A puzzling thought about the Big Bang & after

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Discussion Overview

The discussion revolves around the nature of the Big Bang and the observable universe, particularly the implications of light travel time and the limits of our observational capabilities. Participants explore concepts related to the formation of galaxies, the cosmic microwave background (CMB), and the potential for detecting earlier cosmic events through neutrinos and gravitational waves.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant notes that observing distant galaxies allows us to see the universe as it was in the past, suggesting that if we could look far enough, we might glimpse the conditions before galaxy formation.
  • Another participant emphasizes that the universe was opaque for the first 400,000 years after the Big Bang, and that the CMB represents the limit of our observable universe from that time.
  • Some participants argue that the concept of "before the Big Bang" is contentious and straddles the line between scientific inquiry and theological debate.
  • It is mentioned that while electromagnetic astronomy limits our observations, neutrinos from around 2 seconds after the Big Bang could potentially be detected, offering insights into earlier cosmic conditions.
  • Participants discuss the theoretical possibility of detecting gravitational waves from the early universe, which could provide further information about events preceding the CMB.
  • There is a recognition that various detectable phenomena from the early universe carry signatures of the physics that existed before their emission.

Areas of Agreement / Disagreement

Participants generally agree on the limitations of electromagnetic observations and the significance of the CMB. However, there is contention regarding the interpretation of "before the Big Bang" and the implications of detecting earlier cosmic phenomena, indicating multiple competing views remain.

Contextual Notes

The discussion highlights the unresolved nature of certain assumptions regarding the Big Bang and the definitions of "before" in a cosmological context. The limitations of current observational technologies and methodologies are also acknowledged.

Jussi
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The following started to puzzle me:

I heard George Smoot talk on design of the universe. He made the point that when we look far into the space, to distant galaxies, we see these galaxies "happening" really long time ago, since the speed of light is what it is. That the universe we are looking at is a kind of time machine in that sense. And that if we could look far enough, we could actually see what there was before galaxies were formed. That could give us a hint of a process by which they were formed.

Now if we could really look as far as is the distance that light travels in a time since the Big Bang (that is, to sense these photons, this radiation that was emitted then and reaches us now), would we not see the "moment of the Big Bang" itself? But then, if Bing Bang "came" from a "particle" or "focus" immeasurably small, wouldn't that place 13,7 billion light years away be right here, and not the far end?
 
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In the first 400,000 thousand years following the big bang, the universe was opaque. The remnants of the end of that time, called the surface of last scattering, is what we see as the CMB and that is as far back as we can see.

As for "before the big bang" that is a HIGHLY contentious subject that leads to arguments that are more theological that scientific. By that, I do not mean that they are necessarily religious in nature but that they, like all religion, are not falsifiable and therefore are not science.
 
phinds said:
In the first 400,000 thousand years following the big bang, the universe was opaque. The remnants of the end of that time, called the surface of last scattering, is what we see as the CMB and that is as far back as we can see.

This is the main point, and is true of all electromagnetic astronomy. However, you can detect neutrinos, which have a cosmic neutrino background from around when the universe was 2 seconds old. And, at least theoretically, you could detect gravitational waves from the early universe to probe what's going on, which would get you even further back in time.
 
Nabeshin said:
This is the main point, and is true of all electromagnetic astronomy. However, you can detect neutrinos, which have a cosmic neutrino background from around when the universe was 2 seconds old. And, at least theoretically, you could detect gravitational waves from the early universe to probe what's going on, which would get you even further back in time.
Plus the various things we can detect from the early universe leave signatures of the physics that came before their emission.
 
Chalnoth said:
Plus the various things we can detect from the early universe leave signatures of the physics that came before their emission.

This is a good point, and one that I need to do a better job of keeping in mind. Thanks.
 

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