All of which leaves the biggest questions that Epicurus wanted to address, such as whether there is something outside of "this observable universe" that these physicists are talking about (something which implicitly might be "god") totally unanswered. That larger question is at least as important to our daily lives as it is to get a better understanding of fields.
From my perspective, Epicurus answered the question of "is something outside of 'this observable universe'" explicitly. The answer was yes. The cosmos (kosmos ΚΟΣΜΟΣ), from everything I have read, is akin to our idea of an "observable universe." I'm going to use K kosmos instead of C cosmos because we tend to define cosmos as the "universe" colloquially, but I want to get across the idea of the ancient kosmos. The kosmos is the world-system in which we live. The Library of Congress has a wonderful article on ancient Greek cosmology:
Important points:
- From the 5th c BCE, it was known we live on a sphere.
- "In this system the entire universe was part of a great sphere. This sphere was split into two sections, an outer celestial realm and an inner terrestrial one. The dividing line between the two was the orbit of the moon."
The other stars and planets were thought of as spheres, too, since even Epicurus wrote against people thinking the stars and wandering stars were gods because they were perfect spheres. So, it would have been theoretically possible to travel to other "worlds" - other spheres - without leaving our kosmos. See the diagram below...
So, that's OUR kosmos.
Epicurus also posited other kosmoi - other world-systems - that would be other kosmoi somewhere else in The All, the universe. Such as..
.
with, supposedly the gods residing in the metakosmos/intermundia/"the space between world-systems."
That's my perspective on how Epicurus envisioned The Universe. There is plenty of space "outside our observable universe." It's just filled with other kosmoi with their own worlds, animals, humans, and even philosophers.