The Scientific Method

�Before You Begin:

This section does not require any specific background knowledge.

The Process

Definition

The scientific method is the process of exploration and the organization of science knowledge. The scientific method is based on observation of the physical world.

The ‘How’—Experiment and Hypothesis

There are many ways of describing the process of the scientific method, but it is basically cyclical. Observations lead to conjecture about what those observations mean, which leads to a test of that conjecture, which results in more observations, and so on. The net result is a cycle in which conjecture is refined to account for observation. Another word for these observations is data. An observation conducted so that it can be reproduced is known as an experiment. The supposition that arises from previous experimentation is known as a hypothesis. I have known some college professors who went berserk when students defined a hypothesis as an “educated guess” even though this is a common statement. This vague definition makes scientist a little crazy because a hypothesis isn’t just a guess. It is an inference based on previous observations which we use to direct and design experiments.

The ‘Why’—Law and Theory

The end result of the scientific method is a body of observations. These are used to produce two very different types of knowledge: the law and the theory.

A law is a general statement, often mathematical, of a body of observations. Murphy’s Law is an example: “if anything can go wrong, it will.” Laws do not attempt to explain how or why; they only summarize. Though this may seem narrow, laws are very useful. They provide a short, concise statement that allows us to predict the outcome of an endless variety of situations. The Law of Conservation of Mass states that, during any chemical change, the total amount of matter remains the same. We can use this law to predict the mass of products that will be formed or to calculate the amount of reactants that we need. When we perform these experiments, we are not trying to prove or disprove the Law of Conservation of Mass. We are using that law as one of the many tools at our disposal.

A theory, also known as a model, is an explanation for the body of observations. A Theory gives us a reason why an experiment had a particular outcome. Scientists use theories to extend the body of observations in new directions. If we have a body of observations that can be explained with certain assumptions, we can then test to see what happens when we stretch and bend those assumptions. This allows us to devise new kinds of experiments with new results, some of which match the original body of observations, and some of which may not. An example of a theory is Dalton’s Atomic Theory. One of its postulates is that matter is made up of atoms which are indestructible. This idea was an attempt to explain why the law of conservation of mass works, the explanation being that, if everything is made up of atoms and atoms have mass and you can’t destroy or break them, then you can’t lose mass.

This brings us to another common student question that makes professors crazy: “If Dalton’s Atomic Theory isn’t ‘true,’ why do we have to study it?” Firstly, the concept of truth doesn’t really belong in the scientific method—we have observations which are what they are. Truth is a different kind of tool that is used in the pursuit of aesthetics, religion, and philosophy. Secondly, a theory is used to design experiments and explain results. If a theory is simple to understand and use (like Dalton’s Atomic Theory) and it can explain the behavior of atoms under most circumstances, why use a more complicated and difficult theory (like Quantum Mechanics)? Chemistry students still learn Dalton’s Atomic Theory because it works.

The Difference between a Law and a Theory

Many people get a very wrong impression of the scientific method from the quick and casual explanations they hear in school. They believe that a hypothesis turns into a theory then into a law. A theory is not just an educated guess that will magically turn into a law when it grows up! Unlike a law (which summarizes information), a theory tries to explain observations. “You can never find a pen when you need one” is a subset of Murphy’s Law. The following paragraph attempts to explain that law in a unique theory of pens.

There followed a long period of painstaking research during which he visited all the major centres of ballpoint loss throughout the Galaxy and eventually came up with a quaint little theory which quite caught the public imagination at the time. Somewhere in the cosmos, he said, along with all the planets inhabited by humanoids, reptiloids, fishoids, walking treeoids and superintellegent shades of the colour blue, there was also a planet entirely given over to ballpoint life forms. And it was to this planet that unattended ballpoints would make their way, slipping away quietly through wormholes in space to a world where they knew they could enjoy a uniquely ballpointoid life-style, responding to highly ballpoint-oriented stimuli, and generally leading the ballpoint equivalent of the good life.

By Douglas Adams

The Hitchhiker’s Guide to the Galaxy

The cycle of hypothesis (prediction) and experiment (observation) leads to a body of knowledge used to form a law (summary) and/or a theory (explanation).

4Concept Check: Is this a law or a theory?

"When a distinguished but elderly scientist states that something is possible, his is almost certainly right. When he states that something is impossible, he is very probably wrong." Arthur C. Clarke

Answer: This is a law, because it gives us a means of making predictions but it does not explain why.

This site was last updated 05/12/05