Long before we had the atomic theory of matter, scientists knew the air was real, even though it was invisible. This was because we could see its action as the wind caressed the leaves in trees.
Likewise, we see the influence of another invisible force in the wider cosmos in the movement of stars within galaxies. But we don’t yet know what this mysterious “dark matter“ is made of.
Now a new generation of detectors—including one we’re building in a gold mine in Victoria—is giving us hope that we might finally shed some light on dark matter.
Glow in the Dark
Some models predict that whatever particle makes up dark matter is also its own antiparticle. This leads to the fascinating prediction that if two dark matter particles interact they annihilate into a shower of either exotic particles or radiation.
If it annihilates into particles, then space-based detectors, such as the Alpha Magnetic Spectrometer (AMS) on the International Space Station, might detect unusual numbers of, say, positrons. If it annihiliates into radiation (or if the positrons themselves annihilate), then the radiation will be in the form of highly energetic gamma-rays, which could be detected by NASA’s Fermi Gamma-ray Space Telescope orbiting above the Earth.
