The Scientific Method (A Review for the Global Warming crowd)

The scientific method is the process by which scientists, collectively and over time, endeavor to construct an accurate (that is, reliable, consistent and non-arbitrary) representation of the world.

Recognizing that personal and cultural beliefs influence both our perceptions and our interpretations of natural phenomena, we aim through the use of standard procedures and criteria to minimize those influences when developing a theory. As a famous scientist once said, "Smart people (like smart lawyers) can come up with very good explanations for mistaken points of view." In summary, the scientific method attempts to minimize the influence of bias or prejudice in the experimenter when testing an hypothesis or a theory.

2. Formulation of an hypothesis to explain the phenomena. In physics, the hypothesis often takes the form of a causal mechanism or a mathematical relation.

3. Use of the hypothesis to predict the existence of other phenomena, or to predict quantitatively the results of new observations.

4. Performance of experimental tests of the predictions by several independent experimenters and properly performed experiments.

If the experiments bear out the hypothesis it may come to be regarded as a theory or law of nature (more on the concepts of hypothesis, model, theory and law below). If the experiments do not bear out the hypothesis, it must be rejected or modified. What is key in the description of the scientific method just given is the predictive power (the ability to get more out of the theory than you put in; see Barrow, 1991) of the hypothesis or theory, as tested by experiment. It is often said in science that theories can never be proved, only disproved. There is always the possibility that a new observation or a new experiment will conflict with a long-standing theory.

As just stated, experimental tests may lead either to the confirmation of the hypothesis, or to the ruling out of the hypothesis. The scientific method requires that an hypothesis be ruled out or modified if its predictions are clearly and repeatedly incompatible with experimental tests. Further, no matter how elegant a theory is, its predictions must agree with experimental results if we are to believe that it is a valid description of nature. In physics, as in every experimental science, "experiment is supreme" and experimental verification of hypothetical predictions is absolutely necessary. Experiments may test the theory directly (for example, the observation of a new particle) or may test for consequences derived from the theory using mathematics and logic (the rate of a radioactive decay process requiring the existence of the new particle). Note that the necessity of experiment also implies that a theory must be testable. Theories which cannot be tested, because, for instance, they have no observable ramifications (such as, a particle whose characteristics make it unobservable), do not qualify as scientific theories.

If the predictions of a long-standing theory are found to be in disagreement with new experimental results, the theory may be discarded as a description of reality, but it may continue to be applicable within a limited range of measurable parameters. For example, the laws of classical mechanics (Newton's Laws) are valid only when the velocities of interest are much smaller than the speed of light (that is, in algebraic form, when v/c << 1). Since this is the domain of a large portion of human experience, the laws of classical mechanics are widely, usefully and correctly applied in a large range of technological and scientific problems. Yet in nature we observe a domain in which v/c is not small. The motions of objects in this domain, as well as motion in the "classical" domain, are accurately described through the equations of Einstein's theory of relativity. We believe, due to experimental tests, that relativistic theory provides a more general, and therefore more accurate, description of the principles governing our universe, than the earlier "classical" theory. Further, we find that the relativistic equations reduce to the classical equations in the limit v/c << 1. Similarly, classical physics is valid only at distances much larger than atomic scales (x >> 10-8 m). A description which is valid at all length scales is given by the equations of quantum mechanics.

We are all familiar with theories which had to be discarded in the face of experimental evidence. In the field of astronomy, the earth-centered description of the planetary orbits was overthrown by the Copernican system, in which the sun was placed at the center of a series of concentric, circular planetary orbits. Later, this theory was modified, as measurements of the planets motions were found to be compatible with elliptical, not circular, orbits, and still later planetary motion was found to be derivable from Newton's laws.

Error in experiments have several sources. First, there is error intrinsic to instruments of measurement. Because this type of error has equal probability of producing a measurement higher or lower numerically than the "true" value, it is called random error. Second, there is non-random or systematic error, due to factors which bias the result in one direction. No measurement, and therefore no experiment, can be perfectly precise. At the same time, in science we have standard ways of estimating and in some cases reducing errors. Thus it is important to determine the accuracy of a particular measurement and, when stating quantitative results, to quote the measurement error. A measurement without a quoted error is meaningless. The comparison between experiment and theory is made within the context of experimental errors. Scientists ask, how many standard deviations are the results from the theoretical prediction? Have all sources of systematic and random errors been properly estimated? This is discussed in more detail in the appendix on Error Analysis and in Statistics Lab 1.

As stated earlier, the scientific method attempts to minimize the influence of the scientist's bias on the outcome of an experiment. That is, when testing an hypothesis or a theory, the scientist may have a preference for one outcome or another, and it is important that this preference not bias the results or their interpretation. The most fundamental error is to mistake the hypothesis for an explanation of a phenomenon, without performing experimental tests. Sometimes "common sense" and "logic" tempt us into believing that no test is needed. There are numerous examples of this, dating from the Greek philosophers to the present day.

Another common mistake is to ignore or rule out data which do not support the hypothesis. Ideally, the experimenter is open to the possibility that the hypothesis is correct or incorrect. Sometimes, however, a scientist may have a strong belief that the hypothesis is true (or false), or feels internal or external pressure to get a specific result. In that case, there may be a psychological tendency to find "something wrong", such as systematic effects, with data which do not support the scientist's expectations, while data which do agree with those expectations may not be checked as carefully. The lesson is that all data must be handled in the same way.

Another common mistake arises from the failure to estimate quantitatively systematic errors (and all errors). There are many examples of discoveries which were missed by experimenters whose data contained a new phenomenon, but who explained it away as a systematic background. Conversely, there are many examples of alleged "new discoveries" which later proved to be due to systematic errors not accounted for by the "discoverers."

In a field where there is active experimentation and open communication among members of the scientific community, the biases of individuals or groups may cancel out, because experimental tests are repeated by different scientists who may have different biases. In addition, different types of experimental setups have different sources of systematic errors. Over a period spanning a variety of experimental tests (usually at least several years), a consensus develops in the community as to which experimental results have stood the test of time.

In physics and other science disciplines, the words "hypothesis," "model," "theory" and "law" have different connotations in relation to the stage of acceptance or knowledge about a group of phenomena.

An hypothesis is a limited statement regarding cause and effect in specific situations; it also refers to our state of knowledge before experimental work has been performed and perhaps even before new phenomena have been predicted. To take an example from daily life, suppose you discover that your car will not start. You may say, "My car does not start because the battery is low." This is your first hypothesis. You may then check whether the lights were left on, or if the engine makes a particular sound when you turn the ignition key. You might actually check the voltage across the terminals of the battery. If you discover that the battery is not low, you might attempt another hypothesis ("The starter is broken"; "This is really not my car.")

The word model is reserved for situations when it is known that the hypothesis has at least limited validity. A often-cited example of this is the Bohr model of the atom, in which, in an analogy to the solar system, the electrons are described has moving in circular orbits around the nucleus. This is not an accurate depiction of what an atom "looks like," but the model succeeds in mathematically representing the energies (but not the correct angular momenta) of the quantum states of the electron in the simplest case, the hydrogen atom. Another example is Hook's Law (which should be called Hook's principle, or Hook's model), which states that the force exerted by a mass attached to a spring is proportional to the amount the spring is stretched. We know that this principle is only valid for small amounts of stretching. The "law" fails when the spring is stretched beyond its elastic limit (it can break). This principle, however, leads to the prediction of simple harmonic motion, and, as a model of the behavior of a spring, has been versatile in an extremely broad range of applications.

A scientific theory or law represents an hypothesis, or a group of related hypotheses, which has been confirmed through repeated experimental tests. Theories in physics are often formulated in terms of a few concepts and equations, which are identified with "laws of nature," suggesting their universal applicability. Accepted scientific theories and laws become part of our understanding of the universe and the basis for exploring less well-understood areas of knowledge. Theories are not easily discarded; new discoveries are first assumed to fit into the existing theoretical framework. It is only when, after repeated experimental tests, the new phenomenon cannot be accommodated that scientists seriously question the theory and attempt to modify it. The validity that we attach to scientific theories as representing realities of the physical world is to be contrasted with the facile invalidation implied by the expression, "It's only a theory." For example, it is unlikely that a person will step off a tall building on the assumption that they will not fall, because "Gravity is only a theory."

Changes in scientific thought and theories occur, of course, sometimes revolutionizing our view of the world (Kuhn, 1962). Again, the key force for change is the scientific method, and its emphasis on experiment.

V. Are there circumstances in which the Scientific Method is not applicable?

While the scientific method is necessary in developing scientific knowledge, it is also useful in everyday problem-solving. What do you do when your telephone doesn't work? Is the problem in the hand set, the cabling inside your house, the hookup outside, or in the workings of the phone company? The process you might go through to solve this problem could involve scientific thinking, and the results might contradict your initial expectations.

Like any good scientist, you may question the range of situations (outside of science) in which the scientific method may be applied. From what has been stated above, we determine that the scientific method works best in situations where one can isolate the phenomenon of interest, by eliminating or accounting for extraneous factors, and where one can repeatedly test the system under study after making limited, controlled changes in it.

There are, of course, circumstances when one cannot isolate the phenomena or when one cannot repeat the measurement over and over again. In such cases the results may depend in part on the history of a situation. This often occurs in social interactions between people. For example, when a lawyer makes arguments in front of a jury in court, she or he cannot try other approaches by repeating the trial over and over again in front of the same jury. In a new trial, the jury composition will be different. Even the same jury hearing a new set of arguments cannot be expected to forget what they heard before.

The scientific method is intricately associated with science, the process of human inquiry that pervades the modern era on many levels. While the method appears simple and logical in description, there is perhaps no more complex question than that of knowing how we come to know things. In this introduction, we have emphasized that the scientific method distinguishes science from other forms of explanation because of its requirement of systematic experimentation. We have also tried to point out some of the criteria and practices developed by scientists to reduce the influence of individual or social bias on scientific findings. Further investigations of the scientific method and other aspects of scientific practice may be found in the references listed below.

1. Wilson, E. Bright. An Introduction to Scientific Research (McGraw-Hill, 1952).

2. Kuhn, Thomas. The Structure of Scientific Revolutions (Univ. of Chicago Press, 1962).

I think there are two questions: 1. Is global warming taking place? 2. What is the cause of it?

Good point. And the current debate seems to combine these two quite separate questions into a single scientific question.

As such, a positive answer to #1 will automatically lead to a conclusion that human activity is to blame. Not very good science, in other words, even if human activities form a component of the warming.

Global warming is a great example of science being used for political or other ends, and scientists playing along with it.

There is a corollary activity that should also be noted:

4) Demonize and marginalize those in the field who disagree or contend with your "findings"...

I think there are two questions: 1. Is global warming taking place? 2. What is the cause of it?

I don't think at this point that any serious and even minimally informed individual is going to dispute that the answer to #1 is "Yes". The warming that has occurred within roughly the last 100 years is proven without a doubt.

As far as #2 goes, that's another matter altogether.

This is just socialism.

I agree completely. This is a power grab by the Socialists of the world who are resentful of the US's prominence. In their minds, they are better human beings, they're smarter, they have better intentions therefore, they should be the dominant political system in the world. Having the US powerful was OK so long as the Soviet Union existed. Now that it doesn't, the Socialists feel the need to knock us off our pedestal. They couldn't care less about the environment. They just want power and this is the tool they have chosen to use to get it.

There are a number of scientific discoveries based on this [Reverse Scientific method] approach. You might be surprised by that, but brilliant men knew what the principle should be and when the data didn't fit they found reasons why it didn't fit. So they didn't throw away good data, but bad data in order to get to the truth. Sometimes this method is needed to have progress, although before you publish the results you go back and redo the study the correct way.

The scientific method says nothing about how you come up with a theory or hypothesis. You can use taro cards and still follow the scientific method. What is important is that you devise and carry out a proper experiment. Good scientists often have an intuitive knack for insights into bad results but good luck getting confirming results from those taro card theories.

Rejection of Authority was never a rule in science, although it may have been your teacher's way saying we shouldn't mindlessly heed authority. In the ideal world, science should neither reject nor embrace authority, but proceed with complete neutrality.

Interesting. You've just described what lawyers do.

I never thought about it this way before, but you could say that the global warming hysteria is what you get when you allow lawyers to pose as scientists.

1. Is global warming taking place?

Yes, the Earth has been getting warmer since the 17th century. Before that it got colder for about 500 years, before that it got warmer for about 400 years, before that it got colder, etc.

2. What is the cause of it?

The Sun.

1. Is global warming taking place? 2. What is the cause of it?

Actually, there are three more, all of which are probably more important than the first two:

3. If it's taking place, what will be the net results? (could be bad, but could also be good)

4. Are we capable of significantly influencing those results positively? (some people don't seem to comprehend that the answer could be "no")

5. If so, would it be worth it to do so? (it's possible that there's a global warming/climate change in store for us, that it would be bad, and that we could influence it positively, but it would simply cost more than it's worth to do so. Another possibility lost on many people.)

If your house was flooded, you wouldn't ask what the water was or where it came from, would you?

The real point here is that no one has a solution to remove the excess CO2 and only add back the right amount; yet they want to run the show at our cost.

Agree with your post. Also, most arguments seem to posit that this GW is going to impact us like a tsunami when in reality it is a long and slow process and we as humans will adapt to the slowly changing conditions. E.g., the fact that there were vineyards in England during the midevial warm period. For crying out loud, if it gets warmer that is not such a bad thing. We adapt, until it starts getting colder again as it has over the ages.

But it is interesting that published experiments rarely reveal the entire story about how progress is made in science. You need to rely on biographies and autobiographies to get real insight into how some of the great minds of science worked out a problem and devised experiments. If you just looked at the published articles you sometimes ask yourself how a certain scientist could have had such great insight, when in fact they sometimes worked outside of the rules. Only when they understood the principles involved did they come back and devise the correct experiment. And sometimes even then that didn't work. It is sometimes troubling for someone not working in the field of science to learn that scientists throw out the outlier data based on any legitimate excuse in order to achieve a statistically significant result.

Scientific method? We don't need no stinking scientific method. We got Algore.

It's Bush's fault. Bush and those damned SUVs. Women and minorities will be hardest hit.

scientists throw out the outlier data based on any legitimate excuse in order to achieve a statistically significant result.

As long as it is well outside the bounds of the majority of the data and is statistically insignificant, this is valid. The danger is that sometimes significant amounts of data lie outside the expected range. That is not legitimate to ignore. Any scientific paper which ignores "outlier" data should indicate that this was done and why.

I think there are two questions:
1. Is global warming taking place?

2. What is the cause of it?

3. What are you going to do about it?

Everyone who believes that global warming is happening and evil cars and industry are the cause of it:

1. Get out of your car and make it into a planter.

2. Quit your job if it encourages industry.

C'mon, lets not just TALK about it and force me into doing something, get out there and LEAD.

Your assuming that we have excess CO2 and need to decrease.

If you can give me daily CO2 readings for the last 2 billion years, then we can make a determination if CO2 levels are high, low or part of a cycle.

If your house is flooded, you should ask where it came from. Is it raining? If no is the answer, you probably have a water coming from your own pipes and need to turn the water off.

If the flooding if coming from rain, there isn't much you can do until it stops.

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