The scientific consensus up until now has been that the universe has been in a constant state of expansion since the Big Bang. The reason for this belief was the phenomenon of redshift. Redshift is the stretching of light wavelengths as an object moves away from the viewer. Because more distant objects had higher redshift, scientists interpreted this as universal expansion. There have certainly been disagreements on the various details, but this general assumption has remained relatively constant. But one topic of disagreement — the cosmological constant — has led some scientists to look at the issue from a different perspective.
But what is the cosmological constant, and why is it so contentious? The cosmological constant is the term for the background energy of space. When originally conceived, Einstein thought this constant to be equal to zero. However, when scientists began to notice that the expansion of the universe — as measured by redshift — appeared to be accelerating, they needed an explanation. It turned out that their hypothesis could be explained by having a cosmological constant that is not zero, but a positive number. Unfortunately, while this solved one issue, it created others. More and more calculations started simply not lining up to observations.
Lucas Lombriser, a theoretical physicist at the University of Geneva, thinks Einstein was right about the cosmological constant being zero. Lombriser proposes an alternate explanation for changes in redshift. He suggests that the identity of the elusive dark matter is an axion field. An axion is a hypothetical particle that is already one of the strongest contenders for the true identity of dark matter. According to Lombriser, the specific properties of an axion field could account for both dark energy and changes in redshift, preventing the need for universal expansion as a cause of redshift changes, thereby solving the dark matter problem and the cosmological constant problem at the same time.