It’s not an empty vacuum that can be explored. Stars and planets are lights not places you can visit. 2nd law of thermodynamics says you need a physical barrier to separate a positive pressure system aka earths atmosphere next to a negative pressure system aka space as we are told. Inverse square law of light says light spreads and gets weaker of distances. If the moon was as far as they say it is by the time you reached the surface of the moon it would be brighter than the sun.