The proof

You are browsing the internet looking for some information for historical research on World War II and suddenly you get a message: “PERFORM A TEST OF YOUR KNOWLEDGE: IN AN HOUR CHECK YOUR LEVEL OF LEARNING. DO YOU ACCEPT?” You decide that might be a good way to test yourself and click yes. But what’s going on? Incredibly, you are inside your computer screen, catapulted back in time! A newspaper reports what is probably the date of the day you are on “December 2, 1942”, the day on which Enrico Fermi managed  to ignite the first atomic ‘stack’: it was called ‘Chicago Pile-1’ and had produced the first self-powered and controlled nuclear chain reaction in history. It is the dawn of the atomic age. Damn! What now? You had in mind a very different kind of test!!! In your hand you have an old stopwatch that tells you that there is an hour of time left … Exactly as the message in your computer said! Now all that remains is to face this test … starting from solving a enigma reported in an old notebook that probably belongs to Enrico Fermi …