Dark matter is one of the most fascinating concepts in physics and is thought to account for 85% of the universe’s matter. They have been so talked about that they have taken on a semblance of fact, even though at this stage their presence is purely hypothetical. Of course, in science, truth is always provisional and the intimate relationship of facts and values means that not only is nothing ever truly “proven” in the mathematical sense, but what qualifies as fact hinges on normative decisions. The presence of dark matter is assumed from various astrophysical observations which cannot exist without dark matter. Yet this indirect verification of dark matter’s presence has not crossed a threshold to declare dark matter to be definitively verified as a fact of existence. According to the Universe Today, the search for data matter has so far come up short.
One popular candidate that many physicists believe would verify the existence of dark matter, are axions. Yet, the search for axions has come up short. The results of the latest search demonstrate the extent to which researchers have tried to come to grips with axions.
Axions were first proposed in 1970 in order to resolve problems within the theory of quantum chromodynamics. The theory suggested that there were unchanging particles with low mass that did not interact greatly with light. In other words, they pointed toward dark matter.
If axions exist as a component of dark matter, then we can expect the quantum field to have topological defects in which axions would cluster around oriented regions smaller than a galaxy yet larger than earth. The most recent study used the Global Network of Optical Magnetometers for Exotic Physics Searches (GNOME) to measure an axion domain. GNOME is part of ongoing attempts to search for physics beyond the Standard Model and reconcile it with quantum physics. It is made up of 14 sensitive magnetometers across the world. Nine of those magnetometers were used for this study.
The experimental design was ambitious. A laser light was used to magnetically align a group of atoms. The researchers hypothesized that the interaction of an axion with atoms would result in the atoms’ magnetic field shifting just enough for the magnetometers to detect. Perturbations like this happen naturally with atoms, but given the size of axion fields, axions across GNOME would shift in the way. If the planet moved from one axion field to another, those resultant perturbations would cause similar shifts across the world.
Unfortunately, the study hit a dead end and the perturbations could not be distinguished from random noise. However, although the main mission did not succeed, the study did help researchers to constrain their field of exploration even further. Science is not an unrelenting tale of progress. A lot of the good work comes from simply eliminating possibilities until what is left is as close to truth as we can get.
One of the great tales of scientific patience in the face of adversity is the century long search for evidence of gravitational waves. How long this particular search will take is anyone’s guess.
