Hi Ramses!
}TCP{Ramses wrote:Hehe .... what makes my brain explode is when u get into quantum physics stuff ... multiply all that above by something like 13 dimensions, infinite co-existing universes (the word universe doesn't seem to fit anymore
), gravity leaking from a universe other than our own, time being a human invention and not really existing etc
Hehe... you're mixing up a few things there.
In quantum physics, the main problem is that you have to deal with probabilities because of the limitations of observability. This leads to strange situations like the famous mind experiment called Schroedingers Katze / Schroedinger's Cat.
The physicists have the big problem that both of the important theories, the Quantum Theory on the one hand and the General Theory of Relativity on the other hand, are limited to their own scopes. The first is valid for very small dimensions, the latter for the big dimensions. But whenever the scope of one theory is shifted towards the other, its rules no longer apply. For example, the so called singularities from the Theory of Relativity are impossible in the Quantum Theory.
Therefore, scientists search for a more general theory that combines both of the others, which thereby become parts of the new one and can be derived from it. Meanwhile, there are several new theories, all candidates for this main theory (also called "theory of everything"). The only problem is that they're not practically verifiable at this time. One of the most promising candidates is the so called Superstring Theory, which postulates ultra short strings instead of singularities and thus solves the problem for the quantum theory that can not deal with something having no extent at all.
But the Superstring Theory uses 10, 11 or 26 dimensions (there are several models and right now it's not clear which one is applicable). While the first three are those we know from real life, and the fourth is the time, the extra dimensions are also called compactified dimensions. I think, this is what you meant, isn't it, Ramses?
}TCP{Ramses wrote:What I have never understood and no-one has been able to explain to me is .... how can we see back almost to the big bang ? We have been flying away from the explosion since it happened, but not at the speed of light (otherwise we would see nothing), so surely the image of the big bang would have passed us by long ago
Well, first of all, we can't really see back to the big bang, but approximately until 300000 years after the big bang. The reason is that because of its heat and density, the universe was not transparent for light in the first 300000 years. The first picture of the universe that we can see from that time is the famous Cosmic Microwave Background Radiation.
And with this, we have a direct link to your question. Why is this background image from the beginning only visible in the microwave spectrum? It was visible light with a wavelength of 380-780 nanometers when is was emitted, but we see it as microwave radiation with a wavelength of 0.2-900 millimeters. That means that the waves were stretched by a factor of approximately 1 million compared to their original length. The reason for this, and also the answer to your question, Ramses, is the expansion of space. While the light traverses space towards our planet, the way that is has to go becomes longer all the time. And because the room expands everywhere at the same time, the waves themselves are also being stretched. In the visible spectrum this means that the color of light is shifted from blue towards red. This is why astronomers call this phenomenon "red shift", even if a wavelength is being shifted far below the visible spectrum.
Current measures state that the expansion rate of the universe is something about 72km per second per megaparsec. That means that two points in space with a distance of 3.26 lightyears towards each other move 72km away from each other every second. The expansion rate is cumulative (i.e. two objects with a distance of 2 mpc move away from each other with 144km per second, etc.). That means the greater the distance of an object, the faster it moves away from us.
Coco.
), so 72 km per mpc doesnt seem that much. Distance wise the universe is said to be 78 billion light years (Wiki again you will be glad to know, Kay 
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