12 When he opened the sixth seal, I looked, and there came a great earthquake; the sun became black as sackcloth, the full moon became like blood, 13 and the stars of the sky fell to the earth as the fig tree drops its winter fruit when shaken by a gale. 14 The sky vanished like a scroll rolling itself up, and every mountain and island was removed from its place.
15 Then the kings of the earth and the magnates and the generals and the rich and the powerful, and everyone, slave and free, hid in the caves and among the rocks of the mountains, 16 calling to the mountains and rocks, “Fall on us and hide us from the face of the one seated on the throne and from the wrath of the Lamb; 17 for the great day of their wrath has come, and who is able to stand?”
These verses speak of an apocalyptic event the likes of which has not happened in recorded history. I watched a video recently where a Christian man said that he had a dream in which he saw part of this vision of 'stars' falling to the earth and in his dream they were actually angels leaving their astral bodies to come to earth. I'm including that because I'd never heard that before and found it interesting. In the time period in which this was written it might have seemed feasible for physical stars to fall to earth but we now know even the smallest star is much larger than earth and would destroy it and all life on earth on approach before ever making contact.
Another possibility of course is meteors or some kind of meteor shower...something with enough gravitation could possibly cause an earthquake but would not cause a solar and lunar eclipse at the same time as those are predetermined by orbit patterns. This article from timeanddate.com explains why solar and lunar eclipses are separated in time by about two weeks; it's clear that this vision occupies a span of hours at the very least since lunar eclipses are only seen during nighttime hours and solar eclipses during daytime hours.
Quite a bit of study has gone into trying to place the date of this event, and many Christian writers have been wrong. I think the purpose of this vision given to John of Patmos is to help humans understand that the lifespan of earthly culture and the impact of malevolent spiritual influence on earth is limited, and that we need to keep our behavior in line with Christ's teachings in the Gospels while we are here.
This article at bibleref.com does offer one other perspective, by saying that since the horsemen are metaphors it is possible that the astronomical events might be metaphors for unrest happening all over the earth. Biblehub.com is another great resource for Bible interpretation and commentary from well known pastors; here is Charles Ellicott's take on these verses. This is the most serious warning given in Revelation about the coming cataclysm, and it should strike enough fear in our hearts to move us to repent of our misdeeds and continue to straighten our path to bring it in line with behavior worthy of God and Christ. I have come to realize that this is a lifelong process that occurs day by day, and it begins with the simple step of repenting to Christ of sin and accepting the Salvation that only he can give.
If you want to accept Salvation from Christ here are some resources:
A Prayer for Salvation from Christ:
Lord Jesus, I confess my sins and ask for your forgiveness. Please come into my heart as my Lord and Savior. Take complete control of my life and help me to walk in Your footsteps daily by the power of the Holy Spirit. Thank you Lord for saving me and for answering my prayer.
A more detailed step by step process:
https://www.wikihow.com/Accept-Jesus-Into-Your-Life
