Cze�� wszystkim, It's a nice analogy :).
Of course, just like nearly any analogy, this one is not perfect.
As Micha� said, it's true that the deviations from homogeneity are small on scales anything much bigger than the Schwarzschild horizon of a SMBH http://adjani.astro.uni.torun.pl:9673/zwicky/SuperMBH
Another problem is that in the 2D balloon, the positive fluctuations (the net) are connected in a continuous network, while the negative fluctuations (lowest density) are unconnected, separated from one another.
In the standard (3D) model, at early times the + and - fluctuations are typically of the same typical sizes (e.g. from the hypothesis of "gaussian fluctuations"), and the 2D topology of contours of constant density ("genus analysis") is connected both for + and - fluctns.
If you consider all matter more dense than some value, - a low density value gives a "gruyere (ser) topology" - a critical density values gives a "sponge topology" - a high density gives a "meatball topology"
This is impossible to do with a balloon, which is 2D, since the topology of constant density "1-surfaces" is 1D.
But I still like the analogy, because it gives a feeling of the constraint caused by positive matter density.
na razie boud
On Fri, 6 Dec 2002, Michal Frackowiak wrote:
szajtan odwieczny wrote:
hello everybody. Got an idea to share. Once upon a time I thought about such a thing.
What was observed are the great voids (of size about 100 Mly in diameter or even bigger) separated by some cosmic great scale structures so it altogether looks like a soap foam. Assuming that the voids are empty, than the curvature of out local part of the Universe would look like - example in 2d: as we were pumping the balloon but confined by a fishing net which doesn't allow the surface of the balloon for free expansion, and in the end the balloon is quizzed by the strings of the net but it out stands in the holes of the net between the strings. In 3d this would be little more complicated to imagine but what do you thing about this ?
that is correct. curvature is constant only in homogeneous universe. in the perturbed one it is not. but deviations are really small. good luck michal