In a first, physicists have directly seen Hofstadter’s butterfly—a long-sought-after fractal in the quantum realm

Hofstadter, now age 80, politely declined Scientific American’s request for comment about the new result, noting that he had only rarely revisited his prediction ever since making it about half a century ago and would be unlikely to properly comprehend the paper—which, he added, he had no plans to read. “Over the years I have seen many claims of experimental ‘replication’ of the [predicted] recursiveness,” he says. “But they are all extremely coarse-grained, and none of them has come close to detecting a genuine recursively nested structure. That will perhaps happen in another few decades—if humanity still exists at that point.”