Speed of light vs. the universe's inflation

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Discussion Overview

The discussion centers around the apparent contradiction between the speed of light as a universal speed limit and the rapid expansion of the universe shortly after the Big Bang. Participants explore the implications of cosmic inflation and the nature of space and time in this context.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • One participant asserts that the speed of light is the universal speed limit and questions how the universe could be thousands of light years across just ten minutes after the Big Bang.
  • Another participant argues that space itself does not move, suggesting that the speed of light does not apply to the expansion of space.
  • A participant acknowledges that while space does not move, radiation within that space did move, raising the question of whether the expansion of empty universe could exceed the speed of light.
  • It is proposed that spacetime existed from the beginning of the universe, allowing for the expansion between points in spacetime to exceed the speed of light, as objects do not move within spacetime faster than c.
  • One participant uses an analogy of an expanding polka dot balloon to conceptualize the expansion of the universe, though they note that their explanation may be confusing to others.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between the speed of light and the expansion of the universe. There is no consensus on how to reconcile these ideas, indicating that the discussion remains unresolved.

Contextual Notes

Participants reference concepts such as spacetime, cosmic inflation, and the movement of radiation, but the discussion includes varying interpretations and assumptions about these terms and their implications.

Trailblzn
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I understand that the Speed of light is the universal speed limit (I do not believe this is in question). However, I watched Steven Hawking's show this weekend on TV where they stated "10 minutes after the big bang the universe was thousands of light years across."

How is this possible if the speed of light is the "speed limit?" How could anything be light years across if it has only been 10 minutes? I would think that at most it could be 20 "light minutes" across. I am sure there is an answer, I am just now aware of one.
 
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Space is not a thing that moves, so the speed of light does not apply to its expansion.
 
russ_watters said:
Space is not a thing that moves, so the speed of light does not apply to its expansion.

Russ, thanks for the reply. I understand that space does not move but the things in the "space" of the early universe did move namely radiation. Was there empty universe expanding faster than radiation? The expanding radiation is what made up the universe as there was no space yet. I appreciate your thoughts.
 
Trailblzn said:
Russ, thanks for the reply. I understand that space does not move but the things in the "space" of the early universe did move namely radiation. Was there empty universe expanding faster than radiation? The expanding radiation is what made up the universe as there was no space yet. I appreciate your thoughts.

Spacetime existed at the beginning of the universe. All radiation, matter, and everything occupies spacetime. The expansion between points in spacetime has no limit and as such it can, and does, cause objects to move faster than c. The key is that the objects don't move WITHIN spacetime greater than c, but that spacetime itself is expanding.
 
Drakkith ~

Thank you VERY much that makes a lot of sense. Thank you so much for your help.
 
If you had a Cartesian planes that you "placed" upon the Universe the size that it is right now, from an external vantage point, then yes, however, matter would have traveled a fair bit faster than c. But the speed is only in reference to an already expanding reference point, and so the example is not valid.

I generally think of it as an expanding polka dot balloon, but how it works in my head would probably confuse most.
 

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