Marcus Marritt Imagine you could take a cosmic mixing bowl and cook up reality from scratch. It would be a strange kind of baking, with the end results including everything from space-time and satellites to cats and the cosmic web. But here’s the question: what would be the basic ingredient you’d need to use? I first got introduced to this kind of question in seventh grade, sitting in a class I had never taken before: physics. Although this introductory class was mostly about balls rolling down hills, I was taught that the methods of physics ought to have limitless reach – an idea called reductionism. Physics should be able to identify the essential ingredients of reality and show how to combine them from scratch into anything and everything. Immediately, I decided to become a physicist. But now, many years and several degrees later, I am less sure that physics holds all the answers. Take something like my sense of self: is that really a consequence of some equation that we haven’t yet derived?…