Just a simple explanation please

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Discussion Overview

The discussion revolves around the age and size of the universe, specifically addressing the apparent contradiction between the universe's estimated age (11 to 20 billion years) and its measured size (156 billion light years across). Participants explore concepts related to the expansion of the universe and the implications of this expansion on the speed of light and distances in cosmology.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions how matter could have expanded over 78 billion light years in a universe that is only 11 to 20 billion years old.
  • Another participant asserts that the universe itself expands, which can occur at a rate faster than the speed of light, but this does not allow for information to be transmitted faster than light.
  • A further explanation is provided that while everything in the universe is expanding, local structures like solar systems do not expand; rather, the distances between galaxies increase.
  • One participant expresses confusion about the implications of objects moving away from each other at relativistic speeds and questions whether space itself is expanding in a way that does not contribute to an object's speed.

Areas of Agreement / Disagreement

Participants express differing views on the nature of cosmic expansion and its implications for distances and speeds. There is no consensus on the interpretation of how expansion relates to the speed of light and the age of the universe.

Contextual Notes

Participants highlight the distinction between the expansion of space and the movement of objects within that space, indicating potential misunderstandings about how these concepts interact. The discussion remains open-ended regarding the implications of these ideas.

hedkrash
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Can someone please explain something too me.

From what I understand our current calculations suggest the universe is between 11 and 20 some billion years old.

Astronomers have measured the cosmos to be roughly 156 billion light years across, or 78 billion light years from the outermost edge to the center.

Since nothing can travel faster than light, how could matter have expanded a minimum of 78 billion light years in 11-20 billion years?

Am I missing something?
 
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Yes. You are missing the fact that the universe expands.
 
And the universe can expand faster than light - you just can't send information from one side to the other faster than light. So you can observe anything more than 14Billion light years away.
 
So, in super layman terms...

What was once an centimeter, would now measure a kilometer (if it were possible to observe the universe from the 'outside'). Everything keeps expanding, but since we are part of that expansion, we don't notice it.

Thanks for helping me understand this.
 
hedkrash said:
So, in super layman terms...

Everything keeps expanding, but since we are part of that expansion, we don't notice it.

Be careful of that statement. Objects, say our solar system, earth, you and me, don't expand as part of the expansion. Distance between galaxies *become* further apart. The galaxies themselves don't expand.
 
more confusion

I really thought I had it, alas confusion has set back in.

I can see how the universe could expand faster than the speed of light. If one side was moving away at .9c and the other side moving away at .9c, the combined expansion would be 1.8c away from each other (.8c faster than the speed of light c).

Which means it should still have taken more than 78 billion light years (the distance from the center of the universe to the outermost edge) for the universe to expand as far as it has.

Unless you are suggesting that space itself is expanding, and that expansion doesn't count towards an objects speed.
 

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