Question

If you cant prove a hypothesis, then how do scientist learn?

Answer 1

Scientist learn by doing the experiment over and over again. When they complete it, they learn what to do and what not to do. 

Answer 2

Hypotheses must be provable. If scientists cannot prove a "hypothesis" right or wrong, they need to change it to a legitimate hypothesis - something you can prove.

If it is proven wrong, they can change certain aspects of it to make a more specific experiment.