i have heard that buddism also says that multiverse exists. So, i want to ask something. Before few weeks, i saw two dreams in which I was totally aware of myself and at that time at those places, i can clearly feel that whatever I was experiencing, they are Real. In other word, if somebody would have come at that time and told me, this is your dream, than i would have laughed to much. In other words, I can still remember all the detail of that place(dream) and time, the detail of my hands etc. How can this be possible? As I've heard that worlds are just state of mind, similarly dream also. So does that makes, the dream world also as a real world, if a person is always their? Can I again feel such experience? That was very cool, I can still remember that. Before sleeping that night, I was thinking about how multiverse is possible, which I think sometime a because these things are very cool, specially from spirtual path. Were those two of the universe(world) among infinite other universe?
It is possible that our “dream world” could be a window to our “mind plane”. Our past memories of even past lives could live within us in the “näma thalaya” or the “mind plane”. It is not storage in a physical device like a tape. Mind plane is devoid of any material things, it is all “näma“. It can be thought of as in a “different dimension” - this mind plane that we ‘see’ through our “dream world”.
When we dream, we can “hear”, “see” and “do” things but it is all “näma“. When we “play back” memories, it is somewhat like seeing a dream. If we have a strong memory of some event, even from many years ago, we can recall it in our mind instantaneously. We just think about it and we can “see” it plays back with sounds and the background just like it happened. Our minds can connect to the “mind plane” and recall things without a delay. If our brain is the “transmitter” and “receiver” in communications with the mind plane, then as we get old, the “recall power” would get diminished. Meditation may help keep the brain healthy as we grow old.
As per the Teachings the universe is infinite in time and space. Infinite in space means length of the universe, width of the universe or number of solar systems (lokadhātu) in the universe are infinite. In this sense if you use the term “multiverse”, it may not be incorrect. The following is taken from ‘Attakata” Commentaries.
“The portions which consist of one billion solar systems are called “Thri Sahashri Loka Datu” (trisāhasra-mahāsāhasra-lokadhātu or great trichiliocosm, roughly equals to the galaxy in science).
A collection of 1000 solar systems are called “Sahashri Loka Dhatu”(sāhasra-cūḍika-lokadhātu or small chiliocosm). A collection of 1000,000 solar systems are called “Divi Sahashri Loka Dhatu”( dvisāhasra-madhyama-lokadhātu, or medium dichiliocosm).
After solar system being made it will be stable for some time, after that it will be destroying and it will be made again. The time taken to one of this cycle is called “Maha Kalpa(great kalpa)”. Maha Kalpa is divide in to four equal portions those are time of solar system formation ( Sanwatta Kalpa), time of existence( Sanwatta Sthayi Kalpa), time of destruction(Wiwatta kalpa) and time of emptiness(Wiwatta Sthayi Kalpa). Each one of these time interval is called as an “Asankya Kalpa”. So that one Maha Kalpa is equals to four Asankya Kalpa. One 64th of a Asankya Kalpa is called Antah Kalpa.
31 Planes of existence coming together is one universe. There are infinite similar universes according to the Abhidhamma. This may be similar to multiverse but unlike in Sci Fi there are no duplicates of beings and duplication of events as per my understanding. Generally rebirth is within the universe but there are times beings can be reborn in intergalactic space / hell which are the coldest places every. Such being may end up in other universes. The universe we live in is a lucky place since it is here a Buddha appears. So only the lucky beings inhabit this universe through there are infinite such being in the universe. There are infinite being in each universe. The cycles of creation and destruction in each universe may not be the same as in such universes may not be habitable. Generally I would believe even with psychic powers you may not know the bounds of the universe of see beyond this universe. Perhaps only The Buddha and a few of the great disciples may have managed to do this.
According to Buddhist teaching you can experience the following worlds by practicing meditation (Jhana) except States of Deprivation (apaya).
A multiverse isn't a finite concept (since the number of probabilities of splitting a universe is countless). Similarly, some theories state that all state exist but come to realization based on the observer. You can, at the risk of going against what Buddha advices, go ahead and think in ways such as such States come to existence based on the choices we make. Thus it's still Karma, and such States are just realization of choices we make.
This kind of thinking is clearly detrimental for realizing dhamma according to Buddha. Buddha States clearly that the world, multi or single, starts with our six senses and ceases to exist once we are no longer born. Maybe that gives you a hint on how the six senses, accompanied with inputs, produces vingnana, which Buddha calls an illusion (thereby probably making a multiverse an illusion too) and tricks you into contemplating useless subject matter.
The Blessed One said, "What is the All? Simply the eye & forms, ear & sounds, nose & aromas, tongue & flavors, body & tactile sensations, intellect & ideas. This, monks, is called the All.  Anyone who would say, 'Repudiating this All, I will describe another,' if questioned on what exactly might be the grounds for his statement, would be unable to explain, and furthermore, would be put to grief. Why? Because it lies beyond range."