Scientific Method. Basic Skills

Transcription

1 Scientific Method Basic Skills

2 Whether or no anything can be known, can be settled not by arguing, but by trying Francis Bacon ( ) 2

3 What is Science? A typical dictionary definition is the observation, identification, description, experimental investigation, and theoretical explanation of phenomena. or the field of study which tries to describe and understand the nature of the universe in whole or in part. 3

4 Types of Sciences Experimental: laboratory sciences such as physics and chemistry. Historical: astronomy, geology, paleontology and archaeology. Social: sociology, psychology, and economics. 4

5 Pure vs. Applied Science Basic research or pure research is driven by a scientist s curiosity. The main motivation of this type of research is to expand mankind s knowledge of the world and not to invent or create something new. There is no obvious commercial value in research of this type. Basic science research includes answers to such questions as: How did the universe begin? How does our genetic code determine who we are? What are protons, neutrons and electrons made of? Applied research is designed to solve practical problems that exist in the modern world, rather than to just acquire knowledge for knowledge s sake. One main goal of applied science is to improve human conditions and make the world a better place. Applied science may investigate ways to: improve agricultural crop production get better gas mileage treat or cure a specific disease improve the energy efficiency of homes taken from 5

6 Scientific Method Two earlier supporters of the scientific method were Francis Bacon ( ) and Galileo Galilei ( ). They both saw the importance of testing the validity of scientific hypotheses. This was not common through the middle ages up to their time. Scholars used only logic or often relied on the authority of ancient texts, for example from famous Greek philosophers, to prove their points, instead of observing nature directly. Remember the quote at the beginning you settle disputes by trying that means testing and observing the results! 6

7 Scientific Method The scientific method is not one single thing. It refers to the ideas, rules, techniques, and approaches that the scientific community uses. It is better to focus on the scientific attitude, or a way of looking at the world. It is an attitude that values craftsmanship, with pride in creativity, high-quality standards, and hard work.

8 Norms of the Scientific Community Universalism. Irrespective of who conducts research (e.g.. old or young, male or female) and regardless of where it was conducted (e.g.. United States or France. Harvard or Unknown University), the research is to be judged only on the basis of scientific merit. Organized skepticism. Scientists should not accept new ideas or evidence in a carefree, uncritical manner. They should challenge and question all evidence and subject each study to intense scrutiny. The purpose of their criticism is not to attack the individual, but to ensure that the methods used in research can stand up to close, careful examination. Disinterestedness. Scientists must be neutral, impartial, receptive, and open to unexpected observations or new ideas. They should not be rigidly wedded to a particular idea or point of view. They should accept, even look for, evidence that runs against their positions and should honestly accept all findings based on high-quality research. Communalism. Scientific knowledge must be shared with others; it belongs to everyone. Creating scientific knowledge is a public act, and the findings are public property, available for all to use. The way in which the research is conducted must be described in detail. Honesty. This is a general cultural norm, but it is especially strong in scientific research. Scientists demand honesty in all research; dishonesty or cheating in scientific research is a major taboo. 8

9 Experimental Design An experiment is an organized series of steps used to test a hypothesis. Remember, a hypothesis is not an observation or description of an event. A hypothesis is a possible explanation for a cause and effect of a given situation. The following vocabulary is used in experimental design: INDEPENDENT VARIABLE The factor controlled by the experimenter. The experimenter will purposely manipulate or change the independent variable. DEPENDENT VARIABLE The factor which changes (perhaps!) because of what the experimenter does to the independent variable. Hypothetically the dependent variable depends on the independent variable! CONTROL VARIABLES Other factors that could potentially vary. The experimenter must ensure these factors stay constant, unless they are explicitly changed as part of the experiment. Controlling other variables is very important so that the experimenter may be assured that any changes in the dependent variable are due only to the changes in the independent variable. 9

10 Experimental Design Example Let s say in your grammar school science fair project you hypothesize fertilizer affects plant growth. Your hypothesis might be the more fertilizer given a plant, the taller it will grow. Your independent variable will be the amount of fertilizer you will purposefully give some plants more, and other plants less fertilizer. Your dependent variable is the plant height. Does plant height depend on the amount of fertilizer given? But to have a successful experiment, you must control any other factors that could also affect plant height. Examples of variables you should control include use the same types of plants, give each plant the same amount of sunlight, give each plant the same amount of water. Perhaps the same pot size! You must think about all kinds of other influences besides fertilizer that could also affect plant growth. 10

11 Experimental Design Example A researcher wants to study the effects of sleep deprivation on physical coordination. The researcher selected a group of 22 year-old female college students and deprived the subjects to either 18, 24, 30, or 36 hours of sleep. Label in the following list the variables as: independent, dependent, or control. control the age of the subjects. dependent the physical coordination skills of the subjects. control the gender of the subjects. independent the length of time the subjects were deprived of sleep. control the educational level of the subjects. 11

12 Experimental Design Example In 1747, while serving on HMS Bark Salisbury, James Lind, the ship's surgeon, carried out a controlled experiment to develop a cure for scurvy, a disease at one time common among sailors. Remedies that had been proposed at one time or another were: A quart of cider every day Twenty five drops of elixir vitriol (sulphuric acid) three times a day upon an empty stomach One half-pint of seawater every day A mixture of garlic, mustard, and horseradish in a lump the size of a nutmeg Two spoonfuls of vinegar three times a day Two oranges and one lemon every day Assume you were a ship s surgeon back in the 1700s and half the crew was suffering from scurvy. How might you design an experiment to determine if any of the above potential treatments may work? Do you know why the English sailors are sometimes called Limeys? 12

13 Galileo vs. Aristotle Aristotle supposes bodies of different weight [ ] move [ ] with different speeds [ ] in the same ratio as the weights; so that, for example, a body which is ten times as heavy as another will move ten times as rapidly as the other. How would you determine if this is true? 13

14 Galileo vs. Aristotle What tower is shown to the right? Where is it located? What do you think the results of your experiment would be? Could you come up with a thought experiment to decide if Aristotle is right or wrong without actually doing an physical experiment? 14

15 Theory vs. Hypothesis Sometimes you hear people say well, it's only a theory when they are critical of an idea. The general public sometimes interprets the word theory as a guess or hypothesis, not necessarily proven by science, whereas in science, a theory is a broad comprehensive view of some aspect of nature generally agreed upon by a consensus of scientists given our present state of knowledge. Scientific theories evolve as they are refined, or sometimes discarded and replaced by new theories. This is seen as a strength of science as we approach a better understanding about the universe. 15