This is the ninth follow-up to the post, “Gagarin and the Seven Heavens“. The first follow-up post is here. The second follow-up post is here. The third follow-up post is here. The fourth follow-up post is here.
The fifth follow-up post was broken up into several parts; follow-up post five-one is here, post five-two is here, post five-three is here, post five-four is here, post five-five is here, post five-six is here, and post five-seven is here.
Starting with the sixth follow-up post, I will focus (not indefinitely) on modern Protestant, then modern Catholic, then modern Orthodox interpretations either of the ascension of Jesus in Luke-Acts or of the nearly-identical articles from the Apostles’ and Nicene Creeds that refer to Jesus’ ascension into heaven. The sixth follow-up post (Dodds) is here, the seventh (Erickson) is here, and the eighth (Grudem) is here.
The Reformed author J.I. Packer has a chapter dedicated to this article in his Affirming the Apostle’s Creed (Wheaton, IL: Crossway Books, 2008), 97ff. There, he confronts this question directly as he writes:
what is “heaven”? Is it the sky or outer space? Does the Creed mean that Jesus was the first astronaut? No; both it and the Bible are making a different point. 
Packer goes on:
“Heaven” in the Bible means three things: 1. The endless, self-sustaining life of God. In this sense, God always dwelled in heaven, even when there was no earth. 2. The state of angels or men as they share the life of God, whether in foretaste now or in fullness hereafter. In this sense, the Christian’s reward,  treasure, and inheritance are all in heaven, and heaven is shorthand for the Christian’s final hope. 3. The sky, which, being above us and more like infinity than anything else we know, is an emblem in space and time of God’s eternal life, just as the rainbow is an emblem of his everlasting covenant (see Genesis 9:8–17).
Now, Packer is right that there is something about the sense of the sky as “more like infinity than anything else we know” in ordinary experience, but the biblical text does not take this symbolic approach to the sky, but conceptualizes it as decidedly finite (‘from one end of heaven to the other’).
Packer writes that “Jesus entered heaven in sense 2”, which is about as catechetically clean an answer as can be summarized in such a short space. The problem, of course, is that these senses are not distinct in the Bible, but are required to be distinct for the Bible to be relevant for us. Packer seems to know this on some level, as when he writes that
“Ascended” is, of course, a picture-word implying exaltation (“going up!”) to a condition of supreme dignity and power. […] What happened at the Ascension, then, was not that Jesus became a spaceman, but that his disciples were shown a sign,  just as at the Transfiguration. As C. S. Lewis put it, “they saw first a short vertical movement and then a vague luminosity (that is what ‘cloud’ presumably means . . . ) and then nothing.” In other words, Jesus’ final withdrawal from human sight, to rule until he returns in judgment, was presented to the disciples’ outward eyes as a going up into heaven in sense 3. This should not puzzle us. Withdrawal had to take place somehow, and going up, down, or sideways, failing to appear or suddenly vanishing were the only possible ways. Which would signify most clearly that Jesus would henceforth be reigning in glory? That answers it.
On the assumption that the ascension is an historical event, and that the disciples saw it with their eyes as described, and with the current knowledge we have of cosmology, this answer is the only way to reconcile things together. Packer is aware of the heavenly throne room cosmology behind the concrete images:
It is truly said that our Lord’s presence and life in heaven as the enthroned priest-king, our propitiation, so to speak, in person, is itself his intercession: just for him to be there guarantees all grace to us, and glory too. 
Where is there? It cannot be parsed as simply as Packer wants to parse it from the outset…
Header image found here.