This does not quite fit this category but I can not find any better place. Maybe someone else can.
Everyone knows this sentence which is the test of a scientific hypothesis. It has troubled me ever since the first time I read it. Let's see if someone can clarify.
Scientific standards require that the hypothesis must be not only testable but also falsifiable.
I am asking what does "falsifiable" mean as it is applied to a scientific hypothesis. Does it mean that the hypothesis must be proven wrong? That is the common definition of "falsifiable" but, in this case, it seems that would mean that almost all science "facts" are false. But that isn't what the sentence says. So, does it mean that someone who disagrees with your hypothesis must be able to set up his own hypothesis showing a reasonable possibility that the first hypothesis could be wrong?
Ex: Let's say someone of Einstein's ilk announces that he has found how life started. He explains it in his usual masterminded way. You disagree with his hypothesis. What do you have to do to "falsify" his hypothesis? Prove him wrong or show the possibility of him being wrong?
Falsifiable means capable in principle of being falsified, if the right type of evidence to falsify it were to be found. Obviously it does not mean that that evidence has already been found, since it that were so the hypothesis would be already discredited.
In other words you need to distinguish between falsifiable (in principle, in the future) and falsified.
In order to considered scientific, a hypothesis must allow someone to conceive of an experiment or observation of nature that would test the hypothesis, such that if it failed the test it would be falsified. For instance, relativity and quantum theory have been subjected to a series of tests, to see if their counterintuitive predictions are borne out in reality. So far, all of them have been. But these theories are falsifiable because IF these tests had had outcomes in DISagreement with the theory, then they would have been falsified.
By contrast, the hypothesis that, say, the universe arose from the collapse of another parallel universe is unfalsifiable, because there is absolutely no way to put it to the test observationally. It is a speculation that cannot be tested.
Generally, a scientific hypothesis or theory is falsifiable because it makes predictions about the outcome of future observations. For instance, the theory of evolution asserts ancestral relationships between living organisms which predict which creatures should have similar DNA and which ones should have dissimilar DNA. It also predicts what "missing links" might be found in the fossil record and the age band of the rocks in which they should be found. These prediction are tested every time DNA comparisons are done and every time a new fossil type is found. If we were to find rabbit bones in Cambrian rocks, or that the DNA of a whale was closely related to that of a fish rather than a hippopotamus, then it would be falsified.