Looking back in time to the Big Bang

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Discussion Overview

The discussion revolves around the nature of the Big Bang and its implications for the structure and uniformity of the universe. Participants explore concepts related to the observation of the universe's earliest moments, the idea of the Big Bang as a non-singular event, and the limitations of observational cosmology.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that if the universe is uniform, observers looking in opposite directions could witness the universe at its earliest time, suggesting the Big Bang cannot be a point singularity.
  • One participant draws an analogy to sound waves, arguing that while a sound wave originates from a point source, its wave front spreads out in all directions, implying a similar nature for the Big Bang.
  • Another participant emphasizes the limitation of observational reach, noting that we can only see matter that light has had time to travel, which is currently about 46 billion light-years away.
  • There is a suggestion that all matter, including terrestrial matter, originates from the Big Bang, and that the universe appears uniform to all observers, regardless of their location.
  • Participants reference visual aids and analogies, such as the balloon analogy, to help conceptualize the expansion and uniformity of the universe.
  • Links to external resources, such as diagrams on cosmology, are provided to support the discussion.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of the Big Bang and its implications for the universe's structure. There is no consensus on whether the Big Bang is a point singularity or a more distributed event.

Contextual Notes

The discussion acknowledges limitations in observational cosmology, particularly regarding the finite speed of light and the implications for what can be observed from Earth. There are also assumptions about uniformity that are not universally accepted.

poeteye
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If the universe is uniform no matter in what direction you look , then looking in two opposite directions, two observers, if each looks far enough will see the Universe at its earliest time -- The Big Bang. Therefore, the event of the Big Bang cannot be from a point singularity. It does not exist in anyone (singular) direction, but can be observed in any direction you cast your gaze. Like the electron, then, the Big Bang must be "spread out" in an "orbit" around all that is. The concentration of matter around the time of the Big Bang "spread in all the furthest directions that you can see might be what causes the tug of matter toward it and away from any present observer. Couldn't it be that the universe is actually contracting outward toward the Big Bang instead of expanding as if away from a center?
 
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poeteye said:
If the universe is uniform no matter in what direction you look , then looking in two opposite directions, two observers, if each looks far enough will see the Universe at its earliest time -- The Big Bang. Therefore, the event of the Big Bang cannot be from a point singularity.

Can you explain that? A sound wave originates from some source which we usually consider to be a point source, yet the wave front spreads out in all directions. You can observe it from anywhere.

Also, note that "looking far enough" is a nice statement but without physical meaning: we can only see so far as the light has been able to travel so far.
 
CompuChip said:
... we can only see so far as the light has been able to travel so far.

That's right! Good point. We can only see matter which is 46 billion lightyears away from us, at present.

Because in the whole age of expansion (estimated 13.7 billion years) that is the farthest light has been able to reach.

It's good to think about those numbers and to help visualize you can try some of the basic visualization stuff in this sticky thread:
https://www.physicsforums.com/showthread.php?t=261161

It's basic cosmo one----if you have any questions or don't understand, just ask.

Keep in mind that all matter, including Earth rocks and our bodies, derives from what issued from the Bang.
And the farthest matter we can see----the stuff which is now 46 billion lightyears away at present---has by now presumably evolved into stars and galaxies and planets looking pretty much like our local neighborhood.
The assumption of uniformity covers them as well as us. The heavens to them presumably look very similar to ours. They too are uniformly surrounded, in all directions, by stars and galaxies.
The uniformity that poeteye mentioned means that all space is uniformly filled with matter, more or less evenly distributed----as far as we know there is no space outside space: no emptier place.
Again, the balloon analogy in the Cosmo Basics sticky thread may help visualize.
 
Last edited:
poeteye said:
If the universe is uniform no matter in what direction you look , then looking in two opposite directions, two observers, if each looks far enough will see the Universe at its earliest time -- The Big Bang. Therefore, the event of the Big Bang cannot be from a point singularity.

Take a look at the diagrams on Ned Wright's website: http://www.astro.ucla.edu/~wright/cosmo_02.htm#DH
 

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