Reflections, Reflections

or we haven't been able to explain adequately.

Very interesting article. This is one:

The horizon problem

OUR universe appears to be unfathomably uniform. Look across space from one edge of the visible universe to the other, and you'll see that the microwave background radiation filling the cosmos is at the same temperature everywhere. That may not seem surprising until you consider that the two edges are nearly 28 billion light years apart and our universe is only 14 billion years old.

Nothing can travel faster than the speed of light, so there is no way heat radiation could have travelled between the two horizons to even out the hot and cold spots created in the big bang and leave the thermal equilibrium we see now.

This "horizon problem" is a big headache for cosmologists, so big that they have come up with some pretty wild solutions. "Inflation", for example.

You can solve the horizon problem by having the universe expand ultra-fast for a time, just after the big bang, blowing up by a factor of 1050 in 10-33 seconds. But is that just wishful thinking? "Inflation would be an explanation if it occurred," says University of Cambridge astronomer Martin Rees. The trouble is that no one knows what could have made that happen.

So, in effect, inflation solves one mystery only to invoke another. A variation in the speed of light could also solve the horizon problem - but this too is impotent in the face of the question "why?" In scientific terms, the uniform temperature of the background radiation remains an anomaly.

See more here at wikipedia's "Unsolved problems in physics."

Did the Universe Have a Beginning?

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Does this idea that the universe is expanding make sense to anyone? If the universe is space, how can it be expanding? It's weird. If the universe is space, it can't be sitting and expanding inside some empty space, otherwise, the latter empty space would be the universe.

So how can the universe expand? It doesn't seem to have logic to me, according to rational principles in geometry. Unless we are talking about something with a circular logic.

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Update April 16:

I am glad someone (Lineweaver) has addressed what I am questioning:

"...the standard big bang theory says nothing about what banged, why it banged, or what happened before it banged. The inflationary universe is a theory of the "bang" of the big bang." - Alan Guth (1997).

Although the standard big bang model can explain much about the evolution of the Universe, there are a few things it cannot explain:

1) The Universe is clumpy. Astronomers, stars, galaxies, clusters of galaxies and even larger structures are sprinkled about. The standard big bang model cannot explain where this hierarchy of clumps came from- it cannot explain the origin of structure. We call this the structure problem.

2) In opposite sides of the sky, the most distant regions of the Universe are at almost the same temperature. But in the standard big bang model they have never been in causal contact - they are outside each other's causal horizons. Thus, the standard model cannot explain why such remote regions have the same temperature. We call this the horizon problem.

3) As far as we can tell, the geometry of the Universe is flat - the interior angles of large triangles add up to 180°. If the Universe had started out with a tiny deviation from flatness, the standard big bang model would have quickly generated a measurable degree of non-flatness. The standard big bang model cannot explain why the Universe started out so flat. We call this the flatness problem.

4) Distant galaxies are redshifted. The Universe is expanding. Why is it expanding? The standard big bang model cannot explain the expansion. We call this the expansion problem.

I'm reading a bit on this stuff, but re #3, flat? I hope to find some explanation to what flat here means, because it's obviously not flat as a piece of paper.

#4) I don't think space expansion of the universe makes sense, because linear infinity in space does not make sense, and space expanding itself does not make sense. If an object is inside a space and the space expands, does the object expand too? Or is the object the same, but bigger, because it was the space that expanded? Or does the object remain with the initial dimensions, but space only changes? See this explanation, saying it is the latter. In order for space to expand, it must have a physicality, like that conception of time also having a physicality. I am trying to find a tutorial on Einstein's relativity space-time model, because, as I recall I was able to understand it a long time ago, but then I completely forgot it all. Or maybe at that time, I just read it, and wasn't really able to think about if it really made sense.

Also, in the balloon example linked above, there is always a center, how can you talk about expansion without a center, or a reference point?

OK, I got it. I have pictured a 3D spatial region, full of spheres. With the passage of time, all the distances between all the spheres are bigger than at the beginning, but the size of the spheres does not change. So there is no center of expansion, and the bigger distances can only be explained if the space itself expanded. Conceptually, it makes sense, but is it real? And then you need to throw in time as expanding too?

Confusing, but interesting. Is there another (and better) explanation to this issue? Is this a real explanation or a paradox? Is there something wrong with the measurements?

So this idea of space expanding is an attempt to explain the increasing difference in distance measurements between universe objects in all directions. Obviously a lay person can't measure, verify, or follow the math/physics reasonings for any of this.

You know what I don't get now? Assume the space expansion explanation. If something, like a force or event put space expansion into motion, that is, space is physically changing (expanding), why wouldn't this same force act on all the objects that are within that space region? Why doesn't everything dilate? Why does only space expand and not space plus everything that is within the space expand? It seems not to make sense again. Not at all.

On the other hand, I need to check this out, but why does space need to expand to explain this distance difference? Take a simple model, and maybe the problem lies with the simplicity of my model. Put 5 spheres in a space region. Then increase the distance between them, regarding all distances. They are further apart, but space itself didn't change or expand for them to be further apart. Why is this supposedly wrong regarding objects in the universe that it won't explain the distance differences?

And why would space start expanding in the first place?

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