An experiment is a way to find out whether something is true or not. It is a kind of scientific test or demonstration. In the simplest sort of experiment, the testers vary one thing and measure another thing to discover whether there is a cause and effect relationship between them. If so, the independent variable can be manipulated reliably to produce changes in the dependent variable.
For example, in elementary science classes, we can heat water over a flame and measure the temperature with a thermometer. We can measure how much gas is used in the Bunsen burner, and how close the flame is to the bottom of the flask, and so on. Then we can measure how the temperature changes over time. Perhaps we will discover that more gas means faster heating, or that more distance between flame and flask results in slower heating.
An experiment can confirm or falsify a scientific theory. In one famous example, an hypothesis of Aristotle's was endorsed for over one thousand years before finally being tested. He said that heavy things fall faster than light things. To the consternation of supporters of Aristotle, experimenters found out the hypothesis was untrue in most cases. Falling objects gain speed over time, and a 5-pound cannon ball dropped from a tower will hit the ground at the same time as a 10-pound cannon ball (see Falling objects).
Quotes on Experiment
An experiment is a question which science poses to Nature, and a measurement is the recording of Nature's answer. ... Before an experiment can be performed, it must be planned—the question to nature must be formulated before being posed. Before the result of a measurement can be used, it must be interpreted—nature's answer must be understood properly. These two tasks are those of the theorist, who finds himself always more and more dependent on the tools of abstract mathematics. Of course, this does not mean that the experimenter does not also engage in theoretical deliberations. The foremost classical example of a major achievement produced by such a division of labor is the creation of spectrum analysis by the joint efforts of Robert Bunsen, the experimenter, and Gustav Kirchoff, the theorist. Since then, spectrum analysis has been continually developing and bearing ever richer fruit.