B The most distant object

[desertshaman]

TL;DR Summary

Does the most distant object from us radiate light?

Hi People :)
If we are in an expanding universe, then the nature of the boundary between what exists and what does not exist is of interest. Could one, in principle, stand on some final planet, at the edge of the universe?
If I could travel to that final planet, what would I see? I can hardly believe that there could ever be a direction in which I could point and say: "Nothing exists thataways".
So what happens... how must I try to imagine this astounding boundary?

 

[Ibix]

There is no edge to the universe as far as we know. It's either infinite in extent or closed and boundaryless.

 

[Dale]

There is no edge to the universe as far as we know. It's either infinite in extent or closed and boundaryless.

If the universe is closed then even though there is no boundary there would be a most distant object. Like the South Pole is the most distant point from the North Pole

 

[Ibix]

If the universe is closed then even though there is no boundary there would be a most distant object. Like the South Pole is the most distant point from the North Pole

Good point. In that case, OP would see much the same as if he'd stayed home.

Edit: It's worth noting that not all closed universes allow you to reach the opposite pole. Some collapse too quickly and some expand too quickly. And if you are in a universe where you can get there the universe would be a lot older by the time you did. But all FLRW universes are the same everywhere, so you can see pretty much the same thing just by staying put where you started.

 

[Jaime Rudas]

And if you are in a universe where you can get there the universe would be a lot older by the time you did.

Yes, but in that case, you will be able to see it directly without having to travel there.

 

[desertshaman]

I see wonderful comedy here :)

 

[PeterDonis]

I see wonderful comedy here :)

How so?

 

[DaveC426913]

If we are in an expanding universe, then the nature of the boundary between what exists and what does not exist is of interest. Could one, in principle, stand on some final planet, at the edge of the universe?

As others have said, the general nature of the universe, as it is popularly understood, is that, no matter where you are in it, you will see pretty much the same thing. Your "edge" will appear equidistant in all directions - simpy meaning you can't see anything farther away from you than some distance, X. It's not an actual boundary.

If you were on some planet 46bly from Earth, you would still see stars and galaxies in all directions out to the same distance as if you were on Earth.

If I could travel to that final planet, what would I see? I can hardly believe that there could ever be a direction in which I could point and say: "Nothing exists thataways".

No. As we understand it there is, no "edge".

Think about the spherical equivalent: You, standing in your front yard, can see about three miles to the horizon, beyond which you can't see. Your world is a circle of houses about three miles in radius.

You are asking if the guy in his house, three miles away, sees "the edge of the world" on the opposite side from you.

No. He sees pretty much the same thing as you. His world is a circle of houses within three miles of him.

The same can be said for anyone, anywhere on the Earth.

 

[PeroK]

I see wonderful comedy here :)

The comedy is your laughable combination of ignorance and sarcasm.

 

[pinball1970]

I see wonderful comedy here :)

You are asking scientific questions on a science site and have received informed answers from professionals.

Is this not what you expected?

 

[desertshaman]

Trying to grok the concept of an edgeless, bounded universe. I'd have thought that the fact of distributed centrality would be more obvious to us; to me.
Of course it is obvious, invisible, like that elephant in the room...

The comedy is your laughable combination of ignorance and sarcasm.

I do not wish to offend.
Therefore I find I must explain that, for me, the discovery of distributed locality brings enormous joy. It's really utter wonder that makes me laugh - there's nothing cheap about the illusions that give rise to what seems to be. Perhaps I have erred in calling this comedy.
Please do not be offended.

 

[javisot]

A closed universe that expands rapidly enough is a good approximation of an infinite universe. In both cases if you emit a pulse in any direction, it will never return to the starting point. (Ok, it's not the same, but a good approximation)

What we call "edge of the universe" when representing the universe as a spherical 2D surface are the up and down directions, directions that don't exist (no edge).

In principle, and this means due to several principles, we assume that you can move to any point in the universe and what you observe in the distance is practically the "same".

 

[Ibix]

Trying to grok the concept of an edgeless, bounded universe.

The surface of the earth is a 2-sphere, and is also boundaryless (there's no edge) but finite. A closed FLRW universe is a 3-sphere, which is also edgeless but finite in size.

I'd have thought that the fact of distributed centrality would be more obvious to us; to me.

I don't know what you mean by this.

 

[weirdoguy]

I do not wish to offend.

I guess that language barrier, and some local hard to translate things are at play.

 

[timmdeeg]

distributed centrality

Do you mean by this - perhaps - that you are in the center of the respective observable universe at any arbitrary place in the universe?

 

[sbrothy]

The comedy is your laughable combination of ignorance and sarcasm.

Ouch guys. Gentle there! That was pretty harsh, even for you.

 

[PeterDonis]

Trying to grok the concept of an edgeless, bounded universe.

It's a 3-sphere. As @Ibix has already pointed out, that's no more mysterious than the surface of the Earth being a 2-sphere, edgeless but with a finite area.

I'd have thought that the fact of distributed centrality would be more obvious to us; to me.

One can certainly construct a model of the universe with "distributed centrality". But such a model does not match observations. That's why cosmologists don't use it.

Of course it is obvious, invisible, like that elephant in the room...

No, it's a model that's ruled out by observations. See above.

for me, the discovery of distributed locality brings enormous joy. It's really utter wonder that makes me laugh - there's nothing cheap about the illusions that give rise to what seems to be. Perhaps I have erred in calling this comedy.
Please do not be offended.

It's not a matter of anyone being offended. The model that you say gives you such joy is, unfortunately, wrong--it's ruled out by observations. That's how science works: if it's ruled out by observations, it's wrong, no matter how much joy it brings someone.

 

[PeterDonis]

The OP question has been sufficiently answered, and this thread is now closed. Thanks to all who participated.