Question

What is the big bang theory? last one evidence in support of this theory.

Answer 1

Hint: I offer a resume of why scientists believe the large Bang theory. This might help in chasing down, via the web, the complete story. Within the late 1800s and early 1900s, it had been thought that the Milky Way was the whole Universe. Religion was still paramount. Atheists generally and Darwin, especially, were persona non grata.

Complete step by step answer:
The broadly accepted theory for the origin and evolution of our universe is the explosion model, which states that the universe began as an incredibly hot, dense point roughly 13.7 billion years ago.
These three observations are
the expansion of the universe as measured by the redshift of sunshine emitted from galaxies
(2) the existence of the cosmic background and
the relative amounts of hydrogen, helium, and deuterium within the universe.
The leading lights in astronomy were members of The Royal Society and being religious was virtually compulsory. This was an inheritance intended to honor the memory and recognition of the genius of Sir Newton, a particularly religious man. He reigned as its President for twenty-four years - 1703 until his death in 1727. His impact in setting, as a fact, the assumption that Almighty God was the arbiter of science, had resonated within the Society for 200+ years when, in 1929, the famed American astronomer, Hubble confirmed the existence of other seemingly vastly distant galaxies. The Universe was born.

Note:
A phenomenon, described as Redshifted light, had recently been observed. it had been thought to mean that it signaled the high-speed recession of distant galaxies. Hubble, at that point [1929] thought that it had been the foremost likely interpretation.