Physicist Frank Wilczek has had to defend his ideas more than once during his long and celebrated career. His Nobel-prizewinning work on quarks, the smallest building blocks of matter, was originally considered a bit out there, he says.

Even so, Wilczek, who is at the Massachusetts Institute of Technology in Cambridge, was caught off guard by the severity of an attack on his latest proposal, a type of device in never-ending motion called a time crystal. Patrick Bruno, a theoretical physicist at the European Synchrotron Radiation Facility in Grenoble, France, claims to have torn apart the idea with a mathematical proof published last month in Physical Review Letters.

“He's gone on the warpath,” says Wilczek. Undeterred, Wilczeck is now fighting back with a paper that he posted on 27 August on the arXiv preprint server in which he proposes a new way to physically implement his idea.

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