Not only is gravity absurd, but it's also a big clue regarding what the Church Fathers actually believed regarding cosmology if you consider that gravity wasn't "invented" until recent times, and the notion that things (and people) could stick upside down to a ball was considered to be utterly preposterous.

In fact, there was a debate among the Fathers that St. Augustine actually cites, and St. Ambrose alludes to as well, regarding how the earth (meaning world) can be at the center of the (water-filled) universe, because the heavier substances like earth would sink to the "bottom".  St. Augustine cited the opinion that the earth was at the bottom as tenable, since "bottom center" is still center ... and you'll notice his premise that you MUST hold that the earth is at the center of this water-filled universe.

St. Ambrose, on the other hand, addresses the critics by positing that there's some spinning whirlpool-like action of the water that keeps the earth suspended in the midst of the water ... to counteract its tendency to sink due to its greater density, or else he believed it could just be kept there miraculously.

But the bottom line is that the Church Fathers had an absolute notion of up and down, where heavier (and more dense) things would sink to the bottom, and they would have considered it preposterous and absurd to posit people sticking to the bottom of a ball.