Dark matter was not discovered by a single person; it was inferred over time by several scientists. The earliest major credit usually goes to Fritz Zwicky in the 1930s, and Vera Rubin later provided especially influential evidence from galaxy rotation studies.

Who gets the credit

  • Fritz Zwicky noticed that galaxy clusters moved as if they contained much more mass than could be seen, which pointed to unseen matter.
  • Vera Rubin and her collaborators later showed that stars in galaxies orbit in ways that strongly suggest a large amount of invisible mass, helping make dark matter a central idea in astronomy.

Simple answer

If you want one name, Fritz Zwicky is often called the first to identify the need for dark matter, while Vera Rubin is widely credited with proving the case far more convincingly for modern astronomy.

Why this is tricky

Dark matter is not something someone “saw” directly at first. It was discovered through its gravitational effects, such as how galaxies and clusters move and how gravity bends light.

If you want, I can also give you a one-line version for a post caption.