[Greylorn (OP)]

According to Big Bang theory, e/m radiation and matter were created pretty much simultaneously, after the Bang.  All this stuff moved outward from the center of expansion, eventually coalescing into our universe. 

Matter necessarily moved slower than radiation. 

How can we observe any of this radiation from a planet composed of matter?  The e/m radiation must have moved outward from the same smallish area of space much faster than the configurations of matter we use to observe it, such as the WMAP observing instrument. 

If you send a beam of light from earth out into deep space, you cannot see it.  The best you can do is see reflections of some photons bouncing off dust.  How can we possibly see any form of radiation that was generated at, or nearly at, the same time as the atoms we use to observe it? 

At best, WMAP can only be observing radiation reflected from matter.  What reason might we have to believe that this radiation was generated at the B.Bang, when theory implies a subsequent origin? 

Greylorn

[Kryptid]

I think the problem is that you are imagining the Big Bang occurring as a classical explosion with a center in three-dimensional space. The Big Bang was a rapid expansion of space itself. The best analogy I've heard of is to imagine our entire three-dimensional universe as being the two-dimensional skin of a balloon, with the inflation of the balloon representing cosmic expansion. Points on the balloon's surface grow further apart from each other over time, but the center of the expansion is not located anywhere on the balloon's surface.

[Greylorn (OP)]

I think the problem is that you are imagining the Big Bang occurring as a classical explosion with a center in three-dimensional space. The Big Bang was a rapid expansion of space itself. The best analogy I've heard of is to imagine our entire three-dimensional universe as being the two-dimensional skin of a balloon, with the inflation of the balloon representing cosmic expansion. Points on the balloon's surface grow further apart from each other over time, but the center of the expansion is not located anywhere on the balloon's surface.

Kryptid,
I've been considering the "balloon space" theory since it was invented, and do not buy into it.  It appears to me to be merely another dubious theory invented by Dr. Caca for people who get their physics from TV documentaries.   It does not really solve any problems, but introduces others. 

There's an old mathematical theorem I've been unable to find (help, anyone?) which states that an object existing in n-dimensions cannot move into another dimension unless that other (higher) dimension exists.  For example, a 2-D sheet of paper lying flat on a surface, can only be curled if it also exists within a 3-D space.   This is intuitively obvious. 

It is not obvious that an n-D space could contain an n+1-D space.  I.e. how can a 2-D space contain a 3-D space?  This seems to be what the balloon theory demands.  To me, there's no honest physics here-- just blubbery words and hand-waving obfuscations. 

I am mentally unequipped to imagine or visualize the notion that our 3D universe lies on a 2D surface, and that because the 2D surface is a boundary for another space which is expanding, our universe's space is expanding.  I'm just too stupid to understand how a 2D space could contain a 3D space.

Then there is the question of what the "balloon's" internal space consists of.  It must be 3D, else it cannot expand. 

And then, if that 3D balloon space bounded by a 2D space which contains our 3D space is expanding, it requires yet another space into which it can expand. 

Think about that please, before you mount an argument based upon conventional and potentially dubious theories. 

[evan_au]

The Big Bang theory imagines that the universe started as a hot, dense soup of matter and radiation.
When matter is hot (trillions down to thousands of degrees), it is opaque to radiation. So the CMBR we see today did not come from this era.

The universe became transparent to electromagnetic radiation around 300,000-400,000 years after the Big Bang.
See: https://en.wikipedia.org/wiki/Cosmic_microwave_background#Features

If you want to see events earlier than this, you need to use something that is less obscured by matter, such as neutrinos or gravitational waves, which may allow observations down to a few seconds after the Big Bang.
Cosmologists are searching for both of these, but they know it will be difficult, because they expect them to be extremely red-shifted.

[jeffreyH]

Since the universe is expanding it must have been 'smaller' and denser in the past. What does 'smaller' mean in this context? It just means that the spaces in between particles were smaller. Can we say any more than that?

If the expansion hadn't happened everywhere at once there should be a directional bias to the expansion. Apart from the great attractor this is not the case.

[Bill S]

I've been considering the "balloon space" theory since it was invented, and do not buy into it.

Perhaps referring to it as a “theory” is where your problem starts.  It’s not a theory, it’s an analogy.  I doubt that any serious scientist would suggest that, for example, anything could happen in a dimension that does not exist.  (having said that, I’m neither a scientist, nor very serious, so I’m not sure.)

I gave this some thought when a friend wrote to ask if I could help him get his head round it.  I would welcome comments on this extract from my reply. 

“Excluding the possibility of a pre-existing “somewhere” we can say that it makes no sense to talk of the Big Bang as having happened at a particular place.  Never-the-less, it may be difficult for the non-scientist readily to shake off the idea that there must be some place in the Universe where it all started.  The usual response to this in popular science books is simply to state that the Big Bang “happened everywhere”.  Perhaps this is an area in which the balloon analogy can help, but it is important to keep in mind that it is just an analogy.  Imagine an un-inflated balloon on which you mark a small dot.  As you inflate the balloon, the dot grows.  Now, ask yourself where, within that enlarged patch, you might find your original mark.  Obviously, the answer must be “everywhere”.  The same can be said of the Big Bang.  At the instant of “creation” it encompassed the entire Universe, and as the Universe has expanded it has not left behind some original Big Bang site.  Having said, and perhaps accepted, all this; if we return to the balloon analogy, there must always be a feeling that because the mark expanded evenly in every direction from the centre, that must be its spreading centre.  I suspect that it is this feeling, rather than an inability to accept that the Big Bang happened everywhere, that is the lay-person’s chief difficulty.  Obviously, your original dot has expanded, but has it spread across the balloon?  Is it in contact with any area of the surface with which it was not in contact at the start.  The answer has to be “no”, because the material of the balloon has expanded, carrying your mark with it.  It is tempting to think that your spot was made in the centre of the extended mark, but such is not strictly the case.”

[yor_on]

Pretty good thinking

"There's an old mathematical theorem I've been unable to find (help, anyone?) which states that an object existing in n-dimensions cannot move into another dimension unless that other (higher) dimension exists.  For example, a 2-D sheet of paper lying flat on a surface, can only be curled if it also exists within a 3-D space.   This is intuitively obvious.  "

It's correct if we presume that 'the universe' is/was a 'whole' from any and all origins. You don't need to presume that such must be the case though. What connects a universe is communication, and presumably, a same physics existing. So you can think of it differently, not as dimensions at all. More as if it was 'dots' waiting to be connected into something making sense. And 'c' is what makes it making sense there.

=

Where it leads you if you think that way, is the conclusion that the whole idea of 'dimensions' could be seen as a artifact. Doesn't say they aren't real, but it would be a emergence instead of a origin.

It also will help one with the idea of a 'infinite universe', as that is what it would be in this case. It's communications defining it, time as well as the other three 'dimensions', and they becomes equally true, in a way similar to 'SpaceTime' thought of as a 'whole'.

What I'm arguing here is that everything we decide to exist comes from our position 'inside' this universe, our observations of it. And defining a limit for it becomes meaningless, especially if you treat all those 'dimensions' we see as having a equal importance. In such a case 'time' is no different from length, width and height. And there's no way for you to return to the same point in a 'SpaceTime'.

Ps: there are some good reasons to treat time differently though, a line can be traversed two ways for example whereas 'time' only have one direction for us.

But it helps getting one around the slightly flawed Balloon analogy :)

[Bill S]

.  For example, a 2-D sheet of paper lying flat on a surface, can only be curled if it also exists within a 3-D space.   This is intuitively obvious.

In fact, your sheet of paper could not even exist in 2D – it has to have thickness in order to be there. (nit-pickers of the world unite!)

So you can think of it differently, not as dimensions at all. More as if it was 'dots' waiting to be connected into something making sense. And 'c' is what makes it making sense there.

I don’t follow the connection between random dots and dimensions.

And 'c' is what makes it making sense there.

Do you not need to have defined dimensions in order to make “c” meaningful?

Where it leads you if you think that way, is the conclusion that the whole idea of 'dimensions' could be seen as a artifact. Doesn't say they aren't real, but it would be a emergence instead of a origin.

“Where it leads” is to my concept of an infinite, timeless, dimensionless cosmos; “within” which our Universe is an 3+1D “shadow”.  Time and space are, therefore, the features that allow us to make sense of our Universe.   
Nobody likes my idea ☹

It also will help one with the idea of a 'infinite universe', as that is what it would be in this case. It's communications defining it, time as well as the other three 'dimensions', and they becomes equally true, in a way similar to 'SpaceTime' thought of as a 'whole'.

I’m not going to argue with that, but I think the term 'infinite universe' invites all sorts of difficulties such as the infinite sequence/series, and infinite collections of finite objects.  Mathematically, these things are fine, as in set theory, but they can lead to all manner of problems if you try to apply them to “reality”; whatever that might be.   

And there's no way for you to return to the same point in a 'SpaceTime'.

Absolutely

[Bill S]

But it helps getting one around the slightly flawed Balloon analogy

My own feeling is that the balloon analogy is fine, as long as you don’t try to extrapolate it beyond its intended illustrative scope, as the OP seems to have done.

BTW, Greylorn, I hope you are going to come back with a counter “attack”.  You are, obviously, an original thinker.

[yor_on]

'dots' are just an example of 'something' that needs to connect to become existent from an 'inside' Bill. If you think of cracks in a ice spreading then they has to start somewhere. But a 'Big Bang' from my analogy should be none of that, it would be 'c' connecting it, a 'information universe' without an end. And 'c' is not a physical thing, it's a constant that is presumed to rule all of our universe. It's quite difficult to find a analogy for it, information wise.
=
"Do you not need to have defined dimensions in order to make “c” meaningful?"

No, and Yes. You need to see the limit imposed locally by 'c', and that comes from the ideas we had before relativity. After finding this limit the 'dimensions' we define globally no longer are the same, they are 'observer dependent' in a very new way. So you're right, but that's just the stepping stone. And from it you can define new ideas.

One could start with thinking of rules, laws etc, and then ask oneself if they both can be what imposes itself at the universe, as well as being what becomes defined by the universe. It's the snake eating itself if that becomes the idea. And from a imaginary 'outside', would the universe even be noticed?