Posted: Mon Jan 03, 2011 7:33 am Post subject: Our universe has no center, yet you can't go around it?
I'm a bit confused, hopefully someone can clarify this.
Our universe is certainly flat, as explained by Prof. Lawrence Krauss.
However, while explaining the differences between an open, closed, or flat universe, he points that only in a closed universe can you "look far enough in that direction, and see the back of your head".
Yet, our universe has no center. The only explanation I can find to this is that our universe (if it were 2D) is shaped like a balloon, therefor it is finite but still has no center.
So does a flat universe wrap around itself like a closed universe? Or how else could our universe be flat and not have a center, unless it is infinite?
Edit: I just listened to him more closely and realized he mentioned that both an open and a flat universe would be infinite.
So I am undecided. The idea of an infinite universe is ugly. Yet the idea of a finite universe that has no center is also ugly.
It eases my mind to think of the universe as a torus or mobius strip. That way it is finite and has no center... but the idea of being able to travel around the universe feels limiting.
Yet the idea of the universe being infinite makes me feel uncomfortable. Infinity is a number that I cannot easily wrap my mind around, and makes little sense. Mathematically, yes... logically, no.
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Posted: Mon Jan 03, 2011 2:45 pm Post subject:
Perhaps, the Universe, is just a bunch of dark light? And it just takes up 'space' we don't know how much. But logically it is infinite. _________________
the universe expands faster than the speed of light, so it is infinite. It has no center. You cannot go 'around' it because it is currently impossible for us to travel faster than the speed of light.
Perhaps the universe is like Earth, and we are ants.
Sorry but makes no relevant sense to what I'm discussing. Unless you mean the universe is closed.
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Jorg hi wrote:
Perhaps, the Universe, is just a bunch of dark light? And it just takes up 'space' we don't know how much. But logically it is infinite.
A photon is its own antiparticle, therefor there is no such thing as "dark light". Furthermore, a photon has no mass, just energy, therefor it cannot mathematically consume space. It has nothing to do with the universe being infinite in a spacial meaning.
Farr. wrote:
the universe expands faster than the speed of light, so it is infinite. It has no center. You cannot go 'around' it because it is currently impossible for us to travel faster than the speed of light.
If the universe was finite, flat, and had boundaries, it would have a center... even if it were expanding faster than the speed of light. They key word here is boundaries.
What I mean by "going around the universe" is "does the universe have boundaries".
Not being able to travel faster than the speed of light is a limitation that has nothing to do with whether or not the universe is bound.
The reason we don't know if the universe has a bounded metric space is because of the speed of light limitation. The farther out we look, the farther back in time we are looking. To us, our universe looks like a sphere with a diameter of 156 billion light years. That doesn't mean we can actually see the galaxies that are 156 billion light years away. It means that we can see the galaxies which are about 13.4 billion years old, but the metric expansion of space has caused those galaxies to now be 156 billion light years away from us (which we can calculate due to the redshift of light).
So essentially, we have no way of knowing if the universe is finite or infinite. But due to the cosmic microwave background radiation, we can say that the universe is certainly flat (it's the only mathematically beautiful universe, and the only universe which can be created from nothing, as pointed out by Krauss).
My question is, can a flat universe really be finite? Because the only way a universe can be finite and have no center is if it is a 3D shape, curved over a 4th dimension (like a torus, sphere, or mobius strip). But the very word "curved" implies that it would be... well, not flat.
I guess the main thing is that an infinite universe does not make sense to me, because I don't understand how the big bang itself could produce an infinite amount of matter. The big bang makes sense if I picture the universe as a torus. But if I picture the universe as an infinite plane, condense into a point smaller than an atom... idk, it's just harder to imagine.
Perhaps the universe is like Earth, and we are ants.
Sorry but makes no relevant sense to what I'm discussing. Unless you mean the universe is closed.
Well, if there was no real possible way for one to travel or witness every part of the universe, the conclusion our mind usually assume is that it's infinite, right?
Think about it this way: There is no logical way for an ant to travel across the whole Earth on it's own.
The thing is, we are not ants. And while we may not be capable of going around the universe ever, our minds are advanced enough to come up with theories to explain what we would see if it were possible.
Much like it is impossible to travel to the sun and take a sample of it to see what it's made out of (our instruments would melt). But we still know what it's made out of because we have instruments to measure the wavelengths of light coming from it and use math/science to calculate its composition.
In the same way, we've been able to examine the WMAP. Then we use computer generated WMAPs of an open, closed, and flat universe, and compare them to the real one. We've done that, and found that our universe is indeed flat.
However if a universe is flat, it seems that it must be infinite. It always has been, and always will be.
For a good analogy, think of a bed sheet which is infinite in all directions. It always has been infinite, and always will be. But I'm stretching it. This is our universe.
Infinity works in strange ways. Infinity does not simply mean "so large we cannot count it". Lawrence Krauss does an excellent job of explaining infinity in this clip:
Apparently there is something beyond the known edge of the universe, something we cannot see that pulls on our universe. Does he mention at all about how the closer you get the edge the closer you get to absolute zero? This would make ever reaching the edge impossible. If the edge acts like similar to a black hole's distortion on light then it is plausible that you could see an infinite distance.
I don't want to listen to his boring lectures but I believe you'll find a lot more information on the universe and matter if you search other resources. _________________
Apparently there is something beyond the known edge of the universe, something we cannot see that pulls on our universe. Does he mention at all about how the closer you get the edge the closer you get to absolute zero? This would make ever reaching the edge impossible. If the edge acts like similar to a black hole's distortion on light then it is plausible that you could see an infinite distance.
I don't want to listen to his boring lectures but I believe you'll find a lot more information on the universe and matter if you search other resources.
I don't mean any offense but you are a bit mislead.
There is no edge to our universe. A universe with an edge (or boundary) would also have a center, and our universe clearly has no center. We know this because galaxies are actually somewhat stationary -- it's the space in between them that is expanding.
So our universe is not being pulled, it is being pushed (by dark energy).
I'm not sure what you mean by absolutely zero. The temperature of the universe is completely uniform in all directions, this is also how we know that there is no center. The Copernican Principle tells us that no place in the universe is special. It is the same no matter where you are (or where you look).
We can't look in any single direction of the sky and say "that's there the big bang happened". We look in every direction of the sky and see the same thing. If we look out as far as we can, we can see galaxies that are 150 billion light years away, and they look as though they did 13.5 billion years ago. If we were on one of those galaxies and looked back this way, we'd see the same thing, and if we looked in the other direction, would we also see the same thing. The universe is uniform and infinite.
I would be more than happy to study any other resources you have, as long as they are not by the Discovery Intistitute
Apparently there is something beyond the known edge of the universe, something we cannot see that pulls on our universe. Does he mention at all about how the closer you get the edge the closer you get to absolute zero? This would make ever reaching the edge impossible. If the edge acts like similar to a black hole's distortion on light then it is plausible that you could see an infinite distance.
I don't want to listen to his boring lectures but I believe you'll find a lot more information on the universe and matter if you search other resources.
I don't mean any offense but you are a bit mislead.
There is no edge to our universe. A universe with an edge (or boundary) would also have a center, and our universe clearly has no center. We know this because galaxies are actually somewhat stationary -- it's the space in between them that is expanding.
So our universe is not being pulled, it is being pushed (by dark energy).
I'm not sure what you mean by absolutely zero. The temperature of the universe is completely uniform in all directions, this is also how we know that there is no center. The Copernican Principle tells us that no place in the universe is special. It is the same no matter where you are (or where you look).
We can't look in any single direction of the sky and say "that's there the big bang happened". We look in every direction of the sky and see the same thing. If we look out as far as we can, we can see galaxies that are 150 billion light years away, and they look as though they did 13.5 billion years ago. If we were on one of those galaxies and looked back this way, we'd see the same thing, and if we looked in the other direction, would we also see the same thing. The universe is uniform and infinite.
I would be more than happy to study any other resources you have, as long as they are not by the Discovery Intistitute
Very interesting read. I'm not quite sure what to make of it, because it's not well understood yet.
However I do want to point out that they are talking about an external force that it outside of the observable universe.
What it points to is that there is a region of spacetime which is somewhat different than the region we can see through our telescopes. This would violate the Copernican Principle, and that's why I'm not sure what to think of it.
I'm watching a video on it right now, and then hopefully I'll come to a conclusion about this mysterious "dark flow".
If you look at it this way maybe it will be more clear:
Human minds cannot see(notice, interprate) 2D objects therefore the universe CANNOT be compared to some 2D object !
Quote:
our universe (if it were 2D) is shaped like a balloon
this is a BIG NO! NO!
At the very center of every universe there is a black hole. Black hole can curve light therefore we CANNOT see the center even if we were close enough(that is impossible).
From the biological point of view you can go only where you can look. When if you cant look at the center you cannot go there.
BUT if you even near the universes center(even millions of light years away from the center) the black hole would suck you in. From that we see that we cannot see it but can't not go through it (go around it).
Remember that all this is just theoretical and loose on its feat. None of this cannot be confirmed unless if someone goes to the center.
P.S. Everything about the universe is controversial or it is a paradox so you and me are going to be LOOOOOONG dead before this subject becomes clear. _________________
Posted: Wed Jan 05, 2011 4:50 pm Post subject: Re: Our universe has no center, yet you can't go around it?
Quote:
Yet, our universe has no center. The only explanation I can find to this is that our universe (if it were 2D) is shaped like a balloon, therefor it is finite but still has no center.
You're thinking of an ellipse, and while they don't have centers, they do have foci (plural of focus).
All widely accepted theories support that the universe is infinite, therefore has no shape. While I'm not particularly sure what you mean by "flat," I'm pretty sure that's not correct either. You see, we exist in this thing called the third dimension, and we ain't flat.
edit: @Rex, you're thinking of galaxies, not universes.
And you can get a lot closer than millions of light years from black holes.
Quote:
I guess the main thing is that an infinite universe does not make sense to me, because I don't understand how the big bang itself could produce an infinite amount of matter. The big bang makes sense if I picture the universe as a torus. But if I picture the universe as an infinite plane, condense into a point smaller than an atom... idk, it's just harder to imagine.
It didn't create an infinite amount of matter, it just created quite a lot. More matter than we have words to describe, so we just say it was infinitely dense because, as far as practicality goes, it is. _________________
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FangBanger wrote:
What is the best way for a lv19 Soldier to solo Sledge on Borderlands?
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