Undergrad Observable Universe Size in Different Perspectives

[rootone]

- that was the quote from the original post not (not mine).

Actually, I'm in the center of universe; any other observer may make the same claim...

Ooops sorry, don't know how I did that.
but yes everyone is at the center of what is observable for them.
The whole Universe may or may not be infinite, and need not have a center anywhere,
just as there is no place on the surface of a sphere which could be called a center.

 

[Arman777]

We don't even know the universe is sphere. I don't think there's any meaning calling "center of the universe", in this sense its just meaningless

 

[phinds]

Actually, I'm in the center of universe; any other observer may make the same claim...

Absolutely false. You are in the center of the Observable Universe, NOT "the universe"

EDIT: OOPS ... I see rootone beat me to it.

 

[phinds]

We don't even know the universe is sphere.

Actually, we know that is is NOT a sphere. If it were, it would have a center and it does not.

 

[stefanbanev]

Absolutely false. You are in the center of the Observable Universe, NOT "the universe"
...

Well, it is not false; in fact, the existence of "the universe" if it is not an observable one (in broad information sense) is matter of fate and believe...

 

[PeterDonis]

the existence of "the universe" if it is not an observable one (in broad information sense) is matter of fate and believe...

Only in the sense that we can't directly observe it. But if you want to reject the belief that there is universe beyond the part we can observe, you have to claim that the laws of physics suddenly change at the boundary of our observable universe, for no apparent reason. Because if they don't, then the universe beyond what we can observe must be there, since that's what the laws of physics that we see in our observable universe imply.

 

[stefanbanev]

Only in the sense that we can't directly observe it. But if you want to reject the belief that there is universe beyond the part we can observe, you have to claim that the laws of physics suddenly change at the boundary of our observable universe, for no apparent reason. Because if they don't, then the universe beyond what we can observe must be there, since that's what the laws of physics that we see in our observable universe imply.

Well, if it is not provable then it is matter of assumption what is totally fine to make, pretty much the same as with different kind of multiverses if such assumptions help some brains to construct theories with better predictive power then it definitely has its merits...

 

[PeterDonis]

if it is not provable then it is matter of assumption what is totally fine to make

Yes, but saying that the universe just stops at the boundary of our observable universe is also an assumption--and one which violates Occam's Razor. That's why the assumption that the universe continues past the boundary of our observable universe seems preferable--because it doesn't require claiming that something changes at that particular boundary for no apparent reason.

 

[stefanbanev]

Yes, but saying that the universe just stops at the boundary of our observable universe is also an assumption--and one which violates Occam's Razor. That's why the assumption that the universe continues past the boundary of our observable universe seems preferable--because it doesn't require claiming that something changes at that particular boundary for no apparent reason.

>"but saying that the universe just stops at the boundary of our observable universe"

Pls quote where I made such silly assertion ;o)

 

[PeterDonis]

Pls quote where I made such silly assertion

You made it implicitly here:

the existence of "the universe" if it is not an observable one (in broad information sense) is matter of fate and believe...

It's only a matter of "faith and belief" if you start with the assumption that the universe stops at the boundary of our observable universe, for no apparent reason. If instead you start with the assumption that the laws of physics don't stop at a particular point for no apparent reason, just because that point happens to be the boundary of our observable universe--i.e., if you start with Occam's Razor--then it doesn't take any "faith and belief" to see that there must be universe beyond the boundary of our observable universe.

 

[stefanbanev]

You made it implicitly here:
It's only a matter of "faith and belief" if you start with the assumption that the universe stops at the boundary of our observable universe, for no apparent reason. If instead you start with the assumption that the laws of physics don't stop at a particular point for no apparent reason, just because that point happens to be the boundary of our observable universe--i.e., if you start with Occam's Razor--then it doesn't take any "faith and belief" to see that there must be universe beyond the boundary of our observable universe.

I've made an explicit explanation of my point:

SB>“if it is not provable then it is matter of assumption what is totally fine to make, pretty much the same as with different kind of multiverses if such assumptions help some brains to construct theories with better predictive power then it definitely has its merits... ”

You are definitely free to make your “implicit” interpretations I just see no relation to my point to discuss.

Thanks,
SB

 

[PeterDonis]

if it is not provable then it is matter of assumption

What is "provable" depends on what assumptions you start with. You start with the assumption "anything we can't observe we have to take on faith"--but that requires you to also assume that the laws of physics suddenly change at the boundary of our observable universe, for no apparent reason. Only with that additional assumption--which violates Occam's Razor as well as common sense--can you say it isn't "provable" that there is more to the universe than the part we can directly observe.

Whereas I start from the assumption "the laws of physics stay the same everywhere", which allows me to prove immediately that they don't change at the boundary of our observable universe for no apparent reason, and therefore there is more to the universe than the part we can directly observe.

In other words, your apparent belief that only I have to make "assumptions" and you don't, in order to support our respective viewpoints, is not correct.

I just see no relation to my point to discuss.

Perhaps the above will help to explain its relevance.

 

[Clausen]

No, that's not what is seen from the entire history of the expansion. The entire history of the expansion shows change in the rate of expansion--it was decelerating in the early universe, then a few billion years ago it started accelerating.

Thanks, That is what I thought.

As I understand the current theory, the rapid rate of expansion of the early universe did slow down some 5 billion years ago, but we now see evidence it has sped up again due to dark energy. Is this your understanding also?

Some of the other answers were confusing, at least to me.