Doomsday, Day of Reckoning, and Armageddon are various names for the end of the world.
The four last things at a universal level are: the second coming of Christ, the resurrection of the dead, general judgment, and the end of the world. Jesus said he would return in John 14:3: “I will come back again and take you to myself, so that where I am you also may be”; in Luke 17:26, He says, “When the Son of Man returns….”
The first coming of Christ was the time when He was born in Bethlehem, two millennia ago. The Second Coming of Christ will be at the end of time. Early Christians thought the Parousia (Greek word for the Second Coming) was immanent soon after the Ascension and Pentecost. After the Apostles died off and the Church continued with no Second Coming, they realized Jesus truly meant what he said, “You know neither the day nor the hour” (Matthew 25:13).
The Second Coming is followed by the resurrection of the dead. Christianity firmly believes in the resurrection of all the dead. Jesus rose by his own divine power, but human beings will be reunited body and soul, no matter how many centuries, millennia, or eons have gone by since death separated bodies and souls.
The Catechism teaches the doctrine of the resurrection of the dead in #1038: “The resurrection of all the dead, ‘of both the just and the unjust,’ will precede the Last Judgment. This will be ‘the hour when all who are in the tombs will hear (the Son of man’s) voice and come forth.'” This is based on Acts 24:15 (“That there shall be a resurrection of the dead, both of the just and unjust”) and John 5:28 (“The hour is coming in which all who are in the tombs will hear his voice and will come out”).
The resurrection of the dead makes sense since we are created as a union of body and soul. The pagan Greek philosopher, Plato, held that the soul was a prisoner of the body, and only in death are we free to return to a world of immaterial ideas. Aristotle, his pupil, however, maintained that man was an essential union of body and soul. Without a body there are no senses, and without sight, hearing, or touch, how would we know anything? He held that the fullness of human existence depends on both body and soul.
Since the creation of Adam and Eve in Genesis, and especially since the Incarnation (when divinity and humanity, God and man, were united in the person of Jesus Christ), the union of body and soul are seen as important and part of God’s will.
Forty days after Jesus rose from the dead on Easter, He ascended into heaven, body and soul. If the body were useless or redundant after death, then why take His to heaven, unless that is where it is meant to be, always united to the soul?
General judgment occurs after the dead are raised. Many ask what the need is for a General Judgment if there were a particular judgment at death. General judgment is not an appeal or retrial, nor is it a parole hearing. Those in hell will stay in hell; those in heaven will stay in heaven. General judgment does not change any previous decree—it merely reveals and ratifies it to the whole of Creation. Everyone will know who got into heaven and why, and who ended up in hell and why. Every sin and evil deed will be revealed, and every good, kind, merciful, and compassionate deed will also be made known. Those in heaven will not be embarrassed by their forgiven sins since they are forgiven. Think of general judgment as watching a previously recorded trial on Court TV. The judgment already took place and the sentence has been given, and this is merely the reporting of what transpired at that trial.
After the good and the bad have been exposed, then comes the end of the world. Revelation (Apocalypse) 20:11 says, “Next I saw a large white throne and the one who was sitting on it. The earth and the sky fled from his presence and there was no place for them.” Matthew 24:29 is more explicit: “The sun shall be darkened and the moon shall not give her light and the stars shall fall from heaven and the powers of heaven shall be moved.”
The earth, the moon, the sun, the solar system, and indeed the entire physical universe will one day end. They are all material, and material things break down and decay. Even physics has a law of thermodynamics called entropy where energy (heat) is constantly decreasing and seeking equilibrium. The universe will eventually “run out of gas,” so to speak. There was a moment in which it was created, and there will be a moment when it will cease to exist. We simply do not know when.