Isaac Newton had this theory about space and it's absoluteness. He thought that space was basically a giant grid. And objects could be seen to be moving by their change of coordinates basically. It's really not that bad of an idea. Granted, he was eventually shown to be incorrect and now we even know that space itself is moving-sort of. Expanding would be a better word for it.
That concept just blows my mind. How can space, the areas of life that we perceive as empty, be expanding. Scientifically I have fewer issues understanding the concept. The emptiness isn't really empty. On earth it's full of air which is more of a fluid than anything else (next time someone complains that they can't swim remind them that they're constantly swimming in air and watch for the slow reaction of realization). Outside earth space is still filled-sparsely-with molecules, elements and who knows really what else, dark matter maybe. Aside from the obvious issues with scientists not coming up with interesting names ('dark' matter? really?), I tend to run into a conceptual issue with the word 'space'.
For English speakers and likely most of those of Western Europeans ideological descent space is the absence of everything else. At least that's the first reaction typically. It's what is out past that big blue sky. The eternity of nothingness. At least that's what we can perceive with the naked eye. No optical or radio telescopes to assist. Not even a sextant to guide us like Brahe and Havelius in their recordings. How do we understand our universe then?
Perspective.
