A non-literal interpretation

    While the alien theory may be entertaining, and hey, even if it's a real experience for many in the end as that which is above is made as below, that which is within becomes an outer reality. Ultimately I believe the reference to Jerusalem descending from heaven is the experience of a person who has been enlightened also becoming "grounded", firm on their feet within the state of enlightenment. So many are "taken up" spiritually but are not grounded, they are capable of even greater evils and injustice coming from "love and lightheadedness", imbalanced and incomplete in their reasoning. Others are grounded, void of any real spiritual experience or understanding of things, the literalists and rest of humanity in whose hearts evil does rest, never moving or changing. So, some are taken up until they eventually dissipate and others are dragged down into death and destruction. It is those who are given enlightenment and then the grounding experiences needed to make them solid and steady who inherit the earth and life long lasting.
    How this all manifests physically will probably be determined individually. The age of Aquarius is coming where life giving waters are poured out for and from mankind. Where the invitation is made in the opportunity to "come! drink of life's water freely!".