What are Axions in Physics? A Simple Look at Dark Matter's Building Blocks

We cannot see most of the matter in the cosmos. In fact, roughly 85% of the universe is believed to consist of dark matter, which cannot be observed directly according to physicists at PNNL . To solve this massive cosmic mystery, scientists are hunting for a hypothetical particle. But what are axions in physics, and why are they the leading candidate for this unseen cosmic scaffolding?

If you are a space enthusiast building your library of cosmic terminology, understanding these microscopic building blocks is a great place to start. 

What is Dark Matter Anyway?

We know dark matter exists because of its gravitational pull. It acts like an invisible glue holding galaxies together. Without this extra gravity, fast-spinning galaxies would fly apart.

Astronomers can measure this invisible pull, noting that there is about six times more matter in the universe than we can actually see as detailed in early cluster observations . Because this matter does not interact with light, it remains completely invisible to traditional telescopes.

So, What are Axions in Physics?

An axion is a theoretical, extremely light particle that carries no electric charge. First proposed in the late 1970s, axions were originally dreamed up to solve a mathematical symmetry problem in nuclear physics according to Symmetry Magazine .

Soon after, astrophysicists realised these particles possessed the exact characteristics needed to explain dark matter. If they exist, axions are incredibly abundant. Scientists estimate there could be up to 10 trillion axions packed into every single cubic centimetre of space.

How Scientists Hunt for Invisible Particles

Because axions are weakly interacting low-mass particles, detecting them requires highly specialised equipment. The premier search initiative, the Axion Dark Matter Experiment (ADMX), is located at the University of Washington according to project records .

ADMX works as an "axion haloscope." It uses a super-strong, 8-tesla superconducting magnet to force passing axions to convert into tiny, detectable microwave photons as explained by Fermilab researchers . If the detector registers these weak electromagnetic waves, it will prove that axions make up the missing dark matter.