The proof is in the prophecy.
Genesis chapter 1:1 In the beginning God created the heaven and the earth.
Genesis 1:2 The earth was without form and void, and darkness was over the face of the deep. And the Spirit of God was hovering over the face of the waters.
Genesis 1:3 And God said, “Let there be light,” and there was light.
Genesis 1:4 And God saw that the light was good. Then he separated the light from the darkness.
Genesis 1:5 God called the light "day," and the darkness he called "night." And there was evening, and there was morning--the first day.
This is the money shot.
Genesis 1:6 And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters.
Genesis 1:7 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.
Genesis 1:8 And God called the expanse Heaven. And there was evening and there was morning, the second day.
Genesis 1:9 And God said, “Let the waters under the heavens be gathered together into one place, and let the dry land appear.” And it was so.
Genesis 1:10 God called the dry land Earth, and the waters that were gathered together he called Seas. And God saw that it was good.

Isaiah 40:22 God sits above the circle of the earth. The people below seem like grasshoppers to him! He spreads out the heavens like a curtain and makes his tent from them.