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  • $\begingroup$ It seems you side on the "first moment of time" definition. Note that, as explained in the question, not all definitions of the Big Bang state that it is the first moment of time. BBN is also not considered a Big Bang per se, it is a separate event(s) happening moments after the Big Bang and is distinguished by the word "Nucleosynthesis". The two competing definitions are both valid since they both attempt to preserve part of the spirit of the original meaning of the term. They simply preserve different parts of the original meaning and, in doing so, become mutually exclusive. $\endgroup$
    – Jim
    Commented Oct 21, 2014 at 13:53
  • $\begingroup$ Ī side with mentioned “original meaning” and with neither of two “conflicting definitions”. Big Bang is a theory, also an era in the universe (a coordinate time started from presumed/extrapolated singularity) and, by synecdoche, early universe in general, certainly up to the end of nucleosynthesys and possibly beyond. Ī am unsure whether should the recombination be counted as one of Big Bang events: it is directly observable as CMBR. But all events not directly observed but predicted (or, more precisely, retrodicted) by the theory, should be counted as Big Bang events. But Ī am not an expert. $\endgroup$
    – Incnis Mrsi
    Commented Oct 21, 2014 at 14:16
  • $\begingroup$ The sum of events you refer too is now called the "Big Bang Era" and the description you provide is that of the old Big Bang Cosmology. The Big Bang itself as an event was and is defined as a moment of time. Whereas the Big Bang Events up to recombination are part of the Big Bang Epoch. Regardless, however, there are two competing definitions now because the introduction of inflation has made the old definition impossible. From your points, I gather you would much prefer the definition of the Big Bang as being after inflation. This allows you to group BBN etc under the umbrella of the Big Bang $\endgroup$
    – Jim
    Commented Oct 21, 2014 at 14:25
  • $\begingroup$ Nice update, I like the form of this answer, +1 $\endgroup$
    – Jim
    Commented Oct 21, 2014 at 14:32