No. The claim that “no one else” knew—or even thought—that Earth was not resting on something is too strong.
A major counterexample is Anaximander of Miletus, a Greek thinker generally placed in the early 6th century BCE [3]. Ancient testimony credits him with a striking cosmological idea: Earth is in the centre of the cosmos and is not supported by anything [
1][
2][
4].
According to reports discussed in the ancient tradition, Anaximander explained Earth’s stillness by saying it was equally distant from everything around it. Because there was no privileged direction for it to move, it needed no physical prop or foundation [2].
That does not mean Anaximander had modern astronomy. He did not picture Earth as a modern spherical planet orbiting the Sun. His model is commonly described as placing a cylindrical Earth at the centre of his cosmos [4].
But for this specific question, that distinction matters: the issue is not whether Anaximander was scientifically correct by today’s standards. The issue is whether the idea of an unsupported Earth was unique to Job or the Bible. Anaximander’s model shows that it was not [2][
4].
So the short answer is: the verse in Job is notable, but the exclusivity claim is false. At least one well-attested ancient Greek model also described Earth as unsupported [1][
2][
4].
