Hypotheses are taken to be true given the weight of evidence. [b]This is not proof[/b]. It's as close to proof as we can replicate. Take an imaginary hypothesis about stars. I can hypothesise that "All stars must have property X". I can look at every star, and see whether or not it has property X. If every star has property X, I can say with pretty damn good certainty that my hypothesis is true - but I'll never [i]know[/i] if it's correct. In science "proven" is used as shorthand for "very probably true". Having said that, mathematical proof is quite different, and is indeed empirical and universal, provided mathematical axioms are correct.