Below is the transcript^ of a question and answer video from the late, great Bhikkhu Samahita regarding Early Buddhism and the Multiverse.
^ As English is his second language, I have taken the liberty of changing a few words to make the text easier to read. Any errors are mine and mine only.
There are 31 worlds in this universe, according to Buddha’s teachings, are there other universes as well? Is there such a thing as the Multiverse?
Yes, there is, for many reasons.
The Buddha was asked, “Is there more than one universe?” (That corresponds to a universe in our language). And he said that there was an infinite number of universes.
There are other world systems (he called them) that contain their Buddhas and their deities.
He called these world systems a “Chakavara.” Chakavara means wheel…world wheel. A wheel is a round thing with something in the middle. It seems very likely that the correct translation of Chakavara (world wheel) is galaxy. But it’s not certain that this is so, but it seems to be.
In each galaxy, there is a system with Buddha’s appearing there and a corresponding set of 31 levels of existence in that particular galaxy.
Then, in a broader sense, there can be many different galaxies (there’s at least 100 billion in our universe now) but the Buddha spoke about these universes 2,500 years ago as something dynamic, the universe expands and then it contracts, and expands and contracts.
So, from a “Big Bang” there is a large expansion and then it holds still for a while and then it starts to contract and there’s a “Big Crunch.” This Big Crunch is followed by something you could call a “Nuclear Fire”, where everything is burned up, but not on all the levels of the 31 levels of existence.
So, some beings survive beyond the universe. On another level of time there can be existence staying there, at the Brahma level. They are not affected by the Big Crunch.
And this has some interesting correlation to some parts of modern cosmology that say that due to the “observer effect” of quantum mechanics, there has to be observers for a new universe to appear.
So, some people say that after the Big Bang there are no beings, but that’s not true according to Buddhism. It states that there are many beings after a Big Crunch and before the Big Bang. There are beings. There are observers that can “make things appear.” (See https://en.wikipedia.org/wiki/Observer_effect_(physics)).
So, the interpretive model in modern cosmology, which you could say is quite esoteric, seems to be confirmable from Buddhist theory.
So, if you envisage the multiverse as a very big sponge. While one universe over here (right hand side of the sponge) is contracting, another universe (left hand side of the sponge) is expanding. And this happens all over the place, kind of like a sponge. There’s contraction here and expansion there.
This has a very neat feature, if we take the whole system, there will be conservation of mass, there will be conservation of space, there will be conservation of energy, and there will be conservation of information. And this is very, very neat.
So, the sponge model of the multiverse seems more than likely.
The Buddha says, “Yes, there’s more than one world system, more than one universe. And there’s beings (alive) at the Big Crunch.” So that can be confirmed by what he says about this.