infinite number of parallel universes
There is a criticism of religion as being a religion is just faith in the gaps of science.
Science has concluded in the idea of the big bang, or a beginning of this universe. This created a problem that this universe is singular and so exact as to support life as we experience it could not have come about randomly.
Now atheistic scientists found this proposal too difficult to take, so invented the idea we are just part of an infinite series of universes and we only observe the necessity of certain features to support life, because by chance that is the universe we exist in.
The problem is there is literally no way currently of proving this proposition or showing its impossibility, so is a belief in metaphysics or religion and not science.
And science is founded on limiting itself to measurable empirical statements. This is where it is emotionally hard to be certain about facts or ideas which are outside our ability to grasp.
Another similar problem is the rotational measurements of our galaxy suggest there is a lot more matter present than we can observe. This "matter" is currently called dark matter. The other alternative is some of our assumptions are wrong and not uniform as we believe. So under the current idea, what we observe is only 5% of the universe, and the majority is undetectable.
Now this appears to be a theory of gaps rather than science.