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[Sean Mirrsen]

If it's generated by something at the center of a finite expanding universe in a finite looped space, we're simply seeing it come around. Then again, we could still get that if there was nothing at the center of the universe - since everything is moving away from somewhere, there should be light-turned-spaceray waves emitted into every direction. And then it comes around and visits every point of space eventually due to the looping. There's the strangest thing that half the universe is moving towards and away from us simultaneously. Light reflected off of Earth will become space-ray for an observer on the opposite half, and then it'll loop around and come back to us as visible light...

[Neruz]

To put a metaphorical spanner into relativistic works, how would you tell if background radiation was "background" radiation and not, say, reflected or emitted light flattened due to relative motion? If half the universe is moving away from us, there could be quite a lot of that.

I believe that the key fact here is that the background radiation comes uniformly from every direction and is always of the same wavelenght. If you had light reflected of "something"(skipping over what it could be), then you'd have a broad spectrum of wavelenghts.
I myself find the idea of BR somewhat strange, after all, wouldn't it all just radiate away from the not-as-fast-as-light expanding parts of the universe? How come we can still detect it?

Hyperspherical Universe?

If it's generated by something at the center of a finite expanding universe in a finite looped space, we're simply seeing it come around. Then again, we could still get that if there was nothing at the center of the universe - since everything is moving away from somewhere, there should be light-turned-spaceray waves emitted into every direction. And then it comes around and visits every point of space eventually due to the looping. There's the strangest thing that half the universe is moving towards and away from us simultaneously. Light reflected off of Earth will become space-ray for an observer on the opposite half, and then it'll loop around and come back to us as visible light...

Wrong spectrum, visible light would be a different wavelength to background radiation.

[Il Palazzo]

I guess the question would be: Where should it radiate to? Basically, if you start in a situation where all of space is filled homogeneously with radiation; then at any given point, all light flow in all directions must be symmetrical. So in any given volume, the amount of light that leaves the volume is the same as that entering it. Ergo, the overall distribution must always stay homogeneous.

And this works as long as there are no 'sharp borders' of space as a whole, where light could 'leave' the universe, so either for an infinite space or a finite but looped space...

But, eh, if it's infinite, and not looped, then there should always be more light leaving the finite "sphere" of material universe towards the infinite void than entering it, right? So, wouldn't the existence of detectable BR point to the looped universe?

@Sean, that light still wouldn't be uniformly of the same wavelenght. Unless you can find a reason why every kind of light would get redshifted exactly to the same frequency.

[Flaede]

I guess the question would be: Where should it radiate to? Basically, if you start in a situation where all of space is filled homogeneously with radiation; then at any given point, all light flow in all directions must be symmetrical. So in any given volume, the amount of light that leaves the volume is the same as that entering it. Ergo, the overall distribution must always stay homogeneous.

And this works as long as there are no 'sharp borders' of space as a whole, where light could 'leave' the universe, so either for an infinite space or a finite but looped space...

But, eh, if it's infinite, and not looped, then there should always be more light leaving the finite "sphere" of material universe towards the infinite void than entering it, right? So, wouldn't the existence of detectable BR point to the looped universe?

@Sean, that light still wouldn't be uniformly of the same wavelenght. Unless you can find a reason why every kind of light would get redshifted exactly to the same frequency.

I'm curious whether I'm right about the following, because if not then I have a lot of reading to do, which could be fun: The way I understood it everything the same distance (n) from anything (pic a point) is moving away at the same speed (adjusted for that local large gravity sources thing that I do not quite get). if you pick a direction, and choose something that distance (n) from our starting point, everything that distance from it (n) is moving away at this same speed. This means, coming back to the original starting point, that everything twice that distance from you is moving away from you at... twice the speed*!

Can it really be that simple? I don't know, sounds like. If everything expands like this, isn't there a point where light can never reach us, and so we can't observe what happens at the "edge" of a hypothetically finite universe? Or is this where we get into that "light's speed is weird" stuff that spawned this thread? Is the time it would take for the "horizon" of that unseeable distance to reach us the time left 'till we hit the hypothetical "heat death of the universe"?

*Some restrictions apply, this offer not valid within large galactic clusters.

[Sean Mirrsen]

Initial speeds for many particles at the center of the Big Bang were similar, therefore the emissions would be fairly uniform. High-frequency radiation would have long since fallen victim to space dust and other generic obstructions of space, so only the low-frequency waves remain now. They're still mostly uniform because they were uniform to begin with, and if they've had at least one cycle through the space loop already, they would've been averaged out since the average density of matter on any given vector starting from the center of the Big Bang would be very similar.

(over the course of writing this reply, the Big Bang has been misspelled as, in order, the Big Band, The Big Gang, and the Big Bamf (no, really))

ninja-edit: Yes, twice the speed. Since the speed of galactic clusters has been averaged out, it's unlikely they are moving at anywhere near the speed of light, though it's easily possible it's on the scale of 0.01c. But if any galaxies were to collide when moving toward each other through the "edge" of the hypersphere...  Sucks to be any sentient lifeforms there, I guess. nvm, misread your post a bit.

[Neruz]

I guess the question would be: Where should it radiate to? Basically, if you start in a situation where all of space is filled homogeneously with radiation; then at any given point, all light flow in all directions must be symmetrical. So in any given volume, the amount of light that leaves the volume is the same as that entering it. Ergo, the overall distribution must always stay homogeneous.

And this works as long as there are no 'sharp borders' of space as a whole, where light could 'leave' the universe, so either for an infinite space or a finite but looped space...

But, eh, if it's infinite, and not looped, then there should always be more light leaving the finite "sphere" of material universe towards the infinite void than entering it, right? So, wouldn't the existence of detectable BR point to the looped universe?

@Sean, that light still wouldn't be uniformly of the same wavelenght. Unless you can find a reason why every kind of light would get redshifted exactly to the same frequency.

I'm curious whether I'm right about the following, because if not then I have a lot of reading to do, which could be fun: The way I understood it everything the same distance (n) from anything (pic a point) is moving away at the same speed (adjusted for that local large gravity sources thing that I do not quite get). if you pick a direction, and choose something that distance (n) from our starting point, everything that distance from it (n) is moving away at this same speed. This means, coming back to the original starting point, that everything twice that distance from you is moving away from you at... twice the speed*!

Can it really be that simple? I don't know, sounds like. If everything expands like this, isn't there a point where light can never reach us, and so we can't observe what happens at the "edge" of a hypothetically finite universe? Or is this where we get into that "light's speed is weird" stuff that spawned this thread? Is the time it would take for the "horizon" of that unseeable distance to reach us the time left 'till we hit the hypothetical "heat death of the universe"?

*Some restrictions apply, this offer not valid within large galactic clusters.

Correct. That is why the observable universe is much smaller than the actual universe. Of course we don't know how much smaller, because we can't see it.

Initial speeds for many particles at the center of the Big Bang were similar, therefore the emissions would be fairly uniform. High-frequency radiation would have long since fallen victim to space dust and other generic obstructions of space, so only the low-frequency waves remain now. They're still mostly uniform because they were uniform to begin with, and if they've had at least one cycle through the space loop already, they would've been averaged out since the average density of matter on any given vector starting from the center of the Big Bang would be very similar.

Congratulations; you just described background radiation and confirmed our theories.

Whoops.

[dreiche2]

But, eh, if it's infinite, and not looped, then there should always be more light leaving the finite "sphere" of material universe towards the infinite void than entering it, right? So, wouldn't the existence of detectable BR point to the looped universe?

Well, not if you start with an infinite universe where radiation is evenly distributed to begin with (so there is no material sphere somewhere 'in the middle'). I guess the difficult thing to wrap one's head around is then rather how something infinite can emerge from a singularity anyway...

I'm curious whether I'm right about the following, because if not then I have a lot of reading to do, which could be fun: The way I understood it everything the same distance (n) from anything (pic a point) is moving away at the same speed (adjusted for that local large gravity sources thing that I do not quite get). if you pick a direction, and choose something that distance (n) from our starting point, everything that distance from it (n) is moving away at this same speed. This means, coming back to the original starting point, that everything twice that distance from you is moving away from you at... twice the speed*!

Yes, and that's exactly what is observed: "The more distant the galaxy, the greater its redshift, and therefore the higher the velocity, a relation known as Hubble's Law".

[Flaede]

Thank you for treating my asking the obvious question seriously. I really didn't want to be making any bad assumptions about the whole thing.

Next question: since the 'big bang' is everything, I always assumed that (counterintuitively) there was no center to it, since it made up everything. This is how the 'everything getting farther from itself' finally worked its way into my head. This lead to the idea that there isn't a center to the universe, which hurts my head. Am I wrong? is there a center (and what about an "edge")? I ask because there was some talk above about a "Center" of the big bang, and this 'space-looping' idea doesn't seem necessary (or possible) if light from an "edge" isn't ever going to be visible:

Initial speeds for many particles at the center of the Big Bang were similar, therefore the emissions would be fairly uniform. High-frequency radiation would have long since fallen victim to space dust and other generic obstructions of space, so only the low-frequency waves remain now. They're still mostly uniform because they were uniform to begin with, and if they've had at least one cycle through the space loop already, they would've been averaged out since the average density of matter on any given vector starting from the center of the Big Bang would be very similar.

I guess I just thought that we were and the center of the big bang. As was that galaxy off in the distance, and as was everything, since that is the whole point of the idea.

[Il Palazzo]

I guess the difficult thing to wrap one's head around is then rather how something infinite can emerge from a singularity anyway...

Oh. Hell this is tricky.

[Neruz]

I guess the difficult thing to wrap one's head around is then rather how something infinite can emerge from a singularity anyway...

Oh. Hell this is tricky.

Well a singularity is already infinitely small.

Next question: since the 'big bang' is everything, I always assumed that (counterintuitively) there was no center to it, since it made up everything. This is how the 'everything getting farther from itself' finally worked its way into my head. This lead to the idea that there isn't a center to the universe, which hurts my head. Am I wrong? is there a center (and what about an "edge")? I ask because there was some talk above about a "Center" of the big bang, and this 'space-looping' idea doesn't seem necessary (or possible) if light from an "edge" isn't ever going to be visible:

Correct. If the Big Bang theory is right, there is no center of the Universe, or rather, everywhere is the center of the Universe, as the Universe sprang from a singularity, and everything was a part of that singularity.

[Sean Mirrsen]

Initial speeds for many particles at the center of the Big Bang were similar, therefore the emissions would be fairly uniform. High-frequency radiation would have long since fallen victim to space dust and other generic obstructions of space, so only the low-frequency waves remain now. They're still mostly uniform because they were uniform to begin with, and if they've had at least one cycle through the space loop already, they would've been averaged out since the average density of matter on any given vector starting from the center of the Big Bang would be very similar.

Congratulations; you just described background radiation and confirmed our theories.

Whoops.

Hehe, so you'd think. I entirely omitted expanding space in the explanation. It also works with ambient energy, but to a degree. Granted, the exact relations between speed and lightwaves are different between theories, but the general premise holds regardless. Per current ambient energy, objects moving away would still create reduced-frequency waves, but the waves' speed would also be decreased. As it is now, ambient energy lacks a definite explanation for any mechanic that would let generated low-frequency waves "pick up speed". I'll fix that one eventually. Nevertheless, it still allows for BR to be the "initial pulse" that got thinned out over time, with relatively few side assumptions.

As for the Big Bang theory, it presumes that the Universe is infinite. It also presumes that Space and the Universe are the same thing. I prefer the variant where.. well, you know my explanation already.

[Neruz]

Hehe, so you'd think. I entirely omitted expanding space in the explanation. It also works with ambient energy, but to a degree. Granted, the exact relations between speed and lightwaves are different between theories, but the general premise holds regardless. Per current ambient energy, objects moving away would still create reduced-frequency waves, but the waves' speed would also be decreased. As it is now, ambient energy lacks a definite explanation for any mechanic that would let generated low-frequency waves "pick up speed". I'll fix that one eventually. Nevertheless, it still allows for BR to be the "initial pulse" that got thinned out over time, with relatively few side assumptions.

Objects moving away would have zero effect on the wavelengths already emitted. The only way for ambient background energy to uniformly increase in wavelength across the entire known universe is for space itself to have expanded, stretching the wavelength.

As for the Big Bang theory, it presumes that the Universe is infinite. It also presumes that Space and the Universe are the same thing. I prefer the variant where.

No it doesn't. The size of the Universe is irrelevant, and Space, like Time, is something derived from the Universe itself.

[Sean Mirrsen]

No, if the Universe is infinite, there can be no distinction between it and Space, and it would also mean that the Big Bang happened everywhere at once. If the Universe is finite and the Space is looped, a more localized gigablast of universal proportions can happen.

[Neruz]

No, if the Universe is infinite, there can be no distinction between it and Space, and it would also mean that the Big Bang happened everywhere at once. If the Universe is finite and the Space is looped, a more localized gigablast of universal proportions can happen.

Um, space is a function of the Universe. Before the Universe (assuming such a concept is valid) there was no space, nor time, nor anything. How many dimensions are a function of the universe depend on what theory you ascribe to, the more mainstream string theories for example suggest that the Universe contains 9 of the 10 dimensions, the 10th one containing superstrings being all that existed before the Universe (technically the Multiverse at this point, but i think introducing Calabi Yau manifolds might make Sean tantrum).

The reason the Big Bang happened everywhere at once is because it originated from a singularity, an infinitely small point, from which the Universe, and subsequently space and time, expanded.

[Flaede]

ninja-reply-edit: So wait, red-shifting light is a sign of the galaxies moving away, and red-shifting background radiation is a sign of the space expanding? Double standards again?

The galaxies are observed as moving because of the expansion of space, in the model I was talking about at any rate. The light emitted from them being redshifted is our clue to that. The background radiation is being redshifted for similar reasons. How is that a double standard?

In a finite yet still expanding universe, galaxies would still be observed to move but the background radiation in your "looping" universe would not be changed from the initial "explosion" except in intensity, which is not the same as wavelength.

"Hubble's Law".

Thank you for giving me a search term to use to seek out the math! I can only vaguely understand it, without spending a lot of time wrapping my head around it, but seeing how the bits relate is still helpful, and will be useful when I find I need to wrap my head around the math.

No, if the Universe is infinite, there can be no distinction between it and Space, and it would also mean that the Big Bang happened everywhere at once. If the Universe is finite and the Space is looped, a more localized gigablast of universal proportions can happen.

It could, but this does not fit the data as I've seen it - this does not explain the shift of background radiation, nor the radiation itself, since would it not then be moving in a "shockwave" type pattern ahead of the mass of the universe?* Nor does it explain the apparently even distribution of galaxies (since they would be more dense towards the center of an "explosion" and less towards the "edge").

 * and perhaps lapping them, but still not even in distribution.