What is an explanation for a question or problem that can be tested?
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According to our current understanding of science, a theory or hypothesis can never be shown to be the truth. It can be shown to be consistent with current evidence and experiment. A theory or hypothesis can, however, be falsified. That is we look for evidence that would suggest that the theory is wrong. If a theory cannot be falsified; if there is no (conceivable!) confounding evidence that is possible, the theory is unscientific and merely an interesting conjecture.
We might look to the theory of evolution as an example of a falsifiable theory. What evidence would we expect if the theory of evolution were incorrect? One professor of biology famously suggested
And thus scientists look for experiments that disprove theories and hypotheses, to show that the prevailing understanding, the orthodoxy, is inadequate. To keep using the evolution example, young earth creationists have sometime suggested that God (or his evil twin) created the Earth with the appearance of age, with fossil dinosaurs intact. He sure fooled us if that is the case. Such an hypothesis is not falsifiable; a deceptive creator can do anything.
A hypothesis is a prediction based on a theory or idea. A theory is an explanation of why and how something works. A good theory is able to make predictions ( hypothesis) of what will happen in a new situation based on the theory or explanation.