Astronaut Questions

Scientists believe that dark matter makes up approximately 27% of the universe. However, despite its name, dark matter is not actually “dark.” It does not emit or absorb light, which makes it invisible to us. Instead, scientists infer the existence of dark matter by its gravitational effects on visible matter. For example, dark matter appears to cause galaxies to rotate faster than they should based on the amount of visible matter they contain. Additionally, dark matter seems to hold galaxies together via its gravitational pull, preventing them from being pulled apart by the expansive force of dark energy. While we still have much to learn about dark matter, its presence is essential to our understanding of the universe.