# Big Bang vs Inflation?July 31, 2022 10:28 PM   Subscribe

I've recently been introduced to the idea that inflation existed before the big bang. I guess I'm having trouble understanding how we can have inflation before t=0. Is there any articles or overviews that would help me understand?
posted by Carillon to Science & Nature (5 answers total) 4 users marked this as a favorite

Best answer: This Forbes article explains it well.
posted by underclocked at 11:58 PM on July 31, 2022 [1 favorite]

Best answer: The short explanation is that there is no t=0, singularity. The Big Bang is the moment the initial conditions were right in order for the Universe of matter/energy to begin expanding. Those initial conditions were created by inflation which preceded that Big Bang. I believe Time itself is still a meaningful concept before this Big Bang and during inflation. As Siegel also explains, it is inflation which was responsible for lowering the entropy density but not entropy itself which was increasing during this time.
posted by vacapinta at 2:25 AM on August 1, 2022

Best answer: In the inflationary context, the term "big bang" is sometimes used to mean the "hot big bang", i.e., the cosmic "reheating" that occurs at the end of inflation. Basically, in order for the inflationary picture to be consistent with what needs to occur (working backwards) to give us the universe we observe, at the end of inflation a whole bunch of potential energy (in the inflationary picture, this energy is stored in the field that is driving the inflation) gets "dumped" into particle production, creating a hot dense soup of particles in the still-expanding (but not inflating) universe -- the classic "hot big bang". This does not happen at t=0; time is still meaningful during inflation. In fact I think that in the inflationary picture, there is no singularity before which there is "no such thing as time". [I am a physicist; I am not a cosmologist.]
posted by heatherlogan at 6:35 AM on August 1, 2022

Really high quality writing, great images, etc and etc.

I had no idea that Forbes is as good as that linked page seems to indicate.
posted by dancestoblue at 10:42 AM on August 1, 2022

dancestoblue: I had no idea that Forbes is as good as that linked page seems to indicate.

The article is good, but I’ve found Forbes to be a real mixed bag for some time. They seem to offer all kinds of folks a platform these days. This leads to a very inconsistent level of quality, including platforming some folks whose credentials and views are questionable, at best.
posted by syzygy at 3:43 PM on August 1, 2022

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