Henry David Thoreau famously settled at Walden Pond “to live deliberately” in 1845, departing again in 1847, making 1846 the one full year he passed at the pond. By focusing on 1846 and “the year the universe changed,” we will endeavor to bring an epochal but almost entirely overlooked moment in human history into focus, from which to view all that came before and everything that has come after in a radically new and illuminating light.