“Where were you when I laid the foundation of the earth? Tell me, if you have understanding. Who determined its measurements—surely you know! Or who stretched the line upon it? On what were its bases sunk, or who laid its cornerstone, when the morning stars sang together and all the sons of God shouted for joy?
(Job 38:4-7) ESV
We (that’s me and the Holy spirit) found gravity in the context of the second day of creation, by which God establishes a space between the waters above and the waters below the firmament.
This is part of our core accretion model of planet formation.
Thereof fastened: טָבַע – taba
- Thereof fastened, Job 38:6, were settled, Pr. 8:25.
- to sink, as in water, mud, Jer. 38:6, are sunk down, Ps. 9:15.
- to sink, enter in, penetrate, 1 Sa. 17. 49.
- Pu. to sink, be immersed, also are drowned, Ex. 15. 4.
- Hoph. to be sunk, settled.
Davidson Analytical Hebrew and Chaldee Lexicon page CCLXXXII

The word taba is rendered as thereof fastened or sunk in some English translations such as the one above. This appears to be telling us that when the foundations of the Earth were laid down, their bases were sunk onto a cornerstone. This is the gravitational singularity at the center of the Earth.