Applications Of The Scientific Method Paper 3-5 Pages

SCI 110Course

 

 

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ISBN-10: ISBN-13:

2013

1121838936 9781121838932

 

 

Contents

1. The Scientific Method 1 2. Section for Chapter 1 27 3. Motion 29 4. Section for Chapter 2 65 5. Energy 68 6. Section for Chapter 3 97

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Credits

1. The Scientific Method: Chapter 1 from The Physical Universe, 15th Edition by Krauskopf, Beiser, 2014 1 2. Section for Chapter 1: Chapter from The Physical Universe, 15th Edition by Krauskopf, Beiser, 2014 27 3. Motion: Chapter 2 from The Physical Universe, 15th Edition by Krauskopf, Beiser, 2014 29 4. Section for Chapter 2: Chapter from The Physical Universe, 15th Edition by Krauskopf, Beiser, 2014 65 5. Energy: Chapter 3 from The Physical Universe, 15th Edition by Krauskopf, Beiser, 2014 68 6. Section for Chapter 3: Chapter from The Physical Universe, 15th Edition by Krauskopf, Beiser, 2014 97

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Hell

I Sphe re of the Moon

II Sphe re of Mercury

III Sph ere of Venus

IV Sph ere of the Sun

V Spher e of Mars

VI Spher e of Jupiter

of SaturnVI II Sph

ere of the fixed stars. The Zodiac

IX Cry stalline sphere. Primum Mobile

VII Sphe re

Purgatory

He mis

pher e

of wa

ter

The D ark

W

oo d

Ai r

Jerusalem

Earthly Paradise

H em

isphere

of Earth

Fire

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How Scientists Study Nature 1.1 The Scientific Method

Four Steps • What the scientific method is. • The difference between a law and a

theory. • The role of models in science.

1.2 Why Science Is Successful Science Is a Living Body of Knowledge, Not a Set of Frozen Ideas

• Why the scientific method is so success- ful in understanding the natural world.

The Solar System 1.3 A Survey of the Sky

Everything Seems to Circle the North Star

• Why Polaris seems almost stationary in the sky.

• How to distinguish planets from stars without a telescope.

1.4 The Ptolemaic System The Earth as the Center of the Universe

• How the ptolemaic system explains the astronomical universe.

1.5 The Copernican System A Spinning Earth That Circles the Sun

• How the copernican system explains the astronomical system.

1.6 Kepler’s Laws How the Planets Actually Move

• The significance of Kepler’s laws. 1.7 Why Copernicus Was Right

Evidence Was Needed That Supported His Model While Contradicting Ptolemy’s Model

• How parallax decides which system provides the best explanation for what we see.

Universal Gravitation 1.8 What Is Gravity?

A Fundamental Force • Why gravity is a fundamental force.

1.9 Why the Earth Is Round The Big Squeeze

• What keeps the earth from being a perfect sphere.

1.10 The Tides Up and Down Twice a Day

• The origin of the tides. • The difference between spring and

neap tides and how it comes about.

1.11 The Discovery of Neptune Another Triumph for the Law of Gravity

• The role of the scientific method in finding a hitherto unknown planet.

How Many of What 1.12 The SI System

All Scientists Use These Units • How to go from one system of units to

another. • The use of metric prefixes for small and

large quantities. • What significant figures are and how to

calculate with them.

CHAPTER OUTLINE AND GOALS

Your chief goal in reading each section should be to understand the important findings and ideas indicated (•) below.

The Scientific Method

Medieval picture of the universe.

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2 Chapter 1 The Scientific Method

All of us belong to two worlds, the world of people and the world of nature. As mem- bers of the world of people, we take an interest in human events of the past and present and find such matters as politics and economics worth knowing about. As members of the world of nature, we also owe ourselves some knowledge of the sciences that seek to understand this world. It is not idle curiosity to ask why the sun shines, why the sky is blue, how old the earth is, why things fall down. These are serious ques- tions, and to know their answers adds an important dimension to our personal lives.

We are made of atoms linked together into molecules, and we live on a planet circling a star—the sun—that is a member of one of the many galaxies of stars in the universe. It is the purpose of this book to survey what physics, chemistry, geology, and astronomy have to tell us about atoms and molecules, stars and galaxies, and everything in between. No single volume can cover all that is significant in this vast span, but the basic ideas of each science can be summarized along with the raw mate- rial of observation and reasoning that led to them.

Like any other voyage into the unknown, the exploration of nature is an adven- ture. This book records that adventure and contains many tales of wonder and dis- covery. The search for knowledge is far from over, with no end of exciting things still to be found. What some of these things might be and where they are being looked for are part of the story in the chapters to come.

Every scientist dreams of lighting up some dark corner of the natural world—or, almost as good, of finding a dark corner where none had been suspected. The most careful observations, the most elaborate calculations will not be fruitful unless the right questions are asked. Here is where creative imagination enters science, which is why many of the greatest scientific advances have been made by young, nimble minds.

Scientists study nature in a variety of ways. Some approaches are quite direct: a geologist takes a rock sample to a laboratory and, by inspection and analysis, finds out what it is made of and how and when it was probably formed. Other approaches are indirect: nobody has ever visited the center of the earth or ever will, but by com- bining a lot of thought with clues from different sources, a geologist can say with near certainty that the earth has a core of molten iron.

No matter what the approaches to particular problems may be, however, the work scientists do always fits into a certain pattern of steps. This pattern, a general scheme for gaining reliable information about the universe, has become known as the scientific method.

1.1 The Scientific Method Four Steps We can think of the scientific method in terms of four steps: (1) formulating a problem, (2) observation and experiment, (3) interpreting the data, and (4) testing the interpre- tation by further observation and experiment to check its predictions. These steps are often carried out by different scientists, sometimes many years apart and not always in this order. Whatever way it is carried out, though, the scientific method is not a mechanical process but a human activity that needs creative thinking in all its steps. Looking at the natural world is at the heart of the scientific method, because the results of observation and experiment serve not only as the foundations on which scientists build their ideas but also as the means by which these ideas are checked ( Fig. 1-1 ).

1. Formulating a problem may mean no more than choosing a certain field to work in, but more often a scientist has in mind some specific idea he or she wishes to investigate. In many cases formulating a problem and interpreting the data overlap.

HOW SCIENTISTS STUDY NATURE

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How Scientists Study Nature 3

The scientist has a speculation, perhaps only a hunch, perhaps a fully developed hypothesis, about some aspect of nature but cannot come to a definite conclusion without further study.

2. Observation and experiment are carried out with great care. Facts about nature are the building blocks of science and the ultimate test of its results. This insis- tence on accurate, objective data is what sets science apart from other modes of intellectual endeavor.

3. Interpretation may lead to a general rule or law to which the data seem to con- form. Or it may be a theory, which is a more ambitious attempt to account for what has been found in terms of how nature works. In any case, the interpreta- tion must be able to cover new data obtained under different circumstances. As put forward orginally, a scientific interpretation is usually called a hypothesis.

4. Testing the interpretation involves making new observations or performing new experiments to see whether the interpretation correctly predicts the results. If the results agree with the predictions, the scientist is clearly on the right track. The new data may well lead to refinements of the original idea, which in turn must be checked, and so on indefinitely.

The Laws of Nature The laws of a country tell its citizens how they are supposed to behave. Different countries have different laws, and even in one country laws are changed from time to time. Furthermore, though he or she may be caught and pun- ished for doing so, anybody can break any law at any time.

The laws of nature are different. Everything in the universe, from atoms to gal- axies of stars, behaves in certain regular ways, and these regularities are the laws of nature. To be considered a law of nature, a given regularity must hold everywhere at all times within its range of applicability.

The laws of nature are worth knowing for two reasons apart from satisfying our curiosity about how the universe works. First, we can use them to predict phenomena not yet discovered. Thus Isaac Newton’s law of gravity was applied over a century ago to apparent irregularities in the motion of the planet Uranus, then the farthest known planet from the sun. Calculations not only showed that another, more distant planet should exist but also indicated where in the sky to look for it. Astronomers who looked there found a new planet, which was named Neptune.

Figure 1-1 The scientific method. No hypothesis is ever final because future data may show that it is incorrect or incomplete. Unless it turns out to be wrong, a hypothesis never leaves the loop of experiment, interpretation, testing. Of course, the more times the hypothesis goes around the loop successfully, the more likely it is to be a valid interpretation of nature. Experiment and hypothesis thus evolve together, with experiment having the final word. Although a hypothesis may occur to a scientist as he or she studies experimental results, often the hypothesis comes first and relevant data are sought afterward to test it.

Observation and Experiment

Collecting the data that bear upon the problem

Testing the Interpretation

Predicting the results of new experiments on the basis of the hypothesis

Interpretation

Explaining the data in terms of a hypothesis about how nature works

Statement of Problem What is the question being asked of nature? Are there any preliminary hypotheses?

Finding the Royal Road

Hermann von Helmholtz, a nine- teenth century German physicist and biologist, summed up his experience of scientific research in these words: “I would compare myself to a mountain climber who, not knowing the way, ascends slowly and toilsomely and is often compelled to retrace his steps because his progress is blocked; who, sometimes by rea- soning and sometimes by acci- dent, hits upon signs of a fresh path, which leads him a little farther; and who, finally, when he has reached his goal, discov- ers to his annoyance a royal road which he might have followed if he had been clever enough to find the right starting point at the beginning.”

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4 Chapter 1 The Scientific Method

Second, the laws of nature can give us an idea of what goes on in places we cannot examine directly. We will never visit the sun’s interior (much too hot) or the interior of an atom (much too small), but we know a lot about both regions. The evidence is indirect but persuasive.

Theories A law tells us what; a theory tells us why. A theory explains why cer- tain events take place and, if they obey a particular law, how that law originates in terms of broader considerations. For example, Albert Einstein’s general theory of relativity interprets gravity as a distortion in the properties of space and time around a body of matter. This theory not only accounts for Newton’s law of gravity but goes further, including the prediction—later confirmed—that light should be affected by gravity.

As the French mathematician Henri Poincaré once remarked, “Science is built with facts just as a house is built with bricks, but a collection of facts is not a science any more than a pile of bricks is a house.”

Models It may not be easy to get a firm intellectual grip on some aspect of nature. Therefore a model —a simplified version of reality—is often part of a hypothesis or theory. In developing the law of gravity, Newton considered the earth to be perfectly round, even though it is actually more like a grapefruit than like a billiard ball. New- ton regarded the path of the earth around the sun as an oval called an ellipse, but the actual orbit has wiggles no ellipse ever had. By choosing a sphere as a model for the earth and an ellipse as a model for its orbit, Newton isolated the most important fea- tures of the earth and its path and used them to arrive at the law of gravity.

If Newton had started with a more realistic model—a somewhat squashed earth moving somewhat irregularly around the sun—he probably would have made little progress. Once he had formulated the law of gravity, Newton was then able to explain how the spinning of the earth causes it to become distorted into the shape of a grape- fruit and how the attractions of the other planets cause the earth’s orbit to differ from a perfect ellipse.

1.2 Why Science Is Successful Science Is a Living Body of Knowledge, Not a Set of Frozen Ideas What has made science such a powerful tool for investigating nature is the constant testing and retesting of its findings. As a result, science is a living body of information and not a collection of dogmas. The laws and theories of science are not necessarily the final word on a subject: they are valid only as long as no contrary evidence comes to light. If such contrary evidence does turn up, the law or theory must be modified or even discarded. To rock the boat is part of the game; to overturn it is one way to win. Thus science is a self-correcting search for better understanding of the natural world, a search with no end in sight.

Experiment Is the Test

A master of several sciences, Michael Faraday is best remem- bered for his discoveries in electricity and magnetism (see biography in Sec. 6.18). This statement appears in the entry for March 19, 1849 in his labora- tory notebook: “Nothing is too wonderful to be true if it be con- sistent with the laws of nature, and . . . experiment is the best test of such consistency.”

Faraday was a Fellow of Brit- ain’s Royal Society, which was founded in 1660 to promote the use of observation and experi- ment to study the natural world. The oldest scientific organiza- tion in the world, the Royal Society has as its motto Nullus in Verba —Latin for “Take nobody’s word for it.” On its 350th anni- versary, the Royal Society held a celebration of “the joy and vital- ity of science, its importance to society and culture, and its role in shaping who we are and who we will become.”

the point is that it is a large-scale framework of ideas and relationships.

To people ignorant of science, a theory is a suggestion, a proposal, what in science is called a hypothesis. For instance, believers in creationism, the unsupported notion that all living things simultaneously appeared on

earth a few thousand years ago, scorn Darwin’s theory of evolution (see Sec. 16.8) as “just a theory” despite the wealth of evidence in its favor and its bedrock position in modern biology. In fact, few aspects of our knowledge of the natural world are as solidly established as the theory of evolution.

In science a theory is a fully developed logical structure based on general principles that ties together a variety of observations and experimental findings and permits as-yet-unknown phenomena and connections to be predicted. A theory may be more or less speculative when proposed, but

Theory

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