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Homogenity of the Universe Confirmed
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| HarbingerDawn | Date: Wednesday, 22.08.2012, 04:43 | Message # 1 |
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| The recent WiggleZ Dark Energy Survey confirmed the prediction of general relativity that the universe is homogenous on large scales, not fractal, and that the density of galaxies in an any arbitrarily large volume of the universe is the same as in a random distribution. The results show that clustering of galaxies does not exist at scales much larger than 300 million light-years, and are thus only localized occurrences.
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| Voekoevaka | Date: Wednesday, 22.08.2012, 11:02 | Message # 2 |
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| What are the consequences of this result ?
In cosmology for example...
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| SpaceEngineer | Date: Wednesday, 22.08.2012, 12:34 | Message # 3 |
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| Quote (Voekoevaka) What are the consequences of this result ? In cosmology for example...
Just confirmation of "cosmological principle" - the homogenity and isotropy of matter distribution. So Friedmann solution of Einstein's gravity equation for expanding Universe is worked. We live in an Friedmann Universe, that should have one of three topological forms (depending on the critical density value, which is not known very well) - a 4D hypersphere, 4D pseudosphere, or simple Euclidian 3D space. The first model is closed - have finite volume and lifetime, the 2 and 3 models are infinite in space and time.
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| Voekoevaka | Date: Wednesday, 22.08.2012, 16:29 | Message # 4 |
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| Quote (SpaceEngineer) 4D hypersphere, 4D pseudosphere, or simple Euclidian 3D space...
What are your opinions about it ?
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| neutronium76 | Date: Wednesday, 22.08.2012, 21:01 | Message # 5 |
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| So if the universe is homogenous does it mean there was no Big Bang? Because if there was a Big Bang the universe shouldn't ne homogenous. Logically thinking ...
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| SpaceEngineer | Date: Wednesday, 22.08.2012, 22:39 | Message # 6 |
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| Quote (neutronium76) So if the universe is homogenous does it mean there was no Big Bang? Because if there was a Big Bang the universe shouldn't ne homogenous. Logically thinking ...
You're making a common mistake. Big Bang is not an explosion in space with a shock-wave and other stuff. It is a creation of the entire space-time, filled homogeneously with energy and matter, and it's expanding. There is no "center of explosion" and "shockwave" or "boundary" - the space everywhere is homogeneously filled with galaxies, and expansion of the Univerese is the expansion of space itself. You may imagine a closed model (hypersphere) if you throw out ine dimension - you will have a simple 3D sphere with galaxies indwelling in its 2D surface. Imagine an inflated balloon with dots painted on its surface - the distance between dots is increased, while they not really moving. The Big Bang is a moment in time when the radius of this balloon was zero.
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| neutronium76 | Date: Saturday, 25.08.2012, 11:19 | Message # 7 |
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| Quote (SpaceEngineer) You're making a common mistake. Big Bang is not an explosion in space with a shock-wave and other stuff. It is a creation of the entire space-time, filled homogeneously with energy and matter, and it's expanding. There is no "center of explosion" and "shockwave" or "boundary" - the space everywhere is homogeneously filled with galaxies, and expansion of the Univerese is the expansion of space itself. You may imagine a closed model (hypersphere) if you throw out ine dimension - you will have a simple 3D sphere with galaxies indwelling in its 2D surface. Imagine an inflated balloon with dots painted on its surface - the distance between dots is increased, while they not really moving. The Big Bang is a moment in time when the radius of this balloon was zero.
Now I get it. But the universe, although homogenous, must be diluting itself as time passes. In the beginning all space-matter-energy was concetrated in a very small volume (although volume is not the correct word to use). And our perception that the universe is 14-15 billion years old is also wrong. Because our ultra deep field super-dooper telescopes cannot detect light beyond the red shift is simply because this very very old and far away light from veery distant galaxies has not reached as (or can not reach us due to the limitation of the visible spectrum??) i.e. the radius of the visible bubble of the universe is limited by the red/infrared part of the spectrum. We can only ''see'' up to 14-15 billion LYrs because beyond that distance, light is veery week (energywise) to reach us -right? So the visible universe may be 14-15 gigaLYs old/big. But the whole universe is much much bigger/older. Right?
Oh man I am confused  ...
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| HarbingerDawn | Date: Saturday, 25.08.2012, 12:48 | Message # 8 |
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| Quote (neutronium76) Because our ultra deep field super-dooper telescopes cannot detect light beyond the red shift is simply because this very very old and far away light from veery distant galaxies has not reached as (or can not reach us due to the limitation of the visible spectrum??) i.e. the radius of the visible bubble of the universe is limited by the red/infrared part of the spectrum
No. If light is visible light is redshifted to longer wavelengths, then we can simply look at the light in those wavelengths, like microwave and radio. In any case, ultraviolet wavelengths would then become visible wavelengths and we would be able to see that with our optical telescopes. High redshift does not prevent us from observing objects, it just makes it more difficult to do in the desired wavelengths.
The reason that we cannot detect light from more than 13.7 billion light years away is because the universe has not existed longer than that, so the light from any objects farther than that distance could not possibly have reached us. Besides, when we look out into the very distant universe, we are primarily looking back in time more than outwards in space. If we were able to look back far enough, we could theoretically be able to see matter that would eventually make up the Milky Way and other nearby galaxies; in other words, you could see the material that you and I are composed of as it was billions of years ago. In practice however it's not that simple.
The most distant (most ancient) feature of the universe that we can observe is the cosmic microwave background radiation. The light from the CMB originated when the universe was less than 400 000 years old. If we could look beyond this, and see all the way to the beginning of the universe, we would see the exact same event happening no matter where we looked in the sky, and we would be able to view a singularity in 360°, as if the universe had somehow inverted itself.
The implications of viewing the very distant universe can be pretty mind-bending.
Quote (neutronium76) And our perception that the universe is 14-15 billion years old is also wrong.
No. Unless cosmologists have gotten everything completely wrong (which it seems they haven't) then the universe really is around 13.7 billion years old. That being the true age of the universe is really the only way to explain what we observe about the cosmos. The fact that no object has been measured or estimated at a greater age than this, and that no objects that would be expected if the universe was older exist (like white dwarfs below a certain mass), confirm that the universe really is this old, and not older.
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