What is Science?


We often hear statements like “Scientists say that the Earth goes around the Sun”, “Science tells us that all living things are made of cells” or “It’s a scientific fact that energy cannot be created or destroyed”. 


What’s different about science compared to other ways of knowing things?  How is science different from “common knowledge”, everyday experience or religion?


The difference is that science is a way of finding out how nature works using testable explanations and predictions.  In other words, experiments are done to test scientific ideas.


Science is mostly concerned with finding cause and effect relationships.   Scientists suggest a cause and effect relationship then test their ideas using repeatable experiments.   If the results of the experiment support the idea, the idea becomes known as an hypothesis.  The hypothesis has not been proven to be true - only supported.   If the experiment does not support the hypothesis, the hypothesis is modified or even thrown out altogether.


Examples of cause and effect:

  1. The tides are mainly caused by the gravitational pull of the Moon;

  2. The heart pumps blood to all parts of the human body;

  3. The reaction between a carbonate and an acid produces carbon dioxide gas;

  4. Nerves control the movement of muscles;

  5. Tuberculosis is caused by a kind of bacterium;

  6. Evolution is the result of natural selection;

  7. The period of a pendulum depends on its length;

  8. Smoking causes lung cancer.

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These hypotheses can be tested using controlled experiments.  A controlled experiment has one variable cause that is changed by the experimenter (the independent variable) , and the other possible causes are kept constant (the controlled variables).   As a result of changes in the cause, there may be a change in the effect - the dependent variable.


An example:   Hypothesis “The period of a pendulum depends on its length.”


Cause:  Changing the length of the pendulum....   Effect:  ........Changes the period of the pendulum.


In the experiment to test the hypothesis, the experimenter will change the length of the pendulum - this is the independent variable.   (All the other things which might affect the period are kept the same.  These are the controlled variables.)   If the hypothesis is correct, the period of the pendulum will change - period is the dependent variable.   The period of a pendulum depends on its length.


If the results of the experiment are to be plotted on a graph, the independent variable is the horizontal axis :





For the other cause and effect statements above,  decide which part of each sentence is the cause and which part is the effect


So:   cause = independent variable;   effect = dependent variable.


Another way of looking at experimental design:

cows moo softly = change measure same

Change something (independent variable), measure what changes as a result (dependent variable), keep everything else the same.


For example - change the length of a pendulum;  measure how the time for one swing changes; keep everything else (mass, size of swing) the same.


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