The concept of sinking down occurs in the creation narrative when God laid the foundations of the earth. The occurrences of this phrase fit the creation of a gravitational singularity on the second day.
February 3rd
Life Began in Zero-G
There are three things that we use to deduce that gravity as created on the 2nd day, which means that the during first day, and the time before it, there was no gravity in the universe.