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Chapter 4: How Science Works
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Chapter 4 How Science Works If it disagrees with experiment it is wrong. In that simple statement is the key to science. It does not make any difference how beautiful your guess is. It does not make any difference how smart you are, who made the guess, or what his name is—if it disagrees with experiment it is wrong. That is all there is to it. —Richard Feynman, Nobel Laureate in physics, 1965 We will ARGUE in this book that intelligent-design creationism (ID creationism) is not science but pseudoscience.That is, it uses the terminology of science, seemingly applies the tools of science, but in fact only masquerades as science. Before we can establish what is a pseudoscience and what is not, however, we need to examine how science works. What do scientists do when they want to find a new law? We’ll let you in on a little secret:They guess at it. But they don’t stop there.They don’t presume that their guess is right and proceed to the next guess.To the contrary, they test their guess by figuring out some consequences of their guess and comparing them with nature. If the comparison with nature fails, then the guess is wrong, no matter how appealing it was, no matter how smart the guesser was, no matter how firmly he or she believed it. If, on the contrary, the guess seems to work, then scientists will continue to look for more evidence and make more guesses. A body of knowledge and inference that explains a vast number of related observations is called a theory. In science, a theory is not a guess or a hunch but a complete system of guesses and consequences that supports or explains experimental results or observations.Theories stand or fall on the accuracy of their predictions. In what follows, we’ll examine the manner in which theories are developed and show how science progresses from guesses (or hypotheses) to accepted facts. Newton’s Law of Gravity In the seventeenth century, the English mathematician and natural philosopher Isaac Newton guessed that the gravitational force between two 37 Ch004.qxd 3/26/09 5:26 AM Page 37 bodies would depend on the distance between them (technically, that force is proportional to the inverse square of the distance between them). He already knew from calculations performed by the German astronomer Johannes Kepler that the orbits of the planets were not perfect circles but rather types of ovals called ellipses. Newton used his theory to calculate the expected orbits of the planets and found that the theory correctly derived elliptical orbits. Kepler’s observations and Newton’s theory were thus in good agreement. Does that mean that Newton’s theory is right? No; it means only that the theory is not obviously wrong.Newton and others performed countless additional calculations over two hundred years and found that Newton’s theory of gravitation agreed with experimental observation as closely as anyone could tell. Newton and other astronomers thought that Newton had hit on a universal truth. Today we would conclude that Newton’s theory is only tentatively correct or, more precisely, that it is correct within certain limits. Newton’s theory is a scientific theory in part because it is testable.To be testable means that the theory has inspired some predictions and that those predictions can be compared with nature. If the predictions had not agreed with observations, then the theory would have been rejected, and someone else would have had to make a different guess. That guess would then have been tested, and possibly that person’s theory would have been accepted. Sometimes experimenters lead theorists and make discoveries that theorists had not predicted. It turns out that the orbits of the planets are not precisely ellipses; in fact, they do not quite close on themselves. Why? Mostly because the gravity of the giant planets, Jupiter and Saturn, slightly distorts the orbits of the other planets.Astronomers have used Newton’s theory of gravity to calculate the effects of all the planets on the orbit of Mercury and found that they could account for its path very well, except for a small discrepancy. Even when corrected for the gravitational attraction of the planets, the orbit of Mercury is not precisely a stationary ellipse but is more closely described as an ellipse whose axis rotates at the rate of approximately 43 arcseconds (about 1/100 degree) per century, as shown in...