The ascension of Christ isn't mentioned in Matthew or John.
It's noted in Mark 16:19:
So then the Lord Jesus, after he had spoken to them, was taken up into Heaven and sat down at the right hand of God.
And in Luke 24:51:
While he was blessing them, he withdrew from them and was carried up into heaven.
Crucifer, historians have to study sacred texts like other ancient writings. They can't afford to rule out a theory simply because the Bible disagrees with it (whatever their personal religious beliefs may be). It still needs objective testing.
John's got one of my very favorite verses right at the end (21:25):
But there are also many other things that Jesus did; if every one of them were written down, I suppose that the world itself could not contain the books that would be written.
Sounds like a tired writer on deadline to me.
"I could say so much more! But I won't. The End."
“There, peeping among the cloud-wrack above a dark tor high up in the mountains, Sam saw a white star twinkle for a while. The beauty of it smote his heart, as he looked up out of the forsaken land, and hope returned to him. For like a shaft, clear and cold, the thought pierced him that in the end the Shadow was only a small and passing thing: there was light and high beauty for ever beyond its reach.”
― J.R.R. Tolkien, The Return of the King