Related Story The Standard Model of Particle Physics, ExplainedAnother source of some scientific quandary is whether there might be a fifth fundamental force. You might be familiar with the standard four—the strong force, the weak force, gravity, and electromagnetism—but some physicists wonder if a fifth force that couples together neutrons and electrons could also be at work throughout our universe. Due to the high sensitivity of the experiment, the plot ended up being nonlinear, suggesting that the deviations detected by the team could be evidence of a fifth force. Other efforts have looked at much larger bodies than just atoms for evidence of the fifth force. That team’s ultimate aim, much like that of the team behind this new paper, was to understand the constraints on where this fifth force might reside.