In science, a theory is a reasonable explanation of observed events that are related.
A theory often involves an imaginary model that helps scientists picture the way an
observed event could be produced. A good example of this is found in the kinetic
Line molecular theory, in which gases are pictured as being made up of many small particles
(5) that are in constant motion.
A useful theory, in addition to explaining past observation, helps to predict events
that have not as yet been observed. After a theory has been publicized, scientists design
experiments to test the theory. If observations confirm the scientists' predictions, the
theory is supported. If observations do not confirm the predictions, the scientists must
(10) search further. There may be a fault in the experiment, or the theory may have to be
revised or rejected.
Science involves imagination and creative thinking as will as collecting information
and performing experiments. Facts by themselves are not science. As the mathematician
Jules Henri Poincare said: "Science is built with facts just as a house is built with
(15) bricks, but a collection of facts cannot be called science any more than a pile of bricks
can be called a house."
Most scientists start an investigation by finding out what other scientists have
learned about a particular problem. After known facts have been gathered, the scientist
comes to the part of the investigation that requires considerable imagination. Possible
(20) solutions to the problem are formulated. These possible solutions are called hypotheses.
In a way, any hypothesis is a leap into the unknown. It extends the scientist's
thinking beyond the known facts. The scientist plans experiments, performs calculations,
and makes observations to test hypotheses. For without hypotheses, further investigation
lacks purpose and direction. When hypotheses are confirmed, they are incorporated
into theories,