For most of the 1900's it was the steady-state theory. In recent times it has been pretty much replaced by the big bang theory.
The first therory is that Earth was the centre of the universe.
The most widely accepted hypothesis, and indeed it has become a theory, is the Big Bang theory. Further information can be found in the related questions.
Big-bang theory
Creationism (believed by religious people)
I think there is one more that is scientific but I can't remember it.
The Big Bang
The Big Bang Theory
When the big bang theory started the universe, light was created.
Current scientific meaning of the word universe, is that it includes everything. So there is only one universe - The Universe However the new idea of String Theory is starting to suggest that there may be more than one universe, and so the meaning of the work universe may change in the future. The scientist Brian Greene is one of the leading physicist working on this theory. Science-teacher
It is difficult to estimate the current size of the universe because the universe curves back on itself. (Do not ask how it curves back on itself. The equations are in the Theory of Relativity by Albert Einstein.) Since no one can ever measure the distance to an edge, no way exists to determine the Universe's size.
The steady-state universe theory
The leading scientific theory regarding the start of the universe is a cosmological model called the "Big Bang", which asserts the universe started out compressed, very hot and dense, that visible matter in its current form was consequent to an outward explosion. Evidence to support the theory includes the currently observable expansion of the universe, and a residual background radiation apparent in all directions.
Big Bang Theory
The Big Bang theory is the current scientific theory used to explain the origin of the universe.
That's what the current theory indicates.
The Big Bang Theory
When the big bang theory started the universe, light was created.
Try Big Bang Theory. Universe started as a big explosion, which expandd rapidly etc
The prevailing scientific theory is that the universe started with the Big Bang.
it started because of the scientific theory of The Big Bang it started because of the scientific theory of The Big Bang
It is the majorly accepted scientific theory for how the universe began; what actually happened will never be known for sure.
A "no boundary" universe is a universe where the change in energy is positive or negative everywhere in the universe. Such a universe theory calls for everywhere expansion or everywhere contraction. The current central dogma in Astronomy is for such an expanding universe. The corrected Law of Gravity indicates that the universe is bounded and not expanding.
our planet earth has its own theory.... base on my scientific search, our planet started when the matter of the universe explode... and the left particles... started to grow with the help or the other elements of matter in the universe...