God at the end of the rainbow
God at the end of the rainbow is a theological problem which highlights the limited thinking of people in older religions and the evolution of the realm of the gods. As we look further back in history, the dwelling place of gods becomes more and more mundane. Generally speaking, this problem highlights a moving the goal-posts type fallacy.
Going back to some of the oldest religions, around 3,000 years ago, gods lived in places inaccessible to the people of the day. For example, the ancient Greeks believed their gods lived on Mount Olympus, the ancient Hindus believed their gods lived on Mount Meru, those ancient Hebrews who worshiped Yahweh believed he lived atop Mount Sinai, while those who worshiped Elohim believed he lived atop Mount Horeb. It's not always mountains either: Hapi, one of the Egyptian Nile gods, was believed to live among the caverns far away at the source of the Nile. However, as people began to expand across the land and climb mountains, the idea of gods living on earth seemed a little childish, so beliefs evolved.
Around 2,000 years ago the first Christians believed their god lived up in the clouds (I Thessalonians 4:17), as did Tengri the Turkish god of Tengrism. Over time, people invented gliders, balloons, and other flying machines, and the idea of gods living in the clouds seemed a little silly, so beliefs evolved.
200 years ago, Latter Day Saints and Mormons believed their god lived on a distant planet called Kolob. Then, people developed powerful telescopes, and launched probes to the various planets in our solar system, and the idea of gods living on another planet seemed a little silly, so beliefs evolved.
Now, gods don't live on mountains or in the sky, instead, most modern religious believers now claim that their gods live in a different universe. And so, just like you can never get to the end of the rainbow, you can never get to the home of the gods; they're always living just out of reach.