An important truth about science is that it has been wrong, to one degree or another, more than it has been right. As new means of testing theories are created and new minds ponder them, flaws are found that indicate a new approach is needed. This appears to have happened again, thanks to the recent efforts of some researchers at NIST.
Quantum Electrodynamics (QED) is the theory that describes how electrons orbiting a nucleus react when interacting with other particles. This includes describing what color light is emitted when the electrons are excited by a passing particle. The researchers decided to test this theory by stripping aware all but two electrons of a titanium atom, making it like a very small and very charged helium atom. The researchers then shot a particle at the electrons to force them to jump to a higher energy level, eventually falling and releasing a photon. The frequency of that photon is not what QED predicted though, which is very interesting as QED is a fundamental theory for electromagnetism, which is one the four fundamental forces of the Universe. (The other three are the gravitational force, strong nuclear force, and weak nuclear force.)
The only explanations for this odd behavior are that QED is wrong or that some previously-undiscovered physics is at work. As these results are extremely interesting, other researchers will likely perform the experiments and calculations needed to determine what the correct explanation is.