Imagine if you could look at a snowflake at the South Pole and determine the size and the climate of all of Antarctica. Or study a randomly selected tree in the Amazon rain forest and, from that one tree—be it rare or common, narrow or wide, young or old—deduce characteristics of the forest as a whole. Or, what if, by looking at one galaxy among the hundred billion or so in the observable universe, one could say something substantial about the universe as a whole? A recent paper, whose lead authors include a cosmologist, a galaxy-formation expert, and an undergraduate named Jupiter (who did the initial work), suggests that this may be the case. The result at first seemed “crazy” to the paper’s authors. Now, having discussed their work with other astrophysicists and done various “sanity checks,” trying to find errors in their methods, the results are beginning to seem pretty clear. Francisco Villaescusa-Navarro, one of the lead authors of the work, said, “It does look like galaxies somehow retain a memory of the entire universe.”