hmm Is it impossible to look into heaven? Well, I'm not entire sure. Do you mean like whenever we want to or to see heaven at all? People have seen heaven, in scripture and even in modern time. My pastor saw heaven. Do I think he is a liar? No. Of what testamonies that I have heard, they all tend to have very similar descriptions.
Can we see into heaven whenever we want. If we can, then certainly no one that I know of is doing it. However it is more common for people to see into the spiritual realm around us. Can we do it whenever we want? I dont know, because if we could I certainly would have seen something by now, which I haven't, other than with the eyes of my spirit.
Jesus did say that He did whatever He saw His Father in heaven doing. I dont know exactly how to apply that verse to seeing into the spiritual realm, nor do I pretend that my interpretation and application of it is the only and correct way, therefore I leave it to you.
I do think that peolpe in heaven can see the earth though. I have heard many Christian people's testamonies of visions and heavenly encounters where they meet some of the saints dead and gone who describe themself as the great cloud of Witnesses, described in Hebrews. They say that they can see all that God is doing. Otherwise they would be ignorant to matters that are so dear to God;s heart.
All eyes are on earth, it is the primary focus of the heavenlies right now.
well, there ya go, take it or leave it. Either way the topic doesnt affect our salvation so whether you believe that we can see into heaven or not and that the people in heaven can see us or not does not disqualify you from being used by God. In that sense I am not looking to argue over the subject (directed to anyone who may want to challenge my statements).
Be blessed