Standing in nothingness before the Big Bang

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Discussion Overview

The discussion revolves around the hypothetical scenario of experiencing events before and during the Big Bang, as well as the nature of gravitational and light signals from astronomical events like supernovae. Participants explore concepts related to cosmology, theoretical physics, and the implications of observing phenomena in the universe.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant questions the feasibility of standing in "nothingness" before the Big Bang, suggesting that if one could stand there, it would not be true nothingness.
  • Another participant reflects on the challenge of conceptualizing events in the universe, particularly when considering the limits of human understanding and the nature of space-time.
  • Some participants discuss the sequence of experiencing gravitational effects, light, and gas from the expanding universe, noting the uncertainty in how these would be perceived.
  • A participant introduces the idea that in the case of a supernova, gravitational waves and neutrinos may be detected before visible light, depending on the type of supernova and the distance from the observer.
  • Further elaboration on supernova types, particularly core-collapse and Type 1A supernovae, is provided, highlighting their different mechanisms and implications for detection of signals.
  • There is a mention of the importance of formulating questions correctly in physics discussions, with some participants emphasizing the need for clarity in thought and expression.

Areas of Agreement / Disagreement

Participants express a range of views, with some agreeing on the challenges of conceptualizing pre-Big Bang scenarios, while others debate the nature of signals from supernovae. There is no clear consensus on the initial question regarding the experience of events before the Big Bang, and discussions about supernovae reveal both agreement on certain aspects and ongoing questions.

Contextual Notes

Participants acknowledge the limitations of current understanding regarding events outside the universe and the nature of nothingness. The discussion also reflects varying levels of familiarity with cosmological concepts and the challenges of communicating complex ideas.

Who May Find This Useful

Readers interested in cosmology, theoretical physics, and the nature of astronomical phenomena may find the discussion relevant, particularly those curious about the implications of signal detection in astrophysical events.

  • #61
timmdeeg said:
I am sceptical regarding this conclusion, as the matter density today is about 25% of the total energy density. The universe will approach an exponential expansion ...

I'm not sure what conclusion you find dubious, Tim. I'm saying that right now we have almost exponential distance growth at around 1/144% per My
And eventually in future we will have exponential growth at 1/173% per My (according to standard cosmic model).

Maybe the the word "almost" is too vague for you. It is vague! I think you would like to see a TIMETABLE for the decline in percentage growth rate from 1/144 to 1/173 and that is easy to supply. Just google "lightcone cosmological calculator" and look at the column labeled "R" for Hubble radius.
As that increases from 14.4 to 17.3 the percentage rate declines accordingly.

You can compare that with the "T" column which gives the time since start of expansion, i.e. age.

To get better time resolution, first click "set sample chart range" and then "calculate"

that will give a longer table with more gradual increase from today's 14.4 to eventual 17.3.

It also gives a substantial chunk of the past. You can see for instance that the distance growth rate was approximately 1% per My back in the year 67 million. that is what the first row of the table says (if you have pressed "set sample chart range")

If googling does not work, here is the link:
http://www.einsteins-theory-of-relativity-4engineers.com/LightCone7/LightCone.html

I also keep the link in my signature, it's handy for a LOT of purposes. You get to set the parameters of the table.
 
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  • #62
marcus said:
I'm not sure what conclusion you find dubious, Tim. I'm saying that right now we have almost exponential distance growth at around 1/144% per My
And eventually in future we will have exponential growth at 1/173% per My (according to standard cosmic model).

Maybe the the word "almost" is too vague for you. It is vague! I think you would like to see a TIMETABLE for the decline in percentage growth rate from 1/144 to 1/173 and that is easy to supply. Just google "lightcone cosmological calculator" and look at the column labeled "R" for Hubble radius.
As that increases from 14.4 to 17.3 the percentage rate declines accordingly.
Thanks marcus and congratulation to you and Mordred, this table is very helpful. I haven't realized it till now and for sure will be busy with it from now on. And I agree regarding the development of 1/R , we are now already relatively close to exponential expansion, though it will take another 78 Gy to reach R = 17.2999, corresponding to an almost exponential expansion. Hereby I use 'almost' only in the sense to not hide that the approach is asymptotic.
 
  • #63
Chalnoth said:
Once the matter density goes to zero, the expansion will be exponential, no asymptotic about it.

What is asymptotic is the approach of the matter density to zero.
It seems curious. "Gegen Null gehen" translated into English means "approaching zero", so, seems different from "goes to zero", as I used it wrongly by translating directly. I appreciate your comment.
 

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