Short answers, pulled from the story.
Russian mathematician Alexander Friedmann derived equations from Einstein's field equations that suggested the universe might be expanding. This theoretical work stood in contrast to the static universe model favored by Albert Einstein at the time.
Ten years after 1922, which is 1932, Edwin Hubble published observations showing that galaxies were moving away from Earth at speeds proportional to their distance. This relationship became known as Hubble's law and provided the first empirical evidence for cosmic expansion.
The earliest phase of the universe lasted only up to 10^-43 seconds into the expansion, known as the Planck epoch. During this period, all four fundamental forces existed as one unified force with temperatures around 10^32 degrees Celsius.
Current measurements indicate ordinary matter makes up only 4.9% of total energy density according to Planck space probe data from February 2015. Dark matter accounts for 25.9% while dark energy comprises 69.1% of the universe's content.
English astronomer Fred Hoyle coined the term Big Bang during a March 1949 BBC Radio broadcast describing theories based on matter created in one big bang at a particular time. Hoyle explicitly denied that his phrase was meant pejoratively, though popular reports suggest he intended it as criticism of the explosive theory.