What are the implications of a perfectly flat universe?

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A perfectly flat universe raises significant questions about the roles of inflation, dark matter, dark energy, and the nature of gravity, suggesting that General Relativity (GR) may not be necessary to explain cosmic phenomena. Some argue that if gravity does not influence the universe's expansion, it could be described as a simple initial 'big bang' event with matter moving outward at a constant velocity, eliminating the need for curvature. The discussion highlights the horizon problem and critiques GR's reliance on a fixed dimensional framework, suggesting that the universe's expansion could occur without gravitational constraints. There is contention regarding the evidence for gravitational effects on light and other particles, with some asserting that current models overcomplicate the understanding of cosmic expansion. The conversation emphasizes the need for solid data and simpler models to address these cosmological challenges effectively.
  • #31
Rymer said:
Confusion of terms. The universe is capable of being infinite. It has not gotten there yet (as far as we know). The current measurements indicate 'flat' -- but not necessarily 'perfectly' flat. For the point of view you seemed to have adopted this would could be considered to be consistent with a universe being as flat as it can be -- being very large -- but not quite as yet infinite. Infinite universe in the terms you are using would seem to indicate the necessity of infinite time. Since we can point to a finite start time, the universe is not currently infinite.
In this sense it will never be. It is however -- we think -- 'unbounded'.

But who is confused? As I see it, if the universe is infinite, then it has always been infinite (including time), which would mean that the BB theory is wrong. The universe can be unbounded by being spherical. The so called experts say that the universe can be infinite but still expand, and they call us the crack-pots! On this forum, if you don't know the math they know, you're too ignorant to talk to (by some of them).

The finite start time you spoke of is based on the BB theory. Consider this: The moon moves away from the Earth 2.5 inches per year. We can 'play that movie backwards' and find out when the moon was in contact with the earth. Does anybody think it ever was? I don't think so, but they are using the same 'logic' for the BB theory.
 
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  • #32
Actually I'm pretty sure one of the moon formation theories is that a mars-size planetoid thing hit Earth and expelled a chunk which became the moon. Regardless its an oversimplification to assume that the BB theory is simply an extrapolation of space expanding to a 'point'. As I've said before: the big bang wasn't an explosion in space it was an explosion of space.
 

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