Joy in discovery is the pleasure of figuring things out need not be restricted to professional researchers doing cutting-edge science. The fact that a particular truth has been discovered by someone doesn't mean that particular truth is forever marked with a little XML tag that says <KNOWN>. Knowledge is evidential entanglement between brains and environments; in a disconnected world where it's difficult to explain things, it's hard to see how joy in discovery could feasibly be reserved for one discoverer. The fact that someone else's beliefs are evidentially entangled with their environment doesn't mean that yours can't be, too. Many aspiring rationalists find this (coupled with certain fun-theoretic concerns) a compelling argument for taking joy in every personal discovery, delighting in the truth-finding process without undue concern about what other people already know. Your mileage may vary.