Recent experimental hints of a fifth fundamental force are examined against the established four: gravity, electromagnetism, the weak force and the strong force. A 2016 Physical Review Letters study led by Attila Krasznahorkay in Hungary found that excited beryllium-8 nuclei decayed into electron-positron pairs separating at an unexpected 140-degree angle, an anomaly explainable by a previously unknown particle about thirty times heavier than an electron; a later helium experiment showed a similar anomaly at 115 degrees. The article then explains each of the four known forces, the electroweak unification by Glashow, Weinberg and Salam, the search for a grand unified 'theory of everything', and the role of force-carrying bosons such as photons, W and Z bosons and gluons.
It links the new particle to the dark matter problem, including the hypothesised 'dark photon', and notes that a University of California, Irvine team interpreted the Hungarian result as a boson signalling a fifth force rather than a dark photon. Jonathan Feng is quoted as saying replication would be a 'no-brainer Nobel Prize', and the piece ends by saying future experiments will decide whether the findings overturn long-standing physics.
