An embarrassing question: what were the boundaries of the universe

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Discussion Overview

The discussion revolves around the concept of the universe's boundaries, particularly during its initial expansion from a hot and dense state. Participants explore whether the universe is finite or infinite and the implications of each scenario on the notion of boundaries.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant asserts that the universe has expanded from an initially hot and dense state and questions what the boundaries of the universe were at that time.
  • Another participant suggests that the universe has always been infinite, even at the beginning, and has been expanding since it was about 6 billion years old.
  • Some participants note uncertainty regarding whether the universe is infinite or finite, indicating that current data supports both models equally well.
  • If the universe is infinite, it was always infinite from the Big Bang; if finite, it does not have boundaries, as reaching the edge would lead one back to the starting point.
  • There is curiosity about how an infinite universe can expand, with the explanation that objects within it move further apart from each other.

Areas of Agreement / Disagreement

Participants express differing views on whether the universe is finite or infinite, and the discussion remains unresolved regarding the nature of its boundaries.

Contextual Notes

Participants reference existing discussions and data that support multiple models, highlighting the complexity and uncertainty surrounding the topic.

houhou.trad
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I say always that the universe has expanded, from an initially-hot and dense state, until it get its current forme...
But it will be very natural to ask the question: at the first instances of its expansion, what were the boundaries of this universe, and what were the exterior of this boundaries..?
Can someone explain me this?
 
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Last edited by a moderator:
We're actually not sure if it's infinite or not (according to Marcus, and the FAQ, the current data fits both infinite and finite models, pretty much equally well), but:

-If the universe is infinite, then it was already infinite at the point of the Big Bang; there was never a time that it was finite.

-If the universe is finite, it still does not (and never did) have boundaries. What happens when you reach the edge of the universe? Well, you never reach an edge; try this and you'll only end up back where you started (rather like as if you tried to sail to the edge of the earth).

-In either case, it is expanding. One may wonder: if the infinite universe is true, how would an already infinite space expand further? Well, all the things in it just keep getting further away from each other.
 
Thank you narrator and cephron, I think the idea is now somewhat more clear.
 

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