The gang's back together to celebrate 400 episodes of Probably Science! Erstwhile hosts Jesse Case (@jessecase) and Brooks Wheelan (@brookswheelan) join Matt and Andy to discuss counting magicians, Jesse's proximity to train tracks, Ig Nobel prizes for alligators on helium and narcissist eyebrows, detecting phosphine in the clouds of Venus, finding super old sperm in amber, an earthquake hack to measure ocean warming and podcast recommendations including Our Fake History, Entry Level and Jesse vs. Cancer.

This episode is brought to you by The Great Courses Plus, offering Probably Science listeners a free trial with unlimited access by visiting TheGreatCoursesPlus.com/probably