Unbeknownst to most Christians (and pastors too), the heavenly realm is not far away, or "above", or "in the clouds", though the latter description has some merit. If you study the Bible, you'll come across several stories where the earthly realm is "opened" and reveals angels and other heavenly things.
-Isaiah asked God to "rend the heavens" and come down.
-As he was about to be stoned to death, Stephen looked up and said "Behold, I see the heavens opened", with Jesus at the right hand of God.
-As Jesus himself was being baptized by his cousin, John the Baptist, we read that "heaven was opened" and the Holy Spirit in the form of a dove descended down to Him.
-In a vision of God, Peter "saw heaven opened".
-The entire book of Ezekiel is based on a vision he received when "the heavens were opened" before him.
-Psalms says God "opened the doors of heaven", raining down manna to the desert-bound Hebrews.
-David wrote a song in which God "bowed", "parted", or "opened" the heavens and came down.
-A young man, worried about a battle that was about to take place, was prayed for by Elisha, who said " LORD, I pray thee, open his eyes, that he may see", causing the young man to be able to see the heavens, and the heavenly warriors and their chariots all around him.
So we see that there is some kind of layer or veil separating us from the heavenly realm. Hence, it is the thing that must be "opened" for access to that realm. This used to be common knowledge for believers. The veil separating the public from the Holy of Holies in the Temple in Jerusalem is symbolic of the actual veil. Nowadays, because we are in the part of history the Bible calls "the great falling away", chiefly characterized by believers leaving the faith as clearly is the case in the western world, this knowledge is gone. The French woodwork painting below is from an early period of history where westerners might have still known this as common knowledge, and for that reason I like it.
