Scientific theories cannot be proven. However a hypothesis or a theory is accepted as truth, when it produces the best explanation of what we can observe. We can never prove a research hypothesis true, but by using parsimonious theories in our research we can certainly approach the truth.
According to Karl Popper, falsifiable theory is scientific, and a theory that cannot be falsified is not scientific (1). The principle of Falsifiability was not to determine the true or false, or the acceptability of a theory. Simply saying that something is falsifiable doesn’t mean that it is false. Karl Popper believed that “no theory is completely correct, but if not falsified, it can be accepted as truth.”
Theories are very often strongly backed up with experiments. But no matter how much evidence in form of experiments we have about certain theory we can never prove it. Let’s consider the famous example of black swan problem. One could be reporting white swans for ten years, yet still cannot claim that all swans are white. This is simply because single black or even pink swan will disprove the theory.
As we carry out new experiments, we gather more information about certain field. In some cases we can prove a hypothesis or a theory false. If this happens the entire field might all of a sudden change direction, very often by 180o. This is what Thomas Kuhn named paradigm shift (2). One of the examples of this is that cancer was first thought to arise from ‘germ cells’(3)(Wicha M.S., 2005), now we know that cancer arises from cell mutation.
So to conclude it is not possible to prove are research hypothesis. Even If a theory is backed up with enormous amount of evidence in form of experiments. That’s because one single experiment can change the entire view on the subject.
(2) Thomas Kuhn, 1962, The Structure of Scientific Revolutions