How large is the universe?

Puppycow

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Puppycow
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Also in Hi-def on Youtube

And here's another interesting one:

Cosmic Journeys : The Largest Black Holes in the Universe

Astronomy is just mind-boggling. :boggled:

According to some theories, the whole universe is like 1024 times larger than the observable universe. IOW, the ratio of the size of the observable universe to the entire universe may only be like the ratio of the size of an atom to the size of the observable universe. :eye-poppi

The observable universe is about a sphere with a radius of 13.7 billion light years. We can't see anything farther away than that because that's the age of the universe itself, so light could not have travelled any farther than that. Or, because of the expansion of the universe, it's actually a sphere with a radius of 46 billion light years (it makes my head hurt).
 
Saw a lovely diagram explaining the 46 billion light years thing.

Also, I keep waiting for that narrator to bust out with, "You're a mean one, Mr. Grinch..."
 
Wow. And here I was thinking it was a long way down the road to the chemist!
 
I find all this stuff really confusing, can someone explain, if everything started in the same place 14 B years ago and nothing can travel faster than light speed, how can things be more than 14 B light years apart?
 
bobwtfomg said:
I find all this stuff really confusing, can someone explain, if everything started in the same place 14 B years ago and nothing can travel faster than light speed, how can things be more than 14 B light years apart?
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Just basic cosmology allows things to be 14 bilion light years going in two directions makes the Universe at least 28 bly across. But then, that goes against the concept the Universe has no center and no edges.

I think the center is past time and the edges are future time but that's an against the mainstream concept and probably off topic.

That's all Im going to contribute at this point because I don't know much about cosmology. ;)
 
Things can't move faster than light, but space can expand faster. Space expands at a certain rate based on distance, so the farther away something is now, the faster it appears to be moving away, even though it's actually the expansion of space that's responsible for the apparent movement.
 
bobwtfomg said:
I find all this stuff really confusing, can someone explain, if everything started in the same place 14 B years ago and nothing can travel faster than light speed, how can things be more than 14 B light years apart?
Click to expand...

I believe it has to do with the expansion of space-time itself.

There's a theory called inflation that posits that space-time expanded very fast immediately after the big bang. And due to dark energy space-time continues to expand even today. So even though nothing can move faster than the speed of light, the spaces between objects continue to expand on a cosmic scale, which causes things to be farther apart than the speed of light alone would allow.
 
bobwtfomg said:
I find all this stuff really confusing, can someone explain, if everything started in the same place 14 B years ago and nothing can travel faster than light speed, how can things be more than 14 B light years apart?
Click to expand...

Light left some object 13.#B years ago. Since that time the object has been moving away from us. This means that light leaving the object now will take about 40B years to get to us.
 
Nice video. I wasn't keen on the bit that suggested that the universe is vastly bigger than the observable universe, because we don't actually know that. But I liked the mention of quintessence being space (see arXiv). Only after that I didn't like the bit about energy emerging from space pushing space outwards. Or the many universes. And it avoided the issue of whether the universe has an edge. But hey, like I said, nice video.

NB: it's the expansion of space, Puppycow. Not spacetime. The best way to get a handle on it IMHO is to get a stress ball, squeeze it down in your fist, then let go. Silly putty is interesting too. Stretch a piece of it out and it droops faster and faster. Roll it into a ball, leave it, and it spreads. Imagine light is like a little mite crawling across the surface of it as it spreads. A mite with a pedometer that says it's crawled 13.7cm. But now that the silly putty has spread out, you measure the distance it's crawled as 46cm.
 
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IMST said:
Things can't move faster than light, but space can expand faster. Space expands at a certain rate based on distance, so the farther away something is now, the faster it appears to be moving away, even though it's actually the expansion of space that's responsible for the apparent movement.
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When a fruit loaf cooks and the dough expands between the pieces of fruit, do the pieces of fruit move apart at any speed, or is it merely apparent movement at no speed?
 
Mostly they get moved up or down (the pan' s sides limit any movement of the expanding dough in that direction) at pretty much the speed of the movement of the dough. This is not quite how the movement of space considered as a field works, but is some related -space has no limits AFAIK or have read based on direction but IIRC it expands, or is believed to expand, equally in all directions.
 
fuelair said:
Mostly they get moved up or down (the pan' s sides limit any movement of the expanding dough in that direction) at pretty much the speed of the movement of the dough. This is not quite how the movement of space considered as a field works, but is some related -space has no limits AFAIK or have read based on direction but IIRC it expands, or is believed to expand, equally in all directions.
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“They get moved” is different from “They apparently get moved”. As I understand it the claim seems to be that the distances between objects can change without the objects moving relative to each other. The only way I can imagine this being “possible” is to change the properties of distance. In other words expanding space is essentially a shortening of the unit measurement of distance.
 
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I think the problem (and I cannot help you with it - the physics is above my pay grade) is you are trying to conflate the expansion of matter local to you with the expansion of the space the matter is contained in.
 
Farsight said:
Nice video. I wasn't keen on the bit that suggested that the universe is vastly bigger than the observable universe, because we don't actually know that. But I liked the mention of quintessence being space (see arXiv). Only after that I didn't like the bit about energy emerging from space pushing space outwards. Or the many universes. And it avoided the issue of whether the universe has an edge. But hey, like I said, nice video.

NB: it's the expansion of space, Puppycow. Not spacetime. The best way to get a handle on it IMHO is to get a stress ball, squeeze it down in your fist, then let go. Silly putty is interesting too. Stretch a piece of it out and it droops faster and faster. Roll it into a ball, leave it, and it spreads. Imagine light is like a little mite crawling across the surface of it as it spreads. A mite with a pedometer that says it's crawled 13.7cm. But now that the silly putty has spread out, you measure the distance it's crawled as 46cm.
Click to expand...

Thanks for the correction. I had to look up quintessence because I actually thought it was an outdated concept from the ancient Greeks and medieval alchemists, i.e., the "fifth element" to go along with earth, air, fire and water. I now realize that there is a new use for the word.
 
fuelair said:
I think the problem (and I cannot help you with it - the physics is above my pay grade) is you are trying to conflate the expansion of matter local to you with the expansion of the space the matter is contained in.
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I’m happy to entertain the notion that space is an autonomous thing that can expand while nothing else does. In this context however space is a thing not a distance.
 
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