Before I give my answer to your great question, I wish to lay a good foundation for that answer.
Re 4:1 After this I looked, and, behold, a door was opened in heaven: and the first voice which I heard was as it were of a trumpet talking with me; which said, Come up hither, and I will show thee things which must be hereafter.
Now, please tell me, what and when was that door opened in heaven?