AI summary: The concept of a truly “empty” universe may be impossible, as even if all energy was removed, the universe would still generate new forms of energy. This is due to the universe’s constant expansion, which spontaneously generates radiation. Even in a hypothetical “Universe of nothing”, dark energy would still exist. The universe’s ongoing expansion also creates a cosmological horizon, beyond which communication is impossible. This horizon, like a black hole’s event horizon, creates radiation. Therefore, the universe can never be completely empty as long as dark energy exists.