W bosons mediate the weak interaction, one of the fundamental forces in physics. Because the Standard Model (SM) of particle physics places tight constraints on the mass of the W boson, measuring the mass puts the SM to the test. The Collider Detector at Fermilab (CDF) Collaboration now reports a precise measurement of the W boson mass extracted from data taken at the Tevatron particle accelerator. Surprisingly, the researchers found that the mass of the boson was significantly higher than the SM predicts, with a discrepancy of 7 (seven) standard deviations (link). Link to the CDF analysis here.