments should be set up to test one clearly formu- lated and testable hypothesis. The number of variables (things changing) in the experiment should be limited and carefully controlled. If possible, experiments should contain a control group. For example, if you were to study the effect of a new soil supplement on house plants, the soil supplement should not be used on a few plants, which will comprise the control group. If there is improvement in the growth of only the plants on which the supplement was used, then there is strong indication that the supplement increases the plant growth. If, how- ever, the plants in the control group grow as much as the plants on which the supplement was used, then the causes of growth most likely are not linked to the sup- plement. In this example, there would be two variables— the use of the supplement and the plant growth. How the supplement is administered and how plant growth is measured would need to be carefully described and controlled. For example, the scientist conducting the experiment would need to decide whether the supple- ment would be administered once, several times, or every day throughout the experiment. The scientist would also need to define what constitutes plant growth—the ver- tical increase, the number of new leaves, the growth of new branches and leaves, or some combination of these factors. One choice is not necessarily better than the oth- ers. Measuring the vertical growth wouldn’t necessarily be worse than counting the number of new leaves. Sci- entists must be consistent. If the number of leaves is recorded one day on one plant, it should be recorded every day on all the other plants in the experiment. On the GED, you may be asked to pick out the best design for an experiment. Before you look at the choices, determine the important variables and what would make a good control. Select the choice that contains these vari- ables, that has the most logical experimental control, and in which the variables not studied are held constant. – TIPS AND STRATEGIES FOR THE GED SCIENCE EXAM – 263 Interpreting Others’ Results In some GED questions, you will be asked to interpret others’ results. You will need to make a generalization about the results or draw a conclusion. Don’t base your answer of what you believe is right. Base your answers on the results provided. Look at the choices given. Some could be inaccurate—if one part of the result doesn’t fit the description in the choice, the choice is wrong (unless words such as generally or in most cases make room for exceptions). Make sure you don’t jump to conclusions. A trend doesn’t always indicate a cause and effect relation- ship. For example, every morning, your alarm clock goes off, and every morning, you get hungry. However, the alarm clock is not what is making you hungry. The two events just happen to occur at the same time. Before you conclude that there is a cause and effect relationship on the GED, consider other conclusions, and then pick the most logical one. Analyzing Experimental Flaws A common GED Science question requires you to ana- lyze the flaws of an experiment. Experiments should be based on the scientific method. Common experimental flaws include: ■ not testing the hypothesis ■ having too many variables ■ unforeseen variables ■ lack of experimental control ■ jumping to conclusions Applying Scientific Conclusions What good is science if we don’t benefit from it? How would the finding that keeping a laptop on your lap for too long can damage your pelvic organs influence you? You would not keep the laptop on your lap for too long, right? Many questions on the GED require you to apply a scientific conclusion, either to your personal life or to global phenomena. These are almost always questions from the problem-solving category. You are presented with a fact in one context and asked to apply it in another context. For example, if you read in a passage about dif- ferent methods of determining the sides of the world in nature without a compass, you could be asked which of the methods would best work if you were in a particular situation—lost on a cloudy night in a forest, on the ocean on a clear day, etc. If necessary, as you are reading information provided in the question, make quick dia- grams and summarize the important concepts on a piece of scrap paper. These strategies may help you visualize the concepts or the given situation and could help you make sense of the question.  Other Useful Skills The more material you are exposed to, the easier it will become to understand it. Reading about science and applying science takes practice, just like riding a bike. At first, you may be a bit clumsy with it, but if you stick with it, you improve rapidly and it begins to click. To compre- hend science better, read as much about science as you can—in newspapers, magazines, and on the Internet. Make sure you look at graphics, as well. As you are read- ing, think about what the passage or graphic, is commu- nicating to you. What are the possible applications of the science concepts discussed? What can you conclude based on the information given? What methods were used to arrive at the facts presented? Is anything presented an opinion or belief rather than a fact? Try to make up ques- tions about the passage or graphic you read. Imagine that you are making up the GED: What could you ask the stu- dents? By anticipating the move of your opponent, you are better prepared to respond to it. – TIPS AND STRATEGIES FOR THE GED SCIENCE EXAM – 264 . at nature and tries to understand it. The curiosity CHAPTER History and Nature of Science IN THIS chapter, you will read about what drives science, the nature. that – HISTORY AND NATURE OF SCIENCE – 259 shake the foundations of understanding and lead to new modes of thinking. Thomas Kuhn, philosopher of sci-