1) form a hypothesis based on what you observe. A hypothesis is an idea about how or why something is the way that is is.
2) test that hypothesis with an experiment. Experimental design is complicated but a good experiment should produce an outcome that either supports or rejects your hypothesis.
3) reach a conclusion. Either the experiment supported the hypothesis which is evidence that it is true. Or it did not support the hypothesis which means it is not true.
4) publish your results for others to criticize and attempt to replicate.
5) nothing in science is an absolute, but once enough people replicate results, it is very strong evidence that a hypothesis is true.
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