Is Big Bang Theory the only one to explain the creation of the Universe?
I have read about Big-Bang Theory explaining the creation of Universe. Is there no other theory to explain the creation of Universe?
If there is another theory please explain it to me.
I will appreciate your help
The big bang model$^{1}$ is an attempt to explain a host of observations that tell us how the universe evolved from its first fraction of a second onwards.
It started off by being grounded in fundamental and rather well understood physics (General Relativity, particle physics and nuclear physics at relatively low energies). The model itself has evolved and become more complex in response to new, more detailed observations and has had to add new, poorly understood phenomenological features (incorporating dark energy and dark matter, sometimes referred to as the $\Lambda$CDM model) to remain consistent with those observations.
Whilst the big bang model is a means to describe the past, present and future development of the universe, it does not have the fundamental status of a theory. Notably, it does not explain the creation or origin of the universe.
None of this really answers the question. There are lots of ideas and speculations about how the universe was created, but none of them can claim to be a "theory".
$^1$ Note there is a difference between a theory and a model. The latter is set up to explain a specific set of observations or a specific scenario; whereas the former is much broader and fundamental. See also What is the difference between a "model" and a "theory"?
"Multiverse" theories provide for universes (including our own) to be "local": There is no way to escape whichever one that all of us occupy, because such "local universes" are "causally separated" from each other, with the scales of space and time differing so greatly between them that we cannot travel from one to another, either because we would not fit into those in one spatial direction from our own, or because processes of subatomic decay (that have already been observed) would prevent both us and any of our conceivable descendants (even including robotic beings into whom our nervous systems might've been transferred) from lasting long enough to interact with whatever vastly larger inhabitants they might contain. The latter is the situation characterizing the Conformal Cyclic Cosmology mentioned earlier, and the former is the situation characterizing some "bouncing" cosmologies, which are generally "inflationary", meaning that each "locality's" Big Bang is almost exponentially more intense at the beginning than it had originally been thought to be, but tapers off into the nearly inertial expansion that we see as having occurred relatively nearby (but far outside our solar system) today.
The most popular of the bouncing cosmologies may be Nikodem J. Poplawski's "Cosmology with torsion", which is described in a paper by that name, along with many others he's written between 2010 and 2020, all available free on the "Arxiv" website maintained by Cornell University: Some of them have also been carried in the printed journals endorsed by PSE.
In "Cosmology with torsion", Poplawski describes it as "an alternative to cosmic inflation", but it's generally considered to be a version of inflation, whose older and more plainly "mainstream" version depends on a field of subatomic particles visualized by Alan Guth, who, in the 1980's, greatly simplified the original Big Bang theory by postulating such a field, which would have caused the spatial expansion (the "bang" itself), before deteriorating, at different times in the different sorts of localities I've mentioned, into the subatomic particles (mainly photons and electrons) that we see today. Although the primordial "inflaton" particles would have had some characteristics similar to the Higgs boson, the chances of any one of them being observed today would plainly be extremely low.
As you mention a creation event, it would be the local big bang in the inflationary cosmologies I've just described: Poplawski's cosmology situates each of the local big bangs as occurring in one or another of the black holes for which much astronomical evidence has accumulated. (That evidence, however, only sustains the existence of the black holes themselves, not whatever might be going on "inside" them.) His theory is more complex, mathematically, than Guth's, although simplified plain-English descriptions of it may seem more plausible to laypersons, such as myself. In such descriptions, the spin of fermions materialized through the gravitational field of a star collapsing, after the nearly complete expenditure of the nuclear fuel whose energy had provided the outward pressure that had previously resisted that collapse, interacts with the spin of the much larger stellar fermions themselves, with the interaction reversing and accelerating the trajectories of the newly-materialized fermions outward to form a local universe, within the black hole, whose shape is analogous to a three-dimensional version of the surface of a sphere, and with that local universe thereafter continuing to expand more-or-less inertially, although much more slowly than the larger-scaled "parenting" local universe, within which the star that had eventually collapsed into the black hole had once formed, would itself be continuing a much larger version of just such an expansion: In effect, new particulate matter on a smaller scale is created in a reversal of processes involved in nuclear fusion, with some concentrated remnant of each collapsed star's original matter perhaps remaining at the center of its volume.
Because the Borde-Guth-Vilenkin Theorem of 2003 requires that the inflationary (i.e., almost exponentially rapid) spatial expansion (which greatly simplifies the formation of the elements in the Periodic Table) must have either occurred in a single temporal direction or in a continuous balancing between expansion and contraction, Guth's version of inflation may seem more plausible in a society (ours) that was raised with some familiarity with a one-and-only big bang, which is the concept that prevailed in cosmology from the 1950's into the 1980's. It is also sometimes (incorrectly) identified with spiritual beliefs in general, although, even in the West, at least one major religion considers that time has always existed, which is a possibility consistent with the "balancing" mentioned in my previous sentence.
I am no expert in cosmology, but I do know about shockwaves and the Big Bang is just a shockwave in a compressible medium. It is fundamental that shockwaves lose information, and so observations made after a shock has passed allow only a limited reconstruction of what went before. There are apparently solutions to the Einstein equations that describe an explosion inside a pre-existing medium, and the post-shock properties are said to be indistinguishable from those of a shock that propagates into nothingness. See Smoller, J. and Temple, B., 2004. Cosmology, black holes and shock waves beyond the Hubble length. Methods and Applications of Analysis, 11(1), pp.077-132. I believe that this is not taken seriously by cosmologists but I dont know why.
The Big Bang model doesn't actually explain the creation of the universe. It only explains what happened afterwards. In Alan Guth's words, it did not say "what 'banged', how it 'banged', or what caused it to 'bang'".
Explaining the moment of creation itself is a separate question that, to my knowledge, is very speculative because we don't have solid experimental evidence for physics theories that work at those energies. If you're interested in speculation, then take a look at Eternal inflation. At the popular level, look at Alexander Vilenkin's book Many Worlds In One. At the more technical level, look at Alan Guth's paper Eternal inflation and its implications or Sergei Winitzki's monograph Eternal Inflation.
