Why is space black – I'm a Scientist 2024/25

Question: Why is space black
- Keywords:
  astrophysics,
  colour,
  space
Asked by desk520muon on 12 Feb 2025.
- Ana-Maria Raclariu answered on 12 Feb 2025:
  
  Because most of the universe (about 95%) is made out of dark matter and dark energy. These don’t interact with light hence we don’t really know what they are. Only the matter we know interacts with light and hence we can see it; this is only about 5% of our universe.
- Martin McCoustra answered on 13 Feb 2025:
  
  It’s only black in the visible wavelength range because space is empty and the light sources are pin-pricks compared to the size of the universe… However, if you go out to the microwave and look the sky lights up!