A communication resource from the world's particle physics laboratories.
Take a deep dive into Particle physics topics and learn more about the experiments and those performing them.
There's more of the universe that we don't understand than we do understand. Ordinary matter—the stuff that scientists have spent decades studying—makes up around five percent of the universe. The remainder is thought to be comprised of dark energy (around 70 percent) and dark matter (around 25 percent). What is all this dark stuff and how do we know it's there if we can't even see it directly?
We know that dark matter exists because it acts on the cosmos in a number of ways. In the 1930s, an astrophysicist named Fritz Zwicky realized that, in order to act the way they do, galaxy clusters must contain a lot more mass than was actually visible. If the galaxies also contained unseen "dark" matter, everything made a lot more sense. Then, in the 1970s, astronomer Vera Rubin discovered that stars at the edge of a galaxy move just as quickly as stars near the center. This observation makes sense if the visible stars were surrounded by a halo of something invisible: dark matter. Since then, a number of other astronomical observations have confirmed the effects of dark matter.