In A Course in Miracles, there is a sequence of workbook lessons which clarify this point, and which specifically contrasts Heaven and Earth, even using the term "Earth".
The lessons are:
128: "The world I see holds nothing that I want"
129: "Beyond this world there is a word I want"
130: "It is impossible to see two worlds"
131: "No-one can fail who seeks to reach the truth"
128: Refers to what you see with false perception, a distorted view of the Earth, which shows you what seems to be "hell" due to your misinterpretation.
129: Refers to the possibility of seeing the Earth in a different way. It refers to true perception. It suggests you would want to see the forgiven world rather than hell. It ALSO touches upon there being ANOTHER experience even beyond true perception, a third kind of world, which you will at some point go to... a place which is difficult to describe, but this basically is a reference to Heaven.
130: Tells us that we will either see the world of false perception or true perception - hell, or the "real world" (which is not real). This lesson helps you to get into the swing of practicing distinguishing between the world you don’t want (false perception) and the one you do (true perception).
131: This is the clincher. Jesus now speaks of the contrast between BOTH of these worlds, and Heaven. It literally makes statements about "Earth" using that word, and how this place YOU MADE, is not the likes of which God would create, nor can there be an opposite to the "Heaven" which was introduced in Lesson 129. It contrasts Heaven vs Earth in black and white terms, to teach you that even beyond the Earth that you see with true perception, there is ANOTHER PLACE - Heaven - which is the ONLY PLACE that GOD CREATED.
Let’s look at 131 closer.
"Heaven remains your one alternative to this strange world you made (Earth) and all its ways; its shifting patterns and uncertain goals, its painful pleasures and its tragic joys. God made no contradictions. What denies its own existence and attacks itself is not of Him. He did not make two minds, with Heaven as the glad effect of one, and ***EARTH*** the other's sorry outcome which is HEAVEN’S OPPOSITE IN EVERY WAY."
This clearly is telling us, that Earth (the physical planet) is the TOTAL OPPOSITE to Heaven. Not your perception of Earth. Not false perception or true perception. EARTH. Planet Earth. Solid matter. God did not make two minds, whereby Heaven is one of those minds, and Earth is the other. God ONLY CREATED HEAVEN.
This is what is BEYOND the world of perception, beyond true perception (forgiven/real world) and beyond false perception (hell). Heaven is NOT the Earth. Heaven is NOT hell. Heaven is NOT the real world. Heaven is BEYOND ALL OF THIS.
"How could the Son of God make time to take away the Will of God? He thus denies himself, and contradicts what has no opposite. He thinks he made a hell opposing Heaven, and believes that he abides in what does not exist, while Heaven is the place he cannot find."
He (the Son) thinks he made the Earth, which Jesus just told us is the OPPOSITE of Heaven and opposite to God’s creation. He abides in it (planet Earth) and cannot find Heaven (because Heaven is beyond the dream). Here Jesus also tells us that the hell we made DOES NOT EXIST, refering to the entire EARTH as not existing. And it is exactly this that "there is no world" means!
Jesus also goes on in this lesson to tell us how to practice finding the door to heaven and to go there, where Angels will, light the way and that we cannot fail if we seek to find the truth.
These lessons also correlate directly to Jesus teaching us that God could NOT have created a cruel world where children are born and lose love and wither and suffer and die, which is another reference to EARTH, not perception.
In so many ways, the course tells us that God did not create this world, this planet, or this universe, and that heaven is the ONLY HOME He created, which is beyond all form and beyond this world. Beyond Earth.
Earth, the strange world you made, is simply going to fall away into the nothingness from which it sprang. It is not going to be converted into Heaven, or kept in any way, because it is a world YOU DO NOT WANT, is an opposite to Heaven, and Love HAS NO OPPOSITE. Therefore, Earth does not exist. Hence, "THERE IS NO WORLD" is the she thing as "THERE IS NO EARTH".
You do not want this world. Heaven is EVERYTHING compared to this nothingness.