Speaking strictly to Einstein, he made testable predictions, and that's what made that work a part of the scientific process.
Whether something is science or not doesn't affect whether it's good or worthwhile knowledge, though! You wouldn't stop running user studies just because you're not going to get to population-level significance using them. There are many paths.
Whether something is science or not doesn't affect whether it's good or worthwhile knowledge, though! You wouldn't stop running user studies just because you're not going to get to population-level significance using them. There are many paths.