# Outer Space

josephw
Science 28 Nov '10 23:40
1. 28 Nov '10 23:40
Does anyone know how far it is to the end of the universe?

Does matter end at some point and space continue outward forever?
2. 29 Nov '10 04:46
Originally posted by josephw
Does anyone know how far it is to the end of the universe?

Does matter end at some point and space continue outward forever?
I think space is finite and continuous. Rather like the surface of a sphere. If you keep going in one direction, you will eventually get back home.
I do not think that this is known without doubt to be the case as there are still a few hypothesis that suggest an infinite space, but the Big Bang theory suggests a finite space and the Big Bang theory does have a lot of evidence in its support.
3. 29 Nov '10 09:271 edit
Originally posted by josephw
Does anyone know how far it is to the end of the universe?

Does matter end at some point and space continue outward forever?
In my Universe I see it as a hypersphere.

The Earth's surface (2-dim) is closed, but without edges, and there is no mid-point.
The Úniverse's space (3-dim) is also closed, and without edges, and there is no mid-point here either.

So your question - "Does anyone know how far it is to the end of the universe?" - I would answer: There is no end.
Your other question - "Does matter end at some point and space continue outward forever?" - I would answer: Matter doesn't end anywhere, and the space doesn't continue outward forever.

You can ask me follow-ups, and I will answer how I think the Universe is. In some details established cosmologists don't agree with me, and that is fine with me. So my answers may only be mine and not others. If it's okay with you, then give me your follow-ups.
4. 30 Nov '10 00:42
This question has been in my head for many moons. Since I'm told the universe is expanding, I've often wondered where this perpetually-moving"line" at the end of the universe is. And, if the edge of the universe exists, what would we find if we could exceed the speed at which the U is expanding, what would we see when we passed the "do-not-cross" sign?
5. DeepThought
30 Nov '10 00:56
Originally posted by FabianFnas
In my Universe I see it as a hypersphere.

The Earth's surface (2-dim) is closed, but without edges, and there is no mid-point.
The Úniverse's space (3-dim) is also closed, and without edges, and there is no mid-point here either.

So your question - "Does anyone know how far it is to the end of the universe?" - I would answer: There is no end.
Your ...[text shortened]... may only be mine and not others. If it's okay with you, then give me your follow-ups.
The most recent evidence - in the last decade or so - indicates that the universe is expanding exponentially. This implies that the basic geometry is a de Sitter Universe, not spherical, so the universe isn't closed.

There is no particular reason to believe that there is no region in the universe without matter (allowing for things like great voids which are typically only of the order of a quarter of a billion light years wide and can be neglected on the grounds of being small).
6. 30 Nov '10 11:591 edit
Originally posted by PinkFloyd
This question has been in my head for many moons. Since I'm told the universe is expanding, I've often wondered where this perpetually-moving"line" at the end of the universe is. And, if the edge of the universe exists, what would we find if we could exceed the speed at which the U is expanding, what would we see when we passed the "do-not-cross" sign?
The geometry of spacetime is a bit complicated and cannot be regarded in terms of "normal" (in a mathematical sense: Euclidian) shapes. It is more or less like Fabian says: space is finite, but there is no "center" of the universe. The expansion of space is self-contained.

Unfortunately this is not my particular field of expertise so my explanation may be inaccurate and I do not understand the (mathematical) details myself.
7. sonhouse
Fast and Curious
01 Dec '10 18:00
Originally posted by KazetNagorra
The geometry of spacetime is a bit complicated and cannot be regarded in terms of "normal" (in a mathematical sense: Euclidian) shapes. It is more or less like Fabian says: space is finite, but there is no "center" of the universe. The expansion of space is self-contained.

Unfortunately this is not my particular field of expertise so my explanation may be inaccurate and I do not understand the (mathematical) details myself.
But the size can be guesstimated: Overall the expansion rate is still something like 3 times the speed of light, and we can see back close to 14 billion years in time, with the visible universe close to 14 billion light years, so if you could go in an extremely fast spaceship trillions of times faster than light you might find the universe as a whole about 50 billion light years across, but that is just the distance you could see new stuff in. After that, you keep going and the same stuff you passed originally will reappear because like they said, the universe is like a 4th or 5th dimensional bowl and you cannot escape it by just keep driving. You just come back to where you were before, like a cosmic treadmill.
8. 01 Dec '10 18:38
Originally posted by sonhouse
But the size can be guesstimated: Overall the expansion rate is still something like 3 times the speed of light, and we can see back close to 14 billion years in time, with the visible universe close to 14 billion light years, so if you could go in an extremely fast spaceship trillions of times faster than light you might find the universe as a whole about ...[text shortened]... e it by just keep driving. You just come back to where you were before, like a cosmic treadmill.
When I observe the background radiation I see 13.7 billions lightyears away, because that's the age of our universe. I cannot see 15 billion lightyears away, because 15 billions of years ago, our universe didn't exist. So 13.7 billions lightyears is the limit.
This limit is the same everywhere in whole our universe at this time. Right?
9. 02 Dec '10 14:11
Originally posted by FabianFnas
When I observe the background radiation I see 13.7 billions lightyears away, because that's the age of our universe. I cannot see 15 billion lightyears away, because 15 billions of years ago, our universe didn't exist. So 13.7 billions lightyears is the limit.
This limit is the same everywhere in whole our universe at this time. Right?
If the universe is 13 billion years old we can see more than 13 billion light years away unless you are at the center of the universe. If you were at the edge of the universe you could see about 26 million years away (if it is even possible to see that far away) from on side to the other. If the universe has no center I'd like to hear the explanation for why that is.

That is assuming that the matter in the universe is in a (expanding) sphere shape though. I have read that the universe could be in the shape of a saddle from one source and that it is flat like a pancake from another source. I don't know how they came to that conclusion though, and I always wanted a better explanation of why the universe would be shaped in those ways.
10. 02 Dec '10 17:462 edits
Originally posted by Metal Brain
If the universe is 13 billion years old we can see more than 13 billion light years away unless you are at the center of the universe. If you were at the edge of the universe you could see about 26 million years away (if it is even possible to see that far away) from on side to the other. If the universe has no center I'd like to hear the explanation for h, and I always wanted a better explanation of why the universe would be shaped in those ways.
If you look at an object 1 million of lightyears away, then you see that object as it were 1 million of years ago. Right?
If you look at an object 26 billion lightyears away, then you see that object as it were 26 billion of years ago. Right?
Wrong. Our Universe wasn't born 26 billion of years ago. It is only 13.7 billion years old. There wes nothing to see 26 billion of years ago.

This is an analogy:
Say that you are 30 years old. Then there cannot be any pictures of you older than 30 years. Why? Beacuse you wasn't there beyond the 30 years limit.
Exactly same as there is nothing to see in Universe beyond the 13.7 billion years limit.

Our Universe has no center. That is not difficult to understand. The 2-dim surface of the Earth lack also a center. There is no spot that is more center than any other spot on the surface of the Earth. Right?
If you understand this, then you can understand that our Universe lack a center too.

I see our Universe as an expanding hypersphere, not an expanding ball. Because a 3-dim ball has a center, the Universe has not.
11. 02 Dec '10 19:25
Originally posted by FabianFnas
If you look at an object 1 million of lightyears away, then you see that object as it were 1 million of years ago. Right?
If you look at an object 26 billion lightyears away, then you see that object as it were 26 billion of years ago. Right?
Wrong. Our Universe wasn't born 26 billion of years ago. It is only 13.7 billion years old. There wes nothing t ...[text shortened]... g hypersphere, not an expanding ball. Because a 3-dim ball has a center, the Universe has not.
Then you could argue that the universe is much larger than 13 billion light years distant stars because the light will take 13 billion years to get here from where they are (assuming they are still shining) now, right?
12. 02 Dec '10 19:38
Originally posted by Metal Brain
Then you could argue that the universe is much larger than 13 billion light years distant stars because the light will take 13 billion years to get here from where they are (assuming they are still shining) now, right?
I don't understand this sentence:
"Then you could argue that the universe is much larger than 13 billion light years distant stars"
How could universe be larger than stars, even if they are distant?

As I see it - Light cannot be older than the Universe itself. Light cannot be emmitted before the Big Bang 13.7 billions of years ago.
13. sonhouse
Fast and Curious
03 Dec '10 02:142 edits
Originally posted by FabianFnas
I don't understand this sentence:
"Then you could argue that the universe is much larger than 13 billion light years distant stars"
How could universe be larger than stars, even if they are distant?

As I see it - Light cannot be older than the Universe itself. Light cannot be emmitted before the Big Bang 13.7 billions of years ago.
I think the thing you are not factoring in is the fact that space, even now is being 'pumped up' faster than the speed of light, they estimate something like 3 times the speed of light.

So we can say that the universe is 13 odd billion years old but in that time it has expanded way more than 13 billion light years, maybe as much as 50 billion light years, so if you have a way faster than light spacecraft, and know the major features of the universe, if the universe was 14 billion ly across, you would start seeing what you passed 14 billion ly later, start seeing the stuff you already knew.

But if the universe has expanded, that is somehow each point in space is being systematically pulled apart or points pumped in, essentially the same thing, then there is space we cannot now see because light from those volumes of space could not reach us ever, space is outspeeding light so there is stuff out there we just cannot see ever even if we made a telescope the entire size of the known universe. It would be sensitive as hellðŸ™‚ but could still only see 14 billion light years away.
Only if you could go faster than the speed of light could you drive into realms we cannot ever see with telescopes.

So the gist of that is, yes the universe can be 50 billion light years 'across', in the sense that if you had a super multi trillion times faster than light drive, you would see new stuff that you had not charted in our visible universe and you could continue seeing new stuff till you got to that 50 or so billion light year distance, then old stuff would finally be brought back into view because even at 50 billion light years 'across' we are still on a cosmic treadmill and without access to multidimensional gateways forever will be on that treadmill, just in a bigger box.

The bottom line is that the universe is still 13.7 billion years old but bigger than 14 billion light years because of the ongoing expansion of space. The light cone prevents us from seeing all the other space in our universe.
14. 03 Dec '10 13:55
Originally posted by sonhouse
I think the thing you are not factoring in is the fact that space, even now is being 'pumped up' faster than the speed of light, they estimate something like 3 times the speed of light.

So we can say that the universe is 13 odd billion years old but in that time it has expanded way more than 13 billion light years, maybe as much as 50 billion light year ...[text shortened]... sion of space. The light cone prevents us from seeing all the other space in our universe.
Well said.
15. 03 Dec '10 14:13
Originally posted by sonhouse
I think the thing you are not factoring in is the fact that space, even now is being 'pumped up' faster than the speed of light, they estimate something like 3 times the speed of light.

So we can say that the universe is 13 odd billion years old but in that time it has expanded way more than 13 billion light years, maybe as much as 50 billion light year ...[text shortened]... sion of space. The light cone prevents us from seeing all the other space in our universe.
But the key question here is - Can light be older than 13.7 billion of years old? The oldest light we can se right now is 13.7 billion of years, right? Is older light possible to see?