Large-Scale Anisotropy

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Key Concepts:

• COBE showed that the CMB temperature varied at a level of 1 part in 100,000
• Variations are consistent with begin the quantum noise from inflation that formed structure through gravitational instability

If we remove the dipole and turn up the contrast on the previous map to the level of one part in 100,000, the COBE maps reveal:

Again, ignore the pattern around the equator as that is our own galaxy.

If you've never seen this map before, I'm sure your natural reaction is "Um, well it looks like noise to me".

Well actually that is exactly what it is.

But not in the bad sense.  We believe that we are seeing the direct result of random quantum noise in the early universe.   We think that a rapid period of expansion took these seed fluctuations in the density of matter in the universe and brought them to cosmic scales.  The fluctuations that COBE sees are of exactly the right order of magnitude to have all of large-scale structure in the universe to have grown from them by gravitational attraction.  We call the process of gravitational attraction accreting matter around small seed fluctuations to form ever larger structures the gravitational instability model of structure formation in the universe.

Anyway the bottom line is: sure its noise but it's interesting noise.