No matter how much people have recently discovered of the heavens above us, they remain immeasurable. Also, there is still no instrument capable of penetrating the earth to its core.
These two images are also used to indicate the heart of the king. The commoner cannot fathom this heart. This must be acknowledged.
The king may keep his deepest motives secret. That is even a sign of wisdom. And servants are to halt before the monarch's secret chamber. This last part is especially challenging for people of our time. Democracy has its bounds!
Moreover, a government leader must realize that the Lord stands above all power. Proverbs 21:1 says much in this regard: The king's heart is a stream of water in the hand of the Lord; he turns it wherever he will.
3 As the heavens for height, and the earth for depth, so the heart of kings is unsearchable.