"Heaven" was first described in the Old Testament as a physical place:
Gen 1: 60 (KJV) "And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters. 7 And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so. 8 And God called the firmament Heaven. And the evening and the morning were the second day.
The key to this verse is what "firmament" means! The Hebrew word was "raqia". It was rendered "stereroma" in the Septuagint (original Greek translation from Hebrew which is known as "textus receptus"; "received text" and is considered to be the genuine translation). Stereroma were supposed "crystal spheres" about the earth and other celestial bodies. While science now know that there are no solid spheres around celestial bodies, we do know something which supplements that "theory" of our early philosophers and Biblical patriarchs. That support is "gravity"!
Albert Einstein discovered that gravity bends light. It can be measured. Gravity is a field around celestial bodies and the higher the mass of the body, the greater the force of gravity. Does gravity "pull" from below to keep things on the surface of the earth or does it "push" from above? Einstein proved that there is a gravity force field around the heavenly bodies. That field diminishes the further away from the body one gets. In practice all celestial bodies are enclosed in a "gravity sphere". Of course early man had no idea what gravity was. It was like magic to them. Consequently, early mankind possibly likened gravity to a crystal, both unseen to the eye. (This is the Herrin explanation and is as good as any which I have researched which combines proven science with theology and philosophy; i.e., this is a first!).
One note of caution: We should never make God's Word agree with science, but understand that science is a feeble attempt to explain what God created! Science may be correct in simple matters, but far off in models requiring unprovable hypotheses. These are areas that as much faith is required in science as in religion!
Paul used stereoroma in the context of stedfastness:
Colossians 2:5 " For though I be absent in the flesh, yet am I with you in the spirit, joying and beholding your order, and the stedfastness (steroma) of your faith in Christ."
What are the most stedfast physical aspects in life? Gravity would rank first or at least among to top two. Light might be argued as stedfast, but varies with time because of solar flares, quasars and the like. Let's go with gravity! Here we have two different contexts of steroma which may be synomous: crystal (gravity) spheres and gravity itself!
Raqia (firmament) was later translated as an "expanse". This means that a firmament was a wide open space consisting for example of land, sky or water.
There are two expanses of water in our mileau. There are waters on the surface of the world (seas) and water in the atmosphere (clouds). Hence, we know that Heaven is above the second liquid expanse and whether we go with "expanse" or "crystal (gravity) sphere" Heaven is physically defined as a place above the biosphere; a place outside where physical life can live! Although our present unglorified bodies cannot live without support outside the biosphere, that is where spiritual life DOES LIVE with the support of God!
Many have tried to pinpoint Heaven. Exactly where is it? It should be recognizable because God has a mansion there with many rooms! Is it a physical place or strictly a spiritual one? Will there be material things in Heaven or just spiritual reproductions of the original?
Mark 16:19 "So then after the Lord had spoken unto them, he was received up into heaven, and sat on the right hand of God."
Jesus was physically received "up into heaven" "and sat". In agreement with Genesis, Heaven is above the biosphere and it is real because Jesus' physical body ascended there and sat with God! Do you need more?
2 Kings 2:1 "And it came to pass, when the Lord would take up Elijah into heaven by a whirlwind, that Elijah went with Elisha from Gilgal." Just as the Messiah was, Elisha was also physically taken UP into heaven. He was a living human who never died! Scripture refers to Heaven as a "kingdom" and indeed it is!
Paul himself said of his vision:
2 Corinthians 12:2 "I knew a man in Christ above fourteen years ago, (whether in the body, I cannot tell; or whether out of the body, I cannot tell: God knoweth;) such an one caught up to the third heaven."
The "third heaven" is the Heaven of heavens; God's abode. Paul saw a man who he had known at a specific time caught up "in the body" or "out of the body", making it possible and probable that a MAN go to Heaven, albeit this time (since it was a vision) he didn't know which.
Scientists are just now discovering what's out there. They have yet to catch up with God who knows all things. Science has just recently discovered "black holes", spheres so massive and gravity so high that not even light can escape (This reinforces the idea that gavity is more stedfast than light). Inside black holes are a pinpoint with intense mass called a "singularity", a place where space and time are distorted and all scientific laws are null and void. It's basically a scientist saying "We don't know what it is."
No scientist, you have lost your place! Whereas you admit that you don't know what it is (the singulairity) I do. It's a work of the Creator. It's God's creation. If you don't know what a singularity is, how would you know where Heaven is. We know that "black holes" cannot be proven because they can't be seen or measured. It's only by indirect methods (faith) that hypotheses are made.
If God conceals the secrets of the universe why would he reveal the location of heaven? Just as scientists take the author of physical laws out of the scientific equations, why would they allow God his abode in Heaven if they knew its whereabouts?
Isaiah 66:1 "Thus saith the Lord, The heaven is my throne, and the earth is my footstool..."
Yes, we know that Heaven is a physical place and not just a spiritual realm. We don't know it's exact location, but we don't need to. God will get us there with his power. He is the Creator who made space and time. We don't need a cosmic "worm hole" to transend time, God does that with a twinkle of his eye. In awe I say "I don't know exactly where it is, but I can't wait to get there!"