Dark Matter Makes Up 27% Of Universe

The vast, star-filled cosmos we observe is only a tiny fraction of what’s actually out there. The primary evidence for the universe's unseen majority came from watching galaxies spin. Based on the visible stars and gas, astronomers calculated that stars on the outer edges of spiral galaxies should be moving much slower than those near the center. Instead, observations in the 1970s, pioneered by astronomer Vera Rubin, showed that the outer stars were moving just as fast. The only way to explain this was if the galaxies were embedded in a massive, invisible halo of matter, providing the extra gravitational glue needed to hold them together at such high speeds.

This mysterious substance is not just dark in the way a planet or dust cloud is; it is fundamentally different. It does not appear to interact with light or any other form of electromagnetic radiation, which is why we cannot see it directly. Scientists know it's not made of the same protons and neutrons that form us and everything we can touch. The leading theories suggest it is composed of an entirely new type of subatomic particle, such as a WIMP (Weakly Interacting Massive Particle). While its existence is inferred from its gravitational effects on a massive scale—from bending light around galaxy clusters to shaping the entire cosmic web—the exact nature of dark matter remains one of the greatest unsolved mysteries in modern physics.