CMB fluctuations related to dark matter and normal matter?

In summary, CMB fluctuations are variations in the temperature of the cosmic microwave background radiation, which is the remnant heat from the Big Bang. These fluctuations are believed to be caused by the presence of both dark matter and normal matter in the universe. Dark matter, which makes up about 85% of the total matter in the universe, has a gravitational effect on the distribution of normal matter, leading to variations in the CMB temperature. Studying these fluctuations can provide valuable insights into the composition and evolution of the universe.
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bcrowell
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I came across this http://scienceblogs.com/startswithabang/2010/11/the_simplest_argument_for_dark.php cutesy pop-sci-ish explanation of how we know there's dark matter. If you scroll about 1/3 of the way down, it shows plots of the CMB's power spectrum as a function of multipole moment, l. (Note that the observed plot and the theoretical plots have mismatched x axes.) The observed spectrum has strong oscillations in the region of l=500-850. If you assume only dark matter, or only normal matter, then you don't get these strong oscillations; you mainly get a rapid fall-off. Why is it that you need a mixture of dark matter and normal matter to get the strong oscillations, but if you assume only one or the other you get a rapid fall-off?
 
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Thanks, pervect! I'll have to spend some time studying that.
 

1. What causes CMB fluctuations in the first place?

CMB, or cosmic microwave background, fluctuations are caused by density variations in the early universe. These variations are a result of quantum fluctuations that were amplified during the inflationary period of the universe.

2. How do CMB fluctuations relate to dark matter and normal matter?

CMB fluctuations can give us insight into the distribution and properties of both dark matter and normal matter in the universe. The patterns of fluctuations can help us determine the density and composition of these two types of matter.

3. Can we observe CMB fluctuations directly?

No, we cannot observe CMB fluctuations directly. The fluctuations are only visible in the temperature and polarization patterns of the CMB radiation, which can be detected by specialized instruments such as the Planck satellite or ground-based telescopes.

4. What role do CMB fluctuations play in understanding the structure of the universe?

CMB fluctuations provide crucial evidence for the current model of the universe, known as the Lambda-CDM model. The patterns of fluctuations support the idea of the universe being composed of roughly 5% normal matter, 27% dark matter, and 68% dark energy.

5. How are CMB fluctuations related to the formation of large-scale structures in the universe?

CMB fluctuations are believed to be the initial seeds for the formation of large-scale structures such as galaxies and galaxy clusters. As the universe expanded, these tiny density variations grew and eventually led to the formation of the structures we see today.

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