Thoughts on the scale of the universe?

[genkaus]

For fuck's sake. Are you seriously suggesting that an adult human being in the 21st century doesn't understand the significance of the Cosmic Mircrowave Background Radiation (clue: the universe isn't infinitely large)?

Natural facts are not dependent on human opinion.

Correction: I think that applies to observable universe.

[FallentoReason]

Mathematically, you can. Think of the smallest particle known to us. It has a width. Now take that distance and slice it in half.

You can just keep zooming in on your new line segment and slicing in half forever. I can't really think of anything that wouldn't let you 'zoom in' and slice again. Such is the nature of distances.

I see what you're saying, it's just something I struggle to grasp (puny brain). As far as I'm aware, infinity as a concept is not something that has been observed or proven.

Nah, I wouldn't say 'puny brain'. In that case I have a puny brain compared to novel writers! We all have our different strengths.

I can't remember if it's been proven, but as a concept it works even though there might not be a proof. It's got all sorts of uses in maths and sometimes engineering.

[Dumac Dwarfking]

but as far as I can see, the universe seems to be a finite one.

The universe is generally considered to be infinite in size. Think of it this way - you get a starship and you cruise in it way out to the "edge" of the universe where you reach a "wall" of some kind, representing the "end" of the universe. How thick is that wall? What's on the other side of the wall? Since the Universe is by definition everything, the thickness of the wall and everything on the other side of it is still the universe. Whatever "end" you could find, it's still universe on the other side of the end.

Generally considered infinite by whom? The material I managed find differed in opinion with no particular stance for one conclusion or the other.

---

Could it be a finite universe with infinite universes.

I'm sure Dr who would know.

As far as the multiverse hypothesis, I find it interesting, but is not testable or provable, and by all accounts never will be.

I'm also sure Dr. Who would know though...

[genkaus]

This is a new idea I've been considering for a while, so pardon me if it's bit ill-formed.

Before we ask if the universe is infinite, we've to understand the the concept of infinity better. The commonly understood idea is that something is infinite if it has no boundary or no limit. But what we'd accept as a boundary or limit is completely determined by us. We are the ones who are setting these rules.

For example, a line is infinite while a line segment is finite. The boundary condition in this case are the end points.

A plane is infinite while a geometric figure is finite. The boundaries here are determined by line segments.

However, consider a circle. It has no start or end points. Anytime we do measurements upon it we artificially define the boundary. Similarly, the surface of the sphere has no beginning or the end because there are no line segments to determine the boundaries. Both of these things can - in a sense - be considered infinite.

Imagine you are a single dimensional being capable of moving only along a line. Any boundary you define would be as an endpoint. Imagine you are living on the surface of a circle. Then, you can spend an eternity trying to find an endpoint on it, but still not find one. The same goes for a 2-d being on the surface of a sphere. If it is small enough not notice the curvature, it can spend a lot of time trying to find the edge and not find one. Actually, the second one isn't that hard to imagine. Just look back at a time when people thought that the earth was flat and that it had an edge that you'd fall over.

Currently, we are sort of hard-wired to think in 3-d terms. When we talk about whether the universe if finite or not, what is going on in our minds is that if we go far enough, we'll either find some sort of membrane that we just can't cross, which defined the limit of this universe or we won't find any such membrane, in which case we can call it infinite. But as we know from our practical experience with circles and spheres, it wouldn't really be infinite. So the question of whether the universe is infinite or not would boil down to understanding what boundary conditions are applicable. And since we are not built to think in those terms, trying to imagine it gives me a headache.

On a side note, here's a cool site giving you some idea about the scale of the universe.

http://htwins.net/scale2/

[FallentoReason]

Currently, we are sort of hard-wired to think in 3-d terms. When we talk about whether the universe if finite or not, what is going on in our minds is that if we go far enough, we'll either find some sort of membrane that we just can't cross, which defined the limit of this universe or we won't find any such membrane, in which case we can call it infinite. But as we know from our practical experience with circles and spheres, it wouldn't really be infinite. So the question of whether the universe is infinite or not would boil down to understanding what boundary conditions are applicable. And since we are not built to think in those terms, trying to imagine it gives me a headache.

You were treading on a solution to being able to answer the question. What would help us would be to better understand the shape of the universe. From what I've read (although I'm quite rusty on the topic) the sum of all the energy in the universe is 0, which means that it's linear i.e. 'flat' in a nutshell. It means that everything did begin at a single point and expanded out. I think this would suggest that the universe can't be a sphere type shape which is infinite but something else. But like I said, I'm quite rusty on this topic.

On a bit of a tangent: I find it quite interesting and somewhat chilling that the universe began at a 'single point'. This literally means that the beginning of the universe happened where you and I are sitting simultaneously. The singularity expanded, therefore creating the world we know, which means all this space is the space that came from the singularity. So the big bang technically happened everywhere in the known universe only that it was all squeezed into a singularity.

[Dumac Dwarfking]

Currently, we are sort of hard-wired to think in 3-d terms. When we talk about whether the universe if finite or not, what is going on in our minds is that if we go far enough, we'll either find some sort of membrane that we just can't cross, which defined the limit of this universe or we won't find any such membrane, in which case we can call it infinite. But as we know from our practical experience with circles and spheres, it wouldn't really be infinite. So the question of whether the universe is infinite or not would boil down to understanding what boundary conditions are applicable. And since we are not built to think in those terms, trying to imagine it gives me a headache.

You were treading on a solution to being able to answer the question. What would help us would be to better understand the shape of the universe. From what I've read (although I'm quite rusty on the topic) the sum of all the energy in the universe is 0, which means that it's linear i.e. 'flat' in a nutshell. It means that everything did begin at a single point and expanded out. I think this would suggest that the universe can't be a sphere type shape which is infinite but something else. But like I said, I'm quite rusty on this topic.

On a bit of a tangent: I find it quite interesting and somewhat chilling that the universe began at a 'single point'. This literally means that the beginning of the universe happened where you and I are sitting simultaneously. The singularity expanded, therefore creating the world we know, which means all this space is the space that came from the singularity. So the big bang technically happened everywhere in the known universe only that it was all squeezed into a singularity.

The shape of the universe is calculated using CMB, and the basic geometry of a triangle. Using earth as one apex, and measuring the largest fluctuations in the CMB we can determine the shape of the universe. If the universe was spherical, the angles would be more than 180 degrees, if it had a negative curvature, then it would be less than 180 degrees. Neither of these have turned out to be the case.

[FallentoReason]

You were treading on a solution to being able to answer the question. What would help us would be to better understand the shape of the universe. From what I've read (although I'm quite rusty on the topic) the sum of all the energy in the universe is 0, which means that it's linear i.e. 'flat' in a nutshell. It means that everything did begin at a single point and expanded out. I think this would suggest that the universe can't be a sphere type shape which is infinite but something else. But like I said, I'm quite rusty on this topic.

On a bit of a tangent: I find it quite interesting and somewhat chilling that the universe began at a 'single point'. This literally means that the beginning of the universe happened where you and I are sitting simultaneously. The singularity expanded, therefore creating the world we know, which means all this space is the space that came from the singularity. So the big bang technically happened everywhere in the known universe only that it was all squeezed into a singularity.

The shape of the universe is calculated using CMB, and the basic geometry of a triangle. Using earth as one apex, and measuring the largest fluctuations in the CMB we can determine the shape of the universe. If the universe was spherical, the angles would be more than 180 degrees, if it had a negative curvature, then it would be less than 180 degrees. Neither of these have turned out to be the case.

Oh awesome. I didn't know that. That's more evidence that the universe is most likely flat then.

[jonb]

Ahoy, thar It be a vast sea we be drifting upon, Arrgh!
http://www.youtube.com/watch?v=Ufl_Nwbl8...re=related

[downbeatplumb]

The BBC did a programme on the size of the universe.

http://www.bbc.co.uk/programmes/b01mmrc0

[jonb]

Aye, and when the charts says, here be dragons, because no cove has have made an observation it meaneth not there be dragons, Arrgh it just be that no old salt has seen them thar waters. Arrgh!

http://www.youtube.com/watch?v=j6z7C7Qura8