Space suggests, something exists over here which does not exist over there. Everything in space is not whole, and is not the whole, and does not exist everywhere. Therefore it doesn't fully exist anywhere. Space is in fact the idea that nothing (illusion of something false) exists and everything (God) does not exist. It's the idea of God's absence, opposite to reality in every way.
Time suggests, something which existed just now, no longer exists. Nothing exists forever, everything is always changing, nothing is reliable or constant or permanent, and everything ends. It is the idea of death. It the idea that nothing last forever and therefore reality is in constant flux and HAS no reality. It is the opposite to eternity and the notion that Heaven, God, and the Son of God, have all stopped existing as they were and have been changed into something else. In time, nothing exists at all times, and everything (God) never exists at any single moment at all. It's the idea of not existing.
Some people seem to have great difficulty understanding why this makes sense and why this is true. Or rather, have trouble accepting it.
The reason being, there is great special value placed on all things that exist in space and time. The world, the universe, animals, trees, sunsets, mountain ranges, oceans, favorite coffee houses, buildings, cars, etc. None of these things exist outside of space or time, and none of them can exist without space or time.
If space were to end, it would become impossible for anything to exist in a specific location. Nothing could remain separated off as an object. There could be no individual trees, no planets, no stars. And if time were to end, nothing could move, change, grow, or die. Physical planets cannot be maintained without space and time. The solar system cannot move without space and time. And the human body is totally dependent on spacetime to exist and seem to live.
Without spacetime, there is no world, there is no solar system, no stars, no galaxies, no bodies. They cannot have a form of any kind without spacetime. It's not merely a matter of these things continuing to exist but being joined together by some kind of oneness. That's blatant confusion and a denial of the facts. Even the form of the atoms and particles making up the objects cannot continue existing at all without spacetime. All the atoms would disperse into everywhereness. All the molecules would disappear.
This is the central message in ACIM, that "there is no world". It's a dream, a fictional fantasy place, made of illusions, a denial of reality, a complete opposite to reality, and an attack up on reality. Space attacks Omnipresence. Time attacks eternity. They are completely diametrically opposed and nothing alike. This world is nothing like heaven. "Earth, Heaven's opposite in every way."
There is no spacetime.