Dark Science & Matter: History, Creation, and the Invisible Cosmos

Introduction: Wondering About the Dark

In July 2020, sitting at home during the initial lockdown months of the pandemic, I found myself wondering about the parts of the universe we cannot see. I started reading articles, textbooks, and research papers, compiling notes to understand what scientists mean when they talk about "Dark Matter". This was the very first article I ever published online.

---

I was wondering what Dark Science is, and started reading about it. In this article, I am trying to compile research from various sources about this topic to help understand the basics of Dark Matter.

History of the Dark: From Ancient Elements to Modern Physics

The ancient Greeks had made the universe simple: according to Greek natural philosophers, everything in our universe was composed of just four fundamental elements—Earth, Water, Air, and Fire. Later thinkers added a fifth celestial element: the "Aether", representing the pure material filling the cosmos beyond the terrestrial sphere.

As chemistry and atomic physics advanced, this ancient classification dissolved into the periodic table of elements. We learned that the stars, planets, mountains, and our own bodies are made of atoms: protons, neutrons, and electrons. For centuries, astronomers assumed that all the matter in the universe was visible—or at least emitted, absorbed, or reflected electromagnetic radiation (light, radio waves, X-rays).

In the 20th century, that comfortable assumption shattered.

The Clues: Fritz Zwicky and Galaxy Clusters

In 1933, Swiss astronomer Fritz Zwicky was studying the Coma Galaxy Cluster. By observing the Doppler shift of light from individual galaxies within the cluster, he calculated how fast they were orbiting around the cluster's gravitational center.

Using classical Newtonian gravitational mechanics, the speed of galaxies should be determined by the total visible mass of the cluster (all the billions of stars and gas clouds).

What Zwicky found stunned him: the galaxies were moving far too fast. Based on the amount of visible luminous mass, the gravitational pull was orders of magnitude too weak to hold the cluster together. The galaxies should have flown apart into deep space like stones flung from a spinning sling.

Zwicky concluded that there must be an unseen form of mass providing the missing gravity holding the cluster together. He named this mysterious component dunkle Materie—Dark Matter.

Vera Rubin and Galactic Rotation Curves

For decades, Zwicky’s calculations were treated as an astronomical curiosity. That changed in the 1960s and 1970s through the pioneering observations of American astronomer Vera Rubin and her colleague Kent Ford.

Rubin studied the rotation speeds of stars within individual spiral galaxies (like Andromeda):

• According to Kepler’s laws of planetary motion, planets farther from the Sun move slower than planets close to the Sun. Mercury orbits at $47 ext{ km/s}$, while distant Neptune moves at just $5.4 ext{ km/s}$.
• Astronomers expected stars at the outer edges of a spiral galaxy to orbit much slower than stars near the bright, dense galactic core.
• Instead, Rubin found that galactic rotation curves are flat: stars at the outer perimeter of galaxies orbit just as fast as stars near the center.

The only way to explain this observation within the framework of gravity is that galaxies are not just the visible disks of stars we see through telescopes. Every galaxy is embedded inside an immense, spherical halo of invisible dark matter that extends far beyond the visible spiral arms.

What is Dark Matter?

Today, precision cosmological measurements from the Planck space observatory confirm that:

• Ordinary baryonic matter (everything on Earth, stars, nebulae, black holes) makes up only about 5% of the universe.
• Dark Matter makes up roughly 27%.
• Dark Energy (the repulsive force driving the accelerating expansion of the universe) accounts for the remaining 68%.

What is dark matter made of? We know what it is not:

• It does not emit light (it isn't stars).
• It does not absorb or reflect radiation (it isn't ordinary dust clouds).
• It does not interact with the electromagnetic force at all.

Physicists hypothesize that dark matter consists of exotic non-baryonic particles:

• WIMPs (Weakly Interacting Massive Particles): heavy subatomic particles that interact only through gravity and the weak nuclear force.
• Axions: extremely light, hypothetical neutral bosons originally proposed to solve the strong CP problem in quantum chromodynamics.

Conclusion

It is mind-bending to realize that everything human beings have ever touched, seen, engineered, or imagined represents only 5% of the total cosmic pie. The remaining 95% of the universe is wrapped in mystery.

Writing this first post in July 2020 opened my eyes to how vast the unexplored territory of science really is. Curiosity doesn't end with what is visible; it begins where our vision stops.