Some Layman Cosmology.

[xelasnave]

Thanks Bill.
I had not watched that video until now because I thought I knew what it was going to cover...it was as I expected and was aware of the propositions outlined although it did raise another question for me...the 43 million light year size was of what we now see as the observable universe and it would seem that the actual size of the universe at 380,000 years is not mentioned...so my question as to what the size of the universe was at 380,000 old remains unansweredit seems...the actual universe must have been bigger than 43m light years when 380,000 years old...
Thank you again but I still dont know how big the grape fruit size universe (its size after inflation) grew to in 380,000 years ... or does all this indicate that the "atom" size universe is the portion we observe that grows to the observable universe and that there may have been much more hot and dense stuff than the atom size they talk about...
Alex

[xelasnave]

I have been looking for an answer to my question but can not draw a conclusion as to how big the universe was at 380,000 years..it seems to be 43 million but I am not confident that refers to the size of all the universe or to just that part we today call the observable universe.
Is anyone able to ppint to something that may establish the size beyong doubt..according to BBT.
AS I said my interpretation so far is the 43 million may only refer to todays observable universe...what I want to nail down is ..the universe grew from the size of a grape fruit in 380,000 years to the size of?????
Alex

[cwjohn (Chris)]

Much confusion here.

The size of the current universe is 93 Billion (not million) light years in diameter. This is the size of the observable universe. There is no reason to think the actual universe is actually far larger.

The so called singularity from which the universe started was a region of extremely low entropy. There is no reason to think this was necessarily a singularity but could have been part of a much larger region. However, the term "started" is probably a misnomer as there is no reason to think that "Time" has any meaning in the context of this start point. Further, the energy of this region was so high that the Higgs field could not be creating mass so the intuitive concepts relating to mass and its behaviours cannot be applied to this epoch.

Inflation infers a high scalar field applied for a very small time (far less than a second) such that a universe was created out of the low entropy region which explains the CMB we see today. It would be fair to say that the epoch of inflation remains contentious but nevertheless the majority of cosmologists support it pending any other reasonable explanation for the CMB we see today.

After inflation was complete, the universe expanded as per the standard Friedmann equations and our understanding of the general relativity, the four forces and their explanation via GFT, as well as the standard model of particle physics and also the laws of thermodynamics. A plethora of observations support these theories which range from 50-100 years in duration. Add the exhaustive study of the CMB and Hubbles constant and the big bang theory post a fraction of a second is virtually irrefutable to anyone who studies the science.

Our current best bet for epoch of reionisation is in a timeframe of 200K to 400K years but certainly based on CMB data complete after 400K years. New telescopes like the SKA will enable us to better understand this region in the future.

Size of the universe at any time can be calculated from Friedman equations. My understanding of the math at 380K gives the size of the Universe at 380K at 85 million light years diameter, but you would have to confirm this with someone who is better at the math than me.

This is a complex subject. I remember attending a lecture series that lasted 10 1 hour sessions in which the math relating to the big bang was studied in detail. I still have my notes somewhere, but I remember that at the end a very large whiteboard was filled with many tiny equations.

Modern physics stopped being intuitive when quantum mechanics was discovered 100 years ago and even less so when Quantum Field Theory was discovered 50 years ago. The human mind is simply not equipped to understand these concepts without the associated math. The greatest intuitive mind the world has ever seen (Einstein) has extreme difficulty intuiting general relativity until someone else walked him through the math involved. Of course he rebelled against quantum mechanics famously stating that "God does not play dice" as QM defines statistic probabilities of the outcome of the collapse of any given wave function which is probably as counter intuitive as you can get.

As I said the big bang, like evolution, is a complex subject, which explains why a significant number of people do not accept it. Alternative explanations are more easily accessable. Personally, I have no problem with this at all. Where I have a problem is with people who claim to accept science and criticize those who do not, yet they have no real understanding of the science involved in any given subject, yet nevertheless make unsupported claims based on nothing more than a crude understanding of the world.

[xelasnave]

Hi Chris
I was aware it was billion not million so that was a case of thinking one thing and typing another.
And thank you so much for taking the time to help as I certainly appreciate you doing so.
It is perhaps impossible to understand without the math but I feel the math must indicate a particular chain of events and surely these must be understandable at some level..even mine.
And I make no bomes about my lack of understanding of the finer points nevertheless the picture that unfolds seems to tell us that the universe came from something incredibly small and grew to something incredibly big and although one can point to physics being something not intuitive, which I can accept, I still find the proposition unacceptable ...and so I demand science make other findings that suits my beliefs☺.
I thought however the observation of the "flatness" suggested the universe "must" be very much larger than the observable universe... and reading about these matters I have formed the impression that it is generally accepted that the universe is much larger than the observable universe...and if you think about it the CBMR is as far as we can observe..that fits the theory but I wonder if there could be another way of interpreting such...
And as I have admitted any arguement from incredulity offends the logical fallacy rules and I know that is where I am coming from...and as I think I may have indicated I simply dont like any universe that requires a starting point...hints too much at creation is my unsupported belief...
And I dont think I would be alone..certainly when the BBT was presented that was the concern of those supporting the steady state model as I understand the history.
Again thanks for your help.
Alex

[xelasnave]

Thanks Chris I certainly appreciate you taking the time to help.
I knew it was billion but I typed million.
I thought the flatness indicated the universe is much larger than the observable universe.
Thanks again..I typed a much longer reply but hit "return to previous post" and lost the lot unfortunately..still I wanted to thank you and mention the flatness and that the universe "must" be larger ...that observation was something I read someplace but forgot so I cant offer authority.
Alex

[xelasnave]

Hey the post I thought was lost is here. ...sorry for the confusion.
Alex

[xelasnave]

Re size of universe follow up.
I watched a Brian Cox video and he said they believe the universe is bigger than the observable universe but did not indicate how big.
Alex