17.2: Who Was Fermi? Record your Fermi question.
Make an estimate of the answer. If making an estimate is too hard, consider writing down a number that would definitely be too low and another number that would definitely be too high.
What are some smaller sub-questions we would need to figure out to reasonably answer our bigger question?
Think about how the smaller questions above should be organized to answer the big question. Label each smaller question with a number to show the order in which they should be answered. If you notice a gap in the set of sub-questions (i. e., there is an unlisted question that would need to be answered before the next one could be tackled), write another question to fill the gap.