I was accused of improper hermeneutics. So I will add to my response in case it wasn’t sufficiently clear that imposing a modern day cosmology onto the ancient text makes for bad hermeneutics and this becomes an impossibility of arriving at a true and correct conclusion, due to
conflicting paradigms and axioms
In order to properly exegete, hermeneutics demands proper understanding of the context of the text. This is not limited to text only but can include a broader context such as the cosmology of the day.
I apologize for assuming there was a basic understanding of Biblical cosmology, I will elaborate as concisely as possible the main points relevant to the interpretation of earth and heaven
The earth is flat just like a seal makes a flat imprint on clay or wax
“That it might take hold of the ends of the earth, And the wicked be shaken out of it? "It is changed like clay under the seal; And they stand forth like a garment.”
Job 38:13-14 NASB
The edge of the earth is like a garment encircling the waters, meaning it’s not a sphere
“Who has ascended into heaven and descended? Who has gathered the wind in His fists? Who has wrapped the waters in His garment? Who has established all the ends of the earth? What is His name or His son's name? Surely you know!”
Proverbs 30:4 NASB
The earth does not spin, move or totter.
“He established the earth upon its foundations, So that it will not totter forever and ever.”
Psalms 104:5 NASB
The earth is covered by a dome even after the flood of Noah
“The heavens declare the glory of God; and the firmament sheweth his handywork.”
Psalms 19:1 KJV
OP rightly points out
”"Eretz" consistently and soley refers to arable land (and not planet earth)”
If this is the model of the earth in Genesis then whether it’s translated land or earth it’s one and the same because unlike in modern cosmology the earth can mean a planet, in Biblical cosmology it meant the plane which was made of earth and had water in some places and exposed portions in other places.
OP rightly points out
”Shamayim" consistently and solely refers to only the "air" or atmosphere (and not the entire cosmos)”
And if the heaven was under the firmament dome whether you called it sky or heaven is irrelevant because unlike modern cosmology that interprets heavens to be a vast expanse of vacuum, in Biblical cosmolgy it was one and the same, the sky and the heaven where localized above the earth and beneath the firmament
So Genesis 1:1 whether you change the words to mean land and sky doesn’t change the cosmology and doesn’t change how everything looked.
The rest is my original post which included a shorter version of the answer and why current cosmolgy does not describe the Biblical cosmology.
Assuming a vast vacuum Cosmos
The question you ask is injecting a modern day secular pseudoscientific interpretation of the universe which has no proof and defies the second law of thermodynamics.
That is, is the subject of Gen 1 the creation of our world (for the first time) rather than the entire cosmos?
“Rather than entire cosmos” is assuming that the shâmayim that we observe today is explained by what secular scientists claim are seeing. And that outside a globe earth is a vast vacuum of space the end of which we cannot see. I challenge you to explain this vast expanse of vacuum space next to the open system atmosphere of the earth.
The biggest issue with the current model is that earth is an open system with pressure in the atmosphere next to a vacuum of space. That defies the second law of thermodynamics.
In order to have a gas pressure the gas must have something to press upon. So what is earth’s atmosphere pressing upon, or how is the earth’s atmosphere contained in order to maintain an atmospheric pressure and prevent the vacuum of space reaching equilibrium with the earth’s atmosphere, thereby sucking out the atmosphere into space?
In the current model there is nothing to press upon because earth is not contained inside a container and we can go to the moon and send man-made satélites into space. That means that in the current secular understanding earth, is an OPEN system and it has to be if matter is exchanged, men and rockets leaving and meteors, meterorites and returning rockets can come in.
Second Law of Thermodynamics
The second law of thermodynamics says that when energy changes from one form to another form, or matter moves freely, entropy (disorder) in a closed system increases.
If you have pressure (like earth’s atmosphere) next to a vacuum (like space) unless the pressure is contained, it will move to fill the space.
This is how a closed system works according to Wikipedia.com. Even they describe a closed system.
The second law is about the likely behavior of a system where no energy or matter gets in or out. The bigger the system is, the more likely the second law will be true.
Compare the pressure here on the earth
And the pressure in space
1.322 × 10−11 Pa
The difference is enormous.
That is impossible according to science to have an open system next to a vacuum as strong as space and for it to defy the second law of thermodynamics.
Pressure needs a container
Pressure is a force exerted by the substance per unit area on another substance. The pressure of a gas is the force that the gas exerts on the walls of its container. When you blow air into a balloon, the balloon expands because the pressure of air molecules is greater on the inside of the balloon than the outside.
That means in order to have atmospheric pressure next to a vacuum of space the atmosphere must have a container to press upon. But there is no container in the current understanding of earth and space.
You cannot smuggle into existence an ever expanding “cosmos” that has been fabricated and only exists in the mathematical models of secular pseudoscience.
Therefore if the Biblical model is correct and is all that we have to go by then shâmayim must mean the heavens comprised of sky inside the firmament, the firmament and waters above it. And erets within the Biblical model is the ground placed on pillars, covered by a firmament with waters on the outside and the earth has waters on it.
Therefore whether you call it sky and land or earth and heavens in the Biblical model it’s one and the same.
Therefore as a side note in the Biblical model we cannot have alien invasions, comets hitting the earth or asteroids colliding with the earth. This is only possible in the secular fabrication of the earth traveling at enormous speeds through endless vacuum of space while maintaining an atmosphere without a container.