In this week’s Atlantic coverage, our writers explored a plan to preserve all of human memory , America’s immigration history , how microbes spread through hospitals , the planet that could have been Earth , the evolutionary quirk that whales share with humans, and more. Can you remember the key facts? Find the answers to this week’s questions in the articles linked above-or go ahead and test your memory now: In this week’s Atlantic coverage, our writers explored the history of the sharing economy , how to measure the American Dream , why Trump might be thinking about a moon base , how to choose a reliable hedge-fund manager , problems with the Paleo diet , and more.