Glossary of Scientific Terms


Glossary of Terms Used in Teaching About the Nature of Science

Ranked according to increasing confidence; there is no such thing as "certainty" in science.


Observations and Experiments: Anything you see, hear, smell, taste, or touch, with or without special instruments, is an observation. Observations can be wrong. 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.

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.)

Fact: When an observation is confirmed repeatedly and by many independent and competent observers, it can become a fact.

Hypothesis: A testable statement about the natural world that can be used to build more complex inferences and explanations. If an hypothesis that describes how nature works survives many experimental tests or observations, it may become a law.

Law: A descriptive generalization about how some aspect of the natural world behaves under stated circumstances. A scientific law (sometimes called a principle) is a powerful summary of many previously unrelated facts. (E.g., Newton's Law of Gravitation, 1687)

Theory: An extremely well-substantiated explanation of some aspects of the natural world that incorporates facts, laws, predictions, and tested hypotheses. (E.g., Einstein's Theory of Gravitation, 1916)

Other Important Science Terms

Scientific Method: Principles and procedures for the systematic pursuit of knowledge about natural phenomena, involving the recognition and formulation of a problem, the collection of data through observation and experiment, and the formulation and testing of hypotheses.

The scientific method may be described as consisting of four steps:

1. Observation and description of a phenomenon or a group of related phenomena. When an investigator has little prior information, the first step is often description.

2. Formulation of a testable hypothesis to explain the phenomena. Investigators may speculate about which variables might be related to other variables and in what manner. The hypothesis is often a statement about the relationship between or among variables; it may merely ask whether a connection exists (correlational research), or whether there is a cause-and-effect relationship.

3. Prediction of the existence of other phenomena using the hypothesis, or of the results of future observations.

4. Conducting experiments and observations by several independent experimenters who use proper experimental methods and represent mainstream peer review.

Scientific Inquiry involves asking a question, completing an investigation, answering the question (if possible), and presenting the results to others.

Basic Skills of Scientific Inquiry include: Asking the right question; Observing Classifying and sequencing; Communicating; Measuring; Predicting; Hypothesizing; Inferring; Defining, controlling, and manipulating variables in experimentation; Designing, constructing and interpreting models; Interpreting, analyzing and evaluating data.

Uses of Scientific Inquiry: Making connections with world situations; Encouraging more active problem-solving approach to learning and thinking; Applying math skills; Reviewing what is already known in light of experimental evidence; Proposing answers, explanations and predictions; Using tools to gather, analyze and interpret data

Scientific Model:

A scientific model is an idea that allows us to create explanations of how we think some part of the world works.

An important model was that of the atom, in which there were subatomic particles (protons and neutrons) in a nucleus and electrons (organized into electron shells) that orbit the nucleus. This model of the atom allows scientists to explain why certain atoms (or molecules) combine in the ways that they do and to make predictions about which atoms (or molecules) will or won't combine when brought into contact.

Protons, neutrons, and electrons, in this sense, are not necessarily real in the way that basketballs are. Rather, they are ideas that humans have developed to help explain what we see and to make predictions about what may yet be seen. They are invented by scientists.

Have you ever put together a model airplane? Certainly you've played with toy cars. Both of these are "models" in the sense that they faithfully represent certain aspects of the real, full-size object (the overall shape, for instance) while ignoring others (the size, the way the engines function - or don't function - in the model).

When scientists create a model, they pick and choose what aspects contribute most to its behavior. They say what they are including in the model, and also what they are leaving out that may be significant, but may be too difficult to detect or measure.

With computers, we can create "virtual models," or simulations. Using mathematical formulas to mimic the behavior of as many phenomena as possible, we can run many scenarios of real-life phenomena rapidly, and often inexpensively.

Evolution: Evolution, simply put, is descent with modification. This definition encompasses small-scale evolution (changes in gene frequency in a population from one generation to the next) and large-scale evolution (the descent of different species from a common ancestor over many generations).

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