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PhilKravitz
How does the uniformity of the universe change over time? Or maybe I should say inhomogeneity versus time.
PhilKravitz said:How does the uniformity of the universe change over time? Or maybe I should say inhomogeneity versus time.
bapowell said:Great answer Marcus. I think it's important to emphasize that in order to go from 1) to 2) one needs seed perturbations. In inflationary cosmology, these perturbations are generated during the primordial inflationary era.
You're quite right Phil. Inflation does smooth out initial inhomogeneities leading to a flat universe. This was initially viewed as bittersweet: it gives us a homogeneous and isotropic universe (that we observe on large scales), but seems to simultaneously preclude the formation of structure and local inhomogeneity we see around us.PhilKravitz said:I thought it was just the opposite the inflation flattens any pre-existing lumps. If that were true then lumps must be initial conditions of the universe?
The key point is that inflation leads to a homogeneous universe classically. However, the inflaton field is a quantum field. As such, it is subject to inherent quantum fluctuations. As the universe inflates, these fluctuations are amplified and stretched to large scales (in fact, they are stretched to scales larger than the causal horizon since the inflating spacetime expands faster than the Hubble radius). These quantum fluctuations couple to the background spacetime and generate tiny curvature perturbations. When inflation has completed, one is left with a spectrum of seed perturbations across a continuous range of scales -- from super-horizon down to the galactic. According to inflationary cosmology galaxy clusters, galaxies, and so on, originally arose as a quantum fluctuation in the very early universe. To me, that is the most amazing scientific assertion out there.Or if lumps are not initial conditions how does inflation make lumps? And then all the questions like how many, how big, at what time, etc...
bapowell said:To me, that is the most amazing scientific assertion out there.
The concept of universe uniformity refers to the idea that the physical laws and structures of the universe are consistent throughout its entire history and across all areas of space. This means that the universe appears the same when observed from any location and at any point in time.
Inhomogeneity refers to the uneven distribution of matter and energy in the universe. This plays a significant role in the evolution of the universe as it affects the formation of structures such as galaxies and galaxy clusters. Inhomogeneities in the early universe gave rise to the formation of these structures, which then influenced the overall evolution of the universe.
There is strong evidence for universe uniformity from various cosmological observations, such as the cosmic microwave background radiation and the large-scale distribution of galaxies. These observations show that the universe has the same properties and structures in all directions, providing evidence for its overall uniformity.
The concept of time is crucial in understanding the evolution of universe uniformity. As the universe expands and evolves, inhomogeneities may become more apparent over time due to the gravitational effects of matter and energy. However, the overall uniformity of the universe is maintained over vast periods of time.
Scientists are currently using advanced telescopes and instruments to observe and map the large-scale structure of the universe, looking for any potential inhomogeneities that could challenge the concept of universe uniformity. Additionally, researchers are studying the cosmic microwave background radiation and analyzing data from space missions to gain a better understanding of the evolution of the universe.