Aristotle argues in On the Heavens 1.5-7 that there can be no infinitely large body, and in 1.8-9 that there cannot be more than one physical world. As a corollary in 1.9, he infers that there is no place, vacuum or time beyond the outermost stars. As one argument in favour of a single world, he argues that his four elements, earth, air, fire and water, have only one natural destination apiece. Moreover they accelerate as they approach it, and acceleration cannot be unlimited.
However, the Neoplatonist Simplicius, who wrote the commentary translated here in the sixth century AD, tells us that this whole world view was to be rejected by Strato, the third head of Aristotle's school. At the same time, he tells us the different theories of acceleration in Greek philosophy. The great Aristotelian, Alexander of Aphrodisias, evidently asked why one divine mover should not move several worlds. As regards Aristotle's other question, the finitude of place and the absence of any place beyond the outermost stars, Alexander had to confront the objection that you could surely try sticking your hand out further. He replies that you cannot extend your hand into what is non-existent, and he also raises objections to impossible thought experiments. Simplicius, however, shows that these had been common currency since Plato and Aristotle.
When Aristotle says that there is neither time nor place beyond the heavens, Simplicius, disagreeing with Alexander, takes Aristotle to be referring to the divine intellects which inspire movement in the heavens. In that case he may be saying that they are divorced from time altogether.