Question: I'm sorry, but you are sorely mistaken! Here are a few places where the bible claims a fixed and immovable Earth:
1 Chronicles 16:30: "He has fixed the earth firm, immovable."
Psalm 93:1: "Thou hast fixed the earth immovable and firm ..."
Psalm 96:10: "He has fixed the earth firm, immovable ..."
Psalm 104:5: "Thou didst fix the earth on its foundation so that it never can be shaken."
Isaiah 45:18: "...who made the earth and fashioned it, and himself fixed it fast..."
Response: The claim seems to have an underlying assumption that it is impossible to be "fixed" and "immovable" and yet orbit around the sun. But the fact is, the earth has proven itself to be fixed and immovable:
• The earth is fixed and immovable in relation to its orbit around the sun. Have you ever known the earth to "unfix" itself and "move" itself out of its orbit around the sun? It doesn't happen, because the earth is fixed and immovable in relation to its orbit around the sun.
• The earth also is fixed and immovable in relation to us. There has never been a single day in which we had no place to stand, because the earth unfixed itself and moved itself out from under our feet.
The earth has always been fixed and immovable, both in relation to us and in relation to its orbit around the sun. In fact we've learned to take it for granted that the sun will shine during the day and that there will ground for us to stand on when we awake in the morning.
Having said that, one should at least consider the possibility that the verses cited above are actually using a figure of speech, to express the permanence of God's will and the permanence of his creation.
Next: When were Abraham's descendants supposed to return? After four generations, or seven?