The Inductive (Scientific) Method
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Karl Annotated Notes In Purple
The Inductive (Scientific) Method
Historical Development:
Not everyone from 300 B.C. to 1600 A.D. was willing to bow to the authority of Aristotle. Many of Aristotle's arguments were faulty, but where did he go wrong, and what was the right way to proceed?
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In order to use the deductive method, you need to start with axioms - simple true statements about the way the world works. Then you use these axioms to build your logical system of nature. If your axioms are true, everything that follows will be true, but Galileo and his contemporaries realized that the problem was that it was enormously difficult to determine "simple true statements about the way the world works". In fact, they realized that it should be the goal of science - not the starting place - to determine what the "simple true statements about the way the world works" really are!
Since 1600, the inductive method has been incredibly successful in investigating nature - surely far more successful than its originators could have imagined. The inductive method of investigation has become so entrenched in science that it is often referred to as the scientific method.
Inductive vs. Deductive Method
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The inductive method (usually called the scientific method) is the deductive method "turned upside down". The deductive method starts with a few true statements (axioms) with the goal of proving many true statements (theorems) that logically follow from them. The inductive method starts with many observations of nature, with the goal of finding a few, powerful statements about how nature works (laws and theories).
In the deductive method, logic is the authority. If a statement follows logically from the axioms of the system, it must be true. In the scientific method, observation of nature is the authority. If an idea conflicts with what happens in nature, the idea must be changed or abandoned.
Here is a diagram that attempts to depict the scientific (inductive) method. It is oversimplified and incomplete, but...
Is Science Entirely Inductive?
On the previous page, you learned that although mathematics is deductive in nature - that is, logical proof is the only acceptable evidence of truth - the process of mathematics is not entirely deductive. It is also true that although science is inductive by nature - observations are the only acceptable evidence of truth - the process of science can be deductive! [Karl Note: Mathematics, contrary to this apparently profound statement, is fatally flawed by having axioms that do not include data relative to "life."]
In particular, physicists make extensive use of mathematics as a powerful theoretical tool. Theoretical physicists often construct theories as "mathematical models" deductively, starting with assumptions about the inner workings of stars or atoms, for instance, and then working out the mathematical consequences of their assumptions. An essential difference between a mathematician and a theoretical physicist is that the physicist uses mathematics as a reasoning tool. The success of the mathematical model depends on how well its results agree with observations of nature - if they do not agree the physicist knows that this means that her assumptions - not the observations - need to be adjusted.
Observations
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Science begins with observations of nature. Thus Galileo began his study of falling bodies not by making general statements, but by performing experiments. Tycho Brahe began to make detailed nightly observations of the heavens in order to figure out how the universe was constructed.
An Observation is Something You Notice
Anything you see, hear, smell, taste, or touch is an observation. An observation may be quite casual - "You are wearing a blue shirt.", or it may be quite formal and planned. Formal, carefully planned and executed experiments are designed to make observations. (Actually, experimental data are observations. Scientists also draw conclusions from experiments.)
Can an Observation Be Wrong?
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Optical illusions show us that it is easy to fool our senses - the blue lines in the figure above are straight! (Check it with a straightedge.) |
Scientific Observations Must Be Repeatable.
How do you gain confidence that your observation is correct? If a scientist believes that her observation is correct, she will tell others about it. If other scientists can make the same observation, we can be more confident that an observation is correct. (If your friend sees little green men in the backyard too, then maybe you haven't lost your mind...)
This is why scientific observations must be repeatable. Otherwise, there is no way to tell if the observation is correct. An observation that cannot be repeated might very well be true - but how can we tell? Such observations are called anecdotal evidence. Reports of UFO sightings and miracle cures of disease fall into the category of anecdotal evidence.
Dusty's Question:
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If scientific observations must be repeatable, was the impact of Comet Shoemaker-Levy with Jupiter a scientific observation, since it doesn't seem to be repeatable?
Well, first remember the "disclaimer" that began these notes! Although the comet impact with Jupiter can't be repeated at will, it was observed by just about every astronomer on Earth! There was an enormous amount of data taken during the impacts, so scientists can compare and study the observations made by various instruments. The methods used to collect data, and the data themselves, are a matter of record. In that sense, the observations were scientific.[Karl Note: This is very valid, but he misses the mark because the observer may, in fact, invent an entire new method of "observing." When he does this he must, then, also create a program to teach this method and ensure that the students can learn and apply the information in fields outside his own so that the validity of the METHOD, itself, can be validated.]
Observations of unusual events are accepted as scientific observations all the time - the appearance of a supernova, for instance, might be first observed by just one scientist. This scientist then alerts others, who can then look for themselves. When a scientist says that observations must be repeatable, they mean that the observations can't be done in secret - you don't have to take someone's word that something happened, and that the means of collecting the data must be open and reliable - not an "it only works if you believe" kind of thing.
How Important are Observations?
The importance of observation (experiment) in science would be difficult to exaggerate. Every statement or idea in science must be checked and rechecked by observations of nature, and if the idea conflicts with the observation, the idea must yield and be modified or cast aside. No appeal to "common sense", authority, or anything else can save an idea that conflicts with observation.