Post by: Harri on 25/11/2021 09:33:58
Post by: Halc on 25/11/2021 14:14:55
Is it now agreed that cosmic inflation occurred before the big bang and if so does it make a big difference to our original understanding that inflation occurred after the big bang?From what I can tell, there is but the one mainstream model which is not ambiguous on the ordering of the epochs. The only difference is semantic: which exact moment in time (before inflation, and how much before, or after it) to assign the label 'Big Bang'.
It is legitimately questionable since time as we know it, measured in seconds and such, isn't really a meaningful measure when describing the inflation epoch. Hence the reluctance to assign 'time zero' to the point at which things were most compact.
Post by: Origin on 25/11/2021 14:26:16
Is it now agreed that cosmic inflation occurred before the big bangThat's news to me, do you have a source for that?
Post by: Harri on 25/11/2021 15:22:25
Post by: Origin on 26/11/2021 13:46:30
'is it now agreed that cosmic inflation occurred before the big bang?No, of course not.
Also is there a reliable source of information I could access regarding this point?https://wmap.gsfc.nasa.gov/universe/bb_cosmo_infl.html (https://wmap.gsfc.nasa.gov/universe/bb_cosmo_infl.html)
Post by: Halc on 26/11/2021 15:33:35
The link is pretty accurate. I've had some from nasa that were dumbed down to the point of being wrong, but this doesn't seem to be one of those.'is it now agreed that cosmic inflation occurred before the big bang?No, of course not.Also is there a reliable source of information I could access regarding this point?https://wmap.gsfc.nasa.gov/universe/bb_cosmo_infl.html (https://wmap.gsfc.nasa.gov/universe/bb_cosmo_infl.html)
The article actually seems to support Harri's query about the term Big Bang being applied to an event other than the earliest epoch, or most initial state where the universe was most compact.
Quote from: nasa
The Inflation Theory [...] proposes a period of extremely rapid (exponential) expansion of the universe prior to the more gradual Big Bang expansion, during which time the energy density of the universe was dominated by a cosmological constant-type of vacuum energy that later decayed to produce the matter and radiation that fill the universe today.This wording puts the label 'Big Bang' on the relatively linear expansion phase that commenced after the inflation.
Post by: Origin on 26/11/2021 16:04:25
The article actually seems to support Harri's query about the term Big Bang being applied to an event other than the earliest epoch, or most initial state where the universe was most compact.I think it is too bad that you are encouraging his misunderstanding. That is tantamount to saying inflation occurred before the creation of the universe.
The big bang occurred at T=0. Our current physics breaks down at a time less than T =
sec. The inflation period started at T = 
sec. Inflation clearly did not occur before the big bang.Post by: Halc on 26/11/2021 16:40:39
I think it is too bad that you are encouraging his misunderstanding.But I've seen the community use the term in the same way. It's just a label, and I think the cosmologists put the label where it has always been in the regular big-bang theory, which is the commencement of the (more or less) linear expansion of space. Inflation theory added more before that, and they didn't want to move the label.
Quote
That is tantamount to saying inflation occurred before the creation of the universe.Not even the old big bang theory posited the universe as something created, or its cause. It only posited its evolution from the time when everything was more compact (but never finite in size).
Quote
The big bang occurred at T=0. Our current physics breaks down at a time less than T =If the label refers to T=0 on that scale, agree. But the nasa site does not seem to use your definition of "big bang occurred at T=0", and I've seem such conventions elsewhere. They perhaps use a different label for it.
Out of curiosity, if physics breaks down at
sec, how do they figure that number? How do they know it took that long to get to that point? I'm impressed that the theory is worked out in sufficient detail to account for seven orders of magnitude in age before inflation started. Perhaps that is the time necessary for all the causal interactions to occur before they all become permanently beyond each other's influence.
Post by: evan_au on 26/11/2021 21:28:40
Quote from: OP
Cosmic inflation, before or after the big bang?Most of the discussion seems to be centered on the Big Bang as a point in time, which can be compared to other points in time.
However, more generally, the Big Bang Theory is about the process which led to the universe as we see it today, which includes various phases such as Cosmic Inflation, production of subatomic particles and production of the current Cosmic Microwave Background Radiation (which took about 400,000 years). Somewhere in there is the mysterious process that gave us more matter than antimatter...
See: https://en.wikipedia.org/wiki/Big_Bang
Quote from:
if physics breaks down at 10-43 sec, how do they figure that number?That is when it is predicted that energy levels would have dropped enough so that the 4 forces that we know would have become distinct fields.
- As I understand it, there is theory of how the Electromagnetic & Weak nuclear force would have behaved as a combined entity. https://en.wikipedia.org/wiki/Electroweak_interaction
- But we still don't have a quantum theory of gravity, and gravity would have had a major impact in this environment.
See: https://en.wikipedia.org/wiki/Big_Bang#Inflation_and_baryogenesis