The ORGAN Experiment, Australia’s first major dark matter detector, recently completed a search for a hypothetical particle called an axion—a popular candidate among theories that try to explain dark matter.
People, planets, stars and galaxies are all made of “regular matter.” But we know regular matter makes up just one-sixth of all the matter in the universe.
The rest is made of what we call “dark matter.” Its name tells you almost everything we know about it. It doesn’t emit light (so we call it “dark”) and it has mass (so we call it “matter”).
If it’s invisible, how do we know it’s there?
When we observe the way things move in space, we find time and again that we can’t explain our observations if we consider only what we can see.
Spinning galaxies are a great example. Most galaxies spin at speeds that can’t be explained by the gravitational pull from visible matter alone.
So there must be dark matter in these galaxies, providing extra gravity and allowing them to spin faster—without parts being flung off into space. We think dark matter literally holds galaxies together.
How could we detect it?
Many scientists believe dark matter could be composed of hypothetical particles called axions.
Anyway, after the axion was proposed, scientists realized the particle could also make up dark matter under certain conditions. That’s because axions are expected to have very weak interactions with regular matter, but still have some mass: the two conditions needed for dark matter.
Shining a light on dark matter
An axion is believed to convert into a photon in the presence of a strong magnetic field. In a typical haloscope, we generate this magnetic field using a big electromagnet called a “superconducting solenoid.”
Targeting mass regions
An axion of a certain mass will convert into a photon of a certain frequency, or color. But since the mass of axions is unknown, experiments must target their search to different regions, focusing on those where dark matter is considered more likely to exist.
If no dark matter signal is found, then either the experiment is not sensitive enough to hear the signal above the noise, or there’s no dark matter in the corresponding axion mass region.
But why does dark matter matter?
Well, for one, we know from history that when we invest in fundamental physics, we end up developing important technologies. For instance, all modern computing relies on our understanding of quantum mechanics.
We never would have discovered electricity, or radio waves, if we didn’t pursue things that, at the time, appeared to be strange physical phenomena beyond our understanding. Dark matter is the same.
Consider everything humans have accomplished by understanding just one-sixth of the matter in the universe—and imagine what we could do if we unlocked the rest.Full article at Phys.org.
The point about the value of fundamental research yielding useful technology seems consistent with purposeful intelligent design, otherwise, one would probably have to just chalk it up to luck.