Measurements and analyses have always been integral to science. Through attentive observation, researchers create new knowledge and new theories—in short, they create facts.

But it is often difficult to distinguish facts from credibly presented lies, as was demonstrated by the "Lange Nacht der Wissenschaften" science slam, “Echt oder Fake?” (Real or Fake?). On June 9, 2018, researchers from the Max Planck Institute for the History of Science and the Max Delbrück Center presented the audience with a fact that sounded like nonsense—leaving the audience to decide if it was a plausible lie, or a bizarre but genuine fact. How much truth is there in Predoctoral Fellow Teresa Hollerbach’s claim that a sort of Weight Watchers society already existed in the seventeenth century?