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Cosmology strives to produce models that accurately describe the past, present, and future of spacetime in our universe. The Big Bang theory is one such model, explaining how the universe expanded from an extremely high density and high temperature initial state.
The Inception
While the Belgian physicist and Catholic priest Georges Lemaître was the originator of the idea that the universe evolved from a single-point, the term ‘big bang’ was actually coined by astronomer Fred Hoyle on BBC in the 1940s with the intent of exemplifying the theory’s difference from the steady-state cosmology for which he was a proponent.
Perhaps the most common misconception of the ‘big bang’ is that it purports to be a theory describing the origin of the universe. In fact, the big bang theory is only a description of the origin of matter and the expansion of space from a point of infinite density known as a singularity, while saying nothing specific about the origin of time, space, or energy ( i.e. the universe). So while it is correct to say the universe started with a bang, it is incorrect that the bang started the universe.
The Argument
There are essentially three independent proofs of the big bang. The first of which is the observation of the galactic redshift, indicating the objects seen by our telescopes are collectively increasing in distance.
This universal expansion was predicted from General Relativity by Alexander Friedmann in 1922 and Lemaître in 1927, but it was the observations of astronomer Edwin Hubble that gave credence to the idea. Hubble observed that distant galaxies and quasars receded over time, as evident by the Doppler shift in the frequency of light emitted by these objects.
The second way the big bang may be proven is the cosmic microwave background radiation (CMBR), an omnidirectional microwave signal discovered in the 1960s. This is in-fact the residual radiation left over from the big bang which is still moving through the universe 13.8 billion years later. This radiation was predicted in the 1940s as a consequence of the big bang before any actual observation was made.
The third proof regards the particular manner in which matter in the universe has been created and distributed. In short, the model’s predicted mass values agree with observation, as do the predictions of stellar evolution and distribution throughout the observable universe.
The Status
It is the intersection of concordant facts provided by the redshift, CMBR, and baryon nucleosynthesis that provide such incontrovertible evidence for the big bang. The theory’s widespread acceptance in the scientific community has made it the pinnacle theory of cosmology and there remains no credible alternative hypothesis to the creation of the matter in our universe.
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