This is the weekly Q & A blog post by our Research Professor in Philosophy, Dr. William Lane Craig.
Dear Dr. Craig,
What is the universe expanding into? Atheists claim the universe came into being out of nothing. The universe cannot expand into nothing (i.e., into the absence of anything)! Therefore, given atheism, the Big Bang would be a non-starter! This not only demonstrates the bankruptcy of atheism, it infers the universe is expanding inside of God rather than into nothingness (which is literally impossible)! Even the popular balloon example is unrealistic since it has something to expand into-- the physical universe.
Dr. William Lane Craig's Response
Yours is not a religious question, Mark, but one that could be answered by any secular cosmologist. According the Big Bang theory, the universe is not expanding into anything. Think again about the comparison of the universe’s expansion to an inflating balloon. It is the two-dimensional SURFACE of the balloon which is the analogue to our three-dimensional space. There is no embedding space into which the universe is expanding. Equally, or even more, misconceived is the idea that the universe is expanding inside God, for God is not a spatial being.
To think that there is an embedding space into which the universe is expanding is to lapse into thinking of the material universe as expanding into a pre-existing empty space, which is a fundamental misunderstanding of the model. It is space itself that is expanding. The two-dimensional surface of the balloon is expanding, not in the sense that it is expanding into something, but in the sense that distances between stationary objects on the surface become greater over time. It is a purely internal measure and conception of expansion.
So as you trace the expansion back in time, you eventually come to a place where all distances shrink to zero, and space disappears (or begins to exist). It’s not that the universe disappears at that point, and the empty space in which it was expanding is still there. No, there is nothing prior to that point because it is space itself which is expanding. Just as there is not anything prior to the universe’s beginning, so there is not anything into which it is expanding. The difficulty for the atheist, then, is to explain how the universe could come into existence without a cause.
This Q&A and other resources are available on Dr. William Lane Craig's website.