From the surface of the planet, it is undeniable that day follows night. But from as little as one astronomical unit above the plane of the ecliptic, it becomes clear that day and night are the product of the planet's shape, something experienced only by the inhabitants on the surface of the planet.
If you can grasp that concept, you are ready to proceed to the beginning of understanding what eternity is:
There is no then, no now. There only is. When a Christian prays in the words of the Lord's Prayer "Thy will be done, on Earth as it is in Heaven" they are asking that the completed, perfected state of the eternal kingdom be reflected on Earth. Now, is it possible, for a domain changing with time to truly reflect the changeless, perfect eternal? how might this prayer be answered?