The Scientific Method

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Meredith Carpenter
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1 Chapter 1 The Scientific Method Chapter 1 Outline: Main Ideas Scientists make science work The Scientific Method Science is a process Exploring Nature An important example: The Solar System How early scientists began to understand our solar system Ptolemy Nicolas Copernicus The importance of measurement in science Johannes Kepler Three rules Newton s contribution: Understanding universal gravitation Earth Tides Let s Start with SCIENCE In General THE MOST IMPORTANT THING ABOUT WHAT SCIENCE IS Science is a PROCESS It is really just a way of asking and answering questions about the physical universe It is ONGOING and NEVERENDING SCIENCE is NOTjust a collection of facts you cannot possibly write down WHAT SCIENCE IS in a book Science is something you DO! 1

Two Kinds of Science We either study living things (life science) or nonliving things (physical science) In either case, the goal is to explore and understand NATURE The Scientific Method An

2 Two Kinds of Science We either study living things (life science) or nonliving things (physical science) In either case, the goal is to explore and understand NATURE The Scientific Method An organized approach to discovering evidence and recording observations introduced in the 16th century Provides fundamental foundation for the methods of science What Is It? There are many ways to express WHAT the Scientific Method is. One way is: a continuous creative process by which people learn about the physical universe 2

3 Basic Steps of the Scientific Method Formulate the problem Observation and experiment Interpreting the observations Identify patterns Testing interpretations Further observation Important Parts of the Method Hypothesis an educated guess that can be tested Theory the synthesis of a LARGE body of information encompassing welltested and verified hypotheses from experimental observations Observation vs. Experiment Observation can be done without an actual experiment. An experiment is a careful observation that may require recording quantitative information about the observed phenomenon. An experiment is simply manipulating nature and then observing the results. 3

4 Interpretation of Observations Leads to HYPOTHESIS After observing and experimenting, we may form a hypothesis A hypothesis is often stated as a mathematical expression Remember: ANY VALID SCIENTIFIC HYPOTHESIS MUST BE TESTABLE! Testing Hypotheses Use the hypothesis to make predictions Compare observations with predictions CAREFUL EXPERIMENTATION IS THE KEY Manipulations must be very deliberate! CONTROL in an experiment requires defining variables: Dependent (depends on some circumstance) Independent When the Evidence Is Persuasive A result of summarizing repeated observations and testing Represents our current best understanding Subject to change based upon additional observations Laws of nature CANNOT be characterized by saying that they will never change. 4

5 What Is a Scientific THEORY? A natural law tells us WHAT A theory explains the WHY behind our observations A scientific theory is MORE than a hypothesis or a good idea Fully developed logical structure Based on well-understood general principles Based on NUMEROUS observations and experiments. Must be stated in a matter that will allow it to be tested. These tests define the range/limits of a theory May not prove/disprove the theory The Point? It really is more than The power of science is continual re-examination of the body of knowledge As more observations are made, understanding increases There are no set or frozen ideas Science and Religion Both science and religion are a means of searching for order and meaning in our world Science: observe, record and discover natural phenomena based on experimental evidence acquired by using a rigid scientific method; skepticism is key Religion: a means of understanding the source, purpose and meaning of our world based on faith; many principles are accepted without question 5

6 Predictability A Fundamental Premise Universe abounds with REGULAR, PREDICTABLE phenomenon Key to understanding OPEN YOUR EYES, EARS (ALL YOUR SENSES) in order to observe the world around you. Who were the earliest scientists? The Birth of Modern Astronomy Key Players: Nicolaus Copernicus Claudius Ptolemy Tycho Brahe Johannes Kepler Galileo Galilei Ideas developed over a long period of time often with great CONTROVERSY Ancient Civilizations Created myths and legends to explain what they observed in nature They observed and named CONSTELLATIONS Stars that appear to be closely spaced and whose relative positions remain constant Greeks were the first to include SCIENCE in their explanations Believed in the perfect universe The universe was spherical and finite 6

7 Important Observations Polaris The North Star Seems to remain stationary as other stars move around this star Used as a guide for travelers due to its constancy Why? If a line is extended outward along the direction of the Earth s rotational axis, Polaris would lie on the line Planet motions across the night sky seem to lag behind the stars Difficult to explain Retrograde motion Irregularities in Motion RETROGRADE motion Sometimes celestial bodies, particularly planets, appear to REVERSE their direction of motion Very puzzling to the ancient astronomers The Greek astronomers explanation of the celestial spheres did NOT encompass the phenomenon of retrograde motion. Interpretation of the Data 7

Ptolemy s Idea Ptolemy s description of the universe included an unmoving Earth at the center: GEOCENTRISM Ptolemy attempted to explain retrograde motion using equants, deferents, and epicycles (Math

8 Ptolemy s Idea Ptolemy s description of the universe included an unmoving Earth at the center: GEOCENTRISM Ptolemy attempted to explain retrograde motion using equants, deferents, and epicycles (Math concepts) He used his calculations to make fairly accurate predictions of the positions of celestial objects Ptolemy s theory of the universe was one of the longest lived theories ever devised Ptolemy s System Filled all the requirements of a valid scientific THEORY Based on observations that were possible at the time Testable; could be used to predict positions As observations continued, the Ptolemaic system failed to reliably and accurately predict exact locations of observed celestial objects The Copernican System Copernicus had a different idea for explaining the observed motions of celestial objects. 8

9 Copernicus Ideas Copernicus hypothesized that the SUNwas the center of the universe HELIOCENTRICISM Provided the first serious alternative to Ptolemy s system. Agreed with Ptolemy s ideas about the shape of orbits Both thought that planetary orbits were circular Trouble for Copernicus His ideas were not well liked by all especially by theologians. Copernicus contemporary religious leaders believed that the Earth was the hub of the universe! 1. Improving Observations Even though both Ptolemy and Copernicus could explain most observations, much of what was believed was just speculation Major contributions Tycho Brahe Johannes Kepler To resolve the conflict between the Copernican and the Ptolemaic theories of the universe, astronomers of the Middle Ages needed better measurements 9

Johannes Kepler The world of nature, the world of man, the world of God all these fit together Johannes Kepler (1571-1630) Kepler According to Kepler, the sun is not at the centerof the solar system.

10 Johannes Kepler The world of nature, the world of man, the world of God all these fit together Johannes Kepler ( ) Kepler According to Kepler, the sun is not at the centerof the solar system. CAREFUL observation and measurement led Kepler to develop~ Kepler s THREE Laws #1: Elliptical Foci Each planet moves about the sun in an orbit the shape of an ellipse, while the sun is at one focus. #2: Equal Areas The straight line joining a planet with the sun sweeps out equal areas in equal amounts of time. (A planet travels faster when it is closer to the sun.) #3: Planetary Period The time taken for one orbit is related to the distance from the sun in a specific way. 10

11 Kepler s THREE Laws Kepler s Contribution Kepler s work improved upon Copernicus theories by modifying the heliocentric model of our solar system. Gravity One of the Fundamental Forces Once the motion of the planets was predictable using Kepler s model, the next question was why? The planets must be held in orbit by a force Isaac Newton first addressed the idea of gravitational attraction Newton discovered The Law of Gravity Discovery was dependent upon the Copernican model of the solar system 11

12 What Is a Fundamental Force? Gravity is fundamental It cannot be explained in terms of any other force There are FOUR fundamental forces: Gravitational force Electromagnetic force Weak force Strong force Newton s Law of Gravitation Explains the motion of all observed objects in the universe The Round Earth The earth is not a perfect sphere As the earth spins on its axis, the equatorial region of the planet tends to swing outward 12

13 Newton s Gravity Explains Tides Two factors Gravitational attraction between Earth-Moon Gravitational attraction between Earth-Sun How Can We Begin to Understand Nature? We measure things! We measure distance volume mass weight force charge temperature power... The Language of SCIENCE In order to communicate SCIENCE, we all have to speak the same language! In order to communicate across our world, we use a common languageof UNITS and EQUATIONS 13

14 The Use of MATHEMATICS (screaming gnashing of teeth) Why MATH? We must all speak the same language in order to share ideas and increase understanding. Science is common to the entire human population, so we must use the same language in order to increase understanding for ALL the human race. WHY MATH? Things we can measure MUST be quantitative This means NUMBERS AND for thenumbersto mean anything, we need a United States Common Unit Systems English System SystémèInternationalè(S.I.) (we call this METRIC ) The English system is a product of the Magna Carta. The metric system is a product of the French Revolution. Nothing magical about the metric system good science can be done using other unit schemes! 14

15 Understanding SI Units The unit of LENGTH Meter Centimeter The unit of VOLUME (length x length x length) Liter (1,000 cubes one centimeter each) About 0.26 gallons The most commonly used metric unit in the United States The unit for MASS Kilogram Gram Why METRIC? Multiply by 10 or divide by 10 for each place!!! 1000 s place 100 s place 10 s place 1 s place 10th s place 100th s place Unit Conversions A conversion factor is the multiplier used in changing a quantity from one system of units to an equivalent quantity in another system of units. Examples 1 mile = 1.61 kilometers 1 gallon = 3.79 liters 1 pound = 2.2 kilograms 15

16 Data (Measurements) How can we represent data? Graph, table, or statement Relationships between measured quantities can be express using Words, equations, or symbols Objectivity SUBJECTIVITY is NOT allowed Whether a ruby or a diamond is prettier This does NOT mean that the scientist can not have some ideas going in to an experiment or observation It DOES mean that the scientist must not let the ideas rule the outcome of the scientific investigation The Scientific Method: Summary The scientific method steps Formulation of problem Observation/experiment Interpretation/analysis Formation of a hypothesis Testing/predicting After repeated testing, hypotheses can become theory or law 16

17 The Scientific Method: Summary Astronomers were the first to practice the scientific way of studying nature Polaris (the North star) was a key to understanding the night sky, along with other constellations and planets Two systems were proposed to explain the motion of the stars: the Ptolemaic system and the Copernican system Scientific evidence supports the Copernican idea The Scientific Method: Summary (2) Kepler and Newton formulated laws that explained the motions of the planets and star systems in terms of GRAVITY The tides are the periodic rise and fall of the oceans due to fluctuations in the gravitational pull of the sun and moon on the earth Units are important for the communication of scientific quantities The SI system of units is used world wide by scientists SI unit of length: meter (m) Conceive a problem and describe the solution using the Scientific Method. 17

18 IN-LECTURE QUIZ QUESTIONS CHAPTER 1 Which of the following endeavors involves passion, talent and intelligence? A. Art B. Literature C. Music D. Science E. All of the above Which of the following is NOT a valid scientific hypothesis? A. Neon atoms emit red light. B. There is some attractive force between the earth and a ball. C. Brad Pitt is a good-looking guy. 18

19 In order to conduct respectable scientific research, a scientist can have NO PRECONCEIVED IDEAS. A. TRUE B. FALSE Science and technology A. are really one and the same. B. are responsible for all the good in the world. C. are responsible for all the bad in the world. D. are related, but fundamentally different from each other in their specified purpose. How many laws did Keplercome up with that accurately explained observed planetary motion? A. 1 B. 2 C. 3 D. 4 19

20 A scientific hypothesis may turn out to be right or it may turn out to be wrong. If it is a valid hypothesis, there must be a test that the scientist can do to A. PROVE THE HYPOTHESIS WRONG. B. PROVE THE HYPOTHESIS RIGHT. Whose Planetary Theory had the Earth situated at the center of the universe? A. Ptolemy B. Copernicus C. Brahe D. Galileo A hypothesis is A. a natural law. B. always taken to be true. C. recorded as what happened in an experiment. D. an educated guess that can be tested. 20

21 What language is common to all inhabitants of Earth? A. English B. Mathematics C. Conversion factors D. Units When a planet appears to be moving backwards, modern scientists describe this as A. retrograde motion. B. phenomenon. C. celestial motion. D. Copernican movement. 21

Chapter 2 The Science of Life in the Universe

In ancient times phenomena in the sky were not understood! Chapter 2 The Science of Life in the Universe The Ancient Greeks The Scientific Method Our ideas must always be consistent with our observations!