All matter consists of atoms in motion and these in turn consist of positively charged protons surrounded by a cloud of negatively charged electrons. The vibrating motion of the atoms causes the cloud of electrons to oscillate and this oscillation generates electromagnetic radiation.
All line of sight matters in space attract each other with gravity F=G x m1m2/rr. Electrons are on the surface of all matters.
All line of sight electrons in space repel each other with electrostatic force F=Ke x ee/rr. That force is the conductor of light/electromagnetic radiation in space between matters.
That force is co-exist with matters, is inherited, is immortal and indestructible. Therefore light speed in vacuum space is infinite/instantaneous between maters at any distance.
You can measure light speed in a vacuum glass bottle by using this tool to prove light speed in vacuum is infinite.