There is no mention of Gravity in Genesis or, as far as I know, the rest of the Bible.
That's not really relevant to anything.
"Gravity" is just a name. Why should that be mentioned.
I'm pretty sure you can find plenty of evidence that people understood that things fall. Science has singled out and studied that phenomenon, and given it the name "gravity". So the authors of genesis did not single that out and did not give it a name. But it doesn't follow that they did not know about it.
Of course, they did not know nearly as much about it as today's science. But they would have been quite familiar with the phenomenon.
To be clear, I am not defending Genesis. There's a lot of nonsense there. But, when we criticize it, let's not exaggerate its problems.
Fundamentalism - the anti-American, anti-Christian branch of American Christianity