- supernovas?
- black holes?
- theory of relativity?
- the absolute zero point?
- atoms and quantum mechanics?
- that there's so much energy stored inside atoms that you can create a massive explosion when you split some?
- that there's actually invisible radiation like radio waves?
- galaxies?
- the speed of light?
- that it takes the light 80000 - 100000 years to cross our galaxy?
etc