New limit for range of fine structure constant’s possible variance

Science News : The fine structure constant , α, determines the strength of interactions between electrically charged particles. Why it has the value it does—a dimensionless number currently accepted as 7.297 352 57 × 10⁻³—is still uncertain, and some theories say that it may not be truly constant. Given the theoretical existence of dark energy , it is possible that α’s value varies depending on the amount of matter present in an area. Michael Tarbutt of Imperial College London and his colleagues examined measurements of the frequency of light needed to change an electron’s energy by a set amount in a CH molecule . They used data collected from interstellar gas clouds and compared them with measurements made in a controlled laboratory environment. Their results showed that any variance in α between Earth and interstellar space is less than 1.4 parts in 10 million. Although that is a very small upper limit, it doesn’t disprove the possibility of localized variance. And it also does not examine whether α may have varied over time as the universe has expanded.