How big was the Universe 13 billion years ago?? If we look from the Earth, in opposite directions, at objects that are 13 billion LY away, they are 26 billion LY apart. We are seeing them as/where they were 13 billion years ago, so they must have been 26 billion LY apart then. This cannot mean that, 13 billion years ago, the Universe was, at the very least, 26 billion LY in diameter. How do I even start to explain this to someone who seems to expect me to know, simply because I post on a science forum?