"multiverse" And its not really a theory as (so far) its untestable.
According the the Multiverse Theory, our universe exists as a bubble among a plane of countless other universes, though that's not the limit to how many there are. This plane, which contains many universes, is just a bubble itself, floating in a sea of other bubbles. This sea is just a bubble, too, on a plane of other bubbles, each containing planes, seas, bubbles, planes, and bubbles. According the the Multiverse Theory, there are an infinite number of other universes.
The existence of multiple universes is a theoretical concept in physics, such as the multiverse theory. Some formulations of this theory suggest the possibility of parallel universes or alternate realities, but currently, there is no empirical evidence to support the existence of other universes beyond our own. It remains a topic of ongoing scientific investigation and debate.
I believe that that is true even though we can not travel there.
A group of universes is commonly referred to as a "multiverse." This concept suggests that there are multiple, possibly infinite, universes that exist parallel to each other, each with its own distinct laws of physics and properties. The multiverse theory is often discussed in the context of cosmology and theoretical physics, particularly in relation to string theory and quantum mechanics.
That is a theory. That black holes may warp space and time, to fit an an entire universe inside it.
The theory of extra dimensions, infinite universes, the theory where the Big Bang occurred when a membrane of a different dimension crashed into our membrane, gravitons, the theory that gravity seems weakest because gravitons, (open superstrings) can leak through other dimensions and universes. But the problem was that there were 6 theories, but later they found out that the 6 theories were 6 different point of view of the real theory of everything: M-Theory
At the present time, nothing direct. We have no evidence for the existence of any universe other than the one we happen to live in. The existence of others is purely speculation at this point. However, the existence of other universes -- an almost infinite number of them, most them completely hostile to intelligent life -- would answer the question of how this universe, that we happen to live in, seems to be so well "balanced" so as to permit us to be here. If there are, indeed, an infinite number of universes, then it should be no surprise that at least one of them would allow intelligence to develop within it. The other universes simply have nobody getting upset that they can't exist there.
Simple answer: we don't know. 10^500 is the number of permitted solutions to the equation that is the basis of M-Theory. In other words, M-Theory not only predicts a universe that looks exactly like ours, but it also predicts 10^500 other kinds of universes. It's as if someone wrote down an equation for the current assets of Google Inc ("CA(G)") as CA(G) > $1 and took note that this formula correctly "predicted" Google's assets as of 2014 January 1. At the present time, we don't yet know if 1) M-Theory is anything more than a mathematical oddity with no connection to reality. 2) There are other universes out there. 3) Those other universes also obey the rules of M-Theory. 4) Those other universes -- if they exist at all AND obey M-Theory -- are like ours, or are (instead) a completely different solution to the formula. 5) There is one to one correspondence between "permitted solution" and "other universe." For all we know, 40% of all other universes are like ours, 17% are solution 175,023,985,254....998 to the M-Theory Equation, and the rest are "other solutions." Right now, all we have is speculation about the above questions. There may be one Universe, there may be 100 trillion, there may be 10^500, there may be an infinite number. We just don't know. Perhaps future minds can answer these questions.
The parallel lind is Basulinds answer to the multiple universe theory. Basulind can destroy all universes with multiple linds covering the lyers of universes in super-string theory. Basulind has devised a deadly WMD lind that is intertwined in super-strings to give super-lind-string theory!
It is thought that there are other universes that look like ours. It is also been suggested that there are an infinite number of universes.
There has been a lot of speculation about other universes, but it is just that: speculation. There is no firm evidence that other universes actually exist. Nor, for that matter, is there any firm evidence that other universes DON'T exist.
there is a theory that there are. the choice is up to you! Einstein said that Schwartzchild wormholes may be a gateway to alternate universes the math is quite complicated but on paper it is quite possible ------------------------------------------------------------------------------------------------------------ Theoretically, we do have parallel universes, and some [although not alot] of evidence supporting this theory has come up. Actually, even though the notion seems entirely ludicrous, there is some serious math behind the parallel universes theory or the many-worlds interpretation.