Since this came up in a discussion a while back I have been thinking of it often as to what the meaning might be.
Revelation 12 Authorized (King James) Version (AKJV)
1 And there appeared a great wonder in heaven; a woman clothed with the sun, and the moon under her feet, and upon her head a crown of twelve stars: 2 and she being with child cried, travailing in birth, and pained to be delivered.
Chris gave the clue that it was the church and I could see that, but I couldn't figure out where the moon under the feet fitted in. Over the time I have resisted the easy way out to read any commentary on it, but in the end I gave in and had a look around. I doubt I would have made the connection and I didn't do a word search for moon because I was incorrectly doubtful it would have given any insight.
It would seem it is a reference back to Joseph back in Genesis.
Genesis 37 Authorized (King James) Version (AKJV)
5 And Joseph dreamed a dream, and he told it his brethren: and they hated him yet the more. 6 And he said unto them, Hear, I pray you, this dream which I have dreamed: 7 for, behold, we were binding sheaves in the field, and, lo, my sheaf arose, and also stood upright; and, behold, your sheaves stood round about, and made obeisance to my sheaf. 8 And his brethren said to him, Shalt thou indeed reign over us? or shalt thou indeed have dominion over us? And they hated him yet the more for his dreams, and for his words.
9 And he dreamed yet another dream, and told it his brethren, and said, Behold, I have dreamed a dream more; and, behold, the sun and the moon and the eleven stars made obeisance to me. 10 And he told it to his father, and to his brethren: and his father rebuked him, and said unto him, What is this dream that thou hast dreamed? Shall I and thy mother and thy brethren indeed come to bow down ourselves to thee to the earth? 11 And his brethren envied him; but his father observed the saying.
The sun is Joseph's father and the moon is Joseph's mother and the eleven stars are Joseph's brothers.
Although the other eleven did eventually bow down to Joseph, Joseph is one of the twelve stars representing the twelve tribes of Israel. The woman clothed with the sun is the church clothed with Christ who is the descendant of Jacob.
Re-reading and going through revelation much more slowly and ignoring anything I have picked up over the years I can clearly see now that the burning of Babylon also is likely not a nuclear event but rather the direct work of God Himself judging and burning with fire. Maybe similar to God's judgement on Sodom and Gomorrah.