“We are a way for the cosmos to know itself,” said Carl Sagan about our search towards the cosmos. Dark matter is a big part of the cosmos, which takes up 85% of our universe. It’s an invisible matter that we can’t see, and that’s why it’s always intrigued everyone. The history of dark matter – not as long as other parts of the universe that we study – is full of mysteries from day one.

Check this article out, too: Dark Matter vs Dark Energy: What’s the Difference?

Imagine a universe with five times more invisible matter than we can see. This invisible matter makes galaxies move in harmony. It also makes stars in spiral galaxies move faster than expected. It’s got a lot of use, especially in terms of how the universe works. We’ve made some progress over the years since we first thought about a matter like dark matter that may exist.

From Fritz Zwicky’s first thoughts about dark matter to dark matter experiments by Fermilab, SuperCDMS, and many others, the history of dark matter has gone through a lot. The universe is billions of years old, but the first literal mention of dark matter goes back to only 1933 – a mere 90 years. That’s not even a nanosecond in-universe time. The history of dark matter is relatively short but with exciting developments. Let’s look at that in more detail and see how we’ve arrived at where we are now.

Early Ideas and Pre-Dark Matter Theories

The origins of dark matter began long before scientists could even name it. Early astronomers wanted to understand what shapes the universe – maybe something we can’t see. They noticed unusual movement patterns as they studied the patterns and movements of galaxies, clusters, and stars. These initial observations set the stage for the eventual emergence of dark matter research and that’s when the history of dark matter starts. With time, astrophysicists that studied dark matter slowly realized the significance of dark matter as they became the bedrock of history of dark matter.

In the 16th and 17th centuries, astronomers like Johannes Kepler and Isaac Newton laid the groundwork for studying the motions of planets and stars (kepler’s first, second, and third laws are very famous, I have great articles on the second and third laws). Newton’s laws of gravity seemed to explain much of what astronomers observed. But something was off. By the 19th century, scientists noticed that certain galaxies spun at speeds that gravity alone couldn’t explain. These discoveries showed us an unseen force or substance affecting the universe—dark matter. From this point on, it’d get only more weird because understanding dark matter isn’t easy – despite our technological advancements until now.

The significance of dark matter gained momentum in the early 20th century when Swiss astronomer Fritz Zwicky measured the Coma Cluster‘s gravitational pull and put the first real step of the history of dark matter in the books. His findings revealed that visible stars accounted for only a fraction of the necessary mass. Zwicky’s proposal of “dunkle Materie” (“dark matter”) started the dark matter studies and theories.

Key Contributions by Early Scientists

It’s no secret that Fritz Zwicky is one of the most prominent names in dark matter research and the history of dark matter. After all, he started all this. His groundbreaking work in the 1930s was the first formal suggestion of the name dark matter and dark matter’s existence. Using the “virial theorem,” he calculated the speeds of galaxies within the Coma Cluster and showed that their mass far exceeded the visible matter. These ideas were initially looked at with skepticism by other scientists of the time. It still planted the first seeds for dark matter research.

Later came the second most influential name in dark matter – Vera Rubin. In the 1970s, she made a crucial breakthrough. By studying the rotational curves of galaxies, she showed that stars at the edges of galaxies moved as quickly as those near the center. This observation was against Newtonian physics and focused on a mysterious, invisible mass to account for these missing gravitational effects—supporting the significance of dark matter.

The Discovery of the “Missing Mass”

Here’s where the story really gets interesting. By the early 20th century, astronomers were like detectives with half the clues, trying to make sense of dark matter. The universe wasn’t adding up—literally. Galaxies were moving in ways that defied what we know about astrophysics, and it became clear that something huge was missing. This missing mass wasn’t just a small oversight; it was an elephant in the room, an invisible one at that. Scientists called this “missing mass,” and this led them to rethink everything they knew about the universe. As our technology got better, it was easier to look at this hidden side with new technological advancements. This was when Fritz suggested naming this unseen matter “dark matter.”

Fritz Zwicky and the Coma Cluster

Zwicky’s calculations showed that only 1% of the mass was visible. This was a shocking discovery. It marked the start of dark matter experiments and a deeper understanding of the universe. When Fritz started to study the Coma Cluster, he realized that this cluster of galaxies was spinning so fast that it should have torn itself apart. But it didn’t. Zwicky ran the numbers—and they didn’t lie. The visible stars only accounted for a tiny fraction of the mass needed to keep the cluster intact.

Vera Rubin and Galaxy Rotation Curves

Fast forward to the 1970s, and Vera Rubin enters the scene. Rubin wasn’t just a brilliant astronomer; she was also a trailblazer for women in science. Vera Rubin built on Zwicky’s work. She studied the Andromeda Galaxy and found something surprising. Stars at the edge moved as fast as those near the center.

This was a problem for Newton’s laws if only visible matter was considered. The only explanation was a large, invisible mass around the galaxy. Rubin’s findings were the nail in the coffin for the visible matter being the whole story. She proved that dark matter wasn’t just a theoretical concept—it was real and everywhere. Her work didn’t just confirm Zwicky’s earlier thoughts, it also pushed dark matter into the spotlight in the science community.

Development of Theories Around Dark Matter

As we made more and more efforts in dark matter research, scientists shifted from identifying this missing mass to figuring out what this missing mass could be. Was it something ordinary that we simply couldn’t see, or was it something entirely exotic? I have a whole article about this – click on the blue text to read it! By the mid-20th century, two main ideas emerged: maybe dark matter was made of faint, massive objects like black holes or rogue planets, or perhaps it was composed of tiny, strange particles unlike anything we’d encountered before.

MACHOs, WIMPs, and Other Dark Matter Candidates

1. MACHOs (Massive Compact Halo Objects): These were the early contenders. Scientists thought dark matter might be ordinary stuff like black holes, neutron stars, or even free-floating planets. While MACHOs could account for some missing mass, they fell short of explaining most of the dark matter.
2. WIMPs (Weakly Interacting Massive Particles): WIMPs became the superstar candidates. These hypothetical particles could interact via gravity but not much else, making them invisible to our instruments.
3. Axions: These lightweight, ghost-like particles are another favorite. If axions exist, they could solve several astrophysical puzzles, including the dark matter mystery. Scientists are still on the hunt for proof.
4. Sterile Neutrinos: Neutrinos are already complicated, but sterile ones are even more complicated. Sterile neutrinos don’t interact with regular matter at all. They’re a fascinating possibility but incredibly hard to detect.
5. Primordial Black Holes: Could dark matter be made of ancient black holes from the universe’s earliest days? This idea gained traction recently, though it’s far from confirmed.

Observational Evidence Supporting Dark Matter

While theories about dark matter are fascinating, they’re nothing without solid evidence. How do scientists find evidence for dark matter, which we can’t see? Thankfully, astronomers have uncovered several compelling observations that make the case for dark matter hard to ignore.

Gravitational Lensing Evidence

One of the most striking pieces of evidence comes from gravitational lensing. Gravitational lensing is a major tool for spotting dark matter. It happens when a massive object, like a galaxy cluster, bends light from far-off objects. This bending magnifies the view and shows where the mass is the dark matter. Click on the blue text to read more about gravitational lensing from my very recent blog post.

The Role of Gamma-Ray Telescopes

Gamma-ray telescopes are one of the most important telescopes for finding any sign of dark matter. They look for high-energy gamma rays, which could be from dark matter particles. That’s why they provide another window into the dark matter mystery. Scientists use these instruments to search for faint gamma-ray signals that might hint at dark matter particles interacting or annihilating each other.

The Hunt for Dark Matter Particles

The search for dark matter has become one of the most important things in modern science. Astrophysicists have developed dozens of innovative experiments as our technology evolves every passing day. Even though we still don’t have direct proof of dark matter, we’ve made a lot of progress with these experiments.

Building Sensitive Detectors

Sensitive detectors are key in finding dark matter. Important milestones, like Andrzej Drukier and Leo Stodolsky’s 1984 proposal, have led to today’s detection methods. These advanced detectors aim to spot dark matter by interacting with atomic nuclei. Dark matter particles interact so weakly with normal matter that detecting them requires extreme precision. Scientists have created detectors made of ultra-pure materials, often cooled to near absolute zero to eliminate background noise. These detectors are designed to capture even the faintest signals of dark matter interactions.

Underground Labs and Direct Detection

Many direct detection experiments happen deep underground. This avoids cosmic noise. The 1986 Homestake Mine experiment was a big leap forward, setting strict limits on dark matter interactions. In 1998, DAMA/NaI reported a possible dark matter signal. They saw annual rate changes over nearly 20 years. This was a promising sign of dark matter’s existence. Later, CDMS, EDELWEISS, and CRESST used new technologies to improve detection. Liquid xenon targets in XENON100 and LUX around 2010-2015 narrowed down possibilities. They set strong limits on dark matter models.

Conclusion

The story of dark matter is not going to be concluded in the coming hundred, maybe even thousands of years. From the early observations of Kepler and Newton to the groundbreaking discoveries of Zwicky and Rubin, the history of dark matter is continuously evolving, and we are adding more and more to our dark matter research. Theories have evolved, technologies have advanced, and experiments continue to add more to our knowledge base for dark matter.

Today, dark matter research is extremely important for a lot of reasons. It drives us to build more sensitive detectors, explore the most extreme corners of the cosmos, and rethink the very fabric of reality. While dark matter is still an unknown substance to us, we have answered quite a few questions until now. We will continue to do so in the coming future.

FAQ

What sparked the initial research into dark matter?

Early studies of the universe showed something was off. Celestial bodies moved differently than expected. This led scientists to search for “missing mass.” They found that galaxies and stars were affected by invisible forces. This sparked the dark matter research.

Who were the pioneers in the discovery of dark matter?

Swiss astronomer Fritz Zwicky noticed an invisible mass in the Coma Cluster. Vera Rubin later found key evidence in the Andromeda Galaxy. Her work on galaxy rotation curves was groundbreaking. It showed dark matter’s presence.

What are the theories about the composition of dark matter?

Scientists think dark matter could be MACHOs, axions, primordial black holes, or WIMPs. MACHOs are massive objects like black holes. Axions are particles that are extremely light and doesn’t interact with anything. WIMPs are tiny particles that interact weakly with normal matter.

What evidence supports the existence of dark matter?

Gravitational lensing shows light bending by invisible objects. This suggests a lot of unseen mass. Gamma-ray telescopes also hint at dark matter through particle interactions.