Hebrews 12:1 says, "Therefore, since we have so great a cloud of witnesses surrounding us . . . ." A witness is someone who sees something and can tell others what he sees. I'm not arguing from silence here but only on the plain language of scripture. I realize you don't like it because it doesn't fit your theology so you use linguistic sleight of hand to try to make it mean something else. No, you only believe what you want to believe based on your interpretation of scripture. Incidentally, I didn't say those in heaven can communicate with those on earth and vice versa. Go back and read my post. Wow! it looks like you are making arguments from my silence! For shame!
A witness does not need to be a present witness or a living witness.
One of the greatest attested historical facts of all time is the resurrection, attested by over 500 witnesses--all of whom are dead. But Christ is alive. That doesn't mean the witnesses are invalid. We use this argument all the time. Paul used it.
1 Corinthians 15:6 After that,
he was seen of above five hundred brethren at once; of whom the greater part remain unto this present,
but some are fallen asleep.
--Those that were dead were still witnesses.
My parents were witnesses to my birth though both may be dead now.
The witnesses are historical.
The witnesses are in the Word of God, testifying on behalf of God for our sake urging us on to run the race that is set before us.
That is the context.
Now look again at the verse:
Hebrews 12:1
Wherefore seeing we also are compassed about with so great a cloud of witnesses, let us lay aside every weight, and the sin which doth so easily beset us, and let us run with patience the race that is set before us,
Whenever you see wherefore look before to see why for the therefore is there for.
So go back to chapter 11. Look before.
Hebrews 11:39-40 And these all, having obtained a good report through faith, received not the promise:
40 God having provided some better thing for us, that they without us should not be made perfect.
All of these--men and women of faith, martyrs for the faith, living Godly lives, died and received not the promise. Without us (those in the time of Christ) they would not have been made complete. They needed the sacrifice of Christ for the promises that they had never seen, now, to be fully realized.
Therefore, now, realizing all that these OT saints had gone through,
"let us lay aside every weight, and the sin which doth so easily beset us, and let us run with patience the race that is set before us,"
--They are historical witnesses put there in that chapter to challenge us to run the race that is set before us. There is nothing in the context that tells us that they are up in heaven looking down. Nothing.