Our universe is a vast, mysterious expanse filled with wonders that have captivated humanity for centuries. Yet, despite all our technological advancements and discoveries, what we see—stars, planets, galaxies—is only a tiny fraction of what actually exists. Most of the cosmos is shrouded in a veil of mystery, composed of substances we cannot see or touch. These elusive components are known as dark matter and dark energy, and they make up about 95 percent of the total content of the universe. We are surrounded by a cosmic shadow—an invisible structure that shapes reality as we know it.
The idea that there might be more to the universe than meets the eye first emerged from observations that didn't quite add up. In the early 20th century, astronomers began noticing that galaxies didn't behave the way Newtonian physics predicted. Stars on the outskirts of galaxies were moving much faster than they should have been, given the visible matter present. The gravitational pull from the observable stars and gas simply wasn't enough to hold galaxies together at those speeds. Something unseen had to be adding mass, providing the extra gravity needed to explain the motion. Thus, the concept of dark matter began to take shape—not as a proven substance, but as a placeholder for a profound mystery.
Around the same time, cosmologists studying the large-scale structure of the universe found another surprise. When measuring how galaxies moved relative to one another, it became clear that some unseen force was pushing space apart, causing the universe to expand at an accelerating rate. This discovery, first confirmed through the study of distant supernovae, was not just unexpected—it was revolutionary. To account for this repulsive force, scientists introduced the idea of dark energy, an unknown form of energy permeating space and counteracting gravity on the largest scales.
