Someone should make a site that quizzes you on time travel knowledge. Go through the ages: how do you start a fire, how do you make steel & what's the best method of smelting, what is germ theory & the best methods for preserving food, what are the causes of common diseases, how do you make a steam engine, what is penicillin & how do you produce it at scale, how do you make a battery, how do you make a solar panel, how does nuclear energy work, etc...