The thought of a never-ending universe is almost as unfathomable as one with fixed borders — and yet, it must be one or the other.

The universe is thought to be 13.8 billion years old, and the observable universe is some 28 billion light years across. As vast as those figures are, they aren’t quite infinite — but the scientific consensus is that the universe is still expanding and will continue to do so forever. We aren’t likely to know the truth anytime soon — if ever — but that won’t stop us from wondering as we look up at the night sky.