Why Are Humans Obsessed with Dark Matter? [Thoughts After Dark]

Thoughts After Dark answers the questions you have in the final moments before drifting off to sleep when a simple Google search turns into an hour-long exploration into how things are made and how they work. Your random late-night questions are answered here — even the ones you didn’t know you had.

The most interesting thing about dark matter is that because it’s invisible, everything we know about it is actually just what we think we know. It parallels well with creative nonfiction, a passion of mine, in that the writer’s “truth” is fact (whether it’s 100% accurate or not) because it’s their truth. It’s the way they make sense of a situation, much like scientists have had to make sense of the universe: without dark matter, the behavior of stars, planets, and galaxies wouldn’t make sense. Maybe that’s why I was so interested in understanding what dark matter really is. 

Recently, the U.S. Department of Energy revealed a unique digital camera to better study dark matter. Coined the Legacy Survey of Space and Time (LSST) Camera, scientists will soon be privy to billions of galaxies and over 37 billion astronomical objects in space. 

The camera took more than 20 years to finalize, which demonstrates the growing appetite and commitment to understanding dark matter. So what makes dark matter, well, matter so much to us? And if we do figure it out, what will it prove or solve? 

What Is Dark Matter? 

Dark matter, which makes up about 85% of the total matter in the universe (although this number varies from source to source and includes dark energy), played an important role in the forming of galaxies. However, scientists still know very little about it other than that it only interacts with ordinary matter through gravity. 

Most of our understanding of dark matter comes from indirect evidence, which is how the term dark matter was coined in the first place. In 1933, an employee from the California Institute of Technology, Fritz Zwicky, wanted to explain why galaxies in the Coma Galaxy Cluster hadn’t been flung away into space because they were moving so quickly for their known mass. Zwicky determined it must be dark, invisible matter. 

This is also where scientists have tried to explain what makes up dark matter. One theory is that dark matter is made up of weakly interacting massive particles (WIMPs) that could have one to 1,000 times more mass than a proton. It’s also possible dark matter is made up of a complex set of particles. 

The DOE says the “race is on to detect what new particle physics is responsible for dark matter.”

The Technology Built to Understand Dark Matter

While dark matter is invisible, its influence on the largest structures in the universe isn’t. That’s why scientists are doing what they can to better understand it. 

DOE’s LSST Camera 

The DOE’s LSST Camera, the largest astronomy camera ever built, is 6,000 pounds, about the size of a small car. The camera is built to take pictures every 20 seconds for the next ten years to provide scientists with a deeper understanding of how the solar system was formed.

The camera is located in the Vera C. Rubin Observatory on top of the Chilean mountain Cerro Pachón, more than 8,000 feet above sea level. Dark matter, which scientists think is behind the universe expansion, is a confusing process — but the LSST might help make sense of it. 

DOE’s Axion Dark Matter eXperiment 

Another unique study of dark matter is the Axion Dark Matter eXperiment (ADMX). Using a resonant microwave cavity within a superconducting magnet, it searches for cold dark matter axions and converts them to detectable microwave photons. Basically, the experiment has set out to detect the weak conversion of dark matter axions into microwave photons when a strong magnetic field is present. 

According to the DOE, an axion is “a hypothetical particle that solves both long-standing problems in nuclear physics and could be responsible for some or all of the dark matter of the universe.” The ADMX study is the only experiment by DOE that is focused on uncovering axions.  

Currently, ADMX is undergoing continual upgrades to be more sensitive to a range of dark matter axion masses. 

Image Credit: WMAP, NASA

NASA’s High Latitude Wide Area Survey

NASA is also trying to learn more about the universe and the dark matter hidden within it. The space agency’s Roman survey will make a 3D map of the universe, combining “the powers of imaging and spectroscopy to uncover hundreds of millions of galaxies.” This map will help researchers make sense of the structure and expansion of the universe throughout cosmic time. 

Dark matter, only visible through its effects on “typical” matter that we can actually see, is a mystery — but Roman will help fill in the gaps in our understanding of dark matter and what it’s made of. 

Roman’s imaging will uncover the exact positions, shapes, and sizes of hundreds of millions of faraway, faint galaxies while also revealing how their images have been distorted by “typical” matter and dark matter to map dark matter more precisely.