Why did God create other planets if we can't live on them?

The creation of other planets besides Earth is simply a “byproduct” of the “first cause”. The first cause is referred to in philosophy and theology as the first “spark” of motion that caused the first atoms to form in the material universe. I have argued that God, being this first cause, did not “build” the universe as a child builds a Lego kingdom piece-by-piece. God is the “Force” that put the very first atoms into motion, which eventually led to all that exists, namely through the physics mechanism over tens of billions of years. Every solar system that exists and all of the planets including Earth were formed as a byproduct of the first cause as well. The “foreordination” of mankind and the human soul were all a result of this first cause.

I give a full discourse/analysis of this concept at the following link.

Proof of the existence of God — St. Thomas Aquinas — The Five Ways