Parallel to a story in Berakhot, the mishnah here has an episode starring R. Gamliel and R. Yehoshua, about new moon testimony. Where one day's testimony seems contradicted by the next day's experience. How do we handle the human capacity for error? Also, how we can't compare courts, especially across generations, with biblical examples (it's not an insult to today; it is about authority). Plus, a new mishnah in a new perek - the court and everyone sees the moon, without sanctifying the day - how does this case play out, and why are all its elements in the mishnah? And what happens if the judges are the ones to see the moon? And why can't the moon be sanctified at night? With various permutations as loose ends to close the topic, even if it's at the beginning of a new chapter.