What does the Big Bang theory state?

The universe formed when a single massive star exploded, scattering matter in all directions The universe has always existed in its current form and will continue forever unchanged The universe began about 13.8 billion years ago in an extremely hot, dense state and has been expanding and cooling ever since The universe was created 6,000 years ago from nothing by an external force

Who coined the term Big Bang, and in what spirit was it intended?

Georges Lemaitre, who proposed the theory in 1927 and named it himself Fred Hoyle, during a 1949 BBC radio broadcast, used the term mockingly to contrast with his preferred Steady State model Edwin Hubble, who used the term to describe the sudden beginning implied by his expansion discovery Albert Einstein, who coined the term while working on the equations of general relativity

What is the Steady State model, and why is it now rejected?

The idea that the universe is static and not expanding, rejected by Hubble's Law The idea that the universe oscillates between expansions and contractions forever The idea that the universe is eternal and unchanging, with new matter continuously created to fill expanding space — rejected because the CMB and nucleosynthesis evidence favor a hot, dense early universe The idea that multiple universes exist simultaneously — rejected because no observational evidence supports it

What does it mean that there was no before the Big Bang?

Before the Big Bang, the universe existed as a static, cold cloud of hydrogen gas Before the Big Bang, another universe existed that collapsed, triggering ours Time itself began at the Big Bang — asking what happened before is like asking what is north of the North Pole Before the Big Bang, time ran backward — the universe is actually contracting from our perspective

What is the first pillar of Big Bang evidence?

The observation that all stars eventually die, implying the universe must have had a beginning Hubble's Law — the observation that galaxies are receding at speeds proportional to their distance, indicating the universe is currently expanding The detection of black holes, which require a hot, dense early universe to form The existence of the Moon, whose craters record impacts from the early solar system

What is the second pillar of Big Bang evidence?

The observation that the night sky is dark (Olbers paradox), implying the universe is finite The Cosmic Microwave Background — a faint glow of microwave radiation filling the entire sky, the afterglow of the hot early universe when it cooled enough for light to travel freely The discovery of dark matter, which requires a Big Bang to explain its distribution The aging of stars, which can be dated to show they are about 13.8 billion years old

What is the third pillar of Big Bang evidence?

The chemical composition of asteroids, which contain elements from the Big Bang Big Bang nucleosynthesis — the predicted abundances of hydrogen and helium from the first minutes match what is observed in the oldest, most pristine parts of the universe The radioactive decay of heavy elements, which constrains the age of the universe The formation of the first planets, which required a Big Bang to supply the necessary elements

What is the fourth pillar of Big Bang evidence?

The total number of stars in the observable universe, which matches Big Bang predictions The large-scale structure of the universe — the cosmic web of galaxies and voids — matches predictions based on quantum fluctuations in the early universe amplified by gravity The existence of black holes, which can only form in a universe that began with the Big Bang The rate at which the universe is accelerating, which confirms the Big Bang energy budget

Who first mathematically proposed that the universe had a hot, dense beginning?

Edwin Hubble, who proposed the theory based on his observations of galaxy recession Albert Einstein, who derived the Big Bang from his field equations of general relativity Georges Lemaitre, a Belgian priest and physicist who proposed the primeval atom hypothesis in 1927 and expanded it in 1931 Stephen Hawking, who proved the Big Bang had to have occurred using singularity theorems

Why does the Big Bang theory not explain what caused the Big Bang or what came before it?

Scientists have covered up the true cause of the Big Bang to avoid controversy The cause of the Big Bang is well understood — quantum fluctuations in a prior vacuum caused it The Big Bang theory describes the evolution of the universe from a fraction of a second onward — the initial singularity lies outside current physical theories The cause is not needed because the universe is eternal and the Big Bang was just a phase transition