sample essays of IELTS

27 Scientific Theories

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 molecular theory, in which gases
are pictured as being made up of many small particles that are in
constant motion.

A useful theory, in addition to explaining past observations, 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 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 well 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 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 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
scientists thinking beyond the known facts. The scientist plans
experiments, performs calculations, and makes observations to test
hypotheses. Without hypothesis, further investigation lacks purpose and
direction. When hypotheses are confirmed, they are incorporated into
theories.