Infinite universe but finite beginning?

[duhuhu]

so I read through the cosmological principle and I am having some trouble understanding where you guys pulled out that the universe is infinite. the only place that I think I might see it is in the part that says that when you look at the universe on a large enough scale, parts of it begin to look homogenous. (It is complex so I am just trying to understand what I read)

(I apologize for putting opinion into the conversation earlier, it will not happen again)

 

[bahamagreen]

The present idea suggests we live in a special time...

First there is nothing
Then the Big Bang
Then acceleration of expansion (short fast inflation)
Then deceleration of expansion (and formation of structure)
Later, acceleration of expansion (long (infinite?) slow, dark energy)
Eventually, this acceleration of expansion has the universe approaching total vacuum (back to nothing)

 

[phinds]

so I read through the cosmological principle and I am having some trouble understanding where you guys pulled out that the universe is infinite. the only place that I think I might see it is in the part that says that when you look at the universe on a large enough scale, parts of it begin to look homogenous. (It is complex so I am just trying to understand what I read)

(I apologize for putting opinion into the conversation earlier, it will not happen again)

The universe may be infinite or it may be finite. No one knows. I don't recall anyone stating categorically that it IS infinite and if they did they are offering unsupported personal speculation.

 

[PeterDonis]

The universe may be infinite or it may be finite. No one knows. I don't recall anyone stating categorically that it IS infinite

No, but we can say that our current best-fit model of the universe has it being spatially infinite. The "error bars" around the best-fit model are large enough, however, to include the possibility that it is finite.

 

[julcab12]

so I read through the cosmological principle and I am having some trouble understanding where you guys pulled out that the universe is infinite. the only place that I think I might see it is in the part that says that when you look at the universe on a large enough scale, parts of it begin to look homogenous. (It is complex so I am just trying to understand what I read)

(I apologize for putting opinion into the conversation earlier, it will not happen again)

Our universe 'according' to some solutions/math in Lambda-CDM model(somehow fits with homogenous-U) which is flat naturally has an "infinity" part to it. This is due to metric limitation in the friedman universe where ds2=−dt2+a2(t)[dr21−kr2+r2dΩ2] [assuming of course] 'if' k→0 the maximum possible distance (S) smax→∞ goes to infinity.. 'If' k>0 we have finite. And such special case of nontrivial topology torus (flat but finite).

Ok now. We have observations/data, but funny enough it is dynamic for obvious reasons. We have very small curve that show finite side of the argument and largely flat-infinite. Statistically by comparison we can't tell whether it is infinite or finite. ^^

 

[julcab12]

The present idea suggests we live in a special time...

First there is nothing
Then the Big Bang
Then acceleration of expansion (short fast inflation)
Then deceleration of expansion (and formation of structure)
Later, acceleration of expansion (long (infinite?) slow, dark energy)
Eventually, this acceleration of expansion has the universe approaching total vacuum (back to nothing)

... It becomes mentally complicated when you use 'start and so on'/'nothing'. Try replacing 'nothing' to 'Everything' and the progression to 'phases/transitions'.

 

[bahamagreen]

What do you mean?

If there is anything, then everything cannot include nothing.

But if there is nothing, that includes everything... :)

 

[phinds]

No, but we can say that our current best-fit model of the universe has it being spatially infinite. The "error bars" around the best-fit model are large enough, however, to include the possibility that it is finite.

Agreed. I was more making the point that it is not known for a fact either way.