How to see the invisible (not clickbait)

Dark matter. One of our universe’s great mysteries and theorized to make up 85% of all the matter in it. But what is dark matter?

Unlike the matter we are made of, dark matter does not interact with light—that is, dark matter is invisible. We assume that dark matter interacts with gravity, therefore, it must interact with other matter too. It’s also quite hard to detect, wherein our main problem lies.

Currently scientists think dark matter is made of very heavy particles that interact weakly with its environment. Therefore, they are called WIMPS (Weakly Interacting Massive Particles.) With current research methods, it’s difficult to tell the difference between visible particles (background noise) and actual signals from WIMPS. Here comes the problem: dark matter, or WIMP, signals are incredibly similar to those of visible matter, or solar neutrinos—incredibly small particles forged in the heart of stars.

Researchers, however, thought of a new method, which for now is a computer simulation. Looking at the direction of the signals may help differentiate neutrinos and WIMPS, since they have different origins: solar neutrinos from stars, while dark matter is everywhere. Germanium (Ge) and silicon (Si) single-crystalline semiconductors are the key, due to their atomic structure. This probably sounds like gibberish, so let me break it down for you. Crystalline simply refers to the way atoms are arranged in a material, in this case forming a crystal. A semiconductor is a material that can conduct electricity, but not as well as copper, a strong conductor. With the detectors using these materials, researchers can obtain different signals depending on the orientation of the crystals, even if the signals are scarce, therefore differentiating between neutrinos and WIMPS.

Now, to explain precisely how these detectors would work, let me start with this: Scientists want to use a method that involves nudging around the electrons in the crystals, creating defects—otherwise known as defect formation. They need a certain range of energy to place in the defects. With this, they are hoping to observe dark matter interacting with particles. But for successful results, we also need to take energy loss into account. These energy levels are important because if it’s below the minimum, or it’s too much, the detection won’t work. Using some fancy equations and calculations, scientists use the energy lost in defect formation to tell the difference between the signals they need and the ones they don’t. Meaning, when dark matter interacts with the particles in the detectors, within a certain energy level, scientists will be able to receive a certain signal that tells them it’s dark matter.

It’s important to develop these types of germanium and silicon detectors, which can probe lower energy thresholds, because it could allow for the detection of more dark matter. Moreover, this theoretical method could have a large impact in the scientific community because it could be used to differentiate dark matter from the indistinguishable solar neutrino signal, and greatly improve the direct detection of dark matter.

You might not think of these as very important when we have climate change and energy source issues on our hands, but with every new discovery we realize how little we know about our world and how it works. Finally being able to see what the invisible 85% of our universe is doing in its free time, whether it be partying or holding galaxies together, isn’t a trivial matter. Being able to detect dark matter is crucial to understanding our universe and its future; whether it will stop after expanding a certain amount, or collapse, destroying reality as we understand it.