I think the general concensus now is that there is no such thing as empty space. Empty space is in fact filled with particles...i cannot remember the name of the particles at this time. so there. I'm not a scientist.
Space is not nothing. The opposite of matter would be nothing. Science does not know what space is. They have a bunch of ideas, but that is where they leave science and enter religion. We know it's almost a 100% vacuum though.