Its chief purpose must be considered a certain fundamental change or renewal of the universe. In this way it will be prepared for the revelation of the kingdom of glory and adapted to the new conditions of being and life of the blessed members of this kingdom (below, 2 Pet 3:13).
"But the day of the Lord will come," just as suddenly, "as a thief in the night. In it the heavens will pass away with a noise, the elements will be destroyed by fire, and the earth and the works that are in it will be burned up." Because of it. That is, because of the coming of the day of God, "the heavens, being burned, will be destroyed, and the elements, being scorched, will melt" (2 Pet 3:10, 12-13).
What, then, will become of the earth and the heavens after such terrible destruction and burning by fire? They will not be turned into nothingness. Nor will they remain in their destroyed state. After being dissolved by the fiery process into their component and simplest elements, they will appear in a new, incomparably better and perfect form.
At the beginning of the world, from the formless and shapeless watery chaos, in the six days of creation, it was brought into a beautiful and well-ordered form (2 Pet 3:5). So also at the end of the world, from the fiery chaos, it will again be called forth by the same creative word of the Creator into an even more beautiful and more perfect being.
The word of God gives a very clear idea of this. The same holy Apostle Peter, after speaking of the fiery upheaval of the heavens and earth, immediately adds: "Nevertheless, according to His promise," that is, God's promise, "we await a new heaven and a new earth, in which righteousness dwells" (2 Pet 3:13).
In the Prophet Isaiah it is said in God's name: "Behold, I create a new heaven and a new earth; and the former things shall not be remembered, nor come into the heart" (Isa 65:17). Again: "The new heaven and the new earth which I will make shall always be before My face" (Isa 66:22).
In the Apocalypse, the seer of mysteries John also says that he "saw a new heaven and a new earth; for the former heaven and the former earth had passed away, and the sea was no more" (Rev 21:1). The holy Apostle Paul also says that "creation waits with hope for the revelation of the sons of God. For creation was subjected to vanity, not willingly, but by the will of Him Who subjected it, in hope that creation itself will be delivered from the bondage of corruption into the freedom and glory of the children of God" (Rom 8:19-21).
Among the Fathers of the Church, Blessed Augustine reasons about this more clearly and intelligibly than all. "The fire that will burn the universe on the last day will change the corruptible qualities of its component parts. Everything that was connected with our perishable bodies will receive new qualities corresponding to bodies already incorruptible. Thus the whole world will be renewed and adapted to the nature of risen men" (On the City of God, Book 20, ch. 16).
As for the appearance and form that heaven and earth will assume after the fiery upheaval, this is hidden from men. Likewise, no one can say wherein the perfection of the transformed world will properly consist or how it will be manifested. For example, will the present kinds of animals only be renewed, or will they disappear altogether? Will our eyes be gladdened by plants, and so forth? All this is hidden from human knowledge for the time being. So also is the nature of the glory of spiritualized human bodies after the resurrection.
Therefore let us remember only this: the blessedness of the future kingdom of glory will be so great and ineffable that "eye has not seen, nor ear heard, nor has it entered into the heart of man, what God has prepared for those who love Him" (1 Cor 2:9).