TheDhamma wrote:The interpretation would depend upon what the Buddha meant when referring to the world and world system, perhaps just this world, perhaps this solar system, or perhaps the universe.
The Visuddhimagga explanation about world-cycles and the Buddhas-domain is not very clear. The translation is clumsy. But still, I think there is something to it that might shed light on this question:
"As respects, however, many destructions of a world-cycle etc., when a world-cycle is on the wane, that is known as the destruction of a world-cycle; when it is on the increase, that is known as the renovation of a world-cycle. Here destruction includes the continuance of destruction, from being its beginning, and renovation includes the continuance of renovation. Accordingly the four immensities of the following quotation are all included: "There are four immensities, O bhikkhus, to a world-cycle. And what are the four? The destruction, continuance of destruction, renovation, and continuance of renovation."
Now there are three destructions: the destruction by water, the destruction by fire, the destruction by wind. And there are three boundaries: the Heaven of the Radiant Brahmas, the Heaven of the Completely Lustrous Brahmas, the Heaven of the Richly Rewarded Brahmas. When a world-cycle is destroyed by fire, it is consumed by fire from the Heaven of the Radiant Brahmas down. When it is destroyed by water, it is engulfed by water from the Heaven of the Completely Lustrous Brahmas down. When it is destroyed by wind, it is demolished by wind from the Heaven of the Richly Rewarded Brahmas down. In lateral expansion it always perishes to the extent of a Buddha's domain.
Now a Buddha's domain is threefold: birth-domain, authority-domain, knowledge-domain. Birth-domain comprises ten thousand worlds; all these quake at various periods in the life of a Tathâgata, as, for instance, when he is conceived. Authority-domain comprises one hundred thousand times ten million worlds; over all of these extends the protective power of the Ratana-Sutta, of the Khandha-Paritta, of the Dhajagga-Paritta, of the Âtânâtiya-Paritta, and of the Mora-Paritta. Knowledge-domain is endless and boundless, and the passage which says, "Or as far as he may wish," means that the knowledge of a Tathâgata extends to any place or to any subject he may wish. Of these three Buddha-domains, it is the authority-domain which perishes; but when that perishes, the birth-domain perishes likewise, They perish coincidently, and they exist coincidently."world-cycles - Visuddhimagga (chap. xiii.)
The brahma realms are non-physical realms. Now if the universe collapses and the brahma realms are destroyed then this means that the whole physical universe collapses as well. Like they say in the Big Bang theory. The universe goes through cycles of expansion and destruction. The Visuddhimagga says that it is the authority domain of the Buddha that is destroyed when world-cycle comes to an end. The extend of this authority domain is 100 000 * 10 000 000 = 1000000000000 worlds. I think this number here is not a exact number but an illustration of an incomprehensible large domain.